Special Articles on 3GPP Release 18 Standardization Activities (1)
5G-Advanced Standardization Trends

3GPP 5G-Advanced Release 18

Hiroki Harada, Satoshi Nagata and Kosuke Hirama
6G Network Innovation Department

Shinji Takeda
Device-Tech Development Department

Yuta Sagae
Radio Access Network Design Department

Abstract
Standardization of 3GPP Release 18 specifications was completed in June 2024. Since the standardization of Release 15 specifications in June 2018 as the initial version of 5G, 5G commercial services have been spreading throughout the world with 5G coming to be used in a variety of industrial fields. At 3GPP, improvements to various 5G technologies have been made into specifications after Release 15. Here, Release 18 and later specifications in which studies and specifications toward further advances in 5G have been progressing are defined as “5G-Advanced.” The studies and specifications for Release 19 and some discussions on 6G began in part in 2024. In this article, we describe standardization trends at 3GPP for both 5G-Advanced and 6G.

01. Introduction

  • Up to now, mobile communications technology has undergone ...

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    Up to now, mobile communications technology has undergone a major evolution as a new generation approximately every 10 years along with a growing demand for mobile communications and the birth of new communication services. Specifications for the 5th Generation mobile communications system (5G) were drafted as 3rd Generation Partnership Project (3GPP) Release 15 (Rel-15) in 2018. These 5G specifications achieved the three technical features of high data rate and high capacity, high reliability and low latency, and massive device connectivity by using even higher frequency bands compared with the past and by giving the system high flexibility enabling the application of a wide range of services. As a result, 5G commercial services have been expanding in countries throughout the world with the aim of providing new value and services as a social infrastructure. Since the standardization of Rel-15 as the initial specifications of 5G, 5G has continued to evolve in new releases as Rel-16 and Rel-17 through enhanced functions, new functions, etc.

    At 3GPP, which defines Rel-18 and later specifications as “5G-Advanced,” specifications are being drafted for new functions targeting commercial services in the latter half of the 2020s and studies are being conducted on functions for driving the medium- to long-term evolution of the mobile network. Specifications for Rel-18, which had been worked on since 2022, were completed in June 2024 as the initial specifications for 5G-Advanced, and work on drafting Rel-19 specifications began in 2024. In Rel-19, some studies with a view to 6G are beginning on, for example, a channel model*1 for 7-24 GHz frequencies included in the candidate frequency bands for the initial 6th Generation mobile communications system (6G) agreed upon at World Radiocommunication Conference 2023 (WRC-23)*2 and on radio sensing included in the International Telecommunication Union-Radiocommunication (ITU-R)*3 sector's International Mobile Telecommunications (IMT)-2030*4 Framework Recommendation*5. Discussions are also being held in relation to the 6G standardization schedule. The plan is to draft 3GPP Rel-21 as initial 6G specifications and to propose them for IMT-2030.

    In this article, we describe discussion trends and specification items of 3GPP Rel-18 and Rel-19 as 5G-Advanced standardization trends and discussion trends toward 6G standardization.

    1. Channel model: A model simulating the behavior of radio waves, used for evaluating the performance of wireless communications systems.
    2. WRC-23: A conference that revises ITU Radio Regulations that govern the international radio order including usage of various frequency bands, usage of satellite orbits, and regulations and technical standards related to the operation of radio stations. The administrations of various countries and concerned organizations such as operators registered with the ITU attend the WRC that is normally held every 3-4 years. The next gathering is scheduled for 2027.
    3. ITU-R: A sector within ITU—a specialized agency of the United Nations in the telecommunication field—that performs international management and coordination and makes recommendations on radio communications. This includes making revisions to ITU Radio Regulations and coordinating the use of frequency bands between countries.
    4. IMT-2030: An international mobile communications system standardized by ITU. Systems that have so far been standardized include IMT-2000 (3G), IMT-Advanced (4G/LTE), and IMT-2020 (5G). The plan is to complete the standardization of IMT-2030 by 2030.
    5. Framework Recommendation: The stipulation of an organizational structure, procedure, high-level viewpoints to consider, etc. for conducting a study.

