rfc9913.original   rfc9913.txt 
RAW P. Thubert, Ed. Internet Engineering Task Force (IETF) P. Thubert, Ed.
Internet-Draft Request for Comments: 9913
Intended status: Informational D. Cavalcanti Category: Informational D. Cavalcanti
Expires: 17 October 2025 Intel ISSN: 2070-1721 Intel
X. Vilajosana X. Vilajosana
Universitat Oberta de Catalunya Universitat Oberta de Catalunya
C. Schmitt C. Schmitt
Research Institute CODE, UniBw M Research Institute CODE, UniBw M
J. Farkas J. Farkas
Ericsson Ericsson
15 April 2025 February 2026
Reliable and Available Wireless (RAW) Technologies Reliable and Available Wireless (RAW) Technologies
draft-ietf-raw-technologies-17
Abstract Abstract
This document surveys the short and middle range radio technologies This document surveys the short- and middle-range radio technologies
that are suitable to provide a Deterministic Networking / Reliable over which providing a Deterministic Networking (DetNet) / Reliable
and Available Wireless (RAW) service over, presents the and Available Wireless (RAW) service is suitable, presents the
characteristics that RAW may leverage, and explores the applicability characteristics that RAW may leverage, and explores the applicability
of the technologies to carry deterministic flows, as of its time of of the technologies to carry deterministic flows, as of the time of
publication. The studied technologies are Wi-Fi 6/7, TimeSlotted publication. The studied technologies are Wi-Fi 6/7, Time-Slotted
Channel Hopping (TSCH), 3GPP 5G, and L-band Digital Aeronautical Channel Hopping (TSCH), 3GPP 5G, and L-band Digital Aeronautical
Communications System (LDACS). Communications System (LDACS).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on 17 October 2025. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9913.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology
3. Towards Reliable and Available Wireless Networks . . . . . . 5 3. Towards Reliable and Available Wireless Networks
3.1. Scheduling for Reliability . . . . . . . . . . . . . . . 5 3.1. Scheduling for Reliability
3.2. Diversity for Availability . . . . . . . . . . . . . . . 5 3.2. Diversity for Availability
3.3. Benefits of Scheduling . . . . . . . . . . . . . . . . . 6 3.3. Benefits of Scheduling
4. IEEE 802.11 . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. IEEE 802.11
4.1. Provenance and Documents . . . . . . . . . . . . . . . . 8 4.1. Provenance and Documents
4.2. 802.11ax High Efficiency (HE) . . . . . . . . . . . . . . 10 4.2. 802.11ax High Efficiency (HE)
4.2.1. General Characteristics . . . . . . . . . . . . . . . 10 4.2.1. General Characteristics
4.2.2. Applicability to Deterministic Flows . . . . . . . . 11 4.2.2. Applicability to Deterministic Flows
4.3. 802.11be Extreme High Throughput (EHT) . . . . . . . . . 13 4.3. 802.11be Extreme High Throughput (EHT)
4.3.1. General Characteristics . . . . . . . . . . . . . . . 13 4.3.1. General Characteristics
4.3.2. Applicability to Deterministic Flows . . . . . . . . 14 4.3.2. Applicability to Deterministic Flows
4.4. 802.11ad and 802.11ay (mmWave operation) . . . . . . . . 15 4.4. 802.11ad and 802.11ay (mmWave Operation)
4.4.1. General Characteristics . . . . . . . . . . . . . . . 15 4.4.1. General Characteristics
4.4.2. Applicability to deterministic flows . . . . . . . . 15 4.4.2. Applicability to Deterministic Flows
5. IEEE 802.15.4 Timeslotted Channel Hopping . . . . . . . . . . 16 5. IEEE 802.15.4 Time-Slotted Channel Hopping (TSCH)
5.1. Provenance and Documents . . . . . . . . . . . . . . . . 16 5.1. Provenance and Documents
5.2. General Characteristics . . . . . . . . . . . . . . . . . 18 5.2. General Characteristics
5.2.1. 6TiSCH Tracks . . . . . . . . . . . . . . . . . . . . 19 5.2.1. 6TiSCH Tracks
5.3. Applicability to Deterministic Flows . . . . . . . . . . 23 5.3. Applicability to Deterministic Flows
5.3.1. Centralized Path Computation . . . . . . . . . . . . 24 5.3.1. Centralized Path Computation
6. 5G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6. 5G
6.1. Provenance and Documents . . . . . . . . . . . . . . . . 29 6.1. Provenance and Documents
6.2. General Characteristics . . . . . . . . . . . . . . . . . 31 6.2. General Characteristics
6.3. Deployment and Spectrum . . . . . . . . . . . . . . . . . 33 6.3. Deployment and Spectrum
6.4. Applicability to Deterministic Flows . . . . . . . . . . 34 6.4. Applicability to Deterministic Flows
6.4.1. System Architecture . . . . . . . . . . . . . . . . . 34 6.4.1. System Architecture
6.4.2. Overview of The Radio Protocol Stack . . . . . . . . 36 6.4.2. Overview of the Radio Protocol Stack
6.4.3. Radio (PHY) . . . . . . . . . . . . . . . . . . . . . 37 6.4.3. Radio (PHY)
6.4.4. Scheduling and QoS (MAC) . . . . . . . . . . . . . . 39 6.4.4. Scheduling and QoS (MAC)
6.4.5. Time-Sensitive Communications (TSC) . . . . . . . . . 41 6.4.5. Time-Sensitive Communications (TSC)
7. L-band Digital Aeronautical Communications System . . . . . . 46 7. L-Band Digital Aeronautical Communications System (LDACS)
7.1. Provenance and Documents . . . . . . . . . . . . . . . . 46 7.1. Provenance and Documents
7.2. General Characteristics . . . . . . . . . . . . . . . . . 47 7.2. General Characteristics
7.3. Deployment and Spectrum . . . . . . . . . . . . . . . . . 48 7.3. Deployment and Spectrum
7.4. Applicability to Deterministic Flows . . . . . . . . . . 49 7.4. Applicability to Deterministic Flows
7.4.1. System Architecture . . . . . . . . . . . . . . . . . 49 7.4.1. System Architecture
7.4.2. Overview of the Radio Protocol Stack . . . . . . . . 49 7.4.2. Overview of the Radio Protocol Stack
7.4.3. Radio (PHY) . . . . . . . . . . . . . . . . . . . . . 51 7.4.3. Radio (PHY)
7.4.4. Scheduling, Frame Structure and QoS (MAC) . . . . . . 52 7.4.4. Scheduling, Frame Structure, and QoS (MAC)
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 54 8. IANA Considerations
9. Security Considerations . . . . . . . . . . . . . . . . . . . 55 9. Security Considerations
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 55 10. References
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 55 10.1. Normative References
12. Normative References . . . . . . . . . . . . . . . . . . . . 55 10.2. Informative References
13. Informative References . . . . . . . . . . . . . . . . . . . 56 Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 65 Contributors
Authors' Addresses
1. Introduction 1. Introduction
Deterministic Networking (DetNet) [RFC8557] provides a capability to Deterministic Networking (DetNet) [RFC8557] provides a capability to
carry specified unicast or multicast data flows for real-time carry specified unicast or multicast data flows for real-time
applications with extremely low data loss rates and bounded latency applications with extremely low data loss rates and bounded latency
within a network domain. Techniques that might be used include (1) within a network domain. Techniques that might be used include (1)
reserving data-plane resources for individual (or aggregated) DetNet reserving data plane resources for individual (or aggregated) DetNet
flows in some or all of the intermediate nodes along the path of the flows in some or all of the intermediate nodes along the path of the
flow, (2) providing explicit routes for DetNet flows that do not flow, (2) providing explicit routes for DetNet flows that do not
immediately change with the network topology, and (3) distributing immediately change with the network topology, and (3) distributing
data from DetNet flow packets over time and/or space (e.g., different data from DetNet flow packets over time and/or space (e.g., different
frequencies, or non-Shared Risk Links) to ensure delivery of each frequencies or non-shared risk links) to ensure delivery of each
packet in spite of the unavailability of a path. DetNet operates at packet in spite of the unavailability of a path.
the IP layer and typically delivers service over wired lower-layer
technologies such as Time-Sensitive Networking (TSN) as defined by
IEEE 802.1 and IEEE 802.3.
The Reliable and Available Wireless (RAW) Architecture DetNet operates at the IP layer and typically delivers service over
[I-D.ietf-raw-architecture] extends the DetNet Architecture [RFC8655] wired lower-layer technologies such as Time-Sensitive Networking
to adapt to the specific challenges of the wireless medium, in (TSN) as defined by IEEE 802.1 and IEEE 802.3.
particular intermittently lossy connectivity, by optimizing the use
of diversity and multipathing. [I-D.ietf-raw-architecture] defines The Reliable and Available Wireless (RAW) architecture [RFC9912]
the concepts of Reliability and Availability that are used in this extends the DetNet architecture [RFC8655] to adapt to the specific
document. In turn, this document presents wireless technologies with challenges of the wireless medium, in particular, intermittently
capabilities such as time synchronization and scheduling of lossy connectivity, by optimizing the use of diversity and
transmission, that would make RAW/DetNet operations possible over multipathing. [RFC9912] defines the concepts of reliability and
such media. The technologies studied in this document were availability that are used in this document. In turn, this document
identified in the charter during the RAW WG formation and inherited presents wireless technologies with capabilities, such as time
by DetNet (when the WG picked up the work on RAW). synchronization and scheduling of transmission, that would make RAW/
DetNet operations possible over such media. The technologies studied
in this document were identified in the charter during the RAW
Working Group (WG) formation and inherited by DetNet (when the WG
picked up the work on RAW).
Making wireless reliable and available is even more challenging than Making wireless reliable and available is even more challenging than
it is with wires, due to the numerous causes of radio transmission it is with wires, due to the numerous causes of radio transmission
losses that add up to the congestion losses and the delays caused by losses that add up to the congestion losses and the delays caused by
overbooked shared resources. overbooked shared resources.
RAW, like DetNet, needs and leverages lower-layer capabilities such RAW, like DetNet, needs and leverages lower-layer capabilities such
as time synchronization and traffic shapers. To balance the adverse as time synchronization and traffic shapers. To balance the adverse
effects of the radio transmission losses, RAW leverages additional effects of the radio transmission losses, RAW leverages additional
lower-layer capabilities, some of which may be specific or at least lower-layer capabilities, some of which may be specific or at least
more typically applied to wireless. Such lower-layer techniques more typically applied to wireless. Such lower-layer techniques
include: include:
* per-hop retransmissions (aka Automatic Repeat Request or ARQ), * per-hop retransmissions (also known as Automatic Repeat Request
(ARQ)),
* variation of the modulation and coding scheme (MCS), * variation of the Modulation and Coding Scheme (MCS),
* short range broadcast, * short-range broadcast,
* Multiple User - Multiple Input Multiple Output (MU-MIMO), * Multi-User - Multiple Input Multiple Output (MU-MIMO),
* constructive interference, and * constructive interference, and
* overhearing whereby multiple receivers are scheduled to receive * overhearing whereby multiple receivers are scheduled to receive
the same transmission, which saves both energy on the sender and the same transmission, which saves both energy on the sender and
spectrum. spectrum.
These capabilities may be offered by the lower layer and may be These capabilities may be offered by the lower layer and may be
controlled by RAW, separately or in combination. controlled by RAW, separately or in combination.
RAW defines a network-layer control loop that optimizes the use of RAW defines a network-layer control loop that optimizes the use of
links with constrained spectrum and energy while maintaining the links with constrained spectrum and energy while maintaining the
expected connectivity properties, typically reliability and latency. expected connectivity properties, typically reliability and latency.
The control loop involves communication monitoring through The control loop involves communication monitoring through
Operations, Administration and Maintenance (OAM), path control Operations, Administration, and Maintenance (OAM); path control
through a Path computation Element (PCE) and a runtime distributed through a Path Computation Element (PCE) and a runtime distributed
Path Selection Engine (PSE) and extended packet replication, Path Selection Engine (PSE); and extended Packet Replication,
elimination, and ordering functions (PREOF). Elimination, and Ordering Functions (PREOF).
This document surveys the short and middle range radio technologies This document surveys the short- and middle-range radio technologies
that are suitable to provide a DetNet/RAW service over, presents the over which providing a DetNet/RAW service is suitable, presents the
characteristics that RAW may leverage, and explores the applicability characteristics that RAW may leverage, and explores the applicability
of the technologies to carry deterministic flows. The studied of the technologies to carry deterministic flows. The studied
technologies are Wi-Fi 6/7, TimeSlotted Channel Hopping (TSCH), 3GPP technologies are Wi-Fi 6/7, Time-Slotted Channel Hopping (TSCH), 3GPP
5G, and L-band Digital Aeronautical Communications System (LDACS). 5G, and L-band Digital Aeronautical Communications System (LDACS).
The purpose of this document is to support and enable work on the The purpose of this document is to support and enable work on the
these (and possibly other similar compatible technologies) at the these (and possibly other similar compatible technologies) at the
IETF specifically in the DetNet working group working on RAW. IETF, specifically in the DetNet Working Group working on RAW.
This document surveys existing networking technology and defines no This document surveys existing networking technology; it does not
protocol behaviors or operational practices. The IETF specifications define protocol behaviors or operational practices. The IETF
referenced herein each provide their own Security Considerations, and specifications referenced herein each provide their own security
lower layer technologies provide their own security at Layer-2; a considerations, and lower-layer technologies provide their own
security study of the technologies is explicitly not in scope. security at Layer 2; a security study of the technologies is
explicitly not in scope.
2. Terminology 2. Terminology
This document uses the terminology and acronyms defined in Section 2 This document uses the terminology and acronyms defined in Section 2
of [RFC8655] and Section 2 of [I-D.ietf-raw-architecture]. of [RFC8655] and Section 3 of [RFC9912].
3. Towards Reliable and Available Wireless Networks 3. Towards Reliable and Available Wireless Networks
3.1. Scheduling for Reliability 3.1. Scheduling for Reliability
A packet network is reliable for critical (e.g., time-sensitive) A packet network is reliable for critical (e.g., time-sensitive)
packets when the undesirable statistical effects that affect the packets when the undesirable statistical effects that affect the
transmission of those packets, e.g., delay or loss, are eliminated. transmission of those packets (e.g., delay or loss) are eliminated.
The reliability of a Deterministic Network [RFC8655] often relies on The reliability of a deterministic network [RFC8655] often relies on
precisely applying a tight schedule that controls the use of time- precisely applying a tight schedule that controls the use of time-
shared resources such as CPUs and buffers, and maintains at all time shared resources such as CPUs and buffers, and maintains at all times
the amount of the critical packets within the available resources of the number of the critical packets within the available resources of
the communication hardware (e.g.; buffers) and that of the the communication hardware (e.g., buffers) and the transmission
transmission medium (e.g.; bandwidth, transmission slots). The medium (e.g., bandwidth, transmission slots). The schedule can also
schedule can also be used to shape the flows by controlling the time be used to shape the flows by controlling the time of transmission of
of transmission of the packets that compose the flow at every hop. the packets that compose the flow at every hop.
To achieve this, there must be a shared sense of time throughout the To achieve this, there must be a shared sense of time throughout the
network. The sense of time is usually provided by the lower layer network. The sense of time is usually provided by the lower layer
and is not in scope for RAW. As an example, the Precision Time and is not in scope for RAW. As an example, the Precision Time
Protocol, standardized as IEEE 1588 and IEC 61588, has mapping Protocol (PTP), standardized as IEEE 1588 and IEC 61588, has mapping
through profiles to Ethernet, industrial and SmartGrid protocols, and through profiles to Ethernet, industrial and SmartGrid protocols, and
Wi-Fi with IEEE Std 802.1AS. Wi-Fi with IEEE Std 802.1AS.
3.2. Diversity for Availability 3.2. Diversity for Availability
Equipment (e.g., node) failure, for instance a broken switch or an Equipment (e.g., node) failure can be the cause of multiple packets
being lost in a row before the flows are rerouted or the system
recovers. Examples of equipment failure include a broken switch, an
access point rebooting, a broken wire or radio adapter, or a fixed access point rebooting, a broken wire or radio adapter, or a fixed
obstacle to the transmission, can be the cause of multiple packets obstacle to the transmission.
lost in a row before the flows are rerouted or the system may
recover.
This is not acceptable for critical applications such as related to Equipment failure is not acceptable for critical applications such as
safety. A typical process control loop will tolerate an occasional those related to safety. A typical process control loop will
packet loss, but a loss of several packets in a row will cause an tolerate an occasional packet loss, but a loss of several packets in
emergency stop. In an amusement ride (e.g., at Disneyland, a row will cause an emergency stop. In an amusement ride (e.g., at
Universal, or MGM Studios parks) a continuous loss of packet for a Disneyland, Universal Studios, or MGM Studios parks), a continuous
few 100ms may trigger an automatic interruption of the ride and cause loss of packets for a few 100 ms may trigger an automatic
the evacuation of the attraction floor to restart it. interruption of the ride and cause the evacuation of the attraction
floor to restart it.
Network Availability is obtained by making the transmission resilient Network availability is obtained by making the transmission resilient
against hardware failures and radio transmission losses due to against hardware failures and radio transmission losses due to
uncontrolled events such as co-channel interferers, multipath fading uncontrolled events such as co-channel interferers, multipath fading,
or moving obstacles. The best results are typically achieved by or moving obstacles. The best results are typically achieved by
pseudo-randomly cumulating all forms of diversity, in the spatial pseudorandomly cumulating all forms of diversity -- in the spatial
domain with replication and elimination, in the time domain with ARQ domain with replication and elimination, in the time domain with ARQ
and diverse scheduled transmissions, and in the frequency domain with and diverse scheduled transmissions, and in the frequency domain with
frequency hopping or channel hopping between frames. frequency hopping or channel hopping between frames.
3.3. Benefits of Scheduling 3.3. Benefits of Scheduling
Scheduling redundant transmissions of the critical packets on diverse Scheduling redundant transmissions of the critical packets on diverse
paths improves the resiliency against breakages and statistical paths improves the resiliency against breakages and statistical
transmission loss, such as due to cosmic particles on wires, and transmission loss, such as those due to cosmic particles on wires and
interferences on wireless. While transmission losses are orders of interferences on wireless. While transmission losses are orders of
magnitude more frequent on wireless, redundancy and diversity are magnitude more frequent on wireless, redundancy and diversity are
needed in all cases for life- and mission-critical applications. needed in all cases for life- and mission-critical applications.
When required, the worst case time of delivery can be guaranteed as When required, the worst-case time of delivery can be guaranteed as
part of the end-to-end schedule, and the sense of time that must be part of the end-to-end schedule, and the sense of time that must be
shared throughout the network can be exposed to and leveraged by shared throughout the network can be exposed to and leveraged by
other applications. other applications.
In addition, scheduling provides specific value over the wireless In addition, scheduling provides specific value over the wireless
medium: medium:
* Scheduling allows a time-sharing operation, where every * Scheduling allows a time-sharing operation, where every
transmission is assigned its own time/frequency resource. Sender transmission is assigned its own time/frequency resource. The
and receiver are synchronized and scheduled to talk on a given sender and receiver are synchronized and scheduled to talk on a
frequency resource at a given time and for a given duration. This given frequency resource at a given time and for a given duration.
way, scheduling can avoid collisions between scheduled This way, scheduling can avoid collisions between scheduled
transmissions and enable a high ratio of critical traffic (think transmissions and enable a high ratio of critical traffic (think
60 or 70% of high priority traffic with ultra low loss) compared 60% or 70% of high-priority traffic with ultra low loss) compared
to statistical priority-based schemes. to statistical priority-based schemes.
* Scheduling can be used as a technique for both time and frequency * Scheduling can be used as a technique for both time and frequency
diversity (e.g., between transmission retries), allowing the next diversity (e.g., between transmission retries), allowing the next
transmission to happen on a different frequency as programmed in transmission to happen on a different frequency as programmed in
both the sender and the receiver. This is useful to defeat co- both the sender and the receiver. This is useful to defeat co-
channel interference from un-controlled transmitters as well as channel interference from uncontrolled transmitters as well as
multipath fading. multipath fading.
* Transmissions can be also scheduled on multiple channels in * Transmissions can be also scheduled on multiple channels in
parallel, which enables using the full available spectrum while parallel, which enables the use of the full available spectrum
avoiding the hidden terminal problem, e.g., when the next packet while avoiding the hidden terminal problem, e.g., when the next
in a same flow interferes on a same channel with the previous one packet in a same flow interferes on a same channel with the
that progressed a few hops farther. previous one that progressed a few hops farther.
* On the other hand, scheduling optimizes the bandwidth usage: * Scheduling optimizes the bandwidth usage. Compared to classical
compared to classical Collision Avoidance techniques, there is no collision avoidance techniques, there is no blank time related to
blank time related to inter-frame space (IFS) and exponential Interframe Space (IFS) and exponential back-off in scheduled
back-off in scheduled operations. A minimal Clear Channel operations. A minimal clear channel assessment may be needed to
Assessment may be needed to comply with the local regulations such comply with the local regulations such as ETSI 300-328, but that
as ETSI 300-328, but that will not detect a collision when the will not detect a collision when the senders are synchronized.
senders are synchronized.
* Finally, scheduling plays a critical role to save energy. In IoT, * Scheduling plays a critical role in saving energy. In the
energy is the foremost concern, and synchronizing sender and Internet of Things (IoT), energy is the foremost concern, and
listener enables always maintaining them in deep sleep when there synchronizing the sender and listener enables always maintaining
is no scheduled transmission. This avoids idle listening and long them in deep sleep when there is no scheduled transmission. This
preambles and enables long sleep periods between traffic and avoids idle listening and long preambles, and it enables long
resynchronization, allowing battery-operated nodes to operate in a sleep periods between traffic and resynchronization, allowing
mesh topology for multiple years. battery-operated nodes to operate in a mesh topology for multiple
years.
4. IEEE 802.11 4. IEEE 802.11
In the recent years, the evolution of the IEEE Std 802.11 standard In recent years, the evolution of the IEEE Std 802.11 standard has
has taken a new direction, emphasizing improved reliability and taken a new direction, emphasizing improved reliability and reduced
reduced latency in addition to minor improvements in speed, to enable latency in addition to minor improvements in speed, to enable new
new fields of application such as Industrial IoT and Virtual Reality. fields of application such as industrial IoT and Virtual Reality
(VR).
Leveraging IEEE Std 802.11, the Wi-Fi Alliance [WFA] delivered Wi-Fi Leveraging IEEE Std 802.11, the Wi-Fi Alliance [WFA] delivered Wi-Fi
6, 7, and now 8 with more capabilities to schedule and deliver frames 6, 7, and now 8 with more capabilities to schedule and deliver frames
in due time at fast rates. Still, as any radio technology, Wi-Fi is in due time at fast rates. Still, as with any radio technology, Wi-
sensitive to frame loss, which can only be combated with the maximum Fi is sensitive to frame loss, which can only be combated with the
use of diversity, in space, time, channel, and even technology. maximum use of diversity in space, time, channel, and even
technology.
In parallel, the Avnu Alliance [Avnu], which focuses on applications In parallel, the Avnu Alliance [Avnu], which focuses on applications
of TSN for real time data, formed a workgroup for uses case with TSN of TSN for real-time data, formed a workgroup for uses case with TSN
capabilities over wireless, leveraging both 3GPP and IEEE Std 802.11 capabilities over wireless, leveraging both 3GPP and IEEE Std 802.11
standards. standards.
To achieve the latter, the reliability must be handled at an upper To achieve the latter, the reliability must be handled at an upper
layer that can select Wi-Fi and other wired or wireless technologies layer that can select Wi-Fi and other wired or wireless technologies
for parallel transmissions. This is where RAW comes into play. for parallel transmissions. This is where RAW comes into play.
This section surveys 802.11 features that are most relevant to RAW, This section surveys the IEEE 802.11 features that are most relevant
noting that there are a great many more in the specification, some of to RAW, noting that there are a great many more in the specification,
which possibly of interest as well for a RAW solution. For instance, some of which may also possibly be of interest for a RAW solution.
frame fragmentation reduces the impact of a very transient For instance, frame fragmentation reduces the impact of a very
transmission loss, both on latency and energy consumption. transient transmission loss, both on latency and energy consumption.
4.1. Provenance and Documents 4.1. Provenance and Documents
The IEEE 802 LAN/MAN Standards Committee (SC) develops and maintains The IEEE 802 LAN/MAN Standards Committee (SC) develops and maintains
networking standards and recommended practices for local, networking standards and recommended practices for local,
metropolitan, and other area networks, using an open and accredited metropolitan, and other area networks using an open and accredited
process, and advocates them on a global basis. The most widely used process, and it advocates them on a global basis. The most widely
standards are for Ethernet, Bridging and Virtual Bridged LANs used standards are for Ethernet, Bridging and Virtual Bridged LAN,
Wireless LAN, Wireless PAN, Wireless MAN, Wireless Coexistence, Media Wireless LAN, Wireless Personal Area Network (PAN), Wireless MAN,
Independent Handover Services, and Wireless RAN. An individual Wireless Coexistence, Media Independent Handover Services, and
Working Group provides the focus for each area. Wireless Radio Access Network (RAN). An individual working group
provides the focus for each area.
The IEEE 802.11 Wireless LAN (WLAN) standards define the underlying The IEEE 802.11 Wireless LAN (WLAN) standards define the underlying
MAC and PHY layers for the Wi-Fi technology. While previous 802.11 Medium Access Control (MAC) and Physical (PHY) layers for the Wi-Fi
generations, such as 802.11n and 802.11ac, have focused mainly on technology. While previous 802.11 generations, such as 802.11n and
improving peak throughput, more recent generations are also 802.11ac, focused mainly on improving peak throughput, more recent
considering other performance vectors, such as efficiency generations are also considering other performance vectors, such as
enhancements for dense environments in IEEEE Std 802.11ax [IEEE Std efficiency enhancements for dense environments in IEEEE Std 802.11ax
802.11ax] (approved in 2021), throughput, latency, and reliability [IEEE802.11ax] (approved in 2021) and throughput, latency, and
enhancements in P802.11be [IEEE 802.11be] (approved in 2024). reliability enhancements in IEEE Std 802.11be [IEEE802.11be]
(approved in 2024).
IEEE Std 802.11-2012 includes support for TSN time synchronization IEEE Std 802.11-2012 includes support for TSN time synchronization
based on IEEE 802.1AS over 802.11 Timing Measurement protocol. IEEE based on IEEE 802.1AS over the 802.11 Timing Measurement protocol.
Std 802.11-2016 additionally includes an extension to the 802.1AS IEEE Std 802.11-2016 additionally includes an extension to the
operation over 802.11 for Fine Timing Measurement (FTM), as well as 802.1AS operation over 802.11 for Fine Timing Measurement (FTM), as
the Stream Reservation Protocol (IEEE 802.1Qat). 802.11 WLANs can well as the Stream Reservation Protocol (IEEE 802.1Qat). 802.11 WLANs
also be part of a 802.1Q bridged networks with enhancements enabled can also be part of 802.1Q bridged networks with enhancements enabled
by the 802.11ak amendment retrofitted in IEEE Std 802.11-2020. by the 802.11ak amendment retrofitted in IEEE Std 802.11-2020.
Traffic classification based on 802.1Q VLAN tags is also supported in Traffic classification based on 802.1Q VLAN tags is also supported in
802.11. Other 802.1 TSN capabilities such as 802.1Qbv and 802.1CB, 802.11. Other 802.1 TSN capabilities such as 802.1Qbv and 802.1CB,
which are media agnostic, can already operate over 802.11. The IEEE which are media agnostic, can already operate over 802.11. The IEEE
Std 802.11ax-2021 defines additional scheduling capabilities that can Std 802.11ax-2021 defines additional scheduling capabilities that can
enhance the timeliness performance in the 802.11 MAC and achieve enhance the timeliness performance in the 802.11 MAC and achieve
lower bounded latency. The IEEE 802.11be has introduced features to lower-bounded latency. IEEE 802.11be introduces features to enhance
enhance the support for 802.1 TSN capabilities especially related to the support for 802.1 TSN capabilities, especially those related to
worst-case latency, reliability and availability. worst-case latency, reliability, and availability.
The IEEE 802.11 working group has been working in collaboration with The IEEE 802.11 Working Group has been working in collaboration with
the IEEE 802.1 working group for several years extending some 802.1 the IEEE 802.1 Working Group for several years, extending some 802.1
features over 802.11. As with any wireless media, 802.11 imposes new features over 802.11. As with any wireless media, 802.11 imposes new
constraints and restrictions to TSN-grade QoS, and tradeoffs between constraints and restrictions to TSN-grade QoS, and trade-offs between
latency and reliability guarantees must be considered as well as latency and reliability guarantees must be considered as well as
managed deployment requirements. An overview of 802.1 TSN managed deployment requirements. An overview of 802.1 TSN
capabilities and challenges for their extensions to 802.11 are capabilities and challenges for their extensions to 802.11 are
discussed in [Cavalcanti_2019]. discussed in [Cavalcanti_2019].
Wi-Fi Alliance is the worldwide network of companies that drives The Wi-Fi Alliance is the worldwide network of companies that drives
global Wi-Fi adoption and evolution through thought leadership, global Wi-Fi adoption and evolution through thought leadership,
spectrum advocacy, and industry-wide collaboration. The WFA work spectrum advocacy, and industry-wide collaboration. The WFA work
helps ensure that Wi-Fi devices and networks provide users the helps ensure that Wi-Fi devices and networks provide users the
interoperability, security, and reliability they have come to expect. interoperability, security, and reliability they have come to expect.
Avnu Alliance is also a global industry forum developing The Avnu Alliance is also a global industry forum developing
interoperability testing for TSN capable devices across multiple interoperability testing for TSN-capable devices across multiple
media including Ethernet, Wi-Fi, and 5G. media including Ethernet, Wi-Fi, and 5G.
The following [IEEE Std 802.11] specifications/certifications are The following IEEE Std 802.11 specifications/certifications
relevant in the context of reliable and available wireless services [IEEE802.11] are relevant in the context of reliable and available
and support for time-sensitive networking capabilities: wireless services and support for TSN capabilities:
Time Synchronization: IEEE802.11-2016 with IEEE802.1AS; WFA TimeSync * Time synchronization: IEEE Std 802.11-2016 with IEEE Std 802.1AS;
Certification. WFA TimeSync Certification
Congestion Control: IEEE Std 802.11-2016 Admission Control; WFA * Congestion control: IEEE Std 802.11-2016 Admission Control; WFA
Admission Control. Admission Control
Security: WFA Wi-Fi Protected Access, WPA2 and WPA3. * Security: WFA Wi-Fi Protected Access, WPA2, and WPA3
Interoperating with IEEE802.1Q bridges: IEEE Std 802.11-2020 * Interoperating with IEEE 802.1Q bridges: IEEE Std 802.11-2020
incorporating 802.11ak. incorporating 802.11ak
Stream Reservation Protocol (part of [IEEE Std 802.1Qat]): * Stream Reservation Protocol (part of [IEEE802.1Qat]):
AIEEE802.11-2016 AIEEE802.11-2016
Scheduled channel access: IEEE802.11ad Enhancements for very high * Scheduled channel access: IEEE 802.11ad enhancements for very high
throughput in the 60 GHz band [IEEE Std 802.11ad]. throughput in the 60 GHz band [IEEE802.11ad]
802.11 Real-Time Applications: Topic Interest Group (TIG) ReportDoc * 802.11 Real-Time Applications: Topic Interest Group (TIG)
[IEEE_doc_11-18-2009-06]. ReportDoc [IEEE_doc_11-18-2009-06]
In addition, major amendments being developed by the IEEE802.11 In addition, major amendments being developed by the IEEE 802.11
Working Group include capabilities that can be used as the basis for Working Group include capabilities that can be used as the basis for
providing more reliable and predictable wireless connectivity and providing more reliable and predictable wireless connectivity and
support time-sensitive applications: support time-sensitive applications:
IEEE 802.11ax: Enhancements for High Efficiency (HE). [IEEE Std * [IEEE802.11ax]: Enhancements for High Efficiency (HE)
802.11ax]
IEEE 802.11be Extreme High Throughput (EHT). [IEEE 802.11be] * [IEEE802.11be]: Extreme High Throughput (EHT)
* [IEEE802.11ay]: Enhanced throughput for operation in license-
exempt bands above 45 GHz
IEE 802.11ay Enhanced throughput for operation in license-exempt
bands above 45 GHz. [IEEE Std 802.11ay]
The main 802.11ax, 802.11be, 802.11ad, and 802.11ay capabilities and The main 802.11ax, 802.11be, 802.11ad, and 802.11ay capabilities and
their relevance to RAW are discussed in the remainder of this their relevance to RAW are discussed in the remainder of this
section. As P802.11bn is still in early stages of development, its section. As P802.11bn is still in early stages of development, its
capabilities are not included in this document. capabilities are not included in this document.
4.2. 802.11ax High Efficiency (HE) 4.2. 802.11ax High Efficiency (HE)
4.2.1. General Characteristics 4.2.1. General Characteristics
The next generation Wi-Fi (Wi-Fi 6) is based on the IEEE802.11ax The next generation Wi-Fi (Wi-Fi 6) is based on the IEEE Std 802.11ax
amendment [IEEE Std 802.11ax], which includes specific capabilities amendment [IEEE802.11ax], which includes specific capabilities to
to increase efficiency, control and reduce latency. Some of these increase efficiency, control and reduce latency. Some of these
features include higher order 1024-QAM modulation, support for uplink features include higher-order 1024-QAM modulation, support for uplink
multiple user (MU) multiple input multiple output (MIMO), orthogonal Multi-User - Multiple Input Multiple Output (MU-MIMO), Orthogonal
frequency-division multiple access (OFDMA), trigger-based access and Frequency-Division Multiple Access (OFDMA), trigger-based access, and
Target Wake time (TWT) for enhanced power savings. The OFDMA mode Target Wake Time (TWT) for enhanced power savings. The OFDMA mode
and trigger-based access enable the AP, after reserving the channel and trigger-based access enable the Access Point (AP), after
using the clear channel assessment procedure for a given duration, to reserving the channel using the clear channel assessment procedure
schedule multi-user transmissions, which is a key capability required for a given duration, to schedule multi-user transmissions, which is
to increase latency predictability and reliability for time-sensitive a key capability required to increase latency predictability and
flows. 802.11ax can operate in up to 160 MHz channels and it includes reliability for time-sensitive flows. 802.11ax can operate in up to
support for operation in the new 6 GHz band, which has been open to 160 MHz channels, and it includes support for operation in the new 6
unlicensed use by the FCC and other regulatory agencies worldwide. GHz band, which has been open to unlicensed use by the Federal
Communications Commission (FCC) and other regulatory agencies
worldwide.
4.2.1.1. Multi-User OFDMA and Trigger-based Scheduled Access 4.2.1.1. Multi-User OFDMA and Trigger-Based Scheduled Access
802.11ax introduced an OFDMA mode in which multiple users can be 802.11ax introduced an OFDMA mode in which multiple users can be
scheduled across the frequency domain. In this mode, the Access scheduled across the frequency domain. In this mode, the Access
Point (AP) can initiate multi-user (MU) Uplink (UL) transmissions in Point (AP) can initiate multi-user uplink (UL) transmissions in the
the same PHY Protocol Data Unit (PPDU) by sending a trigger frame. same PHY Protocol Data Unit (PPDU) by sending a trigger frame. This
This centralized scheduling capability gives the AP much more control centralized scheduling capability gives the AP much more control of
of the channel in its Basic Service Set (BSS) and it can remove the channel in its Basic Service Set (BSS), and it can remove
contention between associated stations for uplink transmissions, contention between associated stations for uplink transmissions,
therefore reducing the randomness caused by CSMA-based access between therefore reducing the randomness caused by access based on Carrier
stations within the same BSS. The AP can also transmit Sense Multiple Access (CSMA) between stations within the same BSS.
simultaneously to multiple users in the downlink direction by using a The AP can also transmit simultaneously to multiple users in the
Downlink (DL) MU OFDMA PPDU. In order to initiate a contention free downlink direction by using a downlink (DL) MU OFDMA PPDU. In order
Transmission Opportunity (TXOP) using the OFDMA mode, the AP still to initiate a contention-free Transmission Opportunity (TXOP) using
follows the typical listen before talk procedure to acquire the the OFDMA mode, the AP still follows the typical listen-before-talk
medium, which ensures interoperability and compliance with unlicensed procedure to acquire the medium, which ensures interoperability and
band access rules. However, 802.11ax also includes a multi-user compliance with unlicensed band access rules. However, 802.11ax also
Enhanced Distributed Channel Access (MU-EDCA) capability, which includes a Multi-User Enhanced Distributed Channel Access (MU-EDCA)
allows the AP to get higher channel access priority than other capability, which allows the AP to get higher channel access priority
devices in its BSS. than other devices in its BSS.
4.2.1.2. Traffic Isolation via OFDMA Resource Management and Resource 4.2.1.2. Traffic Isolation via OFDMA Resource Management and Resource
Unit Allocation Unit Allocation
802.11ax relies on the notion of OFDMA Resource Unit (RU) to allocate 802.11ax relies on the notion of an OFDMA Resource Unit (RU) to
frequency chunks to different STAs over time. RUs provide a way to allocate frequency chunks to different stations over time. RUs
allow for multiple stations to transmit simultaneously, starting and provide a way to allow multiple stations to transmit simultaneously,
ending at the same time. The way this is achieved is via padding, starting and ending at the same time. The way this is achieved is
where extra bits are transmitted with the same power level. The via padding, where extra bits are transmitted with the same power
current RU allocation algorithms provide a way to achieve traffic level. The current RU allocation algorithms provide a way to achieve
isolation per station which while per se does not support time-aware traffic isolation per station. While this does not support time-
scheduling, is a key aspect to assist reliability, as it provides aware scheduling per se, it is a key aspect to assist reliability, as
traffic isolation in a shared medium. it provides traffic isolation in a shared medium.
4.2.1.3. Improved PHY Robustness 4.2.1.3. Improved PHY Robustness
The 802.11ax PHY can operate with 0.8, 1.6 or 3.2 microsecond guard The 802.11ax PHY can operate with a 0.8, 1.6, or 3.2 microsecond
interval (GI). The larger GI options provide better protection Guard Interval (GI). The larger GI options provide better protection
against multipath, which is expected to be a challenge in industrial against multipath, which is expected to be a challenge in industrial
environments. The possibility to operate with smaller resource units environments. The possibility of operating with smaller RUs (e.g., 2
(e.g. 2 MHz) enabled by OFDMA also helps reduce noise power and MHz) enabled by OFDMA also helps reduce noise power and improve
improve SNR, leading to better packet error rate (PER) performance. Signal-to-Noise Ratio (SNR), leading to better Packet Error Rate
(PER) performance.
802.11ax supports beamforming as in 802.11ac, but introduces UL MU 802.11ax supports beamforming as in 802.11ac but introduces UL MU-
MIMO, which helps improve reliability. The UL MU MIMO capability is MIMO, which helps improve reliability. The UL MU-MIMO capability is
also enabled by the trigger based access operation in 802.11ax. also enabled by the trigger-based access operation in 802.11ax.
4.2.1.4. Support for 6GHz Band 4.2.1.4. Support for 6 GHz Band
The 802.11ax specification [IEEE Std 802.11ax] includes support for The 802.11ax specification [IEEE802.11ax] includes support for
operation in the 6 GHz band. Given the amount of new spectrum operation in the 6 GHz band. Given the amount of new spectrum
available as well as the fact that no legacy 802.11 device (prior available, as well as the fact that no legacy 802.11 device (prior
802.11ax) will be able to operate in this band, 802.11ax operation in 802.11ax) will be able to operate in this band, 802.11ax operation in
this new band can be even more efficient. this new band can be even more efficient.
4.2.2. Applicability to Deterministic Flows 4.2.2. Applicability to Deterministic Flows
TSN capabilities, as defined by the IEEE 802.1 TSN standards, provide TSN capabilities, as defined by the IEEE 802.1 TSN standards, provide
the underlying mechanism for supporting deterministic flows in a the underlying mechanism for supporting deterministic flows in a
Local Area Network (LAN). The 802.11 working group has incorporated Local Area Network (LAN). The IEEE 802.11 Working Group has
support for absolute time synchronization to extend the TSN 802.1AS incorporated support for absolute time synchronization to extend the
protocol so that time-sensitive flow can experience precise time TSN 802.1AS protocol so that time-sensitive flows can experience
synchronization when operating over 802.11 links. As IEEE 802.11 and precise time synchronization when operating over 802.11 links. As
IEEE 802.1 TSN are both based on the IEEE 802 architecture, 802.11 IEEE 802.11 and IEEE 802.1 TSN are both based on the IEEE 802
devices can directly implement some TSN capabilities without the need architecture, 802.11 devices can directly implement some TSN
for a gateway/translation protocol. Basic features required for capabilities without the need for a gateway/translation protocol.
operation in a 802.1Q LAN are already enabled for 802.11. Some TSN Basic features required for operation in a 802.1Q LAN are already
capabilities, such as 802.1Qbv, can already operate over the existing enabled for 802.11. Some TSN capabilities, such as 802.1Qbv, can
802.11 MAC SAP [Sudhakaran2021]. Implementation and experimental already operate over the existing 802.11 MAC SAP [Sudhakaran2021].
results of TSN capabilities (802.1AS, 802.1Qbv, and 802.1CB) extended Implementation and experimental results of TSN capabilities (802.1AS,
over standard Ethernet and Wi-Fi devices have also been described in 802.1Qbv, and 802.1CB) extended over standard Ethernet and Wi-Fi
[Fang_2021]. Nevertheless, the IEEE 802.11 MAC/PHY could be extended devices have also been described in [Fang_2021]. Nevertheless, the
to improve the operation of IEEE 802.1 TSN features and achieve IEEE 802.11 MAC/PHY could be extended to improve the operation of
better performance metrics [Cavalcanti1287]. IEEE 802.1 TSN features and achieve better performance metrics
[Cavalcanti1287].
TSN capabilities supported over 802.11 (which also extends to TSN capabilities supported over 802.11 (which also extends to
802.11ax), include: 802.11ax) include:
1. 802.1AS based Time Synchronization (other time synchronization 1. 802.1AS-based time synchronization (other time synchronization
techniques may also be used) techniques may also be used)
2. Interoperating with IEEE802.1Q bridges 2. Interoperating with IEEE 802.1Q bridges
3. Time-sensitive Traffic Stream Classification 3. Time-sensitive traffic stream classification
The existing 802.11 TSN capabilities listed above, and the 802.11ax The existing 802.11 TSN capabilities listed above, and the 802.11ax
OFDMA and AP-controlled access within a BSS provide a new set of OFDMA and AP-controlled access within a BSS, provide a new set of
tools to better serve time-sensitive flows. However, it is important tools to better serve time-sensitive flows. However, it is important
to understand the tradeoffs and constraints associated with such to understand the trade-offs and constraints associated with such
capabilities, as well as redundancy and diversity mechanisms that can capabilities, as well as redundancy and diversity mechanisms that can
be used to provide more predictable and reliable performance. be used to provide more predictable and reliable performance.
4.2.2.1. 802.11 Managed Network Operation and Admission Control 4.2.2.1. 802.11 Managed Network Operation and Admission Control
Time-sensitive applications and TSN standards are expected to operate Time-sensitive applications and TSN standards are expected to operate
in a managed network (e.g. industrial/enterprise network). This in a managed network (e.g., an industrial/enterprise network). This
enables to carefully manage and integrate the Wi-Fi operation with enables careful management and integration of the Wi-Fi operation
the overall TSN management framework, as defined in the with the overall TSN management framework, as defined in
[IEEE802.1Qcc] specification. [IEEE802.1Qcc].
Some of the random-access latency and interference from legacy/ Some of the random-access latency and interference from legacy/
unmanaged devices can be reduced under a centralized management mode unmanaged devices can be reduced under a centralized management mode
as defined in [IEEE802.1Qcc]. as defined in [IEEE802.1Qcc].
Existing traffic stream identification, configuration and admission Existing traffic stream identification, configuration, and admission
control procedures defined in [IEEE Std 802.11] QoS mechanism can be control procedures defined in the QoS mechanism in [IEEE802.11] can
re-used. However, given the high degree of determinism required by be reused. However, given the high degree of determinism required by
many time-sensitive applications, additional capabilities to manage many time-sensitive applications, additional capabilities to manage
interference and legacy devices within tight time-constraints need to interference and legacy devices within tight time constraints need to
be explored. be explored.
4.2.2.2. Scheduling for Bounded Latency and Diversity 4.2.2.2. Scheduling for Bounded Latency and Diversity
As discussed earlier, the [IEEE Std 802.11ax] OFDMA mode introduces As discussed earlier, the OFDMA mode in [IEEE802.11ax] introduces the
the possibility of assigning different RUs (time/frequency resources) possibility of assigning different RUs (time/frequency resources) to
to users within a PPDU. Several RU sizes are defined in the users within a PPDU. Several RU sizes are defined in the
specification (26, 52, 106, 242, 484, 996 subcarriers). In addition, specification (26, 52, 106, 242, 484, and 996 subcarriers). In
the AP can also decide on MCS (Modulation and Coding Scheme) and addition, the AP can also decide on a Modulation and Coding Scheme
grouping of users within a given OFMDA PPDU. Such flexibility can be (MCS) and grouping of users within a given OFMDA PPDU. Such
leveraged to support time-sensitive applications with bounded flexibility can be leveraged to support time-sensitive applications
latency, especially in a managed network where stations can be with bounded latency, especially in a managed network where stations
configured to operate under the control of the AP, in a controlled can be configured to operate under the control of the AP, in a
environment (which contains only devices operating on the unlicensed controlled environment (which contains only devices operating on the
band installed by the facility owner and where unexpected unlicensed band installed by the facility owner and where unexpected
interference from other systems and/or radio access technologies only interference from other systems and/or radio access technologies only
sporadically happens), or in a deployment where channel/link sporadically happens), or in a deployment where channel and link
redundancy is used to reduce the impact of unmanaged devices/ redundancy is used to reduce the impact of unmanaged devices and
interference. interference.
When the network is lightly loaded, it is possible to achieve When the network is lightly loaded, it is possible to achieve
latencies under 1 msec when Wi-Fi is operated in contention-based latencies under 1 msec when Wi-Fi is operated in a contention-based
(i.e., without OFDMA) mode. It is also has been shown that it is mode (i.e., without OFDMA). It also has been shown that it is
possible to achieve 1 msec latencies in controlled environment with possible to achieve 1 msec latencies in a controlled environment with
higher efficiency when multi-user transmissions are used (enabled by higher efficiency when multi-user transmissions are used (enabled by
OFDMA operation) [Cavalcanti_2019]. Obviously, there are latency, OFDMA operation) [Cavalcanti_2019]. Obviously, there are latency,
reliability and capacity tradeoffs to be considered. For instance, reliability, and capacity trade-offs to be considered. For instance,
smaller RUs result in longer transmission durations, which may impact smaller RUs result in longer transmission durations, which may impact
the minimal latency that can be achieved, but the contention latency the minimal latency that can be achieved, but the contention latency
and randomness elimination in an interference-free environment due to and randomness elimination in an interference-free environment due to
multi-user transmission is a major benefit of the OFDMA mode. multi-user transmission is a major benefit of the OFDMA mode.
The flexibility to dynamically assign RUs to each transmission also The flexibility to dynamically assign RUs to each transmission also
enables the AP to provide frequency diversity, which can help enables the AP to provide frequency diversity, which can help
increase reliability. increase reliability.
4.3. 802.11be Extreme High Throughput (EHT) 4.3. 802.11be Extreme High Throughput (EHT)
4.3.1. General Characteristics 4.3.1. General Characteristics
The [IEEE 802.11be] ammendment was the next major 802.11 amendment [IEEE802.11be] was the next major 802.11 amendment (after IEEE Std
(after IEEE Std 802.11ax-2021) for operation in the 2.4, 5 and 6 GHz 802.11ax-2021) for operation in the 2.4, 5, and 6 GHz bands. 802.11be
bands. 802.11be includes new PHY and MAC features and it is targeting includes new PHY and MAC features, and it is targeting extremely high
extremely high throughput (at least 30 Gbps), as well as enhancements throughput (at least 30 Gbps), as well as enhancements to worst-case
to worst case latency and jitter. It is also expected to improve the latency and jitter. It is also expected to improve the integration
integration with 802.1 TSN to support time-sensitive applications with 802.1 TSN to support time-sensitive applications over Ethernet
over Ethernet and Wireless LANs. and Wireless LANs.
The 802.11be main features relevant to this document include: The main features of 802.11be that are relevant to this document
include:
1. 320MHz bandwidth and more efficient utilization of non-contiguous 1. 320 MHz bandwidth and more efficient utilization of non-
spectrum. contiguous spectrum
2. Multi-link operation. 2. Multi-Link Operation (MLO)
3. QoS enhancements to reduce latency and increase reliability. 3. QoS enhancements to reduce latency and increase reliability
4.3.2. Applicability to Deterministic Flows 4.3.2. Applicability to Deterministic Flows
The 802.11 Real-Time Applications (RTA) Topic Interest Group (TIG) The 802.11 Real-Time Applications (RTA) Topic Interest Group (TIG)
provided detailed information on use cases, issues and potential provided detailed information on use cases, issues, and potential
solution directions to improve support for time-sensitive solution directions to improve support for time-sensitive
applications in 802.11. The RTA TIG report [IEEE_doc_11-18-2009-06] applications in 802.11. The RTA TIG report [IEEE_doc_11-18-2009-06]
was used as input to the 802.11be project scope. was used as input to the 802.11be project scope.
Improvements for worst-case latency, jitter and reliability were the Improvements for worst-case latency, jitter, and reliability were the
main topics identified in the RTA report, which were motivated by main topics identified in the RTA report, which were motivated by
applications in gaming, industrial automation, robotics, etc. The applications in gaming, industrial automation, robotics, etc. The
RTA report also highlighted the need to support additional TSN RTA report also highlighted the need to support additional TSN
capabilities, such as time-aware (802.1Qbv) shaping and packet capabilities, such as time-aware (802.1Qbv) shaping and packet
replication and elimination as defined in 802.1CB. replication and elimination as defined in 802.1CB.
IEEE Std 802.11be builds on and enhances 802.11ax capabilities to IEEE Std 802.11be builds on and enhances 802.11ax capabilities to
improve worst case latency and jitter. Some of the enhancement areas improve worst case latency and jitter. Some of the enhancement areas
are discussed next. are discussed next.
4.3.2.1. Enhanced Scheduled Operation for Bounded Latency 4.3.2.1. Enhanced Scheduled Operation for Bounded Latency
In addition to the throughput enhancements, 802.11be leverages the In addition to the throughput enhancements, 802.11be leverages the
trigger-based scheduled operation enabled by 802.11ax to provide trigger-based scheduled operation enabled by 802.11ax to provide
efficient and more predictable medium access. efficient and more predictable medium access.
802.11be introduced QoS signaling enhancements, such as an additional 802.11be introduced QoS signaling enhancements, such as an additional
QoS characteristics element, that enables STAs to provide detailed QoS characteristics element, that enables stations to provide
information about deterministic traffic stream to the AP. This detailed information about deterministic traffic stream to the AP.
capability helps AP implementations to better support scheduling for This capability helps AP implementations to better support scheduling
deterministic flows. for deterministic flows.
4.3.2.2. Multi-link operation 4.3.2.2. Multi-Link Operation
802.11be introduces new features to improve operation over multiple 802.11be introduces new features to improve operation over multiple
links and channels. By leveraging multiple links/channels, 802.11be links and channels. By leveraging multiple links and channels,
can isolate time-sensitive traffic from network congestion, one of 802.11be can isolate time-sensitive traffic from network congestion,
the main causes of large latency variations. In a managed 802.11be one of the main causes of large latency variations. In a managed
network, it should be possible to steer traffic to certain links/ 802.11be network, it should be possible to steer traffic to certain
channels to isolate time-sensitive traffic from other traffic and links and channels to isolate time-sensitive traffic from other
help achieve bounded latency. The multi-link operation (MLO) is a traffic and help achieve bounded latency. The Multi-Link Operation
major feature in the 802.11be amendment that can enhance latency and (MLO) is a major feature in the 802.11be amendment that can enhance
reliability by enabling data frames to be duplicated across links. latency and reliability by enabling data frames to be duplicated
across links.
4.4. 802.11ad and 802.11ay (mmWave operation) 4.4. 802.11ad and 802.11ay (mmWave Operation)
4.4.1. General Characteristics 4.4.1. General Characteristics
The IEEE 802.11ad amendment defines PHY and MAC capabilities to The IEEE 802.11ad amendment defines PHY and MAC capabilities to
enable multi-Gbps throughput in the 60 GHz millimeter wave (mmWave) enable multi-Gbps throughput in the 60 GHz millimeter wave (mmWave)
band. The standard addresses the adverse mmWave signal propagation band. The standard addresses the adverse mmWave signal propagation
characteristics and provides directional communication capabilities characteristics and provides directional communication capabilities
that take advantage of beamforming to cope with increased that take advantage of beamforming to cope with increased
attenuation. An overview of the 802.11ad standard can be found in attenuation. An overview of the 802.11ad standard can be found in
[Nitsche_2015]. [Nitsche_2015].
The IEEE 802.11ay is currently developing enhancements to the The IEEE 802.11ay is currently developing enhancements to the
802.11ad standard to enable the next generation mmWave operation 802.11ad standard to enable the next generation mmWave operation
targeting 100 Gbps throughput. Some of the main enhancements in targeting 100 Gbps throughput. Some of the main enhancements in
802.11ay include MIMO, channel bonding, improved channel access and 802.11ay include MIMO, channel bonding, improved channel access, and
beamforming training. An overview of the 802.11ay capabilities can beamforming training. An overview of the 802.11ay capabilities can
be found in [Ghasempour_2017]. be found in [Ghasempour_2017].
4.4.2. Applicability to deterministic flows 4.4.2. Applicability to Deterministic Flows
The high data rates achievable with 802.11ad and 802.11ay can The high-data rates achievable with 802.11ad and 802.11ay can
significantly reduce latency down to microsecond levels. Limited significantly reduce latency down to microsecond levels. Limited
interference from legacy and other unlicensed devices in 60 GHz is interference from legacy and other unlicensed devices in 60 GHz is
also a benefit. However, directionality and short range typical in also a benefit. However, the directionality and short range typical
mmWave operation impose new challenges such as the overhead required in mmWave operation impose new challenges such as the overhead
for beam training and blockage issues, which impact both latency and required for beam training and blockage issues, which impact both
reliability. Therefore, it is important to understand the use case latency and reliability. Therefore, it is important to understand
and deployment conditions in order to properly apply and configure the use case and deployment conditions in order to properly apply and
802.11ad/ay networks for time sensitive applications. configure 802.11ad/ay networks for time-sensitive applications.
The 802.11ad standard includes a scheduled access mode in which the The 802.11ad standard includes a scheduled access mode in which the
central controller, after contending and reserving the channel for a central controller, after contending and reserving the channel for a
dedicated period, can allocate to stations contention-free service dedicated period, can allocate to stations contention-free service
periods. This scheduling capability is also available in 802.11ay, periods. This scheduling capability is also available in 802.11ay,
and it is one of the mechanisms that can be used to provide bounded and it is one of the mechanisms that can be used to provide bounded
latency to time-sensitive data flows in interference-free scenarios. latency to time-sensitive data flows in interference-free scenarios.
An analysis of the theoretical latency bounds that can be achieved An analysis of the theoretical latency bounds that can be achieved
with 802.11ad service periods is provided in [Cavalcanti_2019]. with 802.11ad service periods is provided in [Cavalcanti_2019].
5. IEEE 802.15.4 Timeslotted Channel Hopping 5. IEEE 802.15.4 Time-Slotted Channel Hopping (TSCH)
IEEE Std 802.15.4 TSCH was the first IEEE radio specification aimed IEEE Std 802.15.4 TSCH was the first IEEE radio specification aimed
directly at Industrial IoT applications, for use in Process Control directly at industrial IoT applications, for use in process control
loops and monitoring. It was used as a base for the major industrial loops and monitoring. It was used as a base for the major industrial
wireless process control standards, Wireless HART and ISA100.11a. wireless process control standards, Wireless Highway Addressable
Remote Transducer Protocol (HART) and ISA100.11a.
While the MAC/PHY standards enable the relatively slow rates used in While the MAC/PHY standards enable the relatively slow rates used in
Process Control (typically in the order of 4-5 per second), the process control (typically in the order of 4-5 per second), the
technology is not suited for the faster periods (1 to 10ms) used in technology is not suited for the faster periods used in factory
Factory Automation and motion control. automation and motion control (1 to 10 ms).
5.1. Provenance and Documents 5.1. Provenance and Documents
The IEEE802.15.4 Task Group has been driving the development of low- The IEEE 802.15.4 Task Group has been driving the development of low-
power low-cost radio technology. The IEEE802.15.4 physical layer has power, low-cost radio technology. The IEEE 802.15.4 physical layer
been designed to support demanding low-power scenarios targeting the has been designed to support demanding low-power scenarios targeting
use of unlicensed bands, both the 2.4 GHz and sub GHz Industrial, the use of unlicensed bands, both the 2.4 GHz and sub-GHz Industrial,
Scientific and Medical (ISM) bands. This has imposed requirements in Scientific and Medical (ISM) bands. This has imposed requirements in
terms of frame size, data rate and bandwidth to achieve reduced terms of frame size, data rate, and bandwidth to achieve reduced
collision probability, reduced packet error rate, and acceptable collision probability, reduced packet error rate, and acceptable
range with limited transmission power. The PHY layer supports frames range with limited transmission power. The PHY layer supports frames
of up to 127 bytes. The Medium Access Control (MAC) sublayer of up to 127 bytes. The Medium Access Control (MAC) sublayer
overhead is in the order of 10-20 bytes, leaving about 100 bytes to overhead is in the order of 10-20 bytes, leaving about 100 bytes to
the upper layers. IEEE802.15.4 uses spread spectrum modulation such the upper layers. IEEE 802.15.4 uses spread spectrum modulation such
as the Direct Sequence Spread Spectrum (DSSS). as the Direct Sequence Spread Spectrum (DSSS).
The Timeslotted Channel Hopping (TSCH) mode was added to the 2015 The Time-Slotted Channel Hopping (TSCH) mode was added to the 2015
revision of the IEEE802.15.4 standard [IEEE Std 802.15.4]. TSCH is revision of the IEEE 802.15.4 standard [IEEE802.15.4]. TSCH is
targeted at the embedded and industrial world, where reliability, targeted at the embedded and industrial world, where reliability,
energy consumption and cost drive the application space. energy consumption, and cost drive the application space.
Time sensitive networking on low power constrained wireless networks, Building on IEEE 802.15.4, TSN on low-power constrained wireless
building on IEEE802.15.4, have been partially addressed by ISA100.11a networks has been partially addressed by ISA100.11a [ISA100.11a] and
[ISA100.11a] and WirelessHART [WirelessHART]. Both technologies WirelessHART [WirelessHART]. Both technologies involve a central
involve a central controller that computes redundant paths for controller that computes redundant paths for industrial process
industrial process control traffic over a TSCH mesh. Moreover, control traffic over a TSCH mesh. Moreover, ISA100.11a introduces
ISA100.11a introduces IPv6 [RFC8200] capabilities with a Link-Local IPv6 capabilities [RFC8200] with a link-local address for the join
Address for the join process and a global unicast address for later process and a global unicast address for later exchanges, but the
exchanges, but the IPv6 traffic typically ends at a local application IPv6 traffic typically ends at a local application gateway and the
gateway and the full power of IPv6 for end-to-end communication is full power of IPv6 for end-to-end communication is not enabled.
not enabled.
At the IETF, the 6TiSCH working group [TiSCH] has enabled distributed At the IETF, the 6TiSCH Working Group [TiSCH] has enabled distributed
routing and scheduling to exploit the deterministic access routing and scheduling to exploit the deterministic access
capabilities provided by TSCH for IPv6. The group designed the capabilities provided by TSCH for IPv6. The group designed the
essential mechanisms, the 6top layer and the Scheduling Functions essential mechanisms, the 6TiSCH Operation (6top) sublayer and the
(SFs), to enable the management plane operation while ensuring IPv6 Scheduling Functions (SFs), to enable the management plane operation
is supported: while ensuring IPv6 is supported.
* The 6top Protocol (6P) defined in [RFC8480]. The 6P Protocol * The 6top Protocol (6P) is defined in [RFC8480] and provides a
provides a pairwise negotiation mechanism to the control plane pairwise negotiation mechanism to the control plane operation.
operation. The protocol supports agreement on a schedule between The protocol supports agreement on a schedule between neighbors,
neighbors, enabling distributed scheduling. enabling distributed scheduling.
* 6P goes hand-in-hand with an SF, the policy that decides how to * 6P goes hand in hand with an SF, the policy that decides how to
maintain cells and trigger 6P transactions. The Minimal maintain cells and trigger 6P transactions. The Minimal
Scheduling Function (MSF) [RFC9033] is the default SF defined by Scheduling Function (MSF) [RFC9033] is the default SF defined by
the 6TiSCH WG. the 6TiSCH WG.
* With these mechanisms 6TiSCH can establish layer 2 links between * With these mechanisms, 6TiSCH can establish Layer 2 links between
neighbouring nodes and support best effort traffic. RPL [RFC8480] neighboring nodes and support best-effort traffic. The Routing
provides the routing structure, enabling the 6TiSCH devices to Protocol for Low-Power and Lossy Networks (RPL) [RFC8480] provides
establish the links with well connected neighbours and thus the routing structure, enabling the 6TiSCH devices to establish
forming the acyclic network graphs. the links with well-connected neighbors, thus forming the acyclic
network graphs.
A Track at 6TiSCH is the application to wireless of the concept of a A Track at 6TiSCH is the application to wireless of the concept of a
Recovery Graph in the RAW architecture. A Track can follow a simple recovery graph in the RAW architecture. A Track can follow a simple
sequence of relay nodes or can be structured as a more complex sequence of relay nodes, or it can be structured as a more complex
Destination Oriented Directed Acyclic Graph (DODAG) to a unicast Destination-Oriented Directed Acyclic Graph (DODAG) to a unicast
destination. Along a Track, 6TiSCH nodes reserve the resources to destination. Along a Track, 6TiSCH nodes reserve the resources to
enable the efficient transmission of packets while aiming to optimize enable the efficient transmission of packets while aiming to optimize
certain properties such as reliability and ensure small jitter or certain properties such as reliability and ensure small jitter or
bounded latency. The Track structure enables Layer-2 forwarding bounded latency. The Track structure enables Layer 2 forwarding
schemes, reducing the overhead of taking routing decisions at the schemes, reducing the overhead of making routing decisions at Layer
Layer-3. 3.
The 6TiSCH architecture [RFC9030] identifies different models to The 6TiSCH architecture [RFC9030] identifies different models to
schedule resources along so-called Tracks (see Section 5.2.1) schedule resources along so-called Tracks (see Section 5.2.1),
exploiting the TSCH schedule structure however the focus at 6TiSCH is exploiting the TSCH schedule structure; however, the focus in 6TiSCH
on best effort traffic and the group was never chartered to produce is on best-effort traffic, and the group was never chartered to
standard work related to Tracks. produce standards work related to Tracks.
There are several works that can be used to complement the overview There are several works that can be used to complement the overview
provided in this document. For example [vilajosana21] provides a provided in this document. For example, [vilajosana21] provides a
detailed description of the 6TiSCH protocols, how they are linked detailed description of the 6TiSCH protocols, how they are linked
together and how they are integrated with other standards like RPL together, and how they are integrated with other standards like RPL
and 6Lo. and 6Lo.
5.2. General Characteristics 5.2. General Characteristics
As a core technique in IEEE802.15.4, TSCH splits time in multiple As a core technique in IEEE 802.15.4, TSCH splits time in multiple
time slots that repeat over time. Each device has its own time slots that repeat over time. Each device has its own
perspective of when the send or receive and on which channel the perspective of when the send or receive occurs and on which channel
transmission happens. This constitutes the device's Slotframe where the transmission happens. This constitutes the device's Slotframe,
the channel and destination of a transmission by this device are a where the channel and destination of a transmission by this device
function of time. The overall aggregation of all the Slotframes of are a function of time. The overall aggregation of all the
all the devices constitutes a time/frequency matrix with at most one Slotframes of all the devices constitutes a time/frequency matrix
transmission in each cell of the matrix (more in Section 5.3.1.4). with at most one transmission in each cell of the matrix (see more in
Section 5.3.1.4).
The IEEE 802.15.4 TSCH standard does not define any scheduling The IEEE 802.15.4 TSCH standard does not define any scheduling
mechanism but only provides the architecture that establishes a mechanism but only provides the architecture that establishes a
slotted structure that can be managed by a proper schedule. This slotted structure that can be managed by a proper schedule. This
schedule represents the possible communications of a node with its schedule represents the possible communications of a node with its
neighbors, and is managed by a Scheduling Function such as the neighbors and is managed by a Scheduling Function such as the Minimal
Minimal Scheduling Function (MSF) [RFC9033]. In MSF, each cell in Scheduling Function (MSF) [RFC9033]. In MSF, each cell in the
the schedule is identified by its slotoffset and channeloffset schedule is identified by its slotoffset and channeloffset
coordinates. A cell's timeslot offset indicates its position in coordinates. A cell's timeslot offset indicates its position in
time, relative to the beginning of the slotframe. A cell's channel time, relative to the beginning of the slotframe. A cell's channel
offset is an index which maps to a frequency at each iteration of the offset is an index that maps to a frequency at each iteration of the
slotframe. Each packet exchanged between neighbors happens within slotframe. Each packet exchanged between neighbors happens within
one cell. The size of a cell is a timeslot duration, between 10 to one cell. The size of a cell is a timeslot duration, between 10 to
15 milliseconds. An Absolute Slot Number (ASN) indicates the number 15 milliseconds. An Absolute Slot Number (ASN) indicates the number
of slots elapsed since the network started. It increments at every of slots elapsed since the network started. It increments at every
slot. This is a 5-byte counter that can support networks running for slot. This is a 5-byte counter that can support networks running for
more than 300 years without wrapping (assuming a 10-ms timeslot). more than 300 years without wrapping (assuming a 10 ms timeslot).
Channel hopping provides increased reliability to multi-path fading Channel hopping provides increased reliability to multipath fading
and external interference. It is handled by TSCH through a channel and external interference. It is handled by TSCH through a channel-
hopping sequence referred as macHopSeq in the IEEE802.15.4 hopping sequence referred to as macHopSeq in the IEEE 802.15.4
specification. specification.
The Time-Frequency Division Multiple Access provided by TSCH enables The Time-Frequency Division Multiple Access provided by TSCH enables
the orchestration of traffic flows, spreading them in time and the orchestration of traffic flows, spreading them in time and
frequency, and hence enabling an efficient management of the frequency, and hence enabling an efficient management of the
bandwidth utilization. Such efficient bandwidth utilization can be bandwidth utilization. Such efficient bandwidth utilization can be
combined with OFDM modulations also supported by the IEEE802.15.4 combined with OFDM modulations also supported by the IEEE 802.15.4
standard [IEEE Std 802.15.4] since the 2015 version. standard [IEEE802.15.4] since the 2015 version.
TSCH networks operate in ISM bands in which the spectrum is shared by TSCH networks operate in ISM bands in which the spectrum is shared by
different coexisting technologies. Regulations such as FCC, ETSI and different coexisting technologies. Regulations such as the FCC,
ARIB impose duty cycle regulations to limit the use of the bands but ETSI, and ARIB impose duty cycle regulations to limit the use of the
yet interference may constraint the probability to deliver a packet. bands, but interference may still constrain the probability of
Part of these reliability challenges are addressed at the MAC delivering a packet. Part of these reliability challenges are
introducing redundancy and diversity, thanks to channel hopping, addressed at the MAC introducing redundancy and diversity, thanks to
scheduling and ARQ policies. Yet, the MAC layer operates with a channel hopping, scheduling, and ARQ policies. Yet, the MAC layer
1-hop vision, being limited to local actions to mitigate operates with a 1-hop vision, being limited to local actions to
underperforming links. mitigate underperforming links.
5.2.1. 6TiSCH Tracks 5.2.1. 6TiSCH Tracks
A Track in the 6TiSCH Architecture [RFC9030] is the application to A Track in the 6TiSCH architecture [RFC9030] is the application to
6TiSCH networks of the concept of a protection path in the "Detnet 6TiSCH networks of the concept of a protection path in the DetNet
architecture" [RFC8655]. A Track can be structured as a Destination architecture [RFC8655]. A Track can be structured as a Destination-
Oriented Directed Acyclic Graph (DODAG) to a destination for unicast Oriented Directed Acyclic Graph (DODAG) to a destination for unicast
traffic. Along a Track, 6TiSCH nodes reserve the resources to enable traffic. Along a Track, 6TiSCH nodes reserve the resources to enable
the efficient transmission of packets while aiming to optimize the efficient transmission of packets while aiming to optimize
certain properties such as reliability and ensure small jitter or certain properties such as reliability and ensure small jitter or
bounded latency. The Track structure enables Layer-2 forwarding bounded latency. The Track structure enables Layer 2 forwarding
schemes, reducing the overhead of taking routing decisions at the schemes, reducing the overhead of making routing decisions at Layer
Layer-3. 3.
Serial Tracks can be understood as the concatenation of cells or Serial Tracks can be understood as the concatenation of cells or
bundles along a routing path from a source towards a destination. bundles along a routing path from a source towards a destination.
The serial Track concept is analogous to the circuit concept where The serial Track concept is analogous to the circuit concept where
resources are chained into a multi-hop topology, more in resources are chained into a multi-hop topology; see more in
Section 5.2.1.2 on how that is used in the data plane to forward Section 5.2.1.2 on how that is used in the data plane to forward
packets. packets.
Whereas scheduling ensures reliable delivery in bounded time along Whereas scheduling ensures reliable delivery in bounded time along
any Track, high availability requires the application of PREOF any Track, high availability requires the application of PREOF
functions along a more complex DODAG Track structure. A DODAG has functions along a more complex DODAG Track structure. A DODAG has
forking and joining nodes where the concepts such as Replication and forking and joining nodes where concepts like replication and
Elimination can be exploited. Spatial redundancy increases the elimination can be exploited. Spatial redundancy increases the
overall energy consumption in the network but improves significantly overall energy consumption in the network but significantly improves
the availability of the network as well as the packet delivery ratio. the availability of the network as well as the packet delivery ratio.
A Track may also branch off and rejoin, for the purpose of the so- A Track may also branch off and rejoin, for the purpose of so-called
called Packet Replication and Elimination (PRE), over non congruent Packet Replication and Elimination (PRE), over non-congruent
branches. PRE may be used to complement layer-2 ARQ and receiver-end branches. PRE may be used to complement Layer 2 ARQ and receiver-end
Ordering to complete/extend the PREOF functions. This enables ordering to complete/extend the PREOF functions. This enables
meeting industrial expectations of packet delivery within bounded meeting industrial expectations of packet delivery within bounded
delay over a Track that includes wireless links, even when the Track delay over a Track that includes wireless links, even when the Track
extends beyond the 6TiSCH network. extends beyond the 6TiSCH network.
The RAW Track described in the RAW Architecture The RAW Track described in the RAW architecture [RFC9912] inherits
[I-D.ietf-raw-architecture] inherits directly from that model. RAW directly from that model. RAW extends the graph beyond a DODAG as
extends the graph beyond a DODAG as long as a given packet cannot long as a given packet cannot loop within the Track.
loop within the Track.
+-----+ +-----+
| IoT | | IoT |
| G/W | | G/W |
+-----+ +-----+
^ <---- Elimination ^ <---- Elimination
| | | |
Track branch | | Track branch | |
+-------+ +--------+ Subnet Backbone +-------+ +--------+ Subnet backbone
| | | |
+--|--+ +--|--+ +--|--+ +--|--+
| | | Backbone | | | Backbone | | | Backbone | | | Backbone
o | | | router | | | router o | | | router | | | router
+--/--+ +--|--+ +--/--+ +--|--+
o / o o---o----/ o o / o o---o----/ o
o o---o--/ o o o o o o o---o--/ o o o o o
o \ / o o LLN o o \ / o o LLN o
o v <---- Replication o v <---- Replication
o o
Figure 1: End-to-End deterministic Track Figure 1: End-to-End Deterministic Track
In the example above (see Figure 1), a Track is laid out from a field In Figure 1, a Track is laid out from a field device in a 6TiSCH
device in a 6TiSCH network to an IoT gateway that is located on a network to an IoT gateway that is located on an IEEE 802.1 TSN
IEEE802.1 TSN backbone. backbone.
The Replication function in the field device sends a copy of each The Replication function in the field device sends a copy of each
packet over two different branches, and a PCE schedules each hop of packet over two different branches, and a PCE schedules each hop of
both branches so that the two copies arrive in due time at the both branches so that the two copies arrive in due time at the
gateway. In case of a loss on one branch, hopefully the other copy gateway. In case of a loss on one branch, hopefully the other copy
of the packet still makes it in due time. If two copies make it to of the packet still makes it in due time. If two copies make it to
the IoT gateway, the Elimination function in the gateway ignores the the IoT gateway, the Elimination function in the gateway ignores the
extra packet and presents only one copy to upper layers. extra packet and presents only one copy to upper layers.
At each 6TiSCH hop along the Track, the PCE may schedule more than At each 6TiSCH hop along the Track, the PCE may schedule more than
one timeSlot for a packet, so as to support Layer-2 retries (ARQ). one timeSlot for a packet, so as to support Layer 2 retries (ARQ).
It is also possible that the field device only uses the second branch It is also possible for the field device to only use the second
if sending over the first branch fails. branch if sending over the first branch fails.
In current deployments, a TSCH Track does not necessarily support PRE In current deployments, a TSCH Track does not necessarily support PRE
but is systematically multi-path. This means that a Track is but is systematically multipath. This means that a Track is
scheduled so as to ensure that each hop has at least two forwarding scheduled so as to ensure that each hop has at least two forwarding
solutions, and the forwarding decision is to try the preferred one solutions, and the forwarding decision is to try the preferred one
and use the other in case of Layer-2 transmission failure as detected and use the other in case of Layer 2 transmission failure as detected
by ARQ. by ARQ.
Methods to implement complex Tracks are described in Methods to implement complex Tracks are described in [RFC9914] and
[I-D.ietf-roll-dao-projection] and complemented by extensions to the complemented by extensions to the RPL routing protocol in [NSA-EXT]
RPL routing protocol in [I-D.ietf-roll-nsa-extension] for best effort for best-effort traffic, but a centralized routing technique such as
traffic, but a centralized routing technique such as promoted in one promoted in DetNet is still missing.
DetNet is still missing.
5.2.1.1. Track Scheduling Protocol 5.2.1.1. Track Scheduling Protocol
Section "Schedule Management Mechanisms" of the 6TiSCH architecture Section 4.4 of the 6TiSCH architecture [RFC9030] describes four
describes 4 approaches to manage the TSCH schedule of the LLN nodes: approaches to manage the TSCH schedule of the Low-Power and Lossy
Static Scheduling, neighbor-to-neighbor Scheduling, remote monitoring Network (LLN) nodes: static scheduling, neighbor-to-neighbor
and scheduling management, and Hop-by-hop scheduling. The Track scheduling, remote monitoring and scheduling management, and hop-by-
operation for DetNet corresponds to a remote monitoring and hop scheduling. The Track operation for DetNet corresponds to a
scheduling management by a PCE. remote monitoring and scheduling management by a PCE.
5.2.1.2. Track Forwarding 5.2.1.2. Track Forwarding
By forwarding, the 6TiSCH Architecture [RFC9030] means the per-packet In the 6TiSCH architecture [RFC9030], forwarding is the per-packet
operation that allows delivering a packet to a next hop or an upper operation that allows a packet to be delivered to a next hop or an
layer in this node. Forwarding is based on pre-existing state that upper layer in a node. Forwarding is based on preexisting state that
was installed as a result of the routing computation of a Track by a was installed as a result of the routing computation of a Track by a
PCE. The 6TiSCH architecture supports three different forwarding PCE. The 6TiSCH architecture supports three different forwarding
model, G-MPLS Track Forwarding (TF), 6LoWPAN Fragment Forwarding (FF) models: GMPLS Track Forwarding (TF), 6LoWPAN Fragment Forwarding
and IPv6 Forwarding (6F) which is the classical IP operation (FF), and IPv6 Forwarding (6F), which is the classical IP operation
[RFC9030]. The DetNet case relates to the Track Forwarding operation [RFC9030]. The DetNet case relates to the Track Forwarding operation
under the control of a PCE. under the control of a PCE.
A Track is a unidirectional path between a source and a destination. A Track is a unidirectional path between a source and a destination.
Time/Frequency resources called cells (see Section 5.3.1.4) are Time and frequency resources called cells (see Section 5.3.1.4) are
allocated to enable the forwarding operation along the Track. In a allocated to enable the forwarding operation along the Track. In a
Track cell, the normal operation of IEEE802.15.4 ARQ usually happens, Track cell, the normal operation of IEEE 802.15.4 ARQ usually
though the acknowledgment may be omitted in some cases, for instance happens, though the acknowledgment may be omitted in some cases, for
if there is no scheduled cell for a retry. instance, if there is no scheduled cell for a retry.
Track Forwarding is the simplest and fastest. A bundle of cells set Track Forwarding is the simplest and fastest. A bundle of cells set
to receive (RX-cells) is uniquely paired to a bundle of cells that to receive (RX-cells) is uniquely paired to a bundle of cells that
are set to transmit (TX-cells), representing a layer-2 forwarding are set to transmit (TX-cells), representing a Layer 2 forwarding
state that can be used regardless of the network layer protocol. state that can be used regardless of the network-layer protocol.
This model can effectively be seen as a Generalized Multi-protocol This model can effectively be seen as a Generalized Multiprotocol
Label Switching (G-MPLS) operation in that the information used to Label Switching (GMPLS) operation in that the information used to
switch a frame is not an explicit label, but rather related to other switch a frame is not an explicit label but is rather related to
properties of the way the packet was received, a particular cell in other properties about the way the packet was received (a particular
the case of 6TiSCH. As a result, as long as the TSCH MAC (and cell, in the case of 6TiSCH). As a result, as long as the TSCH MAC
Layer-2 security) accepts a frame, that frame can be switched (and Layer 2 security) accepts a frame, that frame can be switched
regardless of the protocol, whether this is an IPv6 packet, a 6LoWPAN regardless of the protocol, whether this is an IPv6 packet, a 6LoWPAN
fragment, or a frame from an alternate protocol such as WirelessHART fragment, or a frame from an alternate protocol such as WirelessHART
or ISA100.11a. or ISA100.11a.
A data frame that is forwarded along a Track normally has a A data frame that is forwarded along a Track normally has a
destination MAC address that is set to broadcast - or a multicast destination MAC address that is set to broadcast (or a multicast
address depending on MAC support. This way, the MAC layer in the address, depending on MAC support). This way, the MAC layer in the
intermediate nodes accepts the incoming frame and 6top switches it intermediate nodes accepts the incoming frame, and 6top switches it
without incurring a change in the MAC header. In the case of without incurring a change in the MAC header. In the case of IEEE
IEEE802.15.4, this means effectively broadcast, so that along the 802.15.4, this means effectively broadcast, so that the short address
Track the short address for the destination of the frame is set to for the destination of the frame is set to 0xFFFF along the Track.
0xFFFF.
A Track is thus formed end-to-end as a succession of paired bundles, A Track is thus formed end to end as a succession of paired bundles:
a receive bundle from the previous hop and a transmit bundle to the a receive bundle from the previous hop and a transmit bundle to the
next hop along the Track, and a cell in such a bundle belongs to at next hop along the Track. A cell in such a bundle belongs to one
most one Track. For a given iteration of the device schedule, the Track at most. For a given iteration of the device schedule, the
effective channel of the cell is obtained by adding a pseudo-random effective channel of the cell is obtained by adding a pseudorandom
number to the channelOffset of the cell, which results in a rotation number to the channelOffset of the cell, which results in a rotation
of the frequency that used for transmission. The bundles may be of the frequency that was used for transmission. The bundles may be
computed so as to accommodate both variable rates and computed so as to accommodate both variable rates and
retransmissions, so they might not be fully used at a given iteration retransmissions, so they might not be fully used at a given iteration
of the schedule. The 6TiSCH architecture provides additional means of the schedule. The 6TiSCH architecture provides additional means
to avoid waste of cells as well as overflows in the transmit bundle, to avoid waste of cells as well as overflows in the transmit bundle,
as follows: as described in the following paragraphs.
In one hand, a TX-cell that is not needed for the current iteration On one hand, a TX-cell that is not needed for the current iteration
may be reused opportunistically on a per-hop basis for routed may be reused opportunistically on a per-hop basis for routed
packets. When all of the frame that were received for a given Track packets. When all of the frames that were received for a given Track
are effectively transmitted, any available TX-cell for that Track can are effectively transmitted, any available TX-cell for that Track can
be reused for upper layer traffic for which the next-hop router be reused for upper-layer traffic for which the next-hop router
matches the next hop along the Track. In that case, the cell that is matches the next hop along the Track. In that case, the cell that is
being used is effectively a TX-cell from the Track, but the short being used is effectively a TX-cell from the Track, but the short
address for the destination is that of the next-hop router. It address for the destination is that of the next-hop router. It
results that a frame that is received in a RX-cell of a Track with a results that a frame that is received in an RX-cell of a Track with a
destination MAC address set to this node as opposed to broadcast must destination MAC address set to this node as opposed to broadcast must
be extracted from the Track and delivered to the upper layer (a frame be extracted from the Track and delivered to the upper layer (a frame
with an unrecognized MAC address is dropped at the lower MAC layer with an unrecognized MAC address is dropped at the lower MAC layer
and thus is not received at the 6top sublayer). and thus is not received at the 6top sublayer).
On the other hand, it might happen that there are not enough TX-cells On the other hand, it might happen that there are not enough TX-cells
in the transmit bundle to accommodate the Track traffic, for instance in the transmit bundle to accommodate the Track traffic, for
if more retransmissions are needed than provisioned. In that case, instance, if more retransmissions are needed than provisioned. In
the frame can be placed for transmission in the bundle that is used that case, the frame can be placed for transmission in the bundle
for layer-3 traffic towards the next hop along the Track as long as that is used for Layer 3 traffic towards the next hop along the Track
it can be routed by the upper layer, that is, typically, if the frame as long as it can be routed by the upper layer, that is, typically,
transports an IPv6 packet. The MAC address should be set to the if the frame transports an IPv6 packet. The MAC address should be
next-hop MAC address to avoid confusion. It results that a frame set to the next-hop MAC address to avoid confusion. It results that
that is received over a layer-3 bundle may be in fact associated with a frame that is received over a Layer 3 bundle may be in fact
a Track. In a classical IP link such as an Ethernet, off-Track associated with a Track. In a classical IP link such as an Ethernet,
traffic is typically in excess over reservation to be routed along off-Track traffic is typically in excess over reservation to be
the non-reserved path based on its QoS setting. But with 6TiSCH, routed along the non-reserved path based on its QoS setting.
since the use of the layer-3 bundle may be due to transmission However, with 6TiSCH, since the use of the Layer 3 bundle may be due
failures, it makes sense for the receiver to recognize a frame that to transmission failures, it makes sense for the receiver to
should be re-Tracked, and to place it back on the appropriate bundle recognize a frame that should be re-Tracked and to place it back on
if possible. A frame should be re-Tracked if the Per-Hop-Behavior the appropriate bundle if possible. A frame should be re-Tracked if
group indicated in the Differentiated Services Field in the IPv6 the per-hop-behavior group indicated in the Differentiated Services
header is set to Deterministic Forwarding, as discussed in field in the IPv6 header is set to deterministic forwarding, as
Section 5.3.1.1. A frame is re-Tracked by scheduling it for discussed in Section 5.3.1.1. A frame is re-Tracked by scheduling it
transmission over the transmit bundle associated with the Track, with for transmission over the transmit bundle associated with the Track,
the destination MAC address set to broadcast. with the destination MAC address set to broadcast.
5.2.1.2.1. OAM 5.2.1.2.1. OAM
"An Overview of Operations, Administration, and Maintenance (OAM) "An Overview of Operations, Administration, and Maintenance (OAM)
Tools" [RFC7276] provides an overview of the existing tooling for OAM Tools" [RFC7276] provides an overview of the existing tooling for OAM
[RFC6291]. Tracks are complex paths and new tooling is necessary to [RFC6291]. Tracks are complex paths and new tooling is necessary to
manage them, with respect to load control, timing, and the Packet manage them, with respect to load control, timing, and the Packet
Replication and Elimination Functions (PREF). Replication and Elimination Functions (PREF).
An example of such tooling can be found in the context of BIER An example of such tooling can be found in the context of Bit Index
[RFC8279] and more specifically BIER Traffic Engineering [RFC9262] Explicit Replication (BIER) [RFC8279] and, more specifically, BIER
(BIER-TE). Traffic Engineering (BIER-TE) [RFC9262].
5.3. Applicability to Deterministic Flows 5.3. Applicability to Deterministic Flows
In the RAW context, low power reliable networks should address non- In the RAW context, low-power reliable networks should address non-
critical control scenarios such as Class 2 and monitoring scenarios critical control scenarios such as Class 2 and monitoring scenarios
such as Class 4 defined by the RFC5673 [RFC5673]. As a low power such as Class 4, as defined by [RFC5673]. As a low-power technology
technology targeting industrial scenarios radio transducers provide targeting industrial scenarios, radio transducers provide low data
low data rates (typically between 50kbps to 250kbps) and robust rates (typically between 50 kbps to 250 kbps) and robust modulations
modulations to trade-off performance to reliability. TSCH networks to trade-off performance to reliability. TSCH networks are organized
are organized in mesh topologies and connected to a backbone. in mesh topologies and connected to a backbone. Latency in the mesh
Latency in the mesh network is mainly influenced by propagation network is mainly influenced by propagation aspects such as
aspects such as interference. ARQ methods and redundancy techniques interference. ARQ methods and redundancy techniques such as
such as replication and elimination should be studied to provide the replication and elimination should be studied to provide the needed
needed performance to address deterministic scenarios. performance to address deterministic scenarios.
Nodes in a TSCH network are tightly synchronized. This enables Nodes in a TSCH network are tightly synchronized. This enables
building the slotted structure and ensures efficient utilization of building the slotted structure and ensures efficient utilization of
resources thanks to proper scheduling policies. Scheduling is key to resources thanks to proper scheduling policies. Scheduling is key to
orchestrate the resources that different nodes in a Track or a path orchestrate the resources that different nodes in a Track or a path
are using. Slotframes can be split in resource blocks reserving the are using. Slotframes can be split in resource blocks, reserving the
needed capacity to certain flows. Periodic and bursty traffic can be needed capacity to certain flows. Periodic and bursty traffic can be
handled independently in the schedule, using active and reactive handled independently in the schedule, using active and reactive
policies and taking advantage of overprovisioned cells. Along a policies and taking advantage of overprovisioned cells. Along a
Track Section 5.2.1, resource blocks can be chained so nodes in Track (see Section 5.2.1), resource blocks can be chained so nodes in
previous hops transmit their data before the next packet comes. This previous hops transmit their data before the next packet comes. This
provides a tight control to latency along a Track. Collision loss is provides a tight control to latency along a Track. Collision loss is
avoided for best effort traffic by overprovisioning resources, giving avoided for best-effort traffic by overprovisioning resources, giving
time to the management plane of the network to dedicate more time to the management plane of the network to dedicate more
resources if needed. resources if needed.
5.3.1. Centralized Path Computation 5.3.1. Centralized Path Computation
When considering end-to-end communication over TSCH, a 6TiSCH device When considering end-to-end communication over TSCH, a 6TiSCH device
usually does not place a request for bandwidth between itself and usually does not place a request for bandwidth between itself and
another device in the network. Rather, an Operation Control System another device in the network. Rather, an Operation Control System
(OCS) invoked through a Human/Machine Interface (HMI) provides the (OCS) invoked through a Human-Machine Interface (HMI) provides the
Traffic Specification, in particular in terms of latency and traffic specification, in particular, in terms of latency and
reliability, and the end nodes, to a PCE. With this, the PCE reliability, and the end nodes, to a PCE. With this, the PCE
computes a Track between the end nodes and provisions every hop in computes a Track between the end nodes and provisions every hop in
the Track with per-flow state that describes the per-hop operation the Track with per-flow state that describes the per-hop operation
for a given packet, the corresponding timeSlots, and the flow for a given packet, the corresponding timeSlots, and the flow
identification to recognize which packet is placed in which Track, identification to recognize which packet is placed in which Track,
sort out duplicates, etc. An example of Operational Control System sort out duplicates, etc. An example of an OCS and HMI is depicted
and HMI is depicted in Figure 2. in Figure 2.
For a static configuration that serves a certain purpose for a long For a static configuration that serves a certain purpose for a long
period of time, it is expected that a node will be provisioned in one period of time, it is expected that a node will be provisioned in one
shot with a full schedule, which incorporates the aggregation of its shot with a full schedule, which incorporates the aggregation of its
behavior for multiple Tracks. The 6TiSCH Architecture expects that behavior for multiple Tracks. The 6TiSCH architecture expects that
the programing of the schedule is done over the Constrained the programming of the schedule is done over the Constrained
Application Protocol (CoAP) such as discussed in "6TiSCH Resource Application Protocol (CoAP) as discussed in [CoAP-6TiSCH].
Management and Interaction using CoAP" [I-D.ietf-6tisch-coap].
But an Hybrid mode may be required as well whereby a single Track is However, a Hybrid mode may be required as well, whereby a single
added, modified, or removed, for instance if it appears that a Track Track is added, modified, or removed (for instance, if it appears
does not perform as expected. For that case, the expectation is that that a Track does not perform as expected). For that case, the
a protocol that flows along a Track (to be), in a fashion similar to expectation is that a protocol that flows along a Track (to be), in a
classical Traffic Engineering (TE) [CCAMP], may be used to update the fashion similar to classical Traffic Engineering (TE) [CCAMP], may be
state in the devices. In general, that flow was not designed and it used to update the state in the devices. In general, that flow was
is expected that DetNet will determine the appropriate end-to-end not designed, and it is expected that DetNet will determine the
protocols to be used in that case. appropriate end-to-end protocols to be used in that case.
Stream Management Entity Stream Management Entity
Operational Control System and HMI Operational Control System and HMI
-+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
PCE PCE PCE PCE PCE PCE PCE PCE
-+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
--- 6TiSCH------6TiSCH------6TiSCH------6TiSCH-- --- 6TiSCH------6TiSCH------6TiSCH------6TiSCH--
6TiSCH / Device Device Device Device \ 6TiSCH / Device Device Device Device \
Device- - 6TiSCH Device- - 6TiSCH
\ 6TiSCH 6TiSCH 6TiSCH 6TiSCH / Device \ 6TiSCH 6TiSCH 6TiSCH 6TiSCH / Device
----Device------Device------Device------Device-- ----Device------Device------Device------Device--
Figure 2: Architectural Layers Figure 2: Architectural Layers
5.3.1.1. Packet Marking and Handling 5.3.1.1. Packet Marking and Handling
Section "Packet Marking and Handling" of [RFC9030] describes the Section 4.7.1 of [RFC9030] describes the packet tagging and marking
packet tagging and marking that is expected in 6TiSCH networks. that is expected in 6TiSCH networks.
5.3.1.1.1. Tagging Packets for Flow Identification 5.3.1.1.1. Tagging Packets for Flow Identification
Packets that are routed by a PCE along a Track, are tagged to Packets that are routed by a PCE along a Track are tagged to uniquely
uniquely identify the Track and associated transmit bundle of identify the Track and associated transmit bundle of timeSlots.
timeSlots.
It results that the tagging that is used for a DetNet flow outside It results that the tagging that is used for a DetNet flow outside
the 6TiSCH Low Power Lossy Network (LLN) must be swapped into 6TiSCH the 6TiSCH Low-Power and Lossy Network (LLN) must be swapped into
formats and back as the packet enters and then leaves the 6TiSCH 6TiSCH formats and back as the packet enters and then leaves the
network. 6TiSCH network.
5.3.1.1.2. Replication, Retries and Elimination 5.3.1.1.2. Replication, Retries, and Elimination
The 6TiSCH Architecture [RFC9030] leverages PREOF over several The 6TiSCH architecture [RFC9030] leverages PREOF over several
alternate paths in a network to provide redundancy and parallel alternate paths in a network to provide redundancy and parallel
transmissions to bound the end-to-end delay. Considering the transmissions to bound the end-to-end delay. Considering the
scenario shown in Figure 3, many different paths are possible for S scenario shown in Figure 3, many different paths are possible for S
to reach R. A simple way to benefit from this topology could be to to reach R. A simple way to benefit from this topology could be to
use the two independent paths via nodes A, C, E and via B, D, F. But use the two independent paths via nodes A, C, E and via B, D, F, but
more complex paths are possible as well. more complex paths are possible as well.
(A) (C) (E) (A) (C) (E)
source (S) (R) (destination) source (S) (R) (destination)
(B) (D) (F) (B) (D) (F)
Figure 3: A Typical Ladder Shape with Two Parallel Paths Toward Figure 3: A Typical Ladder Shape with Two Parallel Paths Toward
the Destination the Destination
By employing a Packet Replication function, each node forwards a copy By employing a packet replication function, each node forwards a copy
of each data packet over two different branches. For instance, in of each data packet over two different branches. For instance, in
Figure 4, the source node S transmits the data packet to nodes A and Figure 4, the source node S transmits the data packet to nodes A and
B, in two different timeslots within the same TSCH slotframe. B, in two different timeslots within the same TSCH slotframe. S
transmits twice the same data packet to its Destination Parent (DP)
(A) and to its Alternate Parent (AP) (B).
===> (A) => (C) => (E) === ===> (A) => (C) => (E) ===
// \\// \\// \\ // \\// \\// \\
source (S) //\\ //\\ (R) (destination) source (S) //\\ //\\ (R) (destination)
\\ // \\ // \\ // \\ // \\ // \\ //
===> (B) => (D) => (F) === ===> (B) => (D) => (F) ===
Figure 4: Packet Replication: S transmits twice the same data Figure 4: Packet Replication
packet, to its Destination Parent (DP) (A) and to its Alternate
Parent (AP) (B).
By employing Packet Elimination function once a node receives the By employing a packet elimination function once it receives the first
first copy of a data packet, it discards the subsequent copies. copy of a data packet, a node discards the subsequent copies.
Because the first copy that reaches a node is the one that matters, Because the first copy that reaches a node is the one that matters,
it is the only copy that will be forwarded upward. it is the only copy that will be forwarded upward.
Considering that the wireless medium is broadcast by nature, any Considering that the wireless medium is broadcast by nature, any
neighbor of a transmitter may overhear a transmission. By employing neighbor of a transmitter may overhear a transmission. By employing
the Promiscuous Overhearing function, nodes will have multiple the promiscuous overhearing function, nodes will have multiple
opportunities to receive a given data packet. For instance, in opportunities to receive a given data packet. For instance, in
Figure 4, when the source node S transmits the data packet to node A, Figure 4, when the source node S transmits the data packet to node A,
node B may overhear this transmission. node B may overhear the transmission.
6TiSCH expects elimination and replication of packets along a complex 6TiSCH expects elimination and replication of packets along a complex
Track, but has no position about how the sequence numbers would be Track but has no position about how the sequence numbers would be
tagged in the packet. tagged in the packet.
As it goes, 6TiSCH expects that timeSlots corresponding to copies of As it goes, 6TiSCH expects that timeSlots corresponding to copies of
a same packet along a Track are correlated by configuration, and does the same packet along a Track are correlated by configuration, and
not need to process the sequence numbers. does not need to process the sequence numbers.
The semantics of the configuration must enable correlated timeSlots The semantics of the configuration must enable correlated timeSlots
to be grouped for transmit (and respectively receive) with 'OR' to be grouped for transmit (and receive, respectively) with 'OR'
relations, and then an 'AND' relation must be configurable between relations, and then an 'AND' relation must be configurable between
groups. The semantics is that if the transmit (and respectively groups. The semantics are such that if the transmit (and receive,
receive) operation succeeded in one timeSlot in an 'OR' group, then respectively) operation succeeded in one timeSlot in an 'OR' group,
all the other timeslots in the group are ignored. Now, if there are then all the other timeslots in the group are ignored. Now, if there
at least two groups, the 'AND' relation between the groups indicates are at least two groups, the 'AND' relation between the groups
that one operation must succeed in each of the groups. Further indicates that one operation must succeed in each of the groups.
details can be found in the 6TiSCH Architecture document [RFC9030]. Further details can be found in the 6TiSCH architecture document
[RFC9030].
5.3.1.2. Topology and Capabilities 5.3.1.2. Topology and Capabilities
6TiSCH nodes are usually IoT devices, characterized by very limited 6TiSCH nodes are usually IoT devices, characterized by a very limited
amount of memory, just enough buffers to store one or a few IPv6 amount of memory, just enough buffers to store one or a few IPv6
packets, and limited bandwidth between peers. It results that a node packets, and limited bandwidth between peers. It results that a node
will maintain only a small number of peering information, and will will maintain only a small amount of peering information and will not
not be able to store many packets waiting to be forwarded. Peers can be able to store many packets waiting to be forwarded. Peers can be
be identified through MAC or IPv6 addresses. identified through MAC or IPv6 addresses.
Neighbors can be discovered over the radio using mechanism such as Neighbors can be discovered over the radio using mechanisms such as
Enhanced Beacons, but, though the neighbor information is available enhanced beacons, but although the neighbor information is available
in the 6TiSCH interface data model, 6TiSCH does not describe a in the 6TiSCH interface data model, 6TiSCH does not describe a
protocol to pro-actively push the neighborhood information to a PCE. protocol to proactively push the neighborhood information to a PCE.
This protocol should be described and should operate over CoAP. The This protocol should be described and should operate over CoAP. The
protocol should be able to carry multiple metrics, in particular the protocol should be able to carry multiple metrics, in particular, the
same metrics as used for RPL operations [RFC6551]. same metrics that are used for RPL operations [RFC6551].
The energy that the device consumes in sleep, transmit and receive The energy that the device consumes in sleep, transmit, and receive
modes can be evaluated and reported. So can the amount of energy modes can be evaluated and reported, and so can the amount of energy
that is stored in the device and the power that it can be scavenged that is stored in the device and the power that can be scavenged from
from the environment. The PCE should be able to compute Tracks that the environment. The PCE should be able to compute Tracks that will
will implement policies on how the energy is consumed, for instance implement policies on how the energy is consumed, for instance,
balance between nodes and ensure that the spent energy does not policies that balance between nodes and ensure that the spent energy
exceeded the scavenged energy over a period of time. does not exceed the scavenged energy over a period of time.
5.3.1.3. Schedule Management by a PCE 5.3.1.3. Schedule Management by a PCE
6TiSCH supports a mixed model of centralized routes and distributed 6TiSCH supports a mixed model of centralized routes and distributed
routes. Centralized routes can for example be computed by a entity routes. Centralized routes can, for example, be computed by an
such as a PCE [PCE]. Distributed routes are computed by RPL entity such as a PCE [PCE]. Distributed routes are computed by RPL
[RFC6550]. [RFC6550].
Both methods may inject routes in the Routing Tables of the 6TiSCH Both methods may inject routes in the routing tables of the 6TiSCH
routers. In either case, each route is associated with a 6TiSCH routers. In either case, each route is associated with a 6TiSCH
topology that can be a RPL Instance topology or a Track. The 6TiSCH topology that can be a RPL Instance topology or a Track. The 6TiSCH
topology is indexed by an Instance ID, in a format that reuses the topology is indexed by an Instance ID, in a format that reuses the
RPLInstanceID as defined in RPL. RPLInstanceID as defined in RPL.
