3GPP Rel-17: Way forward within 5G standardization
As the first two releases covering the 5G system are completed (i.e. Release-15 and Rel-16), further features and enhancements are being covered within the ongoing 3GPP Rel-17. Currently, stage 2 of the process is taking place, which describes functions and procedures in a general manner, and performs logical analysis, message flows, and functional elements.
3GPP Rel-17 timeline update
As of now, the following timeline (agreed in March 2020) for 3GPP Rel-17 is still valid :
- Rel-17 Stage 3 (describing procedures, messages, and information elements (IE), defining hardware behavior to enable multi-vendor interoperability) freeze: September 2021
- Rel-17 ASN.1 and OpenAPI specification freeze: December 2021
However, according to the latest news from 3GPP, there’s a detailed review of Rel-17 work progress planned for December 2020 to determine potential schedule delay of the release completion .
EDIT: Update (14.12.2020): as per , the timeline has been delayed by half a year, with the following new dates: March 2022 for Stage 3 Protocol Freeze and June 2022 for Protocol Coding Freeze (ASN.1 and OpenAPI).
3GPP Rel-17 feature list
There are over 400 items being worked out in 3GPP for Rel-17 (see  for the full list). However, in the Figure below there is a list of Rel-17 headline features, prioritized during the December 2019 plenaries, which should be enough to have a feeling about what’s currently going on .
Selected features from 3GPP Rel-17
Let me now touch upon on some of those items with more details. The descriptions of the below Study and Work Items is based on SIDs and WIDs (Study / Work Item Description) from .
NR Sidelink enhancement – cover the following elements: resource allocation enhancements (resource allocation to reduce power consumption, enhancements for autonomous mode, for improved reliability and reduced latency); sidelink DRX for broadcast, groupcast and unicast; new sidelink frequency bands for single carrier operation; sidelink operation in determined geographic areas for a given frequency range.
Solutions for NR to support non-terrestrial networks (NTN) – aims to specify the enhancements identified for NR NTN, especially LEO (Low Earth Orbit) and GEO (Geostationary Orbits) including compatibility to support HAPS (high altitude platform station) and ATG (air to ground) scenarios. The detailed objectives include:
- At PHY layer – timing relationships, UL time/frequency synchronization, HARQ, PRACH design, feeder link switch, beam management and BWP (bandwidth parts) operation;
- At protocols side – MAC enhancements (i.e. Random Access, UL scheduling, DRX, Scheduling Request), as well as RLC and PDCP enhancements (i.e. status reporting, sequence numbering), CP procedures (idle and connected mode, service continuity and mobility);
- From the architectural point of view – NG-RAN architecture enhancements (i.e. support for feeder link switch, network identities, registration/paging, cell relation); and RF/Performance aspects – covering bands, RRM and RF requirements, UE timing and frequency accuracy compensation requirements.
Extending current NR operation to 71 GHz – considers both, licensed and unlicensed operation with the following items to be addressed within the higher frequency bands: new numerology/numerologies and its/their impact on BWP, beam switching, HARQ, etc.; support for up to 64 beams; channel access mechanisms including beam-based operation; channel access mechanisms to comply with unlicensed spectrum rules in this spectrum range; specification of new bands in the frequency range of 52.6 GHz to 71 GHz.
Enhancement of RAN Slicing for NR – is investigating enhancements of RAN support for network slicing including: enabling UE fast access to the cell supporting the intendent slice (e.g., slice-based cell reselection, slice-based RACH configuration for cell barring); service continuity support for intra-RAT handover service interruptions (e.g. target cell not supporting current UE slice requiring slice re-mapping, fallback and/or data forwarding procedures).
Enhancements of Self-Organizing Networks (SON) for 5G networks – aims at specifying use cases, requirements, management services and procedures for the following SON functions: coverage and capacity optimization (CCO), Load Balancing Optimization (LBO), NSI (network slice instance) resource allocation optimization, self-establishment of 3GPP network function (including Automated Software Management and Automatic Network Configuration Data Handling).
Management of non-public networks (NPN) and Enhanced support of Non-Public Networks – aims at: specification of deployment scenarios for NPN, like a) verticals independently manage NPN deployed by themselves, b) PLMN operator independently manages NPN providing services to verticals, c) PLMN operator manages NPN with exposure of management capabilities to verticals as customer of the NPN; specifying provisioning of Standalone NPN (SNPN) and Public-Network Integrated NPN (PNI-NPN) with isolation and SLA management, for local deployments of NPN in factories, enterprises and buildings to provide coverage within specified geographical area; study enhancements to enable support for SNPN with subscription / credentials owned by an entity separate from the SNPN; studying UE onboarding and provisioning for NPNs.
