8.16 MBMS Service Request Procedure

23.2463GPPArchitecture and functional descriptionMultimedia Broadcast/Multicast Service (MBMS)Release 17TS

For MBMS, when UTRAN wants to count the number of users that are interested in a specific MBMS service which are present in a cell, it will request a percentage of the interested UEs to transit to PMM-CONNECTED state. The MBMS Service Request procedure is used by a UE in the PMM‑IDLE state to move to the PMM-CONNECTED state. The MBMS Service Request procedure is also used by a UE in PMM IDLE or PMM-CONNECTED state to request to be maintained in PMM-CONNECTED state for the purpose of receiving data over an MBMS point-to-point radio bearer.

Figure 17: MBMS Service Request procedure

1) An RRC connection is established if it doesn’t already exist.

2) The UE sends a Service Request message to the SGSN if MBMS PTP reception shall be used or if otherwise required to do so by the RAN when MBMS reception shall be started. The Service Type shall indicate MBMS multicast service reception or MBMS broadcast service reception. The SGSN shall not release the Iu signalling connection until requested by the RAN.

3) The SGSN may perform the security functions.

4) The SGSN provides the RAN with the IMSI of the UE.

5) The SGSN provides the RAN with the MBMS UE context(s) (IP multicast address/APN, TMGI, MBMS_NSAPI) via MBMS UE Linking procedure, if the SGSN has active MBMS UE context(s) for the UE.

NOTE: Step 6 is independent of steps 4 to 5 and can occur before or simultaneously with any of these steps.

6) The RNC establishes the necessary radio resources for the transfer of MBMS data to the interested UEs.

7) When PTP transmission of a MBMS multicast or MBMS broadcast service is active for a UE then the RNC shall supervise the Iu signalling connection. When the RAN determines that it does not need to keep the UE in RRC-CONNECTED state anymore, it shall trigger a normal Iu release towards SGSN.