8.30 RAB Modification Request

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

8.30.1 General

The purpose of the RAB Modification Request procedure is to allow the RNC to initiate renegotiation of RABs for a given UE after RAB establishment. The procedure uses connection oriented signalling.

8.30.2 Successful Operation

Figure 36: RAB Modification procedure.

The RNC initiates the procedure by generating a RAB MODIFY REQUEST message towards the CN and shall include a list of RABs To Be Modified IEs. For each RAB requested to be modified the RABs To Be Modified Item IE of the RAB MODIFY REQUEST message shall include the RAB ID IE, and the corresponding Requested RAB Parameter Values IE. The Requested RAB Parameter Values IE shall either list those RAB parameters the RNC would like modified and the associated new RAB parameter values it is requesting or shall indicate that the execution of the alternative RAB configuration is requested. For any given RAB, the RNC shall be able to propose modifications to any negotiable RAB parameters.

If the requested maximum bit rate (respectively the requested guaranteed bit rate when applicable) exceeds the maximum value of the Requested Maximum Bit Rate IE (respectively Requested Guaranteed Bit Rate IE), either the Extended Requested Maximum Bit Rate IE (respectively Extended Requested Guaranteed Bit Rate IE) shall be used or the Supported Requested Maximum Bit Rate IE (respectively Supported Requested Guaranteed Bit Rate IE) shall be used.

For a RAB if Extended Requested Maximum Bit Rate IE (respectively Extended Requested Guaranteed Bit Rate IE when applicable) is signalled in one direction RNC shall signal the Extended Requested Maximum Bit Rate IE (respectively Extended Requested Guaranteed Bit Rate IE) also in the other direction for this RAB. If Supported Requested Maximum Bit Rate IE (respectively Supported Requested Guaranteed Bit Rate IE) is used it shall be used in both directions.

If supported the RNC may include the Supported Requested Maximum Bit Rate IE (respectively Supported Requested Guaranteed Bit Rate IE) in Requested RAB Parameter Values IE to define the RAB parameters the RNC would like modified and the associated new RAB parameter values.

If the RNC is allowed to request an alternative RAB Configuration, the RNC may request the CN to trigger the execution of this alternative RAB configuration by including the Alternative RAB Configuration Request IE in the RAB MODIFY REQUEST message.

Upon reception of the RAB MODIFY REQUEST message, it is up to the CN to decide how to react to the request.

8.30.3 Abnormal Conditions

Not applicable.