This blog is a repost from MissionCritical Communications, originally published on January 24, 2022.

This blog post is part of the "Tech Talk" series focused on the First Responder Network Authority’s (FirstNet Authority) standards development activities to support public safety. This post recaps discussions linked to public safety and other related topics from the 3GPP Plenary meetings that were conducted online in December 2021. The FirstNet Authority represented public safety interests at the plenary meetings.

Final scoping of the Release 18 (R18) feature content was the major topic of interest at last month’s quarterly 3GPP Plenary e-meeting. With the support of AT&T and multiple international public safety partners, the First Responder Network Authority (FirstNet Authority) worked to assure that the top features important to public safety will be part of R18. The agreed R18 schedule will result in a December 2023 completion target date.

The decision process for defining the scope of R18 included workshops in both the Radio Access Network (RAN) and the Service and System Aspects (SA) Technical Specification Groups (TSGs) leading up to final scoping of R18 content in the RAN and SA Plenary meetings. The RAN workshop concentrated on radio aspects, while the SA workshop focused on architectural aspects. The output of these two workshops fed into further discussion in the 3GPP Plenary meetings, including a joint meeting of all 3GPP TSGs to shape the final list of features. In parallel, work continues to wind down for Release 17 (R17) with the stage 3 freeze date remaining on schedule for March 2022.

The following TSG reports include details on each of the plenary TSG meetings with a focus on accepted R18 features important to public safety. Participation in 3GPP continues to include representatives from nearly all major mobile equipment vendors, chip manufacturers, software vendors and network operators from about 35 countries. The FirstNet Authority and government agencies of other nations continue to represent public safety interests.

RAN Plenary

There were 810 registrants for the TSG RAN December Plenary meeting. RAN is responsible for defining the requirements, functions and interfaces of the 3GPP radio network.

The major 5G features of interest to public safety that were endorsed for R18 include enhancements to positioning (location), 5G radio (a.k.a. New Radio (NR)) sidelink for the support of multi-carrier aggregation and sidelink operation on FirstNet Band 14, reduced capability (RedCap) user equipment (UE) for additional power savings, NR uplink coverage, and smart repeaters for coverage expansion. The non-terrestrial networks (NTN) (a.k.a. satellite access) evolution included in R18 supports enhancements for the use cases of voice and low-data rate services for commercial smartphones. This NTN feature can provide coverage enhancements for remote areas.

Other 5G features that were included as a part of R18 include enhancements to uncrewed aerial vehicles (UAVs) (a.k.a. drones) and 5G multicast-broadcast services (5MBS). Drones are seeing increased use in public safety by both fire and police. Multicast-broadcast services provide efficient use of available radio spectrum in congested scenarios. Given that R17 5MBS already provides the basic functions to support 5MBS services, the main goal for R18 is to enable better deployment of 5MBS, such as improvement of resource efficiency/capacity over R17 and enhancements for multicast. Vehicle mounted relay (VMR) is added for coverage extension.

Also included in R18 are 5G mechanisms to support single hop Layer 2 and Layer 3 off-network UE to UE relay (i.e., source UE to relay UE to destination UE). This will extend the range for off-network communications and can be extremely important to public-safety users in non-coverage scenarios. During the RAN plenary, the FirstNet Authority submitted a paper describing NR sidelink multihop relay requirements for public safety and expects multihop relay feature inclusion in Release 19 (R19).

The RAN Plenary also completed several R17 topics, which included a sidelink evolution work item relating to resource allocation to reduce the UE’s power consumption, enhancements to reliability and reduced latency, and discontinuous reception (DRX) for UE power savings for broadcast, groupcast and unicast.

SA Plenary

There were 440 registrants for the TSG SA December Plenary meeting, which is responsible for the overall architecture and service capabilities of 3GPP based systems.

The group spent the major portion of the meeting finalizing the R18 5G package feature set. Prior to this SA Plenary Meeting, SA hosted the SA-Rel-18 Prioritization Workshop, which began the discussion of R18 scope and the work prioritization process. The workshop focused on the 28 features that were submitted to SA2 for R18 by member companies. The primary issue was that the submitted work would not fit into the available R18 time budget for SA2 meetings. The prioritization process involved gathering input from 3GPP members on their top work items, including the FirstNet Authority’s input on top priority features.

As input to the SA Plenary, the FirstNet Authority also provided a multinational view of R18 high-priority features for public safety from among the SA2 proposed feature set. The FirstNet Authority identified high-priority features and defended the most important components of those features during determination of the final R18 feature package. These high-priority items include enhancements to 5G Proximity-based Services (5G ProSe) to support UE-to-UE relay for extending the range of off-network communications, 5MBS supporting clusters of high numbers of public-safety UEs, use of VMRs to extend coverage, location-based services and range-based services to improve situational awareness.

