LTE: What capabilities UE should support in order to receive SRVCC or CSFB based voice call ?

Question

Suppose MME is getting CS call notification for MSC then How MME will notify to UE when
1. UE is idle mode. ?
2. UE is in connected mode?

Answer 1

Device should support both legacy networks ( 3G/2G) and LTE ( VoLTE) for SRVCC or CSFB. That means while initial attach device would have requested with attach type2 which means both Combined/IMSI attach.