6.2.1B PS Handover procedures for (v)SRVCC

23.2163GPPRelease 16Single Radio Voice Call Continuity (SRVCC)Stage 2TS

Intra-E-UTRAN S1-based handover and E-UTRAN to UTRAN (HSPA) Iu mode Inter RAT handover procedures for 3GPP SRVCC UE are performed as defined in TS 23.401 [2] with the following additions:

– MS Classmark 2, MS Classmark 3, STN-SR, C‑MSISDN, ICS Indicator and the Supported Codec IE shall be sent from the source MME to the target MME/SGSN if available.

– The target MME includes a "SRVCC operation possible" indication in the S1-AP Handover Request message, meaning that both UE and the target MME are SRVCC-capable and that STN-SR and C-MSISDN are included in the subscription data.

– The target SGSN includes a "SRVCC operation possible" indication in the RANAP Common ID message, meaning that both UE and the target SGSN are SRVCC-capable and that STN-SR and C-MSISDN are included in the subscription data.

For X2-based handover, the source eNodeB includes a "SRVCC operation possible" indication in the X2-AP Handover Request message to the target eNodeB as specified in TS 36.423 [36].

When the MME determines that "SRVCC operation possible" to eNodeB needs to be updated, e.g. when the UE updates its SRVCC capability indication when in connected mode, the MME shall immediately provide the updated "SRVCC operation possible" value in use to eNodeB by modifying an existing UE context. The S1 messages that transfer the "SRVCC operation possible" to the eNodeB are specified in TS 36.413 [30].