    • 02. 5G-Advanced Standardization Trends

  • 2.1 Rel-18

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    At 3GPP, it was decided at Project Coordination Group (PCG)*6 meeting #46 held in April 2021 to define Rel-18 and later releases as 5G-Advanced, and it was announced at the Technical Specification Group Radio Access Network (TSG-RAN)*7 Rel-18 workshop held in June 2021 that the direction that should be taken by Rel-18 is one of balanced evolution from the viewpoints of mobile-broadband evolution and 5G expansion into various industries, technologies that meet short-term needs and technologies that meet medium- to long-term needs, and device and network evolution. A TSG-Service and System Aspects (TSG-SA)*8 Rel-18 workshop was also held in September 2021 and it was approved at TSG meeting #94 held in December 2021 that studies and standardization work would begin in 2022. The Rel-18 standardization schedule and all study/specification items are summarized in Ref. [1]. Overviews of individual standardized functions are given in other articles of this issue or will be given in the next issue [2]-[8].

    Positions and features of releases before Rel-18 and of Rel-18 and beyond are shown in Figure 1. Here, Rel-16 and Rel-17 can be positioned as updates of Rel-15, and among functions supported by LTE, specifications for those not supported in Rel-15 were drafted and more extensions and improvements were made to major functions envisioned from the start as 5G targets. On the other hand, in part of Rel-17 and in Rel-18 and beyond, specifications for new functions were drafted to further expand the application areas of 3GPP and studies and standardization of new functions were carried out with a view toward 6G.

    Figure 1 Positions and features of releases before Rel-18 and of Rel-18 and beyond

    2.2 Rel-19

    At 3GPP, a Rel-19 workshop was held in June 2023 and discussions were held over several meetings to narrow down study and specification items based on over 500 contributions submitted by various companies. Following these discussions, Rel-19 study and specification items were decided and work began. The Rel-19 standardization schedule is shown in Ref. [9].

    The Rel-19 specifications are considered to be a continuation of balanced evolution from the same viewpoints as those of Rel-18 described above as well as a step toward 6G. From among many study items and specification items, a number of distinctive items in Rel-19 are introduced below while considering the content of Rel-18.

    1) Application of AI/ML Technologies to the Radio Interface and RAN

    In Rel-18, studies were performed on the application of Artificial Intelligence and Machine Learning (AI/ML)*9 technologies to the radio interface based on medium- to long-term needs, and specifications were drafted for their application to a Radio Access Network (RAN)*10. Specifically, studies envisioning the feedback of channel state information, beam management, positioning, etc. were conducted throughout the Rel-18 period as use cases of using AI/ML technologies in exchanges between terminals and the network on the radio interface. Also in Rel-18, specifications were drafted for optimizing mobility, load balancing*11, and network power saving as use cases of using AI/ML technologies within a RAN.

    In Rel-19, it was agreed that the results of Rel-18 studies would be used as a basis for drafting specifications to achieve use cases for which the effects of introducing AI/ML technologies could be expected. Additionally, to enable the application of AI/ML technologies to new use cases, it was agreed that studies would be performed again on functions for which specifications had not yet been drafted in Rel-18 and that studies would be performed on new use cases [10]-[12].

    As common and necessary specifications regardless of use cases toward the application of AI/ML technologies in the radio interface, specifications will be drafted in Rel-19 for signaling*12 and protocols essential to the Life Cycle Management (LCM) of AI/ML models. These will include training when implementing AI/ML models on the network side or terminal side, the collection of training data, the design of input/output models, the monitoring of model performance, and the enabling, disabling, and switching of models. Furthermore, based on the results of studies in Rel-18, use cases targeted for the specifications in Rel-19 will include beam prediction in the spatial domain (for example, predicting the quality of unmeasured beams from the results of other measured beams), beam prediction in the temporal domain (for example, predicting the quality of beams whose timing has not been measured from the results of measured beams in other timing), and positioning by an AI/ML model and the generation of auxiliary information toward positioning. For each use case, the drafting of specifications for signaling and mechanisms, the stipulation of performance requirements, the definition of terminal capabilities, etc. will be performed in Rel-19.

    As for applying AI/ML technologies to RANs, studies will be performed in Rel-19 on feasibility, effects, impact of drafting specifications, etc. in relation to a variety of use cases such as the optimization of coverage*13 and capacity, optimization of network slicing*14, prediction of cell quality and prediction of handover*15 failure for mobility purposes, optimization of mobility for dual connectivity*16, and prediction of power consumption.

    2) Studies on New 3GPP-system Application Areas with a View toward 6G

    In Rel-18, studies were conducted on new technology areas based on medium- to long-term needs such as the application of AI/ML technologies to the radio interface as described above, duplex extension to the downlink/uplink, and ultra-low-power receivers for reducing terminal power consumption and wake-up signals for such receivers.

    In Rel-19, which has been positioned as a step toward 6G, a number of new studies will be carried out considering the situation with 6G candidate frequencies at WRC-23 [13] and the IMT-2030 Framework Recommendation at ITU-R [14]. Specifically, studies will be conducted on channel models in relation to 7-24 GHz frequencies, on channel models in relation to Integrated Sensing and Communication (ISAC)*17, and on ultra-low-power, ultra-simple low-end Internet of Things (IoT) devices for Ambient-IoT (A-IoT)*18 [15]-[17].

    • In regard to 7-24 GHz frequencies, these include 7.125-8.4 GHz frequencies and 14.8-15.35 GHz frequencies agreed upon at WRC-23 as agenda items for WRC-27. These frequencies are likely to be used in 6G, so studies will be conducted on the applicability of existing channel models created for 5G to 7-24 GHz frequencies and on the need for channel-model extensions.
    • As for ISAC, this is one of the six representative usage scenarios mentioned in the IMT-2030 Framework Recommendation. At 3GPP, studies will be conducted on channel models for achieving object detection and movement tracking and studies on other than channel models will also be carried out depending on subsequent progress and conditions.
    • As for A-IoT, studies will be conducted on use cases for recognizing and managing things achieved through current Radio Frequency IDentification (RFID)*19 technology and barcode readers and on ultra-low-power devices using backscatter communications*20 and energy harvesting*21.

    2.3 6G Standardization Schedule

    The overall schedule for IMT-2030 was agreed upon in June 2022 at ITU-R [18].

    Since the IMT-2030 and Rel-18/Rel-19 schedules came to be fixed, companies began submitting contributions on the overall 6G schedule at 3GPP from around 2023. Initial discussions on a 6G timeline were held at a TSG meeting in December 2023. In these discussions, the TSG chairs proposed several plans and milestones, and it was agreed that a 3GPP workshop on 6G would be held in March 2025, that studies on 6G would begin in Rel-20, and that proposals toward IMT-2030 and the drafting of initial 6G specifications would be conducted in Rel-21 [19].

    In addition, discussions on the 6G timeline were held again in March 2024. The start/completion period of studies on 6G in Rel-20 was established and it was agreed that 5G-Advanced Rel-20 specifications would be completed by June 2027 [20]. The outlook for the 6G standardization timeline as of March 2024 is shown in Figure 2. The main points of this timeline are summarized below.

