Enhanced eSRVCC Call Continuity

As the LTE Evolved Packet Core (EPC) continues to expand, voice deployments (VoLTE) appear more and more, with the Oracle SBC and P-CSCF playing key roles. 3GPP standards that define how LTE communications take place also continue to evolve, identifying and solving critical issues to increase effectiveness and efficiency. One such issue is session continuity, keeping session transfers between LTE and existing 2G and 3G networks as seamless as possible. Single Radio Voice Call Continuity (eSRVCC) offers one solution for the session continuity issue.

In its role as the P-CSCF and IMS-GW, the Oracle Communications Session Border Controller can provide eSRVCC by acting as signaling and media anchor points to handover calls to 3G networks smoothly. These anchoring points are called Access Transfer Control Function (ATCF) and the Access Transfer Gateway (ATGW), both of which are logical additions to the Oracle Communications Session Border Controller’s IMS support.

The behavior of these two anchoring points, ATCF and ATGW, is defined by 3GPP in Release 12 of Technical Specification TS 24.237. Oracle Communications developed these functional entities based on the initial version of TS 24.237 Release 10. To align with Release 12, Requirement 4944 introduces the following two new elements to the functional design: