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Photo of a 3GPP meeting room with people sitting at tables and working on computers, overlaid with gear icons and wireless network terminology: RAN, 5G, V2X, Core, MCdata.

3GPP Declares Release 17 Stage 2 Architecture Standards Frozen

August 12, 2021

This blog is a repost from MissionCritical Communications, originally published on July 19, 2021.

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 the second quarter of 2021. The FirstNet Authority represented public safety interests at the plenary meetings.

The second quarterly Third Generational Partnership Project (3GPP) Plenary e-meetings of 2021 recently concluded. The group focused on the completion of Release 17 (R17) stage 2 (architecture) work and preparation for prioritization of features for R18. The group declared the stage 2 work frozen, while allowing some work items to continue into the third quarter of 2021. At this time, the R17 stage 3 (protocol) freeze date remains on schedule for March 2022.

The group decided that, given the current conditions, 3GPP will continue to use e-meetings through the fourth quarter of 2021, with a slight chance that plenary meetings in December will be face to face. The group will address the decision in September when to restart face-to-face meetings.

The following technical specification group (TSG) reports provide details on each of the plenary meetings with a focus on the progress on features important to public safety. As in past plenary meetings, representatives from nearly all major mobile equipment vendors, chip manufacturers, software vendors, and network operators from about 35 countries participated, as well as the First Responder Network Authority (FirstNet Authority) and other foreign government agencies representing public safety interests.

The Ran Plenary

There were more than 900 registrants for the TSG Radio Access Network (RAN) plenary meeting. TSG RAN is responsible for defining the functions, requirements and interfaces of the 3GPP radio network. At this meeting, the group confirmed that no timeline change will be considered for R17 completion and the start of RAN's approval of feature content for R18.

RAN approved a new work item to provide non-terrestrial network (NTN, i.e., satellite) narrowband internet of things (NB-IoT) and enhanced machine type communication (eMTC) coverage as a complement to terrestrial deployments. IoT operation is critical in remote areas with low/no cellular connectivity for public safety and many different industries, including transportation and logistics (maritime, road, rail, air), solar, oil and gas harvesting, utilities, farming, environment monitoring, and mining.

RAN agreed to extend the user plane integrity protection (UPIP) support to additionally secure data transferred over the Uu interface (air interface between a mobile and base station) for user equipment (UE), such as mobile devices, connected to the 4G evolved packet core (EPC) via either the 4G LTE or 5G new radio (NR) radio interfaces. This will provide enhanced user plane data security.

A new work item, “Further enhancements on MIMO for NR”, was approved for support of enhancements to multibeam operation. This work item will identify and specify features to facilitate more efficient (lower latency and overhead) downlink and uplink beam management for intra-cell and inter-cell scenarios to support higher UE mobility speeds. Another work item, “Extending current NR operation to 71 GHz,” was endorsed for supporting NR above 52.6 GHz for both licensed and unlicensed operation.

Finally, RAN endorsed a portion of the Ka Band (17.2 – 20.2 GHz and 27.5 – 30 GHz) as the candidate band for satellite-based NR in bands above 10 GHz, given that there is a priority in making the Ka band common across all global regions.

The SA Plenary

There were more than 330 registrants in the TSG Service and Systems Aspect (SA) Plenary meeting, which is responsible for the overall architecture and service capabilities of 3GPP-based systems. The group continued its primary focus of progressing R17 architecture specifications and R18 requirements. In the SA1 working group, a study on sharing of mission-critical (MC) administration configuration between interconnected MC systems was completed. The results of the study will now be consolidated into new requirements in the MC standards. The ability to share MC administration configuration information between MC systems can greatly reduce overhead and support mutual aid scenarios. Other studies that are nearing completion include off-network operation for railways, vehicle mounted relays, ranging-based services and tactile communication services. The current work in SA1 is all targeted toward R18.