    • Workshop on 6G use cases to be held in SA Working Group (WG) 1 (SA1) in May 2024 and 3GPP-wide workshop on 6G to be held in March 2025.
    • Studies on IMT-2030 requirements in ITU will be conducted from December 2024 to June 2025 at the TSG RAN Plenary (RANP) and coordination with requirements/performance discussions at ITU-R will be performed as needed.
    • High-level studies on 6G will be conducted at RANP up to June 2026 following the 3GPP workshop scheduled for March 2025.
    • The periods for 6G-related studies in various WGs in Rel-20 were established. SA1 studies will run from September 2024 to March 2026, SA WG2 (SA2) from June 2025 to December 2026 or March 2027, RAN WG1 (RAN1) from June 2025 to March 2027, RAN WG2/WG3/WG4 (RAN2/3/4) from September 2025 to June 2027, and TSG-Core Networks and Terminals (TSG-CT)*22 WG1/3/4/6 from March 2026, i.e., nine months after the beginning of SA2 studies.
    • The Rel-21 schedule is to be decided by June 2026, but the Rel-21 specifications completion period is set as March 2029 or later.
    • The plan is to draft specifications that satisfy IMT-2030 performance requirements in Rel-21 and to submit them as IMT-2030 proposals to ITU-R.
    Figure 2 Outlook for the 6G standardization timeline
    1. PCG: The highest decision-making body in 3GPP. It performs overall 3GPP activity planning, progress management, etc.
    2. TSG-RAN: A group in 3GPP in charge of drafting technical specifications, namely, radio interface specifications and radio-access-network interface specifications.
    3. TSG-SA: A group in 3GPP in charge of drafting technical specifications, namely, specifications related to service requirements, architecture, and security.
    4. AI/ML: Makes inferences using a model, or generates models for making inferences using ML.
    5. RAN: A network consisting of base stations that control the radio layer, etc., located between the core network and terminals.
    6. Load balancing: Distribution of traffic load between frequencies or between cells.
    7. Signaling: Control signals used for communications between terminals and base stations.
    8. Coverage: An area where radio waves can be transmitted and received in radio communications, by cellular phones etc.
    9. Network slicing: Technology for providing services according to their application by virtualizing the network and splitting network resources.
    10. Handover: A technology for switching base stations without interrupting a call in progress when a terminal straddles two base stations while moving.
    11. Dual connectivity: A technology that achieves wider bandwidths by connecting a terminal to two base stations and simultaneously performing transmission and reception with each base station.
    12. ISAC: The concept of integrating wireless data communications and sensing such as object detection to enable the provision of communication and sensing services through a mobile communications network.
    13. Ultra-low-power, ultra-simple low-end IoT devices for A-IoT: Devices that require minimal battery replacement and maintenance by combining energy harvesting (see *21) technology, energy storage technology, backscatter communications (see *20) technology, low-power signal generation/processing technology, etc.
    14. RFID: A scheme for wirelessly obtaining ID information embedded in small IC chips to identify and manage people and objects.
    15. Backscatter communications: A technology for performing communications by using the reflection and absorption of received radio waves and placing information on the reflected wave.
    16. Energy harvesting: Technology for collecting energy from the environment using at least one of various energy sources such as radio signals, light, vibration, and heat and converting the collected energy into power.
    17. TSG-CT: A group within 3GPP responsible for drafting technical specifications such as core network interface specifications, protocols, etc.

    • 03. Conclusion

  • This article described the positions and features of 3GPP ...

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    This article described the positions and features of 3GPP Rel-18 and the study items and specification items of Rel-19 as 5G-Advanced standardization trends as well as discussion trends in relation to the 6G standardization schedule. NTT DOCOMO will contribute to the standardization of 5G-Advanced at 3GPP and to the further development of mobile communications going forward.