Both RPL and PCE rely on shared sources such as policies to define Both RPL and PCE rely on shared sources such as policies to define
Global and Local RPLInstanceIDs that can be used by either method. Global and Local RPLInstanceIDs that can be used by either method.
It is possible for centralized and distributed routing to share a It is possible for centralized and distributed routing to share the
same topology. Generally they will operate in different slotFrames, same topology. Generally, they will operate in different slotFrames,
and centralized routes will be used for scheduled traffic and will and centralized routes will be used for scheduled traffic and will
have precedence over distributed routes in case of conflict between have precedence over distributed routes in case of conflict between
the slotFrames. the slotFrames.
5.3.1.4. SlotFrames and Priorities 5.3.1.4. SlotFrames and Priorities
IEEE802.15.4 TSCH avoids contention on the medium by formatting time IEEE 802.15.4 TSCH avoids contention on the medium by formatting time
and frequencies in cells of transmission of equal duration. In order and frequencies in cells of transmission of equal duration. In order
to describe that formatting of time and frequencies, the 6TiSCH to describe that formatting of time and frequencies, the 6TiSCH
architecture defines a global concept that is called a Channel architecture defines a global concept that is called a Channel
Distribution and Usage (CDU) matrix; a CDU matrix is a matrix of Distribution and Usage (CDU) matrix; a CDU matrix is a matrix of
cells with an height equal to the number of available channels cells with a height equal to the number of available channels
(indexed by ChannelOffsets) and a width (in timeSlots) that is the (indexed by ChannelOffsets) and a width (in timeSlots) that is the
period of the network scheduling operation (indexed by slotOffsets) period of the network scheduling operation (indexed by slotOffsets)
for that CDU matrix. for that CDU matrix.
The CDU Matrix is used by the PCE as the map of all the channel The CDU matrix is used by the PCE as the map of all the channel
utilization. This organization depends on the time in the future. utilization. This organization depends on the time in the future.
The frequency used by a cell in the matrix rotates in a pseudo-random The frequency used by a cell in the matrix rotates in a pseudorandom
fashion, from an initial position at an epoch time, as the CDU matrix fashion, from an initial position at an epoch time, as the CDU matrix
iterates over and over. iterates over and over.
The size of a cell is a timeSlot duration, and values of 10 to 15 The size of a cell is a timeSlot duration, and values of 10 to 15
milliseconds are typical in 802.15.4 TSCH to accommodate for the milliseconds are typical in 802.15.4 TSCH to accommodate for the
transmission of a frame and an acknowledgement, including the transmission of a frame and an acknowledgement, including the
security validation on the receive side which may take up to a few security validation on the receive side, which may take up to a few
milliseconds on some device architecture. The matrix represents the milliseconds on some device architectures. The matrix represents the
overall utilisation of the spectrum over time by a scheduled network overall utilization of the spectrum over time by a scheduled network
operation. operation.
A CDU matrix is computed by the PCE, but unallocated timeSlots may be A CDU matrix is computed by the PCE, but unallocated timeSlots may be
used opportunistically by the nodes for classical best effort IP used opportunistically by the nodes for classical best-effort IP
traffic. The PCE has precedence in the allocation in case of a traffic. The PCE has precedence in the allocation in case of a
conflict. Multiple schedules may coexist, in which case the schedule conflict. Multiple schedules may coexist, in which case the schedule
adds a dimension to the matrix and the dimensions are ordered by adds a dimension to the matrix, and the dimensions are ordered by
priority. priority.
A slotFrame is the base object that a PCE needs to manipulate to A slotFrame is the base object that a PCE needs to manipulate to
program a schedule into one device. The slotFrame is a device program a schedule into one device. The slotFrame is a device
perspective of a transmission schedule; there can be more than one perspective of a transmission schedule; there can be more than one
with different priorities so in case of a contention the highest with different priorities so in case of a contention the highest
priority applies. In other words, a slotFrame is the projection of a priority applies. In other words, a slotFrame is the projection of a
schedule from the CDU matrix onto one device. Elaboration on that schedule from the CDU matrix onto one device. Elaboration on that
concept can be found in section "SlotFrames and Priorities" of concept can be found in section "SlotFrames and Priorities" of
[RFC9030], and figures 17 and 18 of [RFC9030] illustrate that [RFC9030], and Figures 17 and 18 in [RFC9030] illustrate that
projection. projection.
6. 5G 6. 5G
5G technology enables deterministic communication. Based on the 5G technology enables deterministic communication. Based on the
centralized admission control and the scheduling of the wireless centralized admission control and the scheduling of the wireless
resources, licensed or unlicensed, quality of service such as latency resources, licensed or unlicensed, Quality of Service (QoS) such as
and reliability can be guaranteed. 5G contains several features to latency and reliability can be guaranteed. 5G contains several
achieve ultra-reliable and low latency performance, e.g., support for features to achieve ultra-reliable and low-latency performance (e.g.,
different OFDM numerologies and slot-durations, as well as fast support for different OFDM numerologies and slot durations), as well
processing capabilities and redundancy techniques that lead to as fast processing capabilities and redundancy techniques that lead
achievable latency numbers of below 1ms with 99.999% or higher to achievable latency numbers of below 1 ms with 99.999% or higher
confidence. confidence.
5G also includes features to support Industrial IoT use cases, e.g., 5G also includes features to support industrial IoT use cases, e.g.,
via the integration of 5G with TSN. This includes 5G capabilities via the integration of 5G with TSN. This includes 5G capabilities
for each TSN component, latency, resource management, time for each TSN component, latency, resource management, time
synchronization, and reliability. Furthermore, 5G support for TSN synchronization, and reliability. Furthermore, 5G support for TSN
can be leveraged when 5G is used as subnet technology for DetNet, in can be leveraged when 5G is used as the subnet technology for DetNet,
combination with or instead of TSN, which is the primary subnet for in combination with or instead of TSN, which is the primary subnet
DetNet. In addition, the support for integration with TSN for DetNet. In addition, the support for integration with TSN
reliability was added to 5G by making DetNet reliability also reliability was added to 5G by making DetNet reliability also
applicable, due to the commonalities between TSN and DetNet applicable, due to the commonalities between TSN and DetNet
reliability. Moreover, providing IP service is native to 5G and 3GPP reliability. Moreover, providing IP service is native to 5G, and
Release 18 adds direct support for DetNet to 5G. 3GPP Release 18 adds direct support for DetNet to 5G.
Overall, 5G provides scheduled wireless segments with high Overall, 5G provides scheduled wireless segments with high
reliability and availability. In addition, 5G includes capabilities reliability and availability. In addition, 5G includes capabilities
for integration to IP networks. This makes 5G a suitable technology for integration to IP networks. This makes 5G a suitable technology
to apply RAW upon. upon which to apply RAW.
6.1. Provenance and Documents 6.1. Provenance and Documents
The 3rd Generation Partnership Project (3GPP) incorporates many The 3rd Generation Partnership Project (3GPP) incorporates many
companies whose business is related to cellular network operation as companies whose business is related to cellular network operation as
well as network equipment and device manufacturing. All generations well as network equipment and device manufacturing. All generations
of 3GPP technologies provide scheduled wireless segments, primarily of 3GPP technologies provide scheduled wireless segments, primarily
in licensed spectrum which is beneficial for reliability and in licensed spectrum, which is beneficial for reliability and
availability. availability.
In 2016, the 3GPP started to design New Radio (NR) technology In 2016, the 3GPP started to design New Radio (NR) technology
belonging to the fifth generation (5G) of cellular networks. NR has belonging to the fifth generation (5G) of cellular networks. NR has
been designed from the beginning to not only address enhanced Mobile been designed from the beginning to not only address enhanced Mobile
Broadband (eMBB) services for consumer devices such as smart phones Broadband (eMBB) services for consumer devices such as smart phones
or tablets but is also tailored for future Internet of Things (IoT) or tablets, but it is also tailored for future IoT communication and
communication and connected cyber-physical systems. In addition to connected cyber-physical systems. In addition to eMBB, requirement
eMBB, requirement categories have been defined on Massive Machine- categories have been defined on Massive Machine-Type Communication
Type Communication (M-MTC) for a large number of connected devices/ (M-MTC) for a large number of connected devices/sensors and on Ultra-
sensors, and Ultra-Reliable Low-Latency Communication (URLLC) for Reliable Low-Latency Communications (URLLC) for connected control
connected control systems and critical communication as illustrated systems and critical communication as illustrated in Figure 5. It is
in Figure 5. It is the URLLC capabilities that make 5G a great the URLLC capabilities that make 5G a great candidate for reliable
candidate for reliable low-latency communication. With these three low-latency communication. With these three cornerstones, NR is a
corner stones, NR is a complete solution supporting the connectivity complete solution supporting the connectivity needs of consumers,
needs of consumers, enterprises, and public sector for both wide area enterprises, and the public sector for both wide-area and local-area
and local area, e.g. indoor deployments. A general overview of NR (e.g., indoor) deployments. A general overview of NR can be found in
can be found in [TS38300]. [TS38300].
enhanced enhanced
Mobile Broadband Mobile Broadband
^ ^
/ \ / \
/ \ / \
/ \ / \
/ \ / \
/ 5G \ / 5G \
/ \ / \
skipping to change at page 30, line 43 skipping to change at line 1373
+-----------------+ +-----------------+
Massive Ultra-Reliable Massive Ultra-Reliable
Machine-Type Low-Latency Machine-Type Low-Latency
Communication Communication Communication Communication
Figure 5: 5G Application Areas Figure 5: 5G Application Areas
As a result of releasing the first NR specification in 2018 (Release As a result of releasing the first NR specification in 2018 (Release
15), it has been proven by many companies that NR is a URLLC-capable 15), it has been proven by many companies that NR is a URLLC-capable
technology and can deliver data packets at 10^-5 packet error rate technology and can deliver data packets at 10^-5 packet error rate
within 1ms latency budget [TR37910]. Those evaluations were within a 1 ms latency budget [TR37910]. Those evaluations were
consolidated and forwarded to ITU to be included in the [IMT2020] consolidated and forwarded to ITU to be included in the work on
work. [IMT2020].
In order to understand communication requirements for automation in In order to understand communication requirements for automation in
vertical domains, 3GPP studied different use cases [TR22804] and vertical domains, 3GPP studied different use cases [TR22804] and
released technical specification with reliability, availability and released a technical specification with reliability, availability,
latency demands for a variety of applications [TS22104]. and latency demands for a variety of applications [TS22104].
As an evolution of NR, multiple studies have been conducted in scope As an evolution of NR, multiple studies that focus on radio aspects
of 3GPP Release 16 including the following two, focusing on radio have been conducted in scope of 3GPP Release 16, including the
aspects: following two:
1. Study on physical layer enhancements for NR ultra-reliable and 1. "Study on physical layer enhancements for NR ultra-reliable and
low latency communication (URLLC) [TR38824]. low latency case (URLLC)" [TR38824]
2. Study on NR industrial Internet of Things (I-IoT) [TR38825]. 2. "Study on NR industrial Internet of Things (IoT)" [TR38825]
Resulting of these studies, further enhancements to NR have been As a result of these studies, further enhancements to NR have been
standardized in 3GPP Release 16, hence, available in [TS38300], and standardized in 3GPP Release 16 and are available in [TS38300] and
continued in 3GPP Release 17 standardization (according to continued in 3GPP Release 17 standardization (according to
[RP210854]). [RP210854]).
In addition, several enhancements have been done on system In addition, several enhancements have been made on the system
architecture level which are reflected in System architecture for the architecture level, which are reflected in "System architecture for
5G System (5GS) [TS23501]. These enhancements include multiple the 5G System (5GS)" [TS23501]. These enhancements include multiple
features in support of Time-Sensitive Communications (TSC) by Release features in support of Time-Sensitive Communications (TSC) by Release
16 and Release 17. Further improvements are provided in Release 18, 16 and Release 17. Further improvements, such as support for DetNet
e.g., support for DetNet [TR2370046]. [TR2370046], are provided in Release 18.
The adoption and the use of 5G is facilitated by multiple The adoption and the use of 5G is facilitated by multiple
organizations. For instance, the 5G Alliance for Connected organizations. For instance, the 5G Alliance for Connected
Industries and Automation (5G-ACIA) brings together widely varying 5G Industries and Automation (5G-ACIA) brings together widely varying 5G
stakeholders including Information and Communication Technology (ICT) stakeholders including Information and Communication Technology (ICT)
players and Operational Technology (OT) companies, e.g.: industrial players and Operational Technology (OT) companies (e.g., industrial
automation enterprises, machine builders, and end users. Another automation enterprises, machine builders, and end users). Another
example is the 5G Automotive Association (5GAA), which bridges ICT example is the 5G Automotive Association (5GAA), which bridges ICT
and automotive technology companies to develop end-to-end solutions and automotive technology companies to develop end-to-end solutions
for future mobility and transportation services. for future mobility and transportation services.
6.2. General Characteristics 6.2. General Characteristics
The 5G Radio Access Network (5G RAN) with its NR interface includes The 5G Radio Access Network (5G RAN) with its NR interface includes
several features to achieve Quality of Service (QoS), such as a several features to achieve Quality of Service (QoS), such as a
guaranteeably low latency or tolerable packet error rates for guaranteeably low latency or tolerable packet error rates for
selected data flows. Determinism is achieved by centralized selected data flows. Determinism is achieved by centralized
admission control and scheduling of the wireless frequency resources, admission control and scheduling of the wireless frequency resources,
which are typically licensed frequency bands assigned to a network which are typically licensed frequency bands assigned to a network
operator. operator.
NR enables short transmission slots in a radio subframe, which NR enables short transmission slots in a radio subframe, which
benefits low-latency applications. NR also introduces mini-slots, benefits low-latency applications. NR also introduces mini-slots,
where prioritized transmissions can be started without waiting for where prioritized transmissions can be started without waiting for
slot boundaries, further reducing latency. As part of giving slot boundaries, further reducing latency. As part of giving
priority and faster radio access to URLLC traffic, NR introduces priority and faster radio access to URLLC traffic, NR introduces
preemption where URLLC data transmission can preempt ongoing non- preemption, where URLLC data transmission can preempt ongoing non-
URLLC transmissions. Additionally, NR applies very fast processing, URLLC transmissions. Additionally, NR applies very fast processing,
enabling retransmissions even within short latency bounds. enabling retransmissions even within short latency bounds.
NR defines extra-robust transmission modes for increased reliability NR defines extra-robust transmission modes for increased reliability
both for data and control radio channels. Reliability is further for both data and control radio channels. Reliability is further
improved by various techniques, such as multi-antenna transmission, improved by various techniques, such as multi-antenna transmission,
the use of multiple frequency carriers in parallel and packet the use of multiple frequency carriers in parallel, and packet
duplication over independent radio links. NR also provides full duplication over independent radio links. NR also provides full
mobility support, which is an important reliability aspect not only mobility support, which is an important reliability aspect not only
for devices that are moving, but also for devices located in a for devices that are moving, but also for devices located in a
changing environment. changing environment.
Network slicing is seen as one of the key features for 5G, allowing Network slicing is seen as one of the key features for 5G, allowing
vertical industries to take advantage of 5G networks and services. vertical industries to take advantage of 5G networks and services.
Network slicing is about transforming a Public Land Mobile Network Network slicing is about transforming a Public Land Mobile Network
(PLMN) from a single network to a network where logical partitions (PLMN) from a single network to a network where logical partitions
are created, with appropriate network isolation, resources, optimized are created, with appropriate network isolation, resources, optimized
topology and specific configuration to serve various service topology, and specific configurations to serve various service
requirements. An operator can configure and manage the mobile requirements. An operator can configure and manage the mobile
network to support various types of services enabled by 5G, for network to support various types of services enabled by 5G (e.g.,
example eMBB and URLLC, depending on the different customers’ needs. eMBB and URLLC), depending on the different needs of customers.
Exposure of capabilities of 5G Systems to the network or applications Exposure of capabilities of 5G systems to the network or applications
outside the 3GPP domain have been added to Release 16 [TS23501]. Via outside the 3GPP domain have been added to Release 16 [TS23501].
exposure interfaces, applications can access 5G capabilities, e.g., Applications can access 5G capabilities like communication service
communication service monitoring and network maintenance. monitoring and network maintenance via exposure interfaces.
For several generations of mobile networks, 3GPP has considered how For several generations of mobile networks, 3GPP has considered how
the communication system should work on a global scale with billions the communication system should work on a global scale with billions
of users, taking into account resilience aspects, privacy regulation, of users, taking into account resilience aspects, privacy regulation,
protection of data, encryption, access and core network security, as protection of data, encryption, access and core network security, as
well as interconnect. Security requirements evolve as demands on well as interconnect. Security requirements evolve as demands on
trustworthiness increase. For example, this has led to the trustworthiness increase. For example, this has led to the
introduction of enhanced privacy protection features in 5G. 5G also introduction of enhanced privacy protection features in 5G. 5G also
employs strong security algorithms, encryption of traffic, protection employs strong security algorithms, encryption of traffic, protection
of signaling and protection of interfaces. of signaling, and protection of interfaces.
One particular strength of mobile networks is the authentication, One particular strength of mobile networks is the authentication,
based on well-proven algorithms and tightly coupled with a global based on well-proven algorithms and tightly coupled with a global
identity management infrastructure. Since 3G, there is also mutual identity management infrastructure. Since 3G, there is also mutual
authentication, allowing the network to authenticate the device and authentication, allowing the network to authenticate the device and
the device to authenticate the network. Another strength is secure the device to authenticate the network. Another strength is secure
solutions for storage and distribution of keys fulfilling regulatory solutions for storage and distribution of keys, fulfilling regulatory
requirements and allowing international roaming. When connecting to requirements and allowing international roaming. When connecting to
5G, the user meets the entire communication system, where security is 5G, the user meets the entire communication system, where security is
the result of standardization, product security, deployment, the result of standardization, product security, deployment,
operations and management as well as incident handling capabilities. operations, and management as well as incident-handling capabilities.
The mobile networks approach the entirety in a rather coordinated The mobile networks approach the entirety in a rather coordinated
fashion which is beneficial for security. fashion, which is beneficial for security.
6.3. Deployment and Spectrum 6.3. Deployment and Spectrum
The 5G system allows deployment in a vast spectrum range, addressing The 5G system allows deployment in a vast spectrum range, addressing
use-cases in both wide-area as well as local networks. Furthermore, use cases in both wide-area and local-area networks. Furthermore, 5G
5G can be configured for public and non-public access. can be configured for public and non-public access.
When it comes to spectrum, NR allows combining the merits of many When it comes to spectrum, NR allows combining the merits of many
frequency bands, such as the high bandwidths in millimeter Waves frequency bands, such as the high bandwidths in millimeter waves
(mmW) for extreme capacity locally, as well as the broad coverage (mmWaves) for extreme capacity locally and the broad coverage when
when using mid- and low frequency bands to address wide-area using mid- and low-frequency bands to address wide-area scenarios.
scenarios. URLLC is achievable in all these bands. Spectrum can be URLLC is achievable in all these bands. Spectrum can be either
either licensed, which means that the license holder is the only licensed, which means that the license holder is the only authorized
authorized user of that spectrum range, or unlicensed, which means user of that spectrum range, or unlicensed, which means that anyone
that anyone who wants to use the spectrum can do so. who wants to use the spectrum can do so.
A prerequisite for critical communication is performance A prerequisite for critical communication is performance
predictability, which can be achieved by the full control of the predictability, which can be achieved by full control of access to
access to the spectrum, which 5G provides. Licensed spectrum the spectrum, which 5G provides. Licensed spectrum guarantees
guarantees control over spectrum usage by the system, making it a control over spectrum usage by the system, making it a preferable
preferable option for critical communication. However, unlicensed option for critical communication. However, unlicensed spectrum can
spectrum can provide an additional resource for scaling non-critical provide an additional resource for scaling non-critical
communications. While NR is initially developed for usage of communications. While NR was initially developed for usage of
licensed spectrum, the functionality to access also unlicensed licensed spectrum, the functionality to also access unlicensed
spectrum was introduced in 3GPP Release 16. Moreover, URLLC features spectrum was introduced in 3GPP Release 16. Moreover, URLLC features
are enhanced in Release 17 [RP210854] to be better applicable to are enhanced in Release 17 [RP210854] to be better applicable to
unlicensed spectrum. unlicensed spectrum.
Licensed spectrum dedicated to mobile communications has been Licensed spectrum dedicated to mobile communications has been
allocated to mobile service providers, i.e. issued as longer-term allocated to mobile service providers, i.e., issued as longer-term
licenses by national administrations around the world. These licenses by national administrations around the world. These
licenses have often been associated with coverage requirements and licenses have often been associated with coverage requirements and
issued across whole countries, or in large regions. Besides this, issued across whole countries or large regions. Besides this,
configured as a non-public network (NPN) deployment, 5G can provide configured as a non-public network (NPN) deployment, 5G can also
network services also to a non-operator defined organization and its provide network services to a non-operator defined organization and
premises such as a factory deployment. By this isolation, quality of its premises such as a factory deployment. With this isolation, QoS
service requirements, as well as security requirements can be requirements as well as security requirements can be achieved. An
achieved. An integration with a public network, if required, is also integration with a public network, if required, is also possible.
possible. The non-public (local) network can thus be interconnected The non-public (local) network can thus be interconnected with a
with a public network, allowing devices to roam between the networks. public network, allowing devices to roam between the networks.
In an alternative model, some countries are now in the process of In an alternative model, some countries are now in the process of
allocating parts of the 5G spectrum for local use to industries. allocating parts of the 5G spectrum for local use to industries.
These non-service providers then have a choice of applying for a These non-service providers then have the choice to apply for a local
local license themselves and operating their own network or license themselves and operate their own network or to cooperate with
cooperating with a public network operator or service provider. a public network operator or service provider.
6.4. Applicability to Deterministic Flows 6.4. Applicability to Deterministic Flows
6.4.1. System Architecture 6.4.1. System Architecture
The 5G system [TS23501] consists of the User Equipment (UE) at the The 5G system [TS23501] consists of the User Equipment (UE) at the
terminal side, and the Radio Access Network (RAN) with the gNB as terminal side, the Radio Access Network (RAN) with the gNodeB (gNB)
radio base station node, as well as the Core Network (CN), which is as radio base station node, and the Core Network (CN), which is
connected to the external Data Network (DN). The core network is connected to the external Data Network (DN). The CN is based on a
based on a service-based architecture with the central functions: service-based architecture with the following central functions:
Access and Mobility Management Function (AMF), Session Management Access and Mobility Management Function (AMF), Session Management
Function (SMF) and User Plane Function (UPF) as illustrated in Function (SMF), and User Plane Function (UPF) as illustrated in
Figure 6. "(Note that this document only explains key functions, Figure 6. (Note that this document only explains key functions;
however, Figure 6 provides a more detailed view, and [SYSTOVER5G] however, Figure 6 provides a more detailed view, and [SYSTOVER5G]
summarizes the functions and provides the full definition of acronyms summarizes the functions and provides the full definitions of the
used in the figure.)" acronyms used in the figure.)
The gNB’s main responsibility is the radio resource management, The gNB's main responsibility is radio resource management, including
including admission control and scheduling, mobility control and admission control and scheduling, mobility control, and radio
radio measurement handling. The AMF handles the UE’s connection measurement handling. The AMF handles the UE's connection status and
status and security, while the SMF controls the UE’s data sessions. security, while the SMF controls the UE's data sessions. The UPF
The UPF handles the user plane traffic. handles the user plane traffic.
The SMF can instantiate various Packet Data Unit (PDU) sessions for The SMF can instantiate various Packet Data Unit (PDU) sessions for
the UE, each associated with a set of QoS flows, i.e., with different the UE, each associated with a set of QoS flows, i.e., with different
QoS profiles. Segregation of those sessions is also possible, e.g., QoS profiles). Segregation of those sessions is also possible; for
resource isolation in the RAN and in the CN can be defined (slicing). example, resource isolation in the RAN and CN can be defined
(slicing).
