In case of SRVCC, the home network application server viz., SCC-AS anchors the call.  This anchoring by home network tends to increase the handover delay in case a home subscriber roams to a distant network and latches on to a roaming partner.  The roaming network now awaits signalling from home network before the call can be handed from LTE to 2G/3G and this could result in handover delay exceeding minimum acceptable limits – causing degraded quality of experience for the end subscriber.

In order to avoid this problem, eSRVCC is proposed, wherein when a subscriber roams to a roaming partner network, the call is anchored at the roaming network itself by a new entity called ATCF/ATGW – which results in substantial reduction in delay.  Roaming partner’s ATCF/ATGW coordinates with the home network SCC-AS to complete necessary SIP updates without impacting handover time.

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