8.37 MBMS Session Update

25.4133GPPRelease 17TSUTRAN Iu interface Radio Access Network Application Part (RANAP) signalling

8.37.1 General

The purpose of the MBMS Session Update procedure is to inform the RNC during a MBMS Session whenever the RA List of Idle Mode UEs changes compared to one previously sent. The MBMS Session Update procedure is triggered by the CN (PS domain).

The procedure uses connection oriented signalling.

8.37.2 Successful Operation

Figure 48: MBMS Session Update procedure. Successful operation.

The CN initiates the procedure by sending a MBMS SESSION UPDATE message.

The MBMS SESSION UPDATE message shall contain the Delta RA List of Idle Mode UEs IE and the Session Update ID IE.

Upon reception of the MBMS SESSION UPDATE message, if a MBMS RAB has already been established, the RNC shall initiate allocation of additional MBMS radio resources for this MBMS RAB if the RNC controls at least one cell that is part of both the MBMS Service Area and one of the RNC´s RAs indicated in the New RA List of Idle Mode UEs IE, if this IE is included in the Delta RA List of Idle Mode UEs IE group. The RNC may release the existing MBMS radio resources for the cells part of the RNC’s RAs indicated in the RA List with No Idle Mode UEs Any More IE, if this IE is included in the Delta RA List of Idle Mode UEs IE group.

Upon reception of the MBMS SESSION UPDATE message, if no MBMS RAB has yet been established, the RNC shall establish the MBMS RAB if the RNC controls at least one cell that is part of both the MBMS Service Area and one of the RNC´s RAs indicated in the New RA List of Idle Mode UEs IE, if this IE is included in the Delta RA List of Idle Mode UEs IE group. If the previous condition is not fulfilled, the RNC may decide to wait for either another update of the RA List of Idle Mode UEs or a UE linking to finally establish the MBMS RAB.

In case of successful MBMS RAB establishment, the RNC shall include the Transport Layer Address IE and the Iu Transport Association IE in the MBMS SESSION UPDATE RESPONSE message.

When the update of the RA List of Idle Mode UEs is successfully executed, the UTRAN shall report it to the CN in the MBMS SESSION UPDATE RESPONSE message, which shall include the same Session Update ID IE as received in the MBMS SESSION UPDATE message. The RNC may answer successfully even though MBMS resources have not been established in all relevant cells.

Transmission and reception of a MBMS SESSION UPDATE RESPONSE message terminate the procedure in the UTRAN and in the CN respectively.

8.37.3 Unsuccessful Operation

Figure 49: MBMS Session Update procedure. Unsuccessful operation.

If the RNC is not capable of correctly processing the request (e.g. additional MBMS resources could not be established at all in any cell), the CN shall be informed by the MBMS SESSION UDATE FAILURE message, which shall include the same Session Update ID IE as received in the MBMS SESSION UPDATE message.

Transmission and reception of a MBMS SESSION UPDATE FAILURE message terminate the procedure in the UTRAN and in the CN respectively.

8.37.4 Abnormal Conditions

Not applicable.