+----+ +---+ +---+ +---+ +---+ +---+ +----+ +---+ +---+ +---+ +---+ +---+
|NSSF| |NEF| |NRF| |PCF| |UDM| |AF | |NSSF| |NEF| |NRF| |PCF| |UDM| |AF |
+--+-+ +-+-+ +-+-+ +-+-+ +-+-+ +-+-+ +--+-+ +-+-+ +-+-+ +-+-+ +-+-+ +-+-+
| | | | | | | | | | | |
Nnssf| Nnef| Nnrf| Npcf| Nudm| Naf| Nnssf| Nnef| Nnrf| Npcf| Nudm| Naf|
| | | | | | | | | | | |
---+------+-+-----+-+------------+--+-----+-+--- ---+------+-+-----+-+------------+--+-----+-+---
| | | | | | | |
Nausf| Nausf| Nsmf| | Nausf| Nausf| Nsmf| |
skipping to change at page 36, line 6 skipping to change at line 1582
/ | | / | |
+--+-+ +--+--+ +--+---+ +----+ +--+-+ +--+--+ +--+---+ +----+
| UE +---+(R)AN+--N3--+ UPF +--N6--+ DN | | UE +---+(R)AN+--N3--+ UPF +--N6--+ DN |
+----+ +-----+ ++----++ +----+ +----+ +-----+ ++----++ +----+
| | | |
+-N9-+ +-N9-+
Figure 6: 5G System Architecture Figure 6: 5G System Architecture
To allow UE mobility across cells/gNBs, handover mechanisms are To allow UE mobility across cells/gNBs, handover mechanisms are
supported in NR. For an established connection, i.e., connected mode supported in NR. For an established connection (i.e., connected mode
mobility, a gNB can configure a UE to report measurements of received mobility), a gNB can configure a UE to report measurements of
signal strength and quality of its own and neighbouring cells, received signal strength and quality of its own and neighboring
periodically or event-based. Based on these measurement reports, the cells, periodically or based on events. Based on these measurement
gNB decides to handover a UE to another target cell/gNB. Before reports, the gNB decides to hand over a UE to another target cell/
triggering the handover, it is hand-shaked with the target gNB based gNB. Before triggering the handover, it is handshaked with the
on network signalling. A handover command is then sent to the UE and target gNB based on network signaling. A handover command is then
the UE switches its connection to the target cell/gNB. The Packet sent to the UE, and the UE switches its connection to the target
Data Convergence Protocol (PDCP) of the UE can be configured to avoid cell/gNB. The Packet Data Convergence Protocol (PDCP) of the UE can
data loss in this procedure, i.e., handle retransmissions if needed. be configured to avoid data loss in this procedure, i.e., to handle
Data forwarding is possible between source and target gNB as well. retransmissions if needed. Data forwarding is possible between
To improve the mobility performance further, i.e., to avoid source and target gNB as well. To improve the mobility performance
connection failures, e.g., due to too-late handovers, the mechanism further (i.e., to avoid connection failures due to too-late
of conditional handover is introduced in Release 16 specifications. handovers), the mechanism of conditional handover is introduced in
Therein a conditional handover command, defining a triggering point, Release 16 specifications. Therein, a conditional handover command,
can be sent to the UE before UE enters a handover situation. A defining a triggering point, can be sent to the UE before the UE
further improvement that has been introduced in Release 16 is the enters a handover situation. A further improvement that has been
Dual Active Protocol Stack (DAPS), where the UE maintains the introduced in Release 16 is the Dual Active Protocol Stack (DAPS),
connection to the source cell while connecting to the target cell. where the UE maintains the connection to the source cell while
This way, potential interruptions in packet delivery can be avoided connecting to the target cell. This way, potential interruptions in
entirely. packet delivery can be avoided entirely.
6.4.2. Overview of The Radio Protocol Stack 6.4.2. Overview of the Radio Protocol Stack
The protocol architecture for NR consists of the L1 Physical layer The protocol architecture for NR consists of the Layer 1 Physical
(PHY) and as part of the L2, the sublayers of Medium Access Control (PHY) layer and, as part of Layer 2, the sublayers of Medium Access
(MAC), Radio Link Control (RLC), Packet Data Convergence Protocol Control (MAC), Radio Link Control (RLC), Packet Data Convergence
(PDCP), as well as the Service Data Adaption Protocol (SDAP). Protocol (PDCP), and Service Data Adaption Protocol (SDAP).
The PHY layer handles signal processing related actions, such as The PHY layer handles actions related to signal processing, such as
encoding/decoding of data and control bits, modulation, antenna encoding/decoding of data and control bits, modulation, antenna
precoding and mapping. precoding, and mapping.
The MAC sub-layer handles multiplexing and priority handling of The MAC sublayer handles multiplexing and priority handling of
logical channels (associated with QoS flows) to transport blocks for logical channels (associated with QoS flows) to transport blocks for
PHY transmission, as well as scheduling information reporting and PHY transmission, as well as scheduling information reporting and
error correction through Hybrid Automated Repeat Request (HARQ). error correction through Hybrid Automated Repeat Request (HARQ).
The RLC sublayer handles sequence numbering of higher layer packets, The RLC sublayer handles sequence numbering of higher-layer packets,
retransmissions through Automated Repeat Request (ARQ), if retransmissions through Automated Repeat Request (ARQ), if
configured, as well as segmentation and reassembly and duplicate configured, as well as segmentation and reassembly and duplicate
detection. detection.
The PDCP sublayer consists of functionalities for ciphering/ The PDCP sublayer consists of functionalities for ciphering/
deciphering, integrity protection/verification, re-ordering and in- deciphering, integrity protection/verification, reordering and in-
order delivery, duplication and duplicate handling for higher layer order delivery, and duplication and duplicate handling for higher-
packets, and acts as the anchor protocol to support handovers. layer packets. This sublayer also acts as the anchor protocol to
support handovers.
The SDAP sublayer provides services to map QoS flows, as established The SDAP sublayer provides services to map QoS flows, as established
by the 5G core network, to data radio bearers (associated with by the 5G core network, to data radio bearers (associated with
logical channels), as used in the 5G RAN. logical channels), as used in the 5G RAN.
Additionally, in RAN, the Radio Resource Control (RRC) protocol, Additionally, in RAN, the Radio Resource Control (RRC) protocol
handles the access control and configuration signalling for the handles the access control and configuration signaling for the
aforementioned protocol layers. RRC messages are considered L3 and aforementioned protocol layers. RRC messages are considered Layer 3
thus transmitted also via those radio protocol layers. and are thus also transmitted via those radio protocol layers.
To provide low latency and high reliability for one transmission To provide low latency and high reliability for one transmission link
link, i.e., to transport data (or control signaling) of one radio (i.e., to transport data or control signaling of one radio bearer via
bearer via one carrier, several features have been introduced on the one carrier), several features have been introduced on the user plane
user plane protocols for PHY and L2, as explained in the following. protocols for PHY and Layer 2, as explained below.
6.4.3. Radio (PHY) 6.4.3. Radio (PHY)
NR is designed with native support of antenna arrays utilizing NR is designed with native support of antenna arrays utilizing
benefits from beamforming, transmissions over multiple MIMO layers benefits from beamforming, transmissions over multiple MIMO layers,
and advanced receiver algorithms allowing effective interference and advanced receiver algorithms allowing effective interference
cancellation. Those antenna techniques are the basis for high signal cancellation. Those antenna techniques are the basis for high signal
quality and effectiveness of spectral usage. Spatial diversity with quality and the effectiveness of spectral usage. Spatial diversity
up to 4 MIMO layers in UL and up to 8 MIMO layers in DL is supported. with up to four MIMO layers in UL and up to eight MIMO layers in DL
Together with spatial-domain multiplexing, antenna arrays can focus is supported. Together with spatial-domain multiplexing, antenna
power in desired direction to form beams. NR supports beam arrays can focus power in the desired direction to form beams. NR
management mechanisms to find the best suitable beam for UE initially supports beam management mechanisms to find the best suitable beam
and when it is moving. In addition, gNBs can coordinate their for UE initially and when it is moving. In addition, gNBs can
respective DL and UL transmissions over the backhaul network keeping coordinate their respective DL and UL transmissions over the backhaul
interference reasonably low, and even make transmissions or network, keeping interference reasonably low, and even make
receptions from multiple points (multi-TRP). Multi-TRP can be used transmissions or receptions from multiple points (multi-TRP). Multi-
for repetition of data packet in time, in frequency or over multiple TRP can be used for repetition of a data packet in time, in
MIMO layers which can improve reliability even further. frequency, or over multiple MIMO layers, which can improve
reliability even further.
Any downlink transmission to a UE starts from resource allocation Any downlink transmission to a UE starts from resource allocation
signaling over the Physical Downlink Control Channel (PDCCH). If it signaling over the Physical Downlink Control Channel (PDCCH). If it
is successfully received, the UE will know about the scheduled is successfully received, the UE will know about the scheduled
transmission and may receive data over the Physical Downlink Shared transmission and may receive data over the Physical Downlink Shared
Channel (PDSCH). If retransmission is required according to the HARQ Channel (PDSCH). If retransmission is required according to the HARQ
scheme, a signaling of negative acknowledgement (NACK) on the scheme, a signaling of negative acknowledgement (NACK) on the
Physical Uplink Control Channel (PUCCH) is involved and PDCCH Physical Uplink Control Channel (PUCCH) is involved, and PDCCH
together with PDSCH transmissions (possibly with additional together with PDSCH transmissions (possibly with additional
redundancy bits) are transmitted and soft-combined with previously redundancy bits) are transmitted and soft-combined with previously
received bits. Otherwise, if no valid control signaling for received bits. Otherwise, if no valid control signaling for
scheduling data is received, nothing is transmitted on PUCCH scheduling data is received, nothing is transmitted on PUCCH
(discontinuous transmission - DTX),and the base station upon (discontinuous transmission (DTX)), and upon detecting DTX, the base
detecting DTX will retransmit the initial data. station will retransmit the initial data.
An uplink transmission normally starts from a Scheduling Request (SR) An uplink transmission normally starts from a Scheduling Request
– a signaling message from the UE to the base station sent via PUCCH. (SR), a signaling message from the UE to the base station sent via
Once the scheduler is informed about buffer data in UE, e.g., by SR, PUCCH. Once the scheduler is informed about buffer data in the UE
the UE transmits a data packet on the Physical Uplink Shared Channel (e.g., by SR), the UE transmits a data packet on the Physical Uplink
(PUSCH). Pre-scheduling not relying on SR is also possible (see Shared Channel (PUSCH). Pre-scheduling, not relying on SR, is also
following section). possible (see Section 6.4.4).
Since transmission of data packets require usage of control and data Since transmission of data packets requires usage of control and data
channels, there are several methods to maintain the needed channels, there are several methods to maintain the needed
reliability. NR uses Low Density Parity Check (LDPC) codes for data reliability. NR uses Low Density Parity Check (LDPC) codes for data
channels, Polar codes for PDCCH, as well as orthogonal sequences and channels, polar codes for PDCCH, as well as orthogonal sequences and
Polar codes for PUCCH. For ultra-reliability of data channels, very polar codes for PUCCH. For ultra-reliability of data channels, very
robust (low spectral efficiency) Modulation and Coding Scheme (MCS) robust (low-spectral efficiency) Modulation and Coding Scheme (MCS)
tables are introduced containing very low (down to 1/20) LDPC code tables are introduced containing very low (down to 1/20) LDPC code
rates using BPSK or QPSK. Also, PDCCH and PUCCH channels support rates using BPSK or QPSK. Also, PDCCH and PUCCH channels support
multiple code rates including very low ones for the channel multiple code rates including very low ones for the channel
robustness. robustness.
A connected UE reports downlink (DL) quality to gNB by sending A connected UE reports downlink (DL) quality to gNB by sending
Channel State Information (CSI) reports via PUCCH while uplink (UL) Channel State Information (CSI) reports via PUCCH while uplink (UL)
quality is measured directly at gNB. For both uplink and downlink, quality is measured directly at gNB. For both uplink and downlink,
gNB selects the desired MCS number and signals it to the UE by gNB selects the desired MCS number and signals it to the UE by
Downlink Control Information (DCI) via PDCCH channel. For URLLC Downlink Control Information (DCI) via PDCCH channel. For URLLC
services, the UE can assist the gNB by advising that MCS targeting services, the UE can assist the gNB by advising that MCS targeting a
10^-5 Block Error Rate (BLER) are used. Robust link adaptation 10^-5 Block Error Rate (BLER) are used. Robust link adaptation
algorithms can maintain the needed level of reliability considering a algorithms can maintain the needed level of reliability, considering
given latency bound. a given latency bound.
Low latency on the physical layer is provided by short transmission Low latency on the physical layer is provided by short transmission
duration which is possible by using high Subcarrier Spacing (SCS) and duration, which is possible by using high Subcarrier Spacing (SCS)
the allocation of only one or a few Orthogonal Frequency Division and the allocation of only one or a few Orthogonal Frequency Division
Multiplexing (OFDM) symbols. For example, the shortest latency for Multiplexing (OFDM) symbols. For example, the shortest latency for
the worst case in DL can be 0.23ms and in UL can be 0.24ms according the worst case is 0.23 ms in DL and 0.24 ms in UL (according to
to (section 5.7.1 in [TR37910]). Moreover, if the initial Section 5.7.1 in [TR37910]). Moreover, if the initial transmission
transmission has failed, HARQ feedback can quickly be provided and an has failed, HARQ feedback can quickly be provided and an HARQ
HARQ retransmission is scheduled. retransmission scheduled.
Dynamic multiplexing of data associated with different services is Dynamic multiplexing of data associated with different services is
highly desirable for efficient use of system resources and to highly desirable for efficient use of system resources and to
maximize system capacity. Assignment of resources for eMBB is maximize system capacity. Assignment of resources for eMBB is
usually done with regular (longer) transmission slots, which can lead usually done with regular (longer) transmission slots, which can lead
to blocking of low latency services. To overcome the blocking, eMBB to blocking of low-latency services. To overcome the blocking, eMBB
resources can be pre-empted and re-assigned to URLLC services. In resources can be preempted and reassigned to URLLC services. In this
this way, spectrally efficient assignments for eMBB can be ensured way, spectrally efficient assignments for eMBB can be ensured while
while providing flexibility required to ensure a bounded latency for providing the flexibility required to ensure a bounded latency for
URLLC services. In downlink, the gNB can notify the eMBB UE about URLLC services. In downlink, the gNB can notify the eMBB UE about
pre-emption after it has happened, while in uplink there are two pre- preemption after it has happened, while in uplink there are two
emption mechanisms: special signaling to cancel eMBB transmission and preemption mechanisms: special signaling to cancel eMBB transmission
URLLC dynamic power boost to suppress eMBB transmission. and URLLC dynamic power boost to suppress eMBB transmission.
6.4.4. Scheduling and QoS (MAC) 6.4.4. Scheduling and QoS (MAC)
One integral part of the 5G system is the Quality of Service (QoS) One integral part of the 5G system is the Quality of Service (QoS)
framework [TS23501]. QoS flows are setup by the 5G system for framework [TS23501]. QoS flows are set up by the 5G system for
certain IP or Ethernet packet flows, so that packets of each flow certain IP or Ethernet packet flows, so that packets of each flow
receive the same forwarding treatment, i.e., in scheduling and receive the same forwarding treatment (i.e., in scheduling and
admission control. QoS flows can for example be associated with admission control). For example, QoS flows can be associated with
different priority level, packet delay budgets and tolerable packet different priority levels, packet delay budgets, and tolerable packet
error rates. Since radio resources are centrally scheduled in NR, error rates. Since radio resources are centrally scheduled in NR,
the admission control function can ensure that only those QoS flows the admission control function can ensure that only QoS flows for
are admitted for which QoS targets can be reached. which QoS targets can be reached are admitted.
NR transmissions in both UL and DL are scheduled by the gNB NR transmissions in both UL and DL are scheduled by the gNB
[TS38300]. This ensures radio resource efficiency, fairness in [TS38300]. This ensures radio resource efficiency and fairness in
resource usage of the users and enables differentiated treatment of resource usage of the users, and it enables differentiated treatment
the data flows of the users according to the QoS targets of the of the data flows of the users according to the QoS targets of the
flows. Those QoS flows are handled as data radio bearers or logical flows. Those QoS flows are handled as data radio bearers or logical
channels in NR RAN scheduling. channels in NR RAN scheduling.
The gNB can dynamically assign DL and UL radio resources to users, The gNB can dynamically assign DL and UL radio resources to users,
indicating the resources as DL assignments or UL grants via control indicating the resources as DL assignments or UL grants via control
channel to the UE. Radio resources are defined as blocks of OFDM channel to the UE. Radio resources are defined as blocks of OFDM
symbols in spectral domain and time domain. Different lengths are symbols in spectral domain and time domain. Different lengths are
supported in time domain, i.e., (multiple) slot or mini-slot lengths. supported in time domain, (i.e., multiple slot or mini-slot lengths).
Resources of multiple frequency carriers can be aggregated and Resources of multiple frequency carriers can be aggregated and
jointly scheduled to the UE. jointly scheduled to the UE.
Scheduling decisions are based, e.g., on channel quality measured on Scheduling decisions are based, e.g., on channel quality measured on
reference signals and reported by the UE (cf. periodical CSI reports reference signals and reported by the UE (cf. periodical CSI reports
for DL channel quality). The transmission reliability can be chosen for DL channel quality). The transmission reliability can be chosen
in the scheduling algorithm, i.e., by link adaptation where an in the scheduling algorithm, i.e., chosen by link adaptation where an
appropriate transmission format (e.g., robustness of modulation and appropriate transmission format (e.g., robustness of modulation and
coding scheme, controlled UL power) is selected for the radio channel coding scheme, controlled UL power) is selected for the radio channel
condition of the UE. Retransmissions, based on HARQ feedback, are condition of the UE. Retransmissions, based on HARQ feedback, are
also controlled by the scheduler. The feedback transmission in HARQ also controlled by the scheduler. The feedback transmission in HARQ
loop introduces delays, but there are methods to minimize it by using loop introduces delays, but there are methods to minimize it by using
short transmission formats, sub-slot feedback reporting and PUCCH short transmission formats, sub-slot feedback reporting, and PUCCH
carrier switching. If needed to avoid HARQ round-trip time delays, carrier switching. If needed to avoid HARQ round-trip time delays,
repeated transmissions can be also scheduled beforehand, to the cost repeated transmissions can be also scheduled beforehand, to the cost
of reduced spectral efficiency. of reduced spectral efficiency.
In dynamic DL scheduling, transmission can be initiated immediately In dynamic DL scheduling, transmission can be initiated immediately
when DL data becomes available in the gNB. However, for dynamic UL when DL data becomes available in the gNB. However, for dynamic UL
scheduling, when data becomes available but no UL resources are scheduling, when data becomes available but no UL resources are
available yet, the UE indicates the need for UL resources to the gNB available yet, the UE indicates the need for UL resources to the gNB
via a (single bit) scheduling request message in the UL control via a (single bit) scheduling request message in the UL control
channel. When thereupon UL resources are scheduled to the UE, the UE channel. When thereupon UL resources are scheduled to the UE, the UE
can transmit its data and may include a buffer status report, can transmit its data and may include a buffer status report that
indicating the exact amount of data per logical channel still left to indicates the exact amount of data per logical channel still left to
be sent. More UL resources may be scheduled accordingly. To avoid be sent. More UL resources may be scheduled accordingly. To avoid
the latency introduced in the scheduling request loop, UL radio the latency introduced in the scheduling request loop, UL radio
resources can also be pre-scheduled. resources can also be pre-scheduled.
In particular for periodical traffic patterns, the pre-scheduling can In particular, for periodical traffic patterns, the pre-scheduling
rely on the scheduling features DL Semi-Persistent Scheduling (SPS) can rely on the scheduling features DL Semi-Persistent Scheduling
and UL Configured Grant (CG). With these features, periodically (SPS) and UL Configured Grant (CG). With these features,
recurring resources can be assigned in DL and UL. Multiple parallels periodically recurring resources can be assigned in DL and UL.
of those configurations are supported, in order to serve multiple Multiple parallels of those configurations are supported in order to
parallel traffic flows of the same UE. serve multiple parallel traffic flows of the same UE.
To support QoS enforcement in the case of mixed traffic with To support QoS enforcement in the case of mixed traffic with
different QoS requirements, several features have recently been different QoS requirements, several features have recently been
introduced. This way, e.g., different periodical critical QoS flows introduced. This way, e.g., different periodical critical QoS flows
can be served together with best effort transmissions, by the same can be served, together with best-effort transmissions by the same
UE. Among others, these features (partly Release 16) are: 1) UL UE. These features (partly Release 16) include the following:
logical channel transmission restrictions allowing to map logical
channels of certain QoS only to intended UL resources of a certain * UL logical channel transmission restrictions, allowing logical
frequency carrier, slot-length, or CG configuration, and 2) intra-UE channels of certain QoS to only be mapped to intended UL resources
pre-emption and multiplexing, allowing critical UL transmissions to of a certain frequency carrier, slot length, or CG configuration.
either pre-empt non-critical transmissions or being multiplexed with
non-critical transmissions keeping different reliability targets. * intra-UE preemption and multiplexing, allowing critical UL
transmissions to either preempt non-critical transmissions or be
multiplexed with non-critical transmissions keeping different
reliability targets.
When multiple frequency carriers are aggregated, duplicate parallel When multiple frequency carriers are aggregated, duplicate parallel
transmissions can be employed (beside repeated transmissions on one transmissions can be employed (beside repeated transmissions on one
carrier). This is possible in the Carrier Aggregation (CA) carrier). This is possible in the Carrier Aggregation (CA)
architecture where those carriers originate from the same gNB, or in architecture where those carriers originate from the same gNB or in
the Dual Connectivity (DC) architecture where the carriers originate the Dual Connectivity (DC) architecture where the carriers originate
from different gNBs, i.e., the UE is connected to two gNBs in this from different gNBs (i.e., the UE is connected to two gNBs in this
case. In both cases, transmission reliability is improved by this case). In both cases, transmission reliability is improved by this
means of providing frequency diversity. means of providing frequency diversity.
In addition to licensed spectrum, a 5G system can also utilize In addition to licensed spectrum, a 5G system can also utilize
unlicensed spectrum to offload non-critical traffic. This version of unlicensed spectrum to offload non-critical traffic. This version of
NR is called NR-U, part of 3GPP Release 16. The central scheduling NR, called NR-U, is part of 3GPP Release 16. The central scheduling
approach applies also for unlicensed radio resources, but in addition approach also applies for unlicensed radio resources and the
also the mandatory channel access mechanisms for unlicensed spectrum, mandatory channel access mechanisms for unlicensed spectrum (e.g.,
e.g., Listen Before Talk (LBT) are supported in NR-U. This way, by Listen Before Talk (LBT) is supported in NR-U). This way, by using
using NR, operators have and can control access to both licensed and NR, operators have and can control access to both licensed and
unlicensed frequency resources. unlicensed frequency resources.
6.4.5. Time-Sensitive Communications (TSC) 6.4.5. Time-Sensitive Communications (TSC)
Recent 3GPP releases have introduced various features to support Recent 3GPP releases have introduced various features to support
multiple aspects of Time-Sensitive Communication (TSC), which multiple aspects of Time-Sensitive Communication (TSC), which
includes Time-Sensitive Networking (TSN) and beyond as described in includes Time-Sensitive Networking (TSN) and beyond, as described in
this section. this section.
The main objective of Time-Sensitive Networking (TSN) is to provide The main objective of TSN is to provide guaranteed data delivery
guaranteed data delivery within a guaranteed time window, i.e., within a guaranteed time window (i.e., bounded low latency). IEEE
bounded low latency. IEEE 802.1 TSN [IEEE802.1TSN] is a set of open 802.1 TSN [IEEE802.1TSN] is a set of open standards that provide
standards that provide features to enable deterministic communication features to enable deterministic communication on standard IEEE 802.3
on standard IEEE 802.3 Ethernet [IEEE802.3]. TSN standards can be Ethernet [IEEE802.3]. TSN standards can be seen as a toolbox for
seen as a toolbox for traffic shaping, resource management, time traffic shaping, resource management, time synchronization, and
synchronization, and reliability. reliability.
A TSN stream is a data flow between one end station (Talker) to A TSN stream is a data flow between one end station (talker) to
another end station (Listener). In the centralized configuration another end station (listener). In the centralized configuration
model, TSN bridges are configured by the Central Network Controller model, TSN bridges are configured by the Central Network Controller
(CNC) [IEEE802.1Qcc] to provide deterministic connectivity for the (CNC) [IEEE802.1Qcc] to provide deterministic connectivity for the
TSN stream through the network. Time-based traffic shaping provided TSN stream through the network. Time-based traffic shaping provided
by Scheduled Traffic [IEEE802.1Qbv] may be used to achieve bounded by scheduled traffic [IEEE802.1Qbv] may be used to achieve bounded
low latency. The TSN tool for time synchronization is the low latency. The TSN tool for time synchronization is the
generalized Precision Time Protocol (gPTP) [IEEE802.1AS]), which generalized Precision Time Protocol (gPTP) [IEEE802.1AS], which
provides reliable time synchronization that can be used by end provides reliable time synchronization that can be used by end
stations and by other TSN tools, e.g., Scheduled Traffic stations and by other TSN tools (e.g., scheduled traffic
[IEEE802.1Qbv]. High availability, as a result of ultra-reliability, [IEEE802.1Qbv]). High availability, as a result of ultra-
is provided for data flows by the Frame Replication and Elimination reliability, is provided for data flows by the Frame Replication and
for Reliability (FRER) [IEEE802.1CB] mechanism. Elimination for Reliability (FRER) mechanism [IEEE802.1CB].
