New ITU-T Standards for IMT 2020 (5G) + 3GPP Core Network Systems Architecture

New ITU-T standards related to “5G”:

ITU-T has reached first-stage approval (‘consent’ level) of three new international standards defining the requirements for IMT-2020 (“5G”) network systems as they relate to network operation, softwarization and fixed-mobile convergence.

The standards were developed by ITU-T’s standardization expert group for future networks, ITU-T Study Group 13.

Note: The first-stage approvals come in parallel with ITU-T Study Group 13’s establishment of a new ITU Focus Group to study machine learning in 5G systems.

End-to-end flexibility will be one of the defining features of 5G networks. This flexibility will result in large part from the introduction of network softwarization, the ability to create highly specialized network slices using advanced Software-Defined Networking (SDN), Network Function Virtualization (NFV) and cloud computing capabilities.

The three new ITU-T standards are the following:

  • ITU Y.3101 “Requirements of the IMT-2020 network” describes the features of 5G networks necessary to ensure efficient 5G deployment and high network flexibility.
  • ITU Y.3150 “High-level technical characteristics of network softwarization for IMT-2020” describes the value of slicing in both horizontal and vertical, application-specific environments.
  • ITU Y.3130 “Requirements of IMT-2020 fixed-mobile convergence” calls for unified user identity, unified charging, service continuity, guaranteed support for high quality of service, control plane convergence and smart management of user data.

ITU’s work on “International Mobile Telecommunications for 2020 and beyond (IMT-2020)” defines the framework and overall objectives of the 5G standardization process as well as the roadmap to guide this process to its conclusion by 2020.

ITU’s Radiocommunication Sector (ITU-R) is coordinating the international standardization and identification of spectrum for 5G mobile development. ITU’s Telecommunications Standardization Sector (ITU-T) is playing a similar convening role for the technologies and architectures of the wireline elements of 5G systems.

ITU standardization work on the wireline elements of 5G systems continues to accelerate.

ITU-T Study Group 15 (Transport, access and home networks) is developing a technical report on 5G requirements associated with backbone optical transport networks. ITU-T Study Group 11 (Protocols and test specifications) is studying the 5G control plane, relevant protocols and related testing methodologies. ITU-T Study Group 5 (Environment and circular economy) has assigned priority to its emerging study of the environmental requirements of 5G systems.

ITU-T Study Group 13 (Future networks), ITU’s lead group for 5G wireline studies, continues to support the shift to software-driven network management and orchestration. The group is progressing draft 5G standards addressing subjects including network architectures, network capability exposure, network slicing, network orchestration, network management-control, and frameworks to ensure high quality of service.


The “5G” wireline standards developed by ITU-T Study Group 13 and approved in 2017 include:



“5G” Core Network functions & Services Based Architecture:

The primary focus of  ITU-R WP5D IMT 2020 standardization efforts are on the radio aspects (as per its charter).  That includes the Radio Access Network (RAN)/Radio Interface Technology (RIT), spectral efficiency, latency, frequencies, etc.

To actually deliver services over a 5G RAN, a system architecture and core network are required. The core network provides functions such as authentication, session management, mobility management, forwarding of user data, and (possibly) virtualization of network functions.

3GPP Technical Specification (TS) 23.501 — “System Architecture for the 5G System” — is more commonly referred to as the Service-Based Architecture (SBA) for the 5G Core network.  It uses service-based interfaces between control-plane functions, while user-plane functions connect over point-to-point links. This is shown in the figure below. The service-based interfaces will use HTTP 2.0 over TCP in the initial release, with QUIC transport being considered for later 3GPP releases.

Service-Based Architecture for 5G Core
Source: 3GPP TR 23.501, July 2017, Figure 4.2.3-1
Source: 3GPP TR 23.501, July 2017, Figure 4.2.3-1
Various aspects of this new core network design are described in a new Heavy Reading white paper — Service-Based Architecture for 5G Core Networks.

There are many aspects to this, but the white paper highlights:

  • How the idea of “network function services” (3GPP terminology) aligns with the micro-services based view of network service composition
  • How operators may take advantage of decoupled control- and user-plane to scale performance
  • How the design might enable operators to deploy 5GC functions at edge locations, such as central offices, stadiums or enterprise campuses

The first 5G core standards (really specifications because 3GPP is not a formal standards body) are scheduled to be included in 3GPP Release 15, which “freezes” in June next year and will be formally approved three months later. This will be a critical release for the industry that will set the development path of the 5G system architecture for years to come.

Download white paper:  Service-Based Architecture for 5G Core Networks

Editor’s Note:


“The 3GPP Technical Specifications and Technical Reports have, in themselves, no legal standing. They only become “official” (standards) when transposed into corresponding publications of the Partner Organizations (or the national / regional standards body acting as publisher for the Partner).”


