Content for  TS 29.468  Word version:  16.0.0

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1  ScopeWord‑p. 6
This document defines the protocol for the MB2 reference point between the Group Communication Service Application Server (GCS AS) and the Broadcast-Multicast Service Centre (BM-SC).
The MB2 reference point and related stage 2 procedures are defined in TS 23.468 as part of the Group Communication System Enablers for LTE. The stage 1 requirements for Group Communication System Enablers are specified in TS 22.468.

2  References

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TR 21.905: "Vocabulary for 3GPP Specifications".
TS 22.468: "Group Communication System(GCSE)".
TS 23.246: "Multimedia Broadcast/Multicast Service (MBMS); Architecture and functional description".
TS 23.468: "Group Communication System Enablers for LTE (GCSE_LTE); stage 2".
TS 26.346: "Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs".
TS 29.061: "Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN)".
TS 29.212: "Policy and Charging Control (PCC); Reference points".
TS 29.274: "3GPP Evolved Packet System (EPS); Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C); Stage 3".
TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)".
TS 33.246: "Security of Multimedia Broadcast/Multicast Service (MBMS)".
RFC 791:  "Transmission Control Protocol".
RFC 768:  "User Datagram Protocol".
RFC 2234:  "Augmented BNF for syntax specifications".
[14]  Void
RFC 4960:  "Stream Control Transmission Protocol".
RFC 5719:  "Updated IANA Considerations for Diameter Command Code Allocations".
RFC 5996:  "The Internet Key Exchange (IKE)".
RFC 3947:  "Negotiation of NAT-Traversal in the IKE".
RFC 3948:  "UDP Encapsulation of IPsec ESP Packets".
RFC 4303:  "IP Encapsulating Security Payload (ESP)".
RFC 6347:  "Datagram Transport Layer Security Version 1.2".#
TS 23.007: "Restoration procedures".
TS 29.229: "Cx and Dx interfaces based on the Diameter protocol".
TS 36.300: "E-UTRA and E-UTRAN overall description; Stage 2".
RFC 7944:  "Diameter Routing Message Priority".
RFC 8583:  "Diameter Load Information Conveyance".
RFC 6733:  "Diameter Base Protocol".
TS 23.285: "Architecture Enhancements for V2X services".
RFC 5795:  "The Robust Header Compression (ROHC) Framework".
RFC 3095,  "Robust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed"
RFC 6363:  "Forward Error Correction (FEC) Framework,".
[32]  Void.
TS 29.214: " Policy and Charging Control over Rx reference point".

3  Definitions, symbols and abbreviationsWord‑p. 8

3.1  Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply:
MBMS bearer:
The service provided by the EPS to deliver the same IP datagrams to multiple receivers in a designated location.

3.2  Abbreviations

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
Allocation and Retention Priority
Attribute-Value Pair
Broadcast-Multicast Service Centre
Diameter Routing Message Priority
Differentiated Services Code Point
Datagram Transport Layer Security
Encapsulating Security Payload
Forward Error Correction
Group Communication Service
Group Communication System Enablers
Group Communication Service Application Server
MBMS Gateway
Policy and Charging Rules Function
PDN Gateway
Robust Header Compression
Temporary Mobile Group Identity
User Datagram Protocol

4  Architectural Overview

4.1  Reference Model

Figure 4.1-1 shows a high level reference model of the architectural elements relevant to understand the MB2 reference point. More complete reference models for GCSE are contained in TS 23.468.
Reproduction of 3GPP TS 29.468, Figure 4.1-1: Reference Model
For the V2X Localized User Plane supported feature, the reference model in clause B.3 of TS 23.285 applies.

4.2  Functional ElementsWord‑p. 9

4.2.1  Group Communication Service Application Server (GCS AS)

The GCS AS is defined in TS 23.468 and supports the following functionality:
  • Exchanging GC1 signalling with the UE.
  • Receiving unicast uplink data from the UE via the SGi reference point.
  • Delivery of data to all the UEs belonging to a group using unicast delivery over the SGi reference point and/or MBMS delivery over the MB2 reference point.
  • Support for service continuity procedures for a UE to switch between unicast delivery and MBMS delivery.
  • For MBMS delivery:
    • MB2 C procedures defined in TS 23.468, for requesting the BM SC to activate, deactivate, modify an MBMS bearer, allocate/deallocate TMGI.
    • Forwarding of data to be delivered via an MBMS bearer to the BM SC via the MB2 U reference point.
In addition to the functions defined in TS 23.468, an GCS AS which acts as a V2X Application Server may support the following functions:
  • For the V2X Localized User Plane supported feature, MB2 C procedures defined in TS 23.285, subclause for requesting the BM-SC to activate an MBMS bearer for local MBMS based MBMS data delivery.

4.2.2  Broadcast-Multicast Service Centre (BM-SC)Word‑p. 10
The BM SC is defined in TS 23.246, with additions related to the MB2 reference point in TS 23.468, and supports the following functionality:
  • MBMS Broadcast Mode procedures defined in TS 23.246 (stage 2) and in TS 29.061 (stage 3).
  • MB2 C procedures defined in TS 23.468, for activating, deactivating, modifying an MBMS bearer, allocating/deallocating TMGI and notifying the TMGI expiry or the MBMS Bearer condition to GCS AS.
  • SGmb procedures for controlling MBMS broadcast bearers defined in TS 29.061.
  • Reception of user data from the GCS AS via the MB2 U reference point and forwarding those data via the SGi mb reference point as described in TS 29.061.
In addition to the functions defined in TS 23.468, the BM-SC may support the following functions for V2X services:
  • For the V2X Localized User Plane supported feature, MB2 C procedures defined in TS 23.285, subclause for receiving Local MBMS information defined in TS 23.285 from an GCS AS which acts as a V2X Application Server.

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