  • REFERENCES

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    1. [1] 3GPP: “Release 18.”
      New windowhttps://www.3gpp.org/specifications-technologies/releases/release-18
    2. [2] S. Kumagai et al.: “5G-Advanced Radio Technologies in 3GPP Release 18,” NTT DOCOMO Technical Journal, Vol. 26, No. 2, Oct. 2024.
      https://www.docomo.ne.jp/english/corporate/technology/rd/technical_journal/bn/vol26_2/002.html
    3. [3] S. Yoshioka et al.: “Advanced Technologies for Industry Creation and Solution Co-creation in 3GPP Release 18,” NTT DOCOMO Technical Journal, Vol. 26, No. 2, Oct. 2024.
      https://www.docomo.ne.jp/english/corporate/technology/rd/technical_journal/bn/vol26_2/003.html
    4. [4] Y. Matsumura et al.: “Enhanced Mobile Broadband Technologies in 3GPP Release 18,” NTT DOCOMO Technical Journal, Vol. 26, No. 2, Oct. 2024.
      https://www.docomo.ne.jp/english/corporate/technology/rd/technical_journal/bn/vol26_2/004.html
    5. [5] D. Kurita et al.: “Advanced Technologies for Network Energy Saving, Load Balancing, and High Densification in 3GPP Release 18,” NTT DOCOMO Technical Journal, Vol. 26, No. 2, Oct. 2024.
      https://www.docomo.ne.jp/english/corporate/technology/rd/technical_journal/bn/vol26_2/005.html
    6. [6] J. Mutikainen et al.: “Overview of 5GC Advanced Technologies in 3GPP Release 18—System Architecture—,” NTT DOCOMO Technical Journal, Vol. 26, No. 3, Jan. 2025 (to appear).
    7. [7] S. Dojiri et al.: “Overview of 5GC Advanced Technologies in 3GPP Release 18—Core Network and Terminals—,” NTT DOCOMO Technical Journal, Vol. 26, No. 3, Jan. 2025 (to appear).
    8. [8] B. Bakhshi et al.: “Advanced Technologies for Network Automation and AI/ML in 3GPP Release 18,” NTT DOCOMO Technical Journal, Vol. 26, No. 3, Jan. 2025 (to appear).
    9. [9] 3GPP: “Release 19.”
      New windowhttps://www.3gpp.org/specifications-technologies/releases/release-19
    10. [10] 3GPP RP-234039: “New WID on Artificial Intelligence (AI)/Machine Learning (ML) for NR Air Interface,” Dec. 2023.
    11. [11] 3GPP RP-234054: “New SID: Study on enhancements for Artificial Intelligence (AI)/Machine Learning (ML) for NG-RAN,” Dec. 2023.
    12. [12] 3GPP RP-234055: “Study on AI (Artificial Intelligence)/ML (Machine Learning) for mobility in NR,” Dec. 2023.
    13. [13] Ministry of Internal Affairs and Communications (MIC), Telecommunications Bureau, International Frequency Policy Office: “Results of the 2023 World Radiocommunication Conference (WRC-23),” Jan. 2024.
      New windowhttps://www.soumu.go.jp/main_sosiki/joho_tsusin/eng/pressrelease/2023/12/27_7.html
    14. [14] ITU-R Recommendation M.2160-0: “Framework and overall objectives of the future development of IMT for 2030 and beyond,” Nov. 2023.
    15. [15] 3GPP RP-234018: “Study on Channel Modelling Enhancements for 7-24 GHz for NR,” Dec. 2023.
    16. [16] 3GPP RP-234069: “Study on channel modelling for Integrated sensing and communication (ISAC) for NR,” Dec. 2023.
    17. [17] 3GPP RP-234058: “Study on solutions for Ambient IoT (Internet of Things) in NR,” Dec. 2023.
    18. [18] ITU: “ITU-R timeline for IMT-2030.”
      New windowhttps://www.itu.int/dms_pub/itu-r/oth/0a/06/R0A060000C80001PDFE.pdf
    19. [19] 3GPP RP-232746: “High-level Considerations for 6G Timeline,” Dec. 2023.
    20. [20] 3GPP RP-240823: “Additional Considerations for 6G Timeline,” Mar. 2024.

VOL.26 NO.2

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