5 thoughts on “New ITU-T Standards for IMT 2020 (5G) + 3GPP Core Network Systems Architecture

  1. What frequency bands are under study for the implementation of IMT2020 (5G)?
    The following frequency bands, which are already allocated for mobile communications, will be studied with a view to an IMT-2020 (5G) identification:
    • 24.25 – 27.5 GHz • 37 – 40.5 GHz
    • 42.5 – 43.5 GHz • 45.5 – 47 GHz
    • 47.2 – 50.2 GHz • 50.4 – 52.6 GHz
    • 66 – 76 GHz • 81 – 86 GHz
    The following bands will also be studied, although they do not currently have global mobile allocations:
    • 31.8 – 33.4 GHz
    • 40.5 – 42.5 GHz
    • 47 – 47.2 GHz
    The results of the studies will be submitted for decision to the next ITU World Radio Conference (WRC-19),
    to be held from 28 October to 22 November 2019 in Sharm el-Sheikh, Egypt.

  2. Requirements, evaluation criteria and submission templates for the development of IMT-2020

    Requirements related to technical performance for IMT-2020 radio interface(s)
    Report ITU-R M.2410 – This Report describes key requirements related to the minimum technical performance of IMT-2020 candidate radio interface technologies. It also provides the necessary background information about the individual requirements and the justification for the items and values chosen. Provision of such background information is needed for a broader understanding of the requirements. This Report is based on the ongoing development activities of external research and technology organizations.
    Requirements, evaluation criteria and submission templates for the development of IMT-2020

    Report ITU-R M.2411 – This Report deals with on the requirements, evaluation criteria and submission templates for the development of Recommendations and Reports on IMT-2020, such as the detailed specifications of IMT 2020. It provides the service, spectrum and technical performance requirements for candidate Radio Interface Technologies (RITs)/Set of Radio Interface Technologies (SRITs) for IMT 2020.

    Guidelines for evaluation of radio interface technologies for IMT-2020
    Report ITU-R M.2412 – This Report provides guidelines for the procedure, the methodology and the criteria (technical, spectrum and service) to be used in evaluating the candidate IMT-2020 radio interface technologies (RITs) or Set of RITs (SRITs) for a number of test environments. These test environments are chosen to simulate closely the more stringent radio operating environments. The evaluation procedure is designed in such a way that the overall performance of the candidate RITs/SRITs may be fairly and equally assessed on a technical basis. It ensures that the overall IMT 2020 objectives are met.

  3. Recommendation ITU-T Y.3101: Requirements of the IMT-2020 network

    Recommendation ITU-T Y.3101 describes requirements of the international mobile telecommunications 2020 (IMT-2020) network. Y.3101 first provides general principles of the IMT-2020 network, then specifies requirements for overall non-radio aspects of the IMT-2020 network from both the service and network operation points of view.

    The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision;
    users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
    [ITU-T Y.3110] Recommendation ITU-T Y.3110 (2017), IMT-2020 network management and orchestration requirements.
    [ITU-T Y.3130] Recommendation ITU-T Y.3130 (2018), Requirements of IMT-2020 fixed mobile convergence.
    [ITU-R M.2083-0] Recommendation ITU-R M.2083-0 (2015), IMT Vision – Framework and overall objectives of the future development of IMT for 2020 and beyond.
    Introduction to the IMT-2020 network:
    According to [ITU-R M.2083-0], IMT-2020 can be seen as “systems, system components, and related aspects that provide far more enhanced capabilities than those described in [b-ITU-R M.1645]”. Note that [b-ITU-R M.1645] defines the framework and overall objectives of the future development of IMT-2000, and systems beyond IMT-2000, for the radio access network.
    The IMT-2020 network will differentiate itself from fourth generation (4G) networks [b-ITU-R M.2012] for not only further evolution in terms of radio performance, but also greatly increased end-to-end (E2E) flexibility. This E2E flexibility will come in large part from the introduction of the network softwarization approach [b-ITU-T Y.3150] in IMT-2020 network components. Technologies such as software-defined networking (SDN) [b-ITU-T Y.3300], network functions virtualization (NFV) [b-ETSI NFV-WP1] [b-ETSI NFV-WP5G] and cloud computing [b-ITU-T Y.3501] will together allow unprecedented flexibility in the IMT-2020 network. Such flexibility will enable a lot of new capabilities in the IMT-2020 network, including network slicing [b-ITU-T Y-Sup.44].

    IMT-2020 is essentially not about an increase in bandwidth with respect to legacy IMT networks [b-ITU-R M.1457] [b-ITU-R M.2012], but rather about various fundamental strategic objectives in terms of deployment efficiency and flexibility, including:
    minimized dependency on access network technologies; coping with traffic explosion in
    urban areas;
    – easy incorporation of future emerging services;
    – provision of a cost-efficient infrastructure;
    – expansion of the geographic reach of the network.
    The services expected to be supported by the IMT-2020 network can be classified into three categories [ITU-R M.2083-0]: enhanced mobile broadband services; ultra-reliable and low-latency communication-based services; and massive machine type communication- (MTC-) based services.

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