The SA1 working group announced that it completed the R18 stage 1 requirements. By leveraging 5G advancements such as latency and bandwidth, requirements for new features supporting tactile and multimodality communication services, personal internet of things (IoT), residential network services, mobile base station relays, and ranging-based services were defined. For public safety, R18 includes new requirements for sharing administrative configurations between interconnected mission-critical (MC) systems, enhanced railway features including off-network operation for railways, and the new ad hoc group communication (AHGC) feature. Discussion on proposals for R19 study and work items is now in progress with finalization of the list of R19 projects targeted for June 2022.

The SA2 working group had previously reported the completion of R17 architecture technical specifications with the exception of some open issues that needed input from RAN working groups and the SA3 security working group. At this SA Plenary meeting, SA2 declared the architectural technical specifications for R17 5G ProSe at 99% completion and R17 5MBS at 95% completion. As previously mentioned, the progress of both 5G ProSe and 5MBS in R17 is key to enable the SA6 working group to complete technical specifications work on MC services over 5G to support these features.

The SA3 working group reported to the SA Plenary that 11 R17 work areas are on target for completion as planned, and three work areas will take a bit longer: security aspects of enhancements for edge computing in 5G, UAS security aspects and 5G ProSe security aspects. This represents a significant amount of work on security aspects during the last quarter of 2021. In particular, normative work on security for non-3GPP access (e.g., Wi-Fi) jumped from 20% completion to 100%, increasing the security protections available for public-safety connections to the 3GPP 4G core via Wi-Fi.

Some SA3-specific security topics, for example, false base station protections that intend to advance the security capabilities of the 3GPP system continue to progress more slowly without impacting stage 3 work on building block topics. In addition, almost half of the work on security aspects of 5G ProSe was completed in this quarter with a target completion date of March 2022 for this important public-safety feature. Finally, phase two of the MC security enhancements in R17 achieved its completion target at this SA Plenary meeting.

The SA6 working group reported substantial progress on the architectural work for MC services over 5G. Phase 1 supporting unicast, on-network operation is complete, while a study that includes the phase 2 off-network and multicast aspects achieved 90% completion as details emerged in other working groups for the main 5G MC enablers: sidelink and 5MBS. The stage 2 work on MC services over 5G will be completed in R18.

A new SA6 study item for the AHGC feature will investigate architectural issues around the requirements specified by SA1 in their last meeting. AHGC allows authorized users to make a group call to a set of users based on implementation-specific criteria (e.g., proximity, selected from contacts) without first configuring the group in the group management server. Although initially discussed and excluded from the MC specifications, interest around the world has grown in the last few years to add this capability. The railway community in Europe is keen to investigate AHGC for use in its complex Railway Emergency Alert procedure.

Finally, another new study was approved in SA6 to investigate the requirements from SA1 for administration configuration between interconnected MC systems. The ability to share MC administration configuration information between MC systems can reduce overhead and support mutual-aid scenarios. SA6 is also progressing application-level architectures for non-MC services, and this work can potentially also be leveraged for MC services. Examples include application enablement architectures for edge computing, network slicing, messaging services and uncrewed aerial systems (UAS).

Core Network and Terminals (CT) Plenary

There were 175 registrants for the TSG CT December Plenary meeting, which covers the protocol details that follow the requirements and architectural work performed in the SA TSG.

Enhancements completed so far in R17 for mission-critical push to talk (MCPTT), mission-critical data (MCData), and mission-critical video (MCVideo) include preconfigured regrouping and improvements to message exchange, storage and retrieval. The R17 work plan on MCPTT was revised to match the level of stage 2 architectural work accomplished for R17. Significant progress on a cleanup of the MCVideo protocol has been achieved, going back to R14. The FirstNet Authority provided the changes needed to support the missing "regroup" feature commonly used in legacy LMR systems and already present in MCPTT standards.

Almost all features needed for interworking with LMR systems now exist in the 3GPP standards. Features still needing definition are enhancements to the interworking of MCPTT and MCData with LMR systems (MCCI-CT) to support regrouping. The 3GPP MCCI-CT work needs to wait on the corresponding standards work for P25 LMR systems that do not yet support regrouping across standard inter-system interfaces.

CT work on 5G ProSe was estimated at 65% completion. This work will support vehicle to anything (V2X), as well as direct mode connections for public safety. Work continues in other parts of 3GPP to enhance the radio sidelink to make this feature more usable in mission-critical situations.

Several European Telecommunications Standards Institute (ETSI) Plugtest issues have been resolved in the last quarter. The FirstNet Authority continues to act as a focal point for issues found in ETSI Plugtest events and their resolution. The FirstNet Authority also informally coordinates technical changes needed by the 3GPP RAN5 working group as they define the testing procedures for 3GPP mission-critical protocols.

Further information on the 3GPP’s work and organization can be found at www.3gpp.org.