3GPP Rel-18: The Preliminary Discussions
Today we are going to take a look at some items being discussed within the 3GPP Rel-18 with the status as of today (i.e. May 2021). According to  the prioritization process on Rel-18 features should be completed by the end of 2021 – with the Rel-18 Package Approval scheduled for December 2021. As of now, the decisions are still focused on the Rel-17 schedule (the current deadline for the Rel-17 stage 3 freeze is March 2022). Meanwhile, some Rel-18 Stage 1 studies are underway, even though it’s still very early for this Release. In fact, 3GPP is planning for a Rel-18 workshop to gather inputs from companies for that release (this is touched upon later in the post). Nevertheless, as a “sneak-peek”, the currently discussed new items cover, among others, interesting topics, such as:
- 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.
In this post we’re providing the list of currently available features to be incorporated within Rel-18, the current set of specifications (Technical Specifications and Technical Reports) related to those and elaborate about the contents of the selected ones.
3GPP Rel-18 feature list
There are currently (as of April/May 2021) not many items being worked out in 3GPP for Rel-18. They are captured in  and include the following gathered in Table 1.
|Enhanced Access to and Support of Network Slice
|5G Timing Resiliency System
|Low Power High Accuracy Positioning for industrial IoT scenarios
|Subscriber-aware Northbound API access
|Support for Service Function Chaining
|Data Integrity in 5GS
|Study on Supporting of Railway Smart Station Services
|Study on Off-Network for Rail
|Study of Interconnection and Migration Aspects for Railways
|Study on FRMCS Evolution
|Study on Network Slice Capability Exposure for Application Layer Enablement
|Study on supporting tactile and multi-modality communication services
|Study on vehicle-mounted relays
|Study on 5G Networks Providing Access to Localized Services
|Study of Gateway UE function for Mission Critical Communication
|Study on 5G Smart Energy and Infrastructure
|Study on Enhancements for Residential 5G
|Study on Personal IoT Networks
|Study on evolution of IMS multimedia telephony service
|Study on sharing administrative configuration between interconnected MCX Service systems
|Study on traffic characteristics and performance requirements for AI/ML model transfer in 5GS
|Guidelines for Extra-territorial 5G Systems
3GPP Rel-18 features
Let me now touch upon 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 .
Study on Off-Network for Rail – Off-Network is a new terminology for the Rail sector describing the ability of a User Equipment to communicate directly with each other, independent of the network. The study item aims at studying new use cases for FRMCS (Future Railway Mobile Communications System) within the Off-Network concept, like communication applications (e.g. virtual coupling data communications), complementary services (e.g., QoS, priorities, security, unicast/broadcast/multicast, identification of UEs and location) and additional services, like communication range, potential spectrum. In addition to that this study shall perform gap analysis between potential new and current requirements including service specifications, requirements for 5GS (within Proximity Services) and performance requriements for railway Mobile Communication System (MCS).
Study on Supporting of Railway Smart Station Services – The railway smart station provides various operation and value add service (VAS) for passengers. It could be part of the Mission Critical Services, e.g., subway station evacuation guidance. They also can have more considering points on distinguishing users (e.g. passengers as customers), various devices (e.g. sensors, actuators, devices for passengers) and different environments (e.g. massive connections, limited power sources, external service interfaces). This work shall perform study of the use cases related to Railway Smart Station Services, e.g., station operation monitoring and control, passenger supporting services, business and performance applications. In addition to that the study shall perform gap analysis between requirements and functionality provided within 3GPP already in the previous studies.
Low Power High Accuracy Positioning for Industrial IoT Scenarios – Various utility sectors (e.g., power/chemical plant, mining, nuclear) have their operation environments known as Danger Zones, in which it is necessary for the IoT devices to perform very frequent positioning fix, in order to obtain the real-time location information, while in the same time the IoT devices supporting those shall be low power. This item aims at specifying requirements for such low power high accuracy positioning service for industrial IoT scenarios, in particular requirements for IoT devices as such, requirements related to low power accuracy positioning, etc.
Enhanced Access to and Support of Network Slice – aims at specifying normative requirements related to supporting UE’s access to an NW slice when different types of restrictions apply (restrictions related to frequency bands, radio resources, etc.) with minimized service interruption in a situation of NW slices change or resource allocation change; supporting additional service exposure for NW slices configuration/control by a 3rd party.
Ranging-based Services – Ranging performance requirements include distance accuracy, angular direction accuracy, maximum ranging distance, and ranging latency. This WI aims at deriving normative service requirements for ranging and shall cover: ranging operation among UEs, control of ranging functionality in the licensed spectrum by MNO, KPIs for ranging (e.g., the accuracy of distance and direction), and security aspects.
Study on supporting tactile and multi-modality communication services – is investigating new use cases and service requirements for 5G system to support tactile and multi-modality communication services. The investigation covers the following items: immersive real-time experience involving tactile and multi-modality user interactions (may include closed-loop feedback and control under various degrees of freedom); potential requirements of identified use cases including the coordinated parallel transmission of multi-modality representations (audio/video/haptic/ambient info, etc.) associated with the application, network reliability, and availability, charging, security, KPIs (data rate, latency, transfer interval, etc.); gap analysis between new and existing requirements and functionalities as per current 3GPP support.
5G Timing Resiliency System – aims to introduce additional 5G system requirements and KPIs for timing resiliency, which can enable use of: the 5G system in combination with other timing technologies as a resilient timing source for end-users in complement/back-up/alternate to GNSS; the 5G timing resiliency functionality if GNSS (or other timing sources) are compromised.
Study on Vehicle-Mounted Relays – is investigating use cases and new service requirements for 5G to support relays mounted on vehicles using NR self-backhauling feature to connect with donor gNB and 5GC covering: use case of a vehicle (BS) relays providing service to UEs inside the vehicle or close to the vehicle, a use case for end-to-end service continuity during mobility scenarios, and a use case related to provisioning, policies and control mechanisms (e.g., spectrum use or geographic area restrictions for relays, control of relay operation, UE access and connectivity via relays); aspects related to roaming, security, regulatory requirements, charging, interference with respect to relays scenario; and gap analysis of the identified requirements with respect to existing 5GS functionality and requirements.
Study on 5G Smart Energy and Infrastructure – is investigating use cases and new service requirements for 5G system to support smart grid covering: Smart Grid sevices (IEC standards, communication requriements like capacity, latency, availability, end-to-end QoS, resilience/redundancy and security); deployment requirements when considering constraints (e.g., service lifetime, coverage, electromagnetic applicability like penetration and ability to operate in high EM environments); operational requirements (e.g., ability to configure and monitor the real availability of virtual network topologies); Smart Grid use cases and function requirements (e.g., on-demand power supply, distributed power supply system, distribution automation, high accuracy power load measurement and control, meter automation); and KPI and service requirements for enabling micro-grids, distributed generation that require 5G wireless communications (like wind and solar energy generation, for scenarios of near-residential / near-consumer premises).
Study on Enhancements for Residential 5G – is investigating use cases and provide gap analysis with potential requirements definition for enhancements for Wireline-Wireless Convergence (e.g., identification and application of policy to devices not using 3GPP RAT via a residential gateway, QoS control down to devices and small indoor BS, coordination with Broad-Band Forum of management model and CPE specifications); enhancements for fixed LAN – 5G LAN integration (e.g., integration of 5G LAN with existing fixed broadband LAN within the home / fixed VPN); and enhancements for indoor small base stations (e.g. determination the applicability for use with indoor small base stations in 5G residential use cases of concepts like private slices, SNPN, CAG for private networks).
Study on Personal IoT Networks – is investigating new use cases and requirements to enhance 5GS to support Personal IoT (PIoT) networks. This includes the scenarios where PIoT is connected to 5GC with indirect network communication or macro-network connectivity. PIoT network is a set of Personal IoT devices communicating between themselves and with a UE (smartphone / CPE) using direct device connections. The objectives include the study of use cases like interactions between devices within PIoT network alone and together with devices in a cellular network, onboarding devices with operator managed credentials within the Personal IoT Network from a user/UE; requirements and KPIs to improve performance of short-range direct device connections; position requirements and KPIs (e.g. for 6 Degrees of Freedom). It also includes gap analysis between the identified requirements and KPIs and what is already defined within 3GPP.