3GPP Release 16 includes integration of 5G with TSN, i.e., specifies 3GPP Release 16 includes integration of 5G with TSN, i.e., specifies
functions for the 5G System (5GS) to deliver TSN streams such that functions for the 5G System (5GS) to deliver TSN streams such that
the meet their QoS requirements. A key aspect of the integration is the meet their QoS requirements. A key aspect of the integration is
the 5GS appears from the rest of the network as a set of TSN bridges, the 5GS appears from the rest of the network as a set of TSN bridges,
in particular, one virtual bridge per User Plane Function (UPF) on in particular, one virtual bridge per User Plane Function (UPF) on
the user plane. The 5GS includes TSN Translator (TT) functionality the user plane. The 5GS includes TSN Translator (TT) functionality
for the adaptation of the 5GS to the TSN bridged network and for for the adaptation of the 5GS to the TSN bridged network and for
hiding the 5GS internal procedures. The 5GS provides the following hiding the 5GS internal procedures. The 5GS provides the following
components: components:
1. interface to TSN controller, as per [IEEE802.1Qcc] for the fully 1. interface to TSN controller, as per [IEEE802.1Qcc] for the fully
centralized configuration model centralized configuration model
2. time synchronization via reception and transmission of gPTP PDUs 2. time synchronization via reception and transmission of gPTP PDUs
[IEEE802.1AS] [IEEE802.1AS]
3. low latency, hence, can be integrated with Scheduled Traffic 3. low latency, hence, can be integrated with scheduled traffic
[IEEE802.1Qbv] [IEEE802.1Qbv]
4. reliability, hence, can be integrated with FRER [IEEE802.1CB] 4. reliability, hence, can be integrated with FRER [IEEE802.1CB]
3GPP Release 17 [TS23501] introduced enhancements to generalize 3GPP Release 17 [TS23501] introduced enhancements to generalize
support for Time-Sensitive Communications (TSC) beyond TSN. This support for TSC beyond TSN. This includes IP communications to
includes IP communications to provide time-sensitive service to, provide time-sensitive services (e.g., to Video, Imaging, and Audio
e.g., Video, Imaging and Audio for Professional Applications (VIAPA). for Professional Applications (VIAPA)). The system model of 5G
The system model of 5G acting as a “TSN bridge” in Release 16 has acting as a "TSN bridge" in Release 16 has been reused to enable the
been reused to enable the 5GS acting as a “TSC node” in a more 5GS acting as a "TSC node" in a more generic sense (which includes
generic sense (which includes TSN bridge and IP node). In the case TSN bridge and IP node). In the case of TSC that does not involve
of TSC that does not involve TSN, requirements are given via exposure TSN, requirements are given via exposure interfaces, and the control
interface and the control plane provides the service based on QoS and plane provides the service based on QoS and time synchronization
time synchronization requests from an Application Function (AF). requests from an Application Function (AF).
Figure 7 shows an illustration of 5G-TSN integration where an Figure 7 shows an illustration of 5G-TSN integration where an
industrial controller (Ind Ctrlr) is connected to industrial Input/ industrial controller (Ind Ctrlr) is connected to industrial Input/
Output devices (I/O dev) via 5G. The 5GS can directly transport Output devices (I/O dev) via 5G. The 5GS can directly transport
Ethernet frames since Release 15, thus, end-to-end Ethernet Ethernet frames since Release 15; thus, end-to-end Ethernet
connectivity is provided. The 5GS implements the required interfaces connectivity is provided. The 5GS implements the required interfaces
towards the TSN controller functions such as the CNC, thus adapts to towards the TSN controller functions such as the CNC, thus adapting
the settings of the TSN network. A 5G user plane virtual bridge to the settings of the TSN network. A 5G user plane virtual bridge
interconnects TSN bridges or connects end stations, e.g., I/O devices interconnects TSN bridges or connects end stations (e.g., I/O devices
to the TSN network. TSN Translators (TTs), i.e., the Device-Side TSN to the TSN network). TTs, i.e., the Device-Side TSN Translator (DS-
Translator (DS-TT) at the UE and the Network-Side TSN Translator (NW- TT) at the UE and the Network-Side TSN Translator (NW-TT) at the UPF,
TT) at the UPF have a key role in the interconnection. Note that the have a key role in the interconnection. Note that the introduction
introduction of 5G brings flexibility in various aspects, e.g., more of 5G brings flexibility in various aspects, e.g., a more flexible
flexible network topology because a wireless hop can replace several network topology because a wireless hop can replace several wireline
wireline hops thus significantly reduce the number of hops end-to- hops, thus significantly reducing the number of hops end to end.
end. [TSN5G] dives more into the integration of 5G with TSN. [TSN5G] dives more into the integration of 5G with TSN.
+------------------------------+ +------------------------------+
| 5G System | | 5G System |
| +---+| | +---+|
| +-+ +-+ +-+ +-+ +-+ |TSN|| | +-+ +-+ +-+ +-+ +-+ |TSN||
| | | | | | | | | | | |AF |......+ | | | | | | | | | | | |AF |......+
| +++ +++ +++ +++ +++ +-+-+| . | +++ +++ +++ +++ +++ +-+-+| .
| | | | | | | | . | | | | | | | | .
| -+---+---++--+-+-+--+-+- | . | -+---+---++--+-+-+--+-+- | .
| | | | | | +--+--+ | | | | | | +--+--+
skipping to change at page 43, line 45 skipping to change at line 1938
<----------------- end-to-end Ethernet -------------------> <----------------- end-to-end Ethernet ------------------->
Figure 7: 5G - TSN Integration Figure 7: 5G - TSN Integration
NR supports accurate reference time synchronization in 1us accuracy NR supports accurate reference time synchronization in 1us accuracy
level. Since NR is a scheduled system, an NR UE and a gNB are level. Since NR is a scheduled system, an NR UE and a gNB are
tightly synchronized to their OFDM symbol structures. A 5G internal tightly synchronized to their OFDM symbol structures. A 5G internal
reference time can be provided to the UE via broadcast or unicast reference time can be provided to the UE via broadcast or unicast
signaling, associating a known OFDM symbol to this reference clock. signaling, associating a known OFDM symbol to this reference clock.
The 5G internal reference time can be shared within the 5G network, The 5G internal reference time can be shared within the 5G network
i.e., radio and core network components. Release 16 has introduced (i.e., radio and core network components). Release 16 has introduced
interworking with gPTP for multiple time domains, where the 5GS acts interworking with gPTP for multiple time domains, where the 5GS acts
as a virtual gPTP time-aware system and supports the forwarding of as a virtual gPTP time-aware system and supports the forwarding of
gPTP time synchronization information between end stations and gPTP time synchronization information between end stations and
bridges through the 5G user plane TTs. These account for the bridges through the 5G user plane TTs. These account for the
residence time of the 5GS in the time synchronization procedure. One residence time of the 5GS in the time synchronization procedure. One
special option is when the 5GS internal reference time is not only special option is when the 5GS internal reference time is not only
used within the 5GS, but also to the rest of the devices in the used within the 5GS, but also to the rest of the devices in the
deployment, including connected TSN bridges and end stations. deployment, including connected TSN bridges and end stations.
Release 17 includes further improvements, i.e., methods for Release 17 includes further improvements (i.e., methods for
propagation delay compensation in RAN, further improving the accuracy propagation delay compensation in RAN), further improving the
for time synchronization over-the-air, as well as the possibility for accuracy for time synchronization over the air, as well as the
the TSN grandmaster clock to reside on the UE side. More extensions possibility for the TSN grandmaster clock to reside on the UE side.
and flexibility were added to the time synchronization service making More extensions and flexibility were added to the time
it general for TSC with additional support of other types of clocks synchronization service, making it general for TSC, with additional
and time distribution such as boundary clock, transparent clock peer- support of other types of clocks and time distribution such as
to-peer, transparent clock end-to-end, aside from the time-aware boundary clock, transparent clock peer-to-peer, and transparent clock
system used for TSN. Additionally, it is possible to use internal end-to-end, aside from the time-aware system used for TSN.
access stratum signaling to distribute timing (and not the usual Additionally, it is possible to use internal access stratum signaling
(g)PTP messages), for which the required accuracy can be provided by to distribute timing (and not the usual (g)PTP messages), for which
the AF [TS23501]. The same time synchronization service is expected the required accuracy can be provided by the AF [TS23501]. The same
to be further extended and enhanced in Release 18 to support Timing time synchronization service is expected to be further extended and
Resiliency (according to study item [SP211634]), where the 5G system enhanced in Release 18 to support Timing Resiliency (according to
can provide a back-up or alternative timing source for the failure of study item [SP211634]), where the 5G system can provide a backup or
the local GNSS source (or other primary timing source) used by the alternative timing source for the failure of the local GNSS source
vertical. (or other primary timing source) used by the vertical.
IETF Deterministic Networking (DetNet) is the technology to support IETF DetNet is the technology to support time-sensitive
time-sensitive communications at the IP layer. 3GPP Release 18 communications at the IP layer. 3GPP Release 18 includes a study
includes a study [TR2370046] on interworking between 5G and DetNet. [TR2370046] on interworking between 5G and DetNet. Along the TSC
Along the TSC framework introduced for Release 17, the 5GS acts as a framework introduced for Release 17, the 5GS acts as a DetNet node
DetNet node for the support of DetNet, see Figure 7.1-1 in for the support of DetNet; see Figure 7.1-1 in [TR2370046]. The
[TR2370046]. The study provides details on how the 5GS is exposed by study provides details on how the 5GS is exposed by the Time
the Time Sensitive Communication and Time Synchronization Function Sensitive Communication and Time Synchronization Function (TSCTSF) to
(TSCTSF) to the DetNet controller as a router on a per UPF the DetNet controller as a router on a per-UPF granularity (similar
granularity (similarly to the per UPF Virtual TSN Bridge granularity to the per-UPF Virtual TSN Bridge granularity shown in Figure 11).
shown in Figure 11). In particular, it is listed what parameters are In particular, it lists the parameters that are provided by the
provided by the TSCTSF to the DetNet controller. The study also TSCTSF to the DetNet controller. The study also includes how the
includes how the TSCTSF maps DetNet flow parameters to 5G QoS TSCTSF maps DetNet flow parameters to 5G QoS parameters. Note that
parameters. Note that TSN is the primary subnetwork technology for TSN is the primary subnetwork technology for DetNet. Thus, the work
DetNet. Thus, the DetNet over TSN work, e.g., [RFC9023], can be on DetNet over TSN, e.g., [RFC9023], can be leveraged via the TSN
leveraged via the TSN support built in 5G. support built in 5G.
Redundancy architectures were specified in order to provide Redundancy architectures were specified in order to provide
reliability against any kind of failure on the radio link or nodes in reliability against any kind of failure on the radio link or nodes in
the RAN and the core network. Redundant user plane paths can be the RAN and the core network. Redundant user plane paths can be
provided based on the dual connectivity architecture, where the UE provided based on the dual connectivity architecture, where the UE
sets up two PDU sessions towards the same data network, and the 5G sets up two PDU sessions towards the same data network, and the 5G
system makes the paths of the two PDU sessions independent as system makes the paths of the two PDU sessions independent as
illustrated in Figure 9. There are two PDU sessions involved in the illustrated in Figure 9. There are two PDU sessions involved in the
solution: the first spans from the UE via gNB1 to UPF1, acting as the solution: The first spans from the UE via gNB1 to UPF1, acting as the
first PDU session anchor, while the second spans from the UE via gNB2 first PDU session anchor, while the second spans from the UE via gNB2
to UPF2, acting as second the PDU session anchor. The independent to UPF2, acting as second the PDU session anchor.
paths may continue beyond the 3GPP network. Redundancy Handling
Functions (RHFs) are deployed outside of the 5GS, i.e., in Host A The independent paths may continue beyond the 3GPP network.
(the device) and in Host B (the network). RHF can implement Redundancy Handling Functions (RHFs) are deployed outside of the 5GS,
replication and elimination functions as per [IEEE802.1CB] or the i.e., in Host A (the device) and in Host B (the network). RHF can
Packet Replication, Elimination, and Ordering Functions (PREOF) of implement replication and elimination functions as per [IEEE802.1CB]
IETF Deterministic Networking (DetNet) [RFC8655]. or the Packet Replication, Elimination, and Ordering Functions
(PREOF) of IETF DetNet [RFC8655].
+........+ +........+
. Device . +------+ +------+ +------+ . Device . +------+ +------+ +------+
. . + gNB1 +--N3--+ UPF1 |--N6--+ | . . + gNB1 +--N3--+ UPF1 |--N6--+ |
. ./+------+ +------+ | | . ./+------+ +------+ | |
. +----+ / | | . +----+ / | |
. | |/. | | . | |/. | |
. | UE + . | DN | . | UE + . | DN |
. | |\. | | . | |\. | |
. +----+ \ | | . +----+ \ | |
. .\+------+ +------+ | | . .\+------+ +------+ | |
+........+ + gNB2 +--N3--+ UPF2 |--N6--+ | +........+ + gNB2 +--N3--+ UPF2 |--N6--+ |
+------+ +------+ +------+ +------+ +------+ +------+
Figure 8: Reliability with Single UE Figure 8: Reliability with Single UE
An alternative solution is that multiple UEs per device are used for An alternative solution is that multiple UEs per device are used for
user plane redundancy as illustrated in Figure 9. Each UE sets up a user plane redundancy as illustrated in Figure 9. Each UE sets up a
PDU session. The 5GS ensures that those PDU sessions of the PDU session. The 5GS ensures that the PDU sessions of the different
different UEs are handled independently internal to the 5GS. There UEs are handled independently internal to the 5GS. There is no
is no single point of failure in this solution, which also includes single point of failure in this solution, which also includes RHF
RHF outside of the 5G system, e.g., as per FRER or as PREOF outside of the 5G system, e.g., as per the FRER or PREOF
specifications. specifications.
+.........+ +.........+
. Device . . Device .
. . . .
. +----+ . +------+ +------+ +------+ . +----+ . +------+ +------+ +------+
. | UE +-----+ gNB1 +--N3--+ UPF1 |--N6--+ | . | UE +-----+ gNB1 +--N3--+ UPF1 |--N6--+ |
. +----+ . +------+ +------+ | | . +----+ . +------+ +------+ | |
. . | DN | . . | DN |
. +----+ . +------+ +------+ | | . +----+ . +------+ +------+ | |
. | UE +-----+ gNB2 +--N3--+ UPF2 |--N6--+ | . | UE +-----+ gNB2 +--N3--+ UPF2 |--N6--+ |
. +----+ . +------+ +------+ +------+ . +----+ . +------+ +------+ +------+
. . . .
+.........+ +.........+
Figure 9: Reliability with Dual UE Figure 9: Reliability with Dual UE
Note that the abstraction provided by the RHF and the location of the Note that the abstraction provided by the RHF and the location of the
RHF being outside of the 5G system make 5G equally supporting RHF being outside of the 5G system make 5G equally supporting
integration for reliability both with FRER of TSN and PREOF of DetNet integration for reliability with both FRER of TSN and PREOF of
as they both rely on the same concept. DetNet, as they both rely on the same concept.
7. L-band Digital Aeronautical Communications System 7. L-Band Digital Aeronautical Communications System (LDACS)
One of the main pillars of the modern Air Traffic Management (ATM) One of the main pillars of the modern Air Traffic Management (ATM)
system is the existence of a communication infrastructure that system is the existence of a communication infrastructure that
enables efficient aircraft guidance and safe separation in all phases enables efficient aircraft guidance and safe separation in all phases
of flight. Although current systems are technically mature, they are of flight. Although current systems are technically mature, they
suffering from the VHF band’s increasing saturation in high-density suffer from the VHF band's increasing saturation in high-density
areas and the limitations posed by analogue radio. Therefore, areas and the limitations posed by analog radio. Therefore, aviation
aviation globally and the European Union (EU) in particular, strives (globally and in the European Union (EU) in particular) strives for a
for a sustainable modernization of the aeronautical communication sustainable modernization of the aeronautical communication
infrastructure. infrastructure.
In the long-term, ATM communication shall transition from analogue In the long term, ATM communication shall transition from analog VHF
VHF voice and VDL2 communication to more spectrum efficient digital voice and VDL Mode 2 communication to more spectrum-efficient digital
data communication. The European ATM Master Plan foresees this data communication. The European ATM Master Plan foresees this
transition to be realized for terrestrial communications by the transition to be realized for terrestrial communications by the
development and implementation of the L-band Digital Aeronautical development and implementation of the L-band Digital Aeronautical
Communications System (LDACS). Communications System (LDACS).
LDACS has been designed with applications related to the safety and LDACS has been designed with applications related to the safety and
regularity of the flight in mind. It has therefore been designed as regularity of the flight in mind. It has therefore been designed as
a deterministic wireless data link (as far as possible). a deterministic wireless data link (as far as possible).
It is a secure, scalable and spectrum efficient data link with It is a secure, scalable, and spectrum-efficient data link with
embedded navigation capability and thus, is the first truly embedded navigation capability; thus, it is the first truly
integrated Communications, Navigation, and Surveillance (CNS) system integrated Communications, Navigation, and Surveillance (CNS) system
recognized by the International Civil Aviation Organization (ICAO) recognized by the International Civil Aviation Organization (ICAO).
During flight tests the LDACS capabilities have been successfully During flight tests, the LDACS capabilities have been successfully
demonstrated. A viable roll-out scenario has been developed which demonstrated. A viable rollout scenario has been developed, which
allows gradual introduction of LDACS with immediate use and revenues. allows gradual introduction of LDACS with immediate use and revenues.
Finally, ICAO is developing LDACS standards to pave the way for the Finally, ICAO is developing LDACS standards to pave the way for the
future. future.
LDACS shall enable IPv6 based air-ground communication related to the LDACS shall enable IPv6-based air-ground communication related to the
safety and regularity of the flight. The particular challenge is safety and regularity of the flight. The particular challenge is
that no new frequencies can be made available for terrestrial that no new frequencies can be made available for terrestrial
aeronautical communication. It was thus necessary to develop aeronautical communication. It was thus necessary to develop
procedures to enable the operation of LDACS in parallel with other procedures to enable the operation of LDACS in parallel with other
services in the same frequency band, more in [RFC9372]. services in the same frequency band; see [RFC9372] for more
information.
7.1. Provenance and Documents 7.1. Provenance and Documents
The development of LDACS has already made substantial progress in the The development of LDACS has already made substantial progress in the
Single European Sky ATM Research (SESAR) framework, and is currently Single European Sky ATM Research (SESAR) framework, and it is
being continued in the follow-up program, SESAR2020 [RIH18]. A key currently being continued in the follow-up program, SESAR2020
objective of the SESAR activities is to develop, implement and [RIH18]. A key objective of the SESAR activities is to develop,
validate a modern aeronautical data link able to evolve with aviation implement, and validate a modern aeronautical data link able to
needs over long-term. To this end, an LDACS specification has been evolve with aviation needs over the long term. To this end, an LDACS
produced [GRA19] and is continuously updated; transmitter specification has been produced [GRA19] and is continuously updated;
demonstrators were developed to test the spectrum compatibility of transmitter demonstrators were developed to test the spectrum
LDACS with legacy systems operating in the L-band [SAJ14]; and the compatibility of LDACS with legacy systems operating in the L-band
overall system performance was analyzed by computer simulations, [SAJ14], and the overall system performance was analyzed by computer
indicating that LDACS can fulfill the identified requirements simulations, indicating that LDACS can fulfill the identified
[GRA11]. requirements [GRA11].
LDACS standardization within the framework of the ICAO started in LDACS standardization within the framework of the ICAO started in
December 2016. The ICAO standardization group has produced an December 2016. The ICAO standardization group has produced an
initial Standards and Recommended Practices (SARPs) document initial Standards and Recommended Practices (SARPs) document
[ICAO18]. The SARPs document defines the general characteristics of [ICAO18]. The SARPs document defines the general characteristics of
LDACS. LDACS.
Up to now the LDACS standardization has been focused on the Up to now, the LDACS standardization has been focused on the
development of the physical layer and the data link layer, only development of the physical layer and the data link layer; only
recently have higher layers come into the focus of the LDACS recently have higher layers come into the focus of the LDACS
development activities. There is currently no "IPv6 over LDACS" development activities. There is currently no "IPv6 over LDACS"
specification; however, SESAR2020 has started the testing of specification; however, SESAR2020 has started the testing of
IPv6-based LDACS testbeds. The IPv6 architecture for the IPv6-based LDACS testbeds. The IPv6 architecture for the
aeronautical telecommunication network is called the Future aeronautical telecommunication network is called the Future
Communications Infrastructure (FCI). FCI shall support quality of Communications Infrastructure (FCI). FCI shall support QoS,
service, diversity, and mobility under the umbrella of the "multi- diversity, and mobility under the umbrella of the "multi-link
link concept". This work is conducted by ICAO working group WG-I. concept". This work is conducted by the ICAO WG-I Working Group.
In addition to standardization activities several industrial LDACS In addition to standardization activities, several industrial LDACS
prototypes have been built. One set of LDACS prototypes has been prototypes have been built. One set of LDACS prototypes has been
evaluated in flight trials confirming the theoretical results evaluated in flight trials, confirming the theoretical results
predicting the system performance [GRA18][BEL22][GRA23] . predicting the system performance [GRA18] [BEL22] [GRA23].
7.2. General Characteristics 7.2. General Characteristics
LDACS will become one of several wireless access networks connecting LDACS will become one of several wireless access networks connecting
aircraft to the Aeronautical Telecommunications Network (ATN). The aircraft to the Aeronautical Telecommunications Network (ATN). The
LDACS access network contains several ground stations, each of them LDACS access network contains several ground stations, each of which
providing one LDACS radio cell. The LDACS air interface is a provides one LDACS radio cell. The LDACS air interface is a cellular
cellular data link with a star-topology connecting aircraft to data link with a star topology connecting aircraft to ground stations
ground-stations with a full duplex radio link. Each ground-station with a full duplex radio link. Each ground station is the
is the centralized instance controlling all air-ground communications centralized instance controlling all air-ground communications within
within its radio cell. its radio cell.
The user data rate of LDACS is 315 kbit/s to 1428 kbit/s on the The user data rate of LDACS is 315 kbit/s to 1428 kbit/s on the
forward link, and 294 kbit/s to 1390 kbit/s on the reverse link, forward link and 294 kbit/s to 1390 kbit/s on the reverse link,
depending on coding and modulation. Due to strong interference from depending on coding and modulation. Due to strong interference from
legacy systems in the L-band, the most robust coding and modulation legacy systems in the L-band, the most robust coding and modulation
should be expected for initial deployment, i.e., 315/294 kbit/s on should be expected for initial deployment, i.e., 315 kbit/s on the
the forward/reverse link, respectively. forward link and 294 kbit/s on the reverse link.
In addition to the communications capability, LDACS also offers a In addition to the communications capability, LDACS also offers a
navigation capability. Ranging data, similar to DME (Distance navigation capability. Ranging data, similar to DME (Distance
Measuring Equipment), is extracted from the LDACS communication links Measuring Equipment), is extracted from the LDACS communication links
between aircraft and LDACS ground stations. This results in LDACS between aircraft and LDACS ground stations. This results in LDACS
providing an APNT (Alternative Position, Navigation and Timing) providing an APNT (Alternative Position, Navigation and Timing)
capability to supplement the existing on-board GNSS (Global capability to supplement the existing on-board GNSS (Global
Navigation Satellite System) without the need for additional Navigation Satellite System) without the need for additional
bandwidth. Operationally, there will be no difference for pilots bandwidth. Operationally, there will be no difference for pilots
whether the navigation data are provided by LDACS or DME. This whether the navigation data are provided by LDACS or DME. This
capability was flight tested and proven during the MICONAV flight capability was flight tested and proven during the MICONAV flight
trials in 2019 [BAT19]. trials in 2019 [BAT19].
In previous works and during the MICONAV flight campaign in 2019, it In previous works and during the MICONAV flight campaign in 2019, it
was also shown, that LDACS can be used for surveillance capability. was also shown that LDACS can be used for surveillance capability.
Filip et al. [FIL19] shown passive radar capabilities of LDACS and Filip et al. [FIL19] have shown the passive radar capabilities of
Automatic Dependence Surveillance – Contract (ADS-C) was demonstrated LDACS, and Automatic Dependence Surveillance - Contract (ADS-C) was
via LDACS during the flight campaign 2019 [SCH19]. demonstrated via LDACS during the flight campaign 2019 [SCH19].
Since LDACS has been mainly designed for air traffic management Since LDACS has been mainly designed for air traffic management
communication it supports mutual entity authentication, integrity and communication, it supports mutual entity authentication, integrity
confidentiality capabilities of user data messages and some control and confidentiality capabilities of user data messages, and some
channel protection capabilities [MAE18], [MAE191], [MAE192], [MAE20]. control channel protection capabilities [MAE18] [MAE191] [MAE192]
[MAE20].
Overall this makes LDACS the world's first truly integrated CNS Overall, this makes LDACS the world's first truly integrated CNS
system and is the worldwide most mature, secure, terrestrial long- system and is the most mature, secure, and terrestrial long-range CNS
range CNS technology for civil aviation. technology for civil aviation worldwide.
7.3. Deployment and Spectrum 7.3. Deployment and Spectrum
LDACS has its origin in merging parts of the B-VHF [BRA06], B-AMC LDACS has its origin in merging parts of the B-VHF [BRA06], B-AMC
[SCH08], TIA-902 (P34) [HAI09], and WiMAX IEEE 802.16e technologies [SCH08], TIA-902 (P34) [HAI09], and WiMAX IEEE 802.16e [EHA11]
[EHA11]. In 2007 the spectrum for LDACS was allocated at the World technologies. In 2007, the spectrum for LDACS was allocated at the
Radio Conference (WRC). World Radio Conference (WRC).
