4.10 Single Radio Voice Call Continuity (SRVCC)

29.0103GPPInformation element mapping between Mobile Station - Base Station System (MS - BSS) and Base Station System - Mobile-services Switching Centre (BSS - MSC)Release 17Signalling Procedures and the Mobile Application Part (MAP)TS

4.10.1 General

The general principles of the SRVCC handover procedures are specified in 3GPP TS 23.009 [2]. This clause provides a detailed specification for the interworking performed by the MSC Server enhanced for SRVCC. It defines in particular the encoding of RANAP and BSSMAP cause values to avoid different encodings in different implementations.

4.10.2 SRVCC Handover from UTRAN (HSPA) to GERAN

Encoding of the cause code sent in BSSMAP Handover Request:

When it receives the SRVCC PS to CS Request message from the SGSN (see 3GPP TS 29.280 [25]), the MSC Server enhanced for SRVCC shall set the BSSMAP Cause to the value ‘Uplink quality’ in the Handover Request message.

4.10.3 SRVCC Handover from UTRAN (HSPA) to UTRAN

Encoding of the cause code sent in RANAP Relocation Request:

When it receives the SRVCC PS to CS Request message from the SGSN (see 3GPP TS 29.280 [25]), the MSC Server enhanced for SRVCC shall set the RANAP Cause to the value ‘Time critical Relocation ‘ in the Relocation Request message.

4.10.4 SRVCC Handover from E-UTRAN to GERAN

Encoding of the cause code sent in BSSMAP Handover Request:

When it receives the SRVCC PS to CS Request message from the MME (see 3GPP TS 29.280 [25]), the MSC Server enhanced for SRVCC shall set the BSSMAP Cause to the value ‘Uplink quality’ in the Handover Request message.

4.10.5 SRVCC Handover from E-UTRAN to UTRAN

Encoding of the cause code sent in RANAP Relocation Request:

When it receives the SRVCC PS to CS Request message from the MME (see 3GPP TS 29.280 [25]), the MSC Server enhanced for SRVCC shall set the RANAP Cause to the value ‘Time critical Relocation ‘ in the Relocation Request message.