The SA2 working group declared that all technical reports for R17 of interest to public safety have reached at least 100% completion and related SA2 technical specifications have reached at least 75% completion. This progress in the SA2 architecture technical specification will allow the Core Network and Terminals (CT) working groups to progress their stage-3 work in their upcoming meetings. SA2 declared the technical report for 5G Proximity Services (5G ProSe) at 100% completion and has progressed the related technical specification to 85% completion. It was agreed that the scope of 5G ProSe in R17 will include direct UE-to-UE communication as well as UE-to-network relay. 5G ProSe UE-to-UE relay will be considered for R18 scope, and there is significant discussion to expand the scope to include multiple-hop relays to further extend off-network coverage which is important to public safety.

Following the completion of the technical studies for 5G multicast broadcast services (5MBS) as reported previously, the technical specification for 5MBS architecture has reached 85% completion. The 5MBS feature will provide the ability for multiple UEs to receive the same transmission, thus saving bandwidth. The progress of both 5G ProSe and 5MBS in R17 is key to enable the SA6 working group to complete its phase two technical specifications work on mission-critical (MC) services over 5G to support these features.

Normative work is continuing in the SA3 working group on mission-critical security enhancements phase 2 with the goal to improve security for MC media content storage and for the 5G ProSe and 5MBS features. This work introduces appropriate changes to maintain the MC security architecture alignment with architecture features being defined in SA6. Progress is being made studying security issues and potential solutions for the security aspects of the enhancements to 5G ProSe. Conclusions on this topic are being drawn, and the study phase is expected to be complete by December 2021. Security solutions will be required when 5G ProSe normative work completes in other groups. These solutions will address security issues that those groups have highlighted. One specific area is security features for the sidelink relay architecture. Other ongoing normative work in SA3 is focused on various 5G system security enhancements for R17, including 256-bit encryption algorithm specification.

In the SA6 working group, the first phase of architecture work for MC services over 5G was completed. This phase supports on-network, unicast operation. Work continues on a study of the off-network and multicast aspects while 5G MC enablers, such as sidelink and the 5MBS feature, are still under development in other working groups. The plan is to complete work on the subsequent phases of MC services over 5G in R18. Also, stage 2 R17 architectural enhancements for mission-critical push-to-talk (MCPTT) were completed with a focus on location services. Continued enhancements of mission-critical data (MCData) services were also completed.

In related work, the Alliance for Telecommunications Industry Solutions (ATIS) Joint LMR LTE (JLMRLTE) working group continues development of an architecture study on interworking between 3GPP mission-critical services and legacy land mobile radio (LMR) services such as Project 25 (P25) LMR systems. The work in the JLMRLTE working group is organized in phases with the current fourth phase focused on completing interworking with LMR conventional systems, including systems based on TIA-603 (analog FM). The most recent work has focused on interworking of analog LMR systems.

The CT Plenary

There were 202 registrants for the TSG Core Network and Terminals (CT) plenary meeting, which covers the protocol details that follow the requirements and architectural work performed in the SA TSG.

Of the four new work items for the CT1 working group, those of special interest to public safety are the work item on Mission Critical Services over 5GS (MCOver5GS) and the work item on Application Layer Support for Uncrewed Aerial Systems (UAS). Due to the relatively clean design of mission-critical services over 4G-LTE, the work for MCOver5GS is expected to be a simple, clean evolution. The work on UAS is important for the use of drones by public safety, especially in coordination with air traffic control authorities.

Work during the second quarter of 2021 on mission critical topics concentrated on bug fixes and smaller technical improvements. With the completion of stage 2 for R17 at this Plenary e meeting, work on the R17 mission critical features will intensify. Areas of interest include: improved location information for both on-network and off-network situations, improvements for use of multiple devices by one person (e.g., an officer logged into both a phone and a laptop), and improved distribution of files to group members, such as distribution of updated floor plans of a burning building to fire fighters on the scene.

Work continues for resolving issues identified by European Telecommunications Standards Institute (ETSI) Plugtest events. This work provides interoperability testing for 3GPP standardized MC services products. The FirstNet Authority continues to act as a focus for the reporting of issues found in ETSI Plugtest events and their resolution. Through the cooperation of several companies, only a few issues remain; however, another ETSI Plugtest event is taking place in parallel with the 3GPP Plenary e-meetings that could result in more identified issues.

Further information on the 3GPP’s work and organization can be found at:


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