It was decided to allocate the spectrum next to Distance Measuring It was decided to allocate the spectrum next to Distance Measuring
Equipment (DME), resulting in an in-lay approach between the DME Equipment (DME), resulting in an in-lay approach between the DME
channels for LDAC [SCH14]. channels for LDAC [SCH14].
LDACS is currently being standardized by ICAO and several roll-out LDACS is currently being standardized by ICAO and several rollout
strategies are discussed: strategies are discussed.
The LDACS data link provides enhanced capabilities to existing The LDACS data link provides enhanced capabilities to existing
Aeronautical communications infrastructure enabling them to better aeronautical communications infrastructures, enabling them to better
support user needs and new applications. The deployment scalability support user needs and new applications. The deployment scalability
of LDACS allows its implementation to start in areas where most of LDACS allows its implementation to start in areas where it is most
needed to Improve immediately the performance of already fielded needed to immediately improve the performance of and already-fielded
infrastructure. Later the deployment is extended based on infrastructure. Later, the deployment is extended based on
operational demand. An attractive scenario for upgrading the operational demand. An attractive scenario for upgrading the
existing VHF communication systems by adding an additional LDACS data existing VHF communication systems by adding an additional LDACS data
link is described below. link is described below.
When considering the current VDL Mode 2 infrastructure and user base, When considering the current VDL Mode 2 infrastructure and user base,
a very attractive win-win situation comes about, when the a very attractive win-win situation comes about when the
technological advantages of LDACS are combined with the existing VDL technological advantages of LDACS are combined with the existing VDL
mode 2 infrastructure. LDACS provides at least 50 time more capacity Mode 2 infrastructure. LDACS provides at least 50 times more
than VDL Mode 2 and is a natural enhancement to the existing VDL Mode capacity than VDL Mode 2 and is a natural enhancement to the existing
2 business model. The advantage of this approach is that the VDL VDL Mode 2 business model. The advantage of this approach is that
Mode 2 infrastructure can be fully reused. Beyond that, it opens the the VDL Mode 2 infrastructure can be fully reused. Beyond that, it
way for further enhancements [ICAO19]. opens the way for further enhancements [ICAO19].
7.4. Applicability to Deterministic Flows 7.4. Applicability to Deterministic Flows
As LDACS is a ground-based digital communications system for flight As LDACS is a ground-based digital communications system for flight
guidance and communications related to safety and regularity of guidance and communications related to safety and regularity of
flight, time-bounded deterministic arrival times for safety critical flight, time-bounded deterministic arrival times for safety critical
messages are a key feature for its successful deployment and roll- messages are a key feature for its successful deployment and rollout.
out.
7.4.1. System Architecture 7.4.1. System Architecture
Up to 512 Aircraft Station (AS) communicate to an LDACS Ground Up to 512 Aircraft Stations (ASes) communicate to an LDACS Ground
Station (GS) in the Reverse Link (RL). GS communicate to an AS in Station (GS) in the reverse link (RL). A GS communicates to an AS in
the Forward Link (FL). Via an Access-Router (AC-R) GSs connect the the Forward Link (FL). Via an Access-Router (AC-R), GSs connect the
LDACS sub-network to the global Aeronautical Telecommunications LDACS subnetwork to the global Aeronautical Telecommunications
Network (ATN) to which the corresponding Air Traffic Services (ATS) Network (ATN) to which the corresponding Air Traffic Services (ATS)
and Aeronautical Operational Control (AOC) end systems are attached. and Aeronautical Operational Control (AOC) end systems are attached.
7.4.2. Overview of the Radio Protocol Stack 7.4.2. Overview of the Radio Protocol Stack
The protocol stack of LDACS is implemented in the AS and GS: It The protocol stack of LDACS is implemented in the AS and GS; it
consists of the Physical Layer (PHY) with five major functional consists of the physical (PHY) layer with five major functional
blocks above it. Four are placed in the Data Link Layer (DLL) of the blocks above it. Four are placed in the data link layer (DLL) of the
AS and GS: (1) Medium Access Layer (MAC), (2) Voice Interface (VI), AS and GS:
(3) Data Link Service (DLS), and (4) LDACS Management Entity (LME).
The last entity resides within the Sub-Network Layer: Sub-Network 1. Medium Access Layer (MAC),
2. Voice Interface (VI),
3. Data Link Service (DLS), and
4. LDACS Management Entity (LME).
The last entity resides within the subnetwork layer: the Subnetwork
Protocol (SNP). The LDACS network is externally connected to voice Protocol (SNP). The LDACS network is externally connected to voice
units, radio control units, and the ATN Network Layer. units, radio control units, and the ATN network layer.
Communications between MAC and LME layer is split into four distinct Communications between the MAC and LME layers is split into four
control channels: The Broadcast Control Channel (BCCH) where LDACS distinct control channels:
ground stations announce their specific LDACS cell, including
physical parameters and cell identification; the Random Access 1. the Broadcast Control Channel (BCCH), where LDACS ground stations
Channel (RACH) where LDACS airborne radios can request access to an announce their specific LDACS cell, including physical parameters
LDACS cell; the Common Control Channel (CCCH) where LDACS ground and cell identification;
stations allocate resources to aircraft radios, enabling the airborne
side to transmit user payload; the Dedicated Control Channel (DCCH) 2. the Random Access Channel (RACH), where LDACS airborne radios can
where LDACS airborne radios can request user data resources from the request access to an LDACS cell;
LDACS ground station so the airborne side can transmit user payload.
Communications between MAC and DLS layer is handled by the Data 3. the Common Control Channel (CCCH), where LDACS ground stations
Channel (DCH) where user payload is handled. allocate resources to aircraft radios, enabling the airborne side
to transmit the user payload; and
4. the Dedicated Control Channel (DCCH), where LDACS airborne radios
can request user data resources from the LDACS ground station so
the airborne side can transmit the user payload.
Communications between the MAC and DLS layers is handled by the Data
Channel (DCH) where the user payload is handled.
Figure 10 shows the protocol stack of LDACS as implemented in the AS Figure 10 shows the protocol stack of LDACS as implemented in the AS
and GS. and GS.
IPv6 Network Layer IPv6 Network Layer
| |
| |
+------------------+ +----+ +------------------+ +----+
| SNP |--| | Sub-Network | SNP |--| | Subnetwork
| | | | Layer | | | | Layer
+------------------+ | | +------------------+ | |
| | LME| | | LME|
+------------------+ | | +------------------+ | |
| DLS | | | Logical Link | DLS | | | Logical Link
| | | | Control Layer | | | | Control Layer
+------------------+ +----+ +------------------+ +----+
| | | |
DCH DCCH/CCCH DCH DCCH/CCCH
| RACH/BCCH | RACH/BCCH
skipping to change at page 51, line 34 skipping to change at line 2288
+--------------------------+ +--------------------------+
| |
+--------------------------+ +--------------------------+
| PHY | Physical Layer | PHY | Physical Layer
+--------------------------+ +--------------------------+
| |
| |
((*)) ((*))
FL/RL radio channels FL/RL radio channels
separated by separated by
Frequency Division Duplex frequency division duplex
Figure 10: LDACS protocol stack in AS and GS Figure 10: LDACS Protocol Stack in AS and GS
7.4.3. Radio (PHY) 7.4.3. Radio (PHY)
The physical layer provides the means to transfer data over the radio The physical layer provides the means to transfer data over the radio
channel. The LDACS ground-station supports bi-directional links to channel. The LDACS ground station supports bidirectional links to
multiple aircraft under its control. The forward link direction (FL; multiple aircraft under its control. The forward link direction
ground-to-air) and the reverse link direction (RL; air-to-ground) are (which is ground to air) and the reverse link direction (which is air
separated by frequency division duplex. Forward link and reverse to ground) are separated by frequency division duplex. Forward link
link use a 500 kHz channel each. The ground-station transmits a and reverse link use a 500 kHz channel each. The ground station
continuous stream of OFDM symbols on the forward link. In the transmits a continuous stream of OFDM symbols on the forward link.
reverse link different aircraft are separated in time and frequency In the reverse link, different aircrafts are separated in time and
using a combination of Orthogonal Frequency-Division Multiple-Access frequency using a combination of Orthogonal Frequency-Division
(OFDMA) and Time-Division Multiple-Access (TDMA). Aircraft thus Multiple Access (OFDMA) and Time-Division Multiple-Access (TDMA).
transmit discontinuously on the reverse link with radio bursts sent Thus, aircraft transmit discontinuously on the reverse link with
in precisely defined transmission opportunities allocated by the radio bursts sent in precisely defined transmission opportunities
ground-station. The most important service on the PHY layer of LDACS allocated by the ground station. The most important service on the
is the PHY time framing service, which indicates that the PHY layer PHY layer of LDACS is the PHY time framing service, which indicates
is ready to transmit in a given slot and to indicate PHY layer that the PHY layer is ready to transmit in a given slot and indicates
framing and timing to the MAC time framing service. LDACS does not PHY layer framing and timing to the MAC time framing service. LDACS
support beam-forming or Multiple Input Multiple Output (MIMO). does not support beam-forming or Multiple Input Multiple Output
(MIMO).
7.4.4. Scheduling, Frame Structure and QoS (MAC) 7.4.4. Scheduling, Frame Structure, and QoS (MAC)
The data-link layer provides the necessary protocols to facilitate The data link layer provides the necessary protocols to facilitate
concurrent and reliable data transfer for multiple users. The LDACS concurrent and reliable data transfer for multiple users. The LDACS
data link layer is organized in two sub-layers: The medium access data link layer is organized in two sublayers: the medium access
sub-layer and the logical link control sub-layer. The medium access sublayer and the logical link control sublayer. The medium access
sub-layer manages the organization of transmission opportunities in sublayer manages the organization of transmission opportunities in
slots of time and frequency. The logical link control sub-layer slots of time and frequency. The logical link control sublayer
provides acknowledged point-to-point logical channels between the provides acknowledged point-to-point logical channels between the
aircraft and the ground-station using an automatic repeat request aircraft and the ground station using an automatic repeat request
protocol. LDACS supports also unacknowledged point-to-point channels protocol. LDACS also supports unacknowledged point-to-point channels
and ground-to-air broadcast. Before going more into depth about the and ground-to-air broadcast.
LDACS medium access, the frame structure of LDACS is introduced:
Next, the frame structure of LDACS is introduced, followed by a more
in-depth discussion of the LDACS medium access.
The LDACS framing structure for FL and RL is based on Super-Frames The LDACS framing structure for FL and RL is based on Super-Frames
(SF) of 240 ms duration. Each SF corresponds to 2000 OFDM symbols. (SF) of 240 ms duration. Each SF corresponds to 2000 OFDM symbols.
The FL and RL SF boundaries are aligned in time (from the view of the The FL and RL SF boundaries are aligned in time (from the view of the
GS). GS).
In the FL, an SF contains a Broadcast Frame of duration 6.72 ms (56 In the FL, an SF contains a broadcast frame with a duration of 6.72
OFDM symbols) for the Broadcast Control Channel (BCCH), and four ms (56 OFDM symbols) for the Broadcast Control Channel (BCCH) and
Multi-Frames (MF), each of duration 58.32 ms (486 OFDM symbols). four Multi-Frames (MF), each with a duration of 58.32 ms (486 OFDM
symbols).
In the RL, each SF starts with a Random Access (RA) slot of length In the RL, each SF starts with a Random Access (RA) slot with a
6.72 ms with two opportunities for sending RL random access frames length of 6.72 ms with two opportunities for sending RL random access
for the Random Access Channel (RACH), followed by four MFs. These frames for the Random Access Channel (RACH), followed by four MFs.
MFs have the same fixed duration of 58.32 ms as in the FL, but a These MFs have the same fixed duration of 58.32 ms as in the FL but a
different internal structure different internal structure.
Figure 11 and Figure 12 illustrate the LDACS frame structure. Figures 11 and 12 illustrate the LDACS frame structure. This fixed
frame structure allows for the reliable and dependable transmission
of data.
^ ^
| +------+------------+------------+------------+------------+ | +------+------------+------------+------------+------------+
| FL | BCCH | MF | MF | MF | MF | | FL | BCCH | MF | MF | MF | MF |
F +------+------------+------------+------------+------------+ F +------+------------+------------+------------+------------+
r <---------------- Super-Frame (SF) - 240ms ----------------> r <---------------- Super-Frame (SF) - 240 ms --------------->
e e
q +------+------------+------------+------------+------------+ q +------+------------+------------+------------+------------+
u RL | RACH | MF | MF | MF | MF | u RL | RACH | MF | MF | MF | MF |
e +------+------------+------------+------------+------------+ e +------+------------+------------+------------+------------+
n <---------------- Super-Frame (SF) - 240ms ----------------> n <---------------- Super-Frame (SF) - 240 ms --------------->
c c
y y
| |
----------------------------- Time ------------------------------> ----------------------------- Time ------------------------------>
| |
Figure 11: SF structure for LDACS Figure 11: SF Structure for LDACS
^ ^
| +-------------+------+-------------+ | +-------------+------+-------------+
| FL | DCH | CCCH | DCH | | FL | DCH | CCCH | DCH |
F +-------------+------+-------------+ F +-------------+------+-------------+
r <---- Multi-Frame (MF) - 58.32ms --> r <--- Multi-Frame (MF) - 58.32 ms -->
e e
q +------+---------------------------+ q +------+---------------------------+
u RL | DCCH | DCH | u RL | DCCH | DCH |
e +------+---------------------------+ e +------+---------------------------+
n <---- Multi-Frame (MF) - 58.32ms --> n <--- Multi-Frame (MF) - 58.32 ms -->
c c
y y
| |
-------------------- Time ------------------> -------------------- Time ------------------>
| |
Figure 12: MF Structure for LDACS Figure 12: MF Structure for LDACS
This fixed frame structure allows for a reliable and dependable Next, the LDACS medium access layer is introduced.
transmission of data. Next, the LDACS medium access layer is
introduced:
LDACS medium access is always under the control of the ground-station LDACS medium access is always under the control of the ground station
of a radio cell. Any medium access for the transmission of user data of a radio cell. Any medium access for the transmission of user data
has to be requested with a resource request message stating the has to be requested with a resource request message stating the
requested amount of resources and class of service. The ground- requested amount of resources and class of service. The ground
station performs resource scheduling on the basis of these requests station performs resource scheduling on the basis of these requests
and grants resources with resource allocation messages. Resource and grants resources with resource allocation messages. Resource
request and allocation messages are exchanged over dedicated request and allocation messages are exchanged over dedicated
contention-free control channels. contention-free control channels.
LDACS has two mechanisms to request resources from the scheduler in LDACS has two mechanisms to request resources from the scheduler in
the ground-station. Resources can either be requested "on demand", the ground station. Resources can either be requested "on demand" or
or permanently allocated by a LDACS ground station, with a given permanently allocated by a LDACS ground station with a given class of
class of service. On the forward link, this is done locally in the service. On the forward link, this is done locally in the ground
ground-station, on the reverse link a dedicated contention-free station; on the reverse link, a dedicated contention-free control
control channel is used (Dedicated Control Channel (DCCH); roughly 83 channel is used (the Dedicated Control Channel (DCCH); roughly 83
bit every 60 ms). A resource allocation is always announced in the bits every 60 ms). A resource allocation is always announced in the
control channel of the forward link (Common Control Channel (CCCH); control channel of the forward link (Common Control Channel (CCCH);
variable sized). Due to the spacing of the reverse link control variable sized). Due to the spacing of the reverse link control
channels of every 60 ms, a medium access delay in the same order of channels of every 60 ms, a medium access delay in the same order of
magnitude is to be expected. magnitude is to be expected.
Resources can also be requested "permanently". The permanent Resources can also be requested "permanently". The permanent
resource request mechanism supports requesting recurring resources in resource request mechanism supports requesting recurring resources at
given time intervals. A permanent resource request has to be given time intervals. A permanent resource request has to be
canceled by the user (or by the ground-station, which is always in canceled by the user (or by the ground station, which is always in
control). User data transmissions over LDACS are therefore always control). User data transmissions over LDACS are therefore always
scheduled by the ground-station, while control data uses statically scheduled by the ground station, while control data uses statically
(i.e. at net entry) allocated recurring resources (DCCH and CCCH). (i.e., at net entry) allocated recurring resources (DCCH and CCCH).
The current specification documents specify no scheduling algorithm. The current specification documents specify no scheduling algorithm.
However performance evaluations so far have used strict priority However, performance evaluations so far have used strict priority
scheduling and round robin for equal priorities for simplicity. In scheduling and round robin for equal priorities for simplicity. In
the current prototype implementations LDACS classes of service are the current prototype implementations, LDACS classes of service are
thus realized as priorities of medium access and not as flows. Note thus realized as priorities of medium access and not as flows. Note
that this can starve out low priority flows. However, this is not that this can starve out low-priority flows. However, this is not
seen as a big problem since safety related message always go first in seen as a big problem since safety-related messages always go first
any case. Scheduling of reverse link resources is done in physical in any case. Scheduling of reverse link resources is done in
Protocol Data Units (PDU) of 112 bit (or larger if more aggressive physical Protocol Data Units (PDU) of 112 bits (or larger if more
coding and modulation is used). Scheduling on the forward link is aggressive coding and modulation is used). Scheduling on the forward
done Byte-wise since the forward link is transmitted continuously by link is done byte wise since the forward link is transmitted
the ground-station. continuously by the ground station.
In order to support diversity, LDACS supports handovers to other In order to support diversity, LDACS supports handovers to other
ground-stations on different channels. Handovers may be initiated by ground stations on different channels. Handovers may be initiated by
the aircraft (break-before-make) or by the ground-station (make- the aircraft (break before make) or by the ground station (make
before-break). Beyond this, FCI diversity shall be implemented by before break). Beyond this, FCI diversity shall be implemented by
the multi-link concept. the multi-link concept.
8. IANA Considerations 8. IANA Considerations
This specification does not require IANA action. This document has no IANA actions.
9. Security Considerations 9. Security Considerations
Most RAW technologies integrate some authentication or encryption Most RAW technologies integrate some authentication or encryption
mechanisms that were defined outside the IETF. The IETF mechanisms that are defined outside the IETF. The IETF
specifications referenced herein each provide their own Security specifications referenced herein each provide their own security
Considerations, and the lower layer technologies used provide their considerations, and the lower-layer technologies used provide their
own security at Layer-2. own security at Layer 2.
10. Contributors
This document aggregates articles from authors specialized in each
technologies. Beyond the main authors listed in the front page, the
following contributors proposed additional text and refinement that
improved the document.
Georgios Z. Papadopoulos: Contributed to the TSCH section.
Nils Maeurer: Contributed to the LDACS section.
Thomas Graeupl: Contributed to the LDACS section.
Torsten Dudda, Alexey Shapin, and Sara Sandberg: Contributed to the
5G section.
Rocco Di Taranto: Contributed to the Wi-Fi section
Rute Sofia: Contributed to the Introduction and Terminology sections
11. Acknowledgments
Many thanks to the participants of the RAW WG where a lot of the work 10. References
discussed here happened, and Malcolm Smith for his review of the
802.11 section. Special thanks for post directorate and IESG
reviewers, Roman Danyliw, Victoria Pritchard, Donald Eastlake,
Mohamed Boucadair, Jiankang Yao, Shivan Kaul Sahib, Mallory Knodel,
Ron Bonica, Ketan Talaulikar, Eric Vyncke, and Carlos Jesus Bernardos
Cano.
12. Normative References 10.1. Normative References
[RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T. [RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T.
Phinney, "Industrial Routing Requirements in Low-Power and Phinney, "Industrial Routing Requirements in Low-Power and
Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October
2009, <https://www.rfc-editor.org/info/rfc5673>. 2009, <https://www.rfc-editor.org/info/rfc5673>.
[RFC8557] Finn, N. and P. Thubert, "Deterministic Networking Problem [RFC8557] Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019, Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019,
<https://www.rfc-editor.org/info/rfc8557>. <https://www.rfc-editor.org/info/rfc8557>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655, "Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019, DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>. <https://www.rfc-editor.org/info/rfc8655>.
[I-D.ietf-raw-architecture] [RFC9912] Thubert, P., Ed., "Reliable and Available Wireless (RAW)
Thubert, P., "Reliable and Available Wireless Architecture", RFC 9912, DOI 10.17487/RFC9912, February
Architecture", Work in Progress, Internet-Draft, draft- 2026, <https://www.rfc-editor.org/info/rfc9912>.
ietf-raw-architecture-24, 28 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-raw-
architecture-24>.
13. Informative References 10.2. Informative References
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time- [RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)", Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021, RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>. <https://www.rfc-editor.org/info/rfc9030>.
[RFC8480] Wang, Q., Ed., Vilajosana, X., and T. Watteyne, "6TiSCH [RFC8480] Wang, Q., Ed., Vilajosana, X., and T. Watteyne, "6TiSCH
Operation Sublayer (6top) Protocol (6P)", RFC 8480, Operation Sublayer (6top) Protocol (6P)", RFC 8480,
DOI 10.17487/RFC8480, November 2018, DOI 10.17487/RFC8480, November 2018,
<https://www.rfc-editor.org/info/rfc8480>. <https://www.rfc-editor.org/info/rfc8480>.
skipping to change at page 58, line 5 skipping to change at line 2537
"Deterministic Networking (DetNet) Data Plane: IP over "Deterministic Networking (DetNet) Data Plane: IP over
IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9023, IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9023,
DOI 10.17487/RFC9023, June 2021, DOI 10.17487/RFC9023, June 2021,
<https://www.rfc-editor.org/info/rfc9023>. <https://www.rfc-editor.org/info/rfc9023>.
[RFC9262] Eckert, T., Ed., Menth, M., and G. Cauchie, "Tree [RFC9262] Eckert, T., Ed., Menth, M., and G. Cauchie, "Tree
Engineering for Bit Index Explicit Replication (BIER-TE)", Engineering for Bit Index Explicit Replication (BIER-TE)",
RFC 9262, DOI 10.17487/RFC9262, October 2022, RFC 9262, DOI 10.17487/RFC9262, October 2022,
<https://www.rfc-editor.org/info/rfc9262>. <https://www.rfc-editor.org/info/rfc9262>.
[I-D.ietf-roll-nsa-extension] [NSA-EXT] Koutsiamanis, R., Ed., Papadopoulos, G. Z., Montavont, N.,
Koutsiamanis, R., Papadopoulos, G. Z., Montavont, N., and and P. Thubert, "Common Ancestor Objective Function and
P. Thubert, "Common Ancestor Objective Function and Parent Parent Set DAG Metric Container Extension", Work in
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[I-D.ietf-roll-dao-projection] [RFC9914] Thubert, P., Ed., Jadhav, R.A., and M. Richardson, "Root-
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[I-D.ietf-6tisch-coap] [CoAP-6TiSCH]
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[IEEE Std 802.11] [IEEE802.11]
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[IEEE Std 802.11ay] [IEEE802.11ay]
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skipping to change at page 62, line 5 skipping to change at line 2777
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Acknowledgments
Many thanks to the participants of the RAW WG, where a lot of the
work discussed in this document happened, and to Malcolm Smith for
his review of the section on IEEE 802.11. Special thanks for post
directorate and IESG reviewers Roman Danyliw, Victoria Pritchard,
Donald Eastlake, Mohamed Boucadair, Jiankang Yao, Shivan Kaul Sahib,
Mallory Knodel, Ron Bonica, Ketan Talaulikar, Éric Vyncke, and Carlos
J. Bernardos.
Contributors
This document aggregates articles from authors specialized in each
technology. Beyond the main authors listed on the front page, the
following contributors proposed additional text and refinements that
improved the document.
* Georgios Z. Papadopoulos contributed to the TSCH section.
* Nils Maeurer and Thomas Graeupl contributed to the LDACS section.
* Torsten Dudda, Alexey Shapin, and Sara Sandberg contributed to the
5G section.
* Rocco Di Taranto contributed to the Wi-Fi section.
* Rute Sofia contributed to the Introduction and Terminology
sections.
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
06330 Roquefort-les-Pins 06330 Roquefort-les-Pins
France France
Email: pascal.thubert@gmail.com Email: pascal.thubert@gmail.com
Dave Cavalcanti Dave Cavalcanti
Intel Corporation Intel Corporation
2111 NE 25th Ave 2111 NE 25th Ave
Hillsboro, OR, 97124 Hillsboro, OR 97124
United States of America United States of America
Phone: 503 712 5566 Phone: 503 712 5566
Email: dave.cavalcanti@intel.com Email: dave.cavalcanti@intel.com
Xavier Vilajosana Xavier Vilajosana
Universitat Oberta de Catalunya Universitat Oberta de Catalunya
156 Rambla Poblenou 156 Rambla Poblenou
08018 Barcelona Catalonia 08018 Barcelona Catalonia
Spain Spain
Email: xvilajosana@uoc.edu Email: xvilajosana@uoc.edu
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