China Mobile demonstrates world’s first LTE TDD to GSM eSRVCC

China Mobile successfully demonstrated the world’s first LTE TDD to GSM eSRVCC (enhanced Single Radio Voice Call Continuity) in a live network, in advance of the China Mobile Global Partner Conference 2013 held on December 18, 2013.

SRVCC is a technology which enables a seamless handover of voice over LTE (VoLTE) calls to 2G or 3G networks when the user moves out of LTE coverage. It is a milestone for China Mobile to demonstrate that seamless voice services can be delivered to consumers over the operator’s new LTE TDD network in co-existence with its large installed base GSM network. This paves the way for the future commercial deployment of VoLTE by China Mobile, and also underscores the maturity of the VoLTE solution for LTE TDD.

Demonstrations of the voice handover functionality from LTE TDD to GSM were tested in the Luogang district of Guangzhou in China Mobile’s present network environment with Ericsson’s end-to-end voice over LTE (VoLTE) network solution in conjunction with the conference.

In the demonstration, the testing devices in a moving vehicle showed seamless eSRVCC voice handover without any perceivable interruption. The eSRVCC technology applied in the demonstration is based on 3GPP R10 standard. Compared with SRVCC defined in 3GPP R8, when handover occurs during roaming, the newly added ATCF and ATGW functionality in R10 in the IMS domain can prevent the update of E2E signaling and bearer carrier, therefore avoiding call drops caused by long handover delay, which improves the user perception for cross-domain handover in spotty LTE coverage.

In the demonstration, Ericsson provided the end–to-end commercial equipment covering LTE TDD and GSM radio access with RBS 6000, Evolved Packet Core, a complete IP Multimedia Subsystem (IMS) with TAS (Telephony Application Server), CSCF (Call Session Call Function), SBC (Session Border Controller), MRS (Media Resource System), MGC (Media Gateway Controller), and the MