Single Radio Voice Call Connectivity (SR-VCC)

SR-VCC is a widely used buzz word which in simple terms means "Handover of PS domain Voice Call in LTE to CS Domain voice call in UMTS or GSM"

This procedure is initiated in source RAT LTE, where source RAT sends "Handover to UMTS' message to 3G RAT.

This HO message contains RB Information to Setup list containing the following:

• SRVCC - Info: This IE indicates to UE that the HO is basically SR-VCC i.e. its a PS to CS domain HO
• SRVCC Info contains an IE called 'NONCE' which is basically a bit string

Handover from PS Domain to CS domain (SR - VCC) brings slight complexity in security aspects.

When the domain is changed from PS to CS, so the security context of PS Domain in LTE needs to be mapped to security context of CS domain in 3G.

The concept of SR - VCC has been extended to the following:

1. Reverse SR - VCC: This is basically Handover of CS Domain Voice Call in 3G to PS Domain Voice call in LTE
2. Video SR - VCC: This is basically Handover of PS domain Video Call in LTE to CS Domain CS Data Call in UMTS.