Enhancement of Network Slicing Phase 2 – is investigating gaps in the current 5G System (5GS) procedures to support Generic Slice Template (GST) as per GSMA definition and studying solutions to cover the gaps including parameters like: maximum number of UEs per NW slice, maximum number of PDU sessions per NW slice, maximum DL and UL data rates per UE within a NW slice. This should bring slicing to a common understanding and practical realization of it.
Supporting Unmanned Aerial Systems (UAS) Connectivity, Identification, and Tracking – studies the architecture and system aspects to support UAS command-and-control functions, e.g. UAV Controller and UAV identification and tracking; authorization and authentication within communication scenarios (like UAV Controller to UAV, UAV to UAV, UAV to UAV Controller); potential connectivity enhancements needs for traffic exchange between UAV Controller and UAV, considering both LOS and NLOS connectivity.
Enhancement of support for Edge Computing in 5GC – is studying the enhancements for edge computing support including investigation of the key issues and solutions to support forwarding UE application traffic to applications/contents deployed in the Edge, like: discovery of IP address of application server deployed in edge computing environment; improvements to 5GC support for seamless change of application server serving UE; efficient (i.e. low delay) provisioning of local applications with information on e.g. QoS; impacts on charging and policy control. This will be studied taking solutions from Rel-15 and Rel-16 as baseline.
Taking a look at the above, we may see that part of 3GPP Rel-17 is a “clean-up” of the basic 5G from Rel-15 and Rel-16. That includes both, gaps and enhancements to the already defined features (like slicing, sidelink). On the other end, there are new features to allow introducing new services like UAS or operation in the higher spectrum bands. Having a strong background and cleaned up basic system features from Rel-15/16, it’s now time to put emphasis on the certain verticals and provide tailored solutions taking a subset of the functionality to realize the particular need, like by addressing Non-Public Networks (NPN) topic. The most interesting items from the above discussion for me, in terms of practical application, is the topic of NPN, as in my opinion this is the way forward in which 5G could bring the actual benefit to the ecosystem (BTW – there will be a separate post about this soon, but an overview of Private Mobile Networks is provided here). From the technical standpoint and technical challenges, the interesting ones include slicing in the RAN and higher frequency applications. I’m also interested to get your opinion, what you think are the most interesting features discussed currently within 3GPP and why?
…and a word about 3GPP Rel-18
It’s still very early for this one, but stay tuned for the Rel-18 update, which I’m going to address in a separate post in the coming months. However, as a “sneak-peek”, the currently discussed new items cover, e.g. :
- Study on Personal IoT Networks;
- Study on traffic characteristics and performance requirements for AI/ML model transfer in 5GS;
- Guidelines for Extra-territorial 5G Systems;
- Study on Ranging-based Services;
- Study on vehicle-mounted relays;
- Study on 5G Smart Energy and Infrastructure.
Definitely, an interesting set.
Just to mention one of them, namely the AI/ML model transfer within 5GS, it aims at studying the use cases and requirements for identifying traffic characteristics of AI/ML model distribution/transfer and training for various applications, like video/speech processing, automotive and other, as well as gap analysis on performance requirements for AI/ML model distribution and transfer (i.e. AI/ML model downloading/uploading): like data rate, latency, reliability, coverage&capacity.
EDIT: The preliminary discussions of Rel-18 are already provided in the following blog post: 3GPP Rel-18: The Preliminary Discussions
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Marcin Dryjanski received his Ph.D. (with distinction) from the Poznan University of Technology in September 2019. Over the past 12 years, Marcin served as an R&D engineer and consultant, technical trainer, technical leader, advisor, and board member. Marcin has been involved in 5G design since 2012 when he was a work-package leader in the FP7 5GNOW project. Since 2018, he is a Senior IEEE Member. He is a co-author of many articles on 5G and LTE-Advanced Pro and a co-author of the book „From LTE to LTE-Advanced Pro and 5G” (M. Rahnema, M. Dryjanski, Artech House 2017). From October 2014 to October 2017, he was an external advisor at Huawei Technologies Sweden AB, working on algorithms and architecture of the RAN network for LTE-Advanced Pro and 5G systems. Marcin is a co-founder of Grandmetric, where he served as a board member and wireless architect between 2015 and 2020. Currently, he serves as CEO and principal consultant at Rimedo Labs.