Guidelines for Extra-territorial 5G Systems – aims at the identification of use cases for provisioning of extra-territoriality services with respect to 5G public network and addresses the following: HAPS covering multiple countries, satellite access covering international waters, aeronautical networks; identification of 3GPP features (like emergency calls, PWS, charging) and technical aspects (e.g., MCC/MNC, UE/NW location) for which extra-territoriality may be relevant / for which regulations may be applicable; guidelines on the fulfillment of regulatory requirements (e.g., routing to CN of the specific country). The document resulting from the study (i.e., TR 22.926) shall be useful as a basis for technical work in other 3GPP Working Groups (WG).
Study on traffic characteristics and performance requirements for AI/ML model transfer in 5GS – is studying 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.
3GPP Rel-18 Specifications
The current set of specifications and technical reports for Rel-18, where those items are to be captured are provided in the table below, as per  (most of them are in draft, thus not available for general public).
|Spec/Tech Report Number
|Service requirements for cyber-physical control applications in vertical domains
|Service requirements for the 5G system
|Study on enhanced access to and support of network slices
|Study on 5G Networks Providing Access to Localized Services
|Study on supporting tactile and multi-modality communication services
|Study on ranging-based services
|Study on enhancements for residential 5G
|Study on Personal Internet of Things (PIoT) networks
|Study on 5G smart energy and infrastructure
|Study on evolution of the IP Multimedia Subsystem (IMS) multimedia telephony service
|5G System (5GS); Study on traffic characteristics and performance requirements for AI/ML model transfer
|Study on 5G timing resiliency system
|Study on sharing administrative configuration information between interconnected Mission Critical (MCX) service systems
|Guidelines for extra-territorial 5G Systems (5GS)
|Study on off-network for rail
|Study of gateway User Equipment (UE) function for Mission Critical (MC) communications
|Study of interconnection and migration aspects for railways
|Study on traffic characteristics and performance requirements for AI/ML model transfer in 5G Systems (5GS)
„Rel-18 Workshop: 5G Advanced”
The current 3GPP plan [6, 7] assumes conducting the Rel-18 Workshop at the end of June 2021 being separately managed from the regular TSG RAN meeting. The 3GPP Rel-18 Workshop shall have similar goals as the one held back in 2015 for 5G, i.e. to discuss the further evolution based on the priorities, to make sure that the work responds to the commercial needs. The Workshop aims to invite people from the industry to share ideas and involve in the standardization process.
As per [6, 7] the preliminary workshop’s submissions could cover the three key proposal types, namely:
- eMBB-driven functional evolution
- non-eMBB-driven functional evolution
- cross-functionalities for both eMBB and non-eMBB evolution
The potential title of the workshop as per  is „Rel-18: 5G Advanced” and is to be held between 28.06 and 02.07, where potential contributions could be captured within 10-15 min presentations subject to be selected for endorsements after the workshop. After the workshop within the September 2021 timeframe, the proposals shall be consolidated and the Rel-18 package approval shall be made within December 2021 timeframe.
As of now (per [6, 7]), the Rel-18 is expected to be balanced (considering eMBB evolution, non-eMBB evolution and cross-functional evolution), capture both immediate (short term) commercial needs and long term commercial needs, and rooted to true commercial requirements.
At the current stage of 3GPP Rel-18, we only can see some „foggy paths” where things are going. The general direction is towards the vertical sectors. There are interesting topics to be potentially addressed by that release, including applications of 5G to smart grid, personal IoT, railways, high accuracy positioning, timing resiliency, tactile communications, vehicle-mounted relays, and extra-territorial systems. Another area deals with the optimization of the 5G system in general, and by this I mean, features like AI/ML models usage and incorporation into the 5G framework, enhancements and optimizations related to network slicing, data integrity, and service function chaining within 5G. According to the latest status information from 3GPP [6, 7], more concrete items to be covered, and prioritization work is scheduled for the December of 2021. I’m going to touch upon those when the detailed plan for Rel-18 will be available.
If you are interested in the 3GPP Rel-17 items, check out my previous blog post on this topic: 3GPP Rel-17: Way forward within 5G standardization.
 „New 3GPP RAN Chair in conversation”, ETSI Webinar, 05.05.2021, available at: ETSI – Webinar standardization – Webinar Organized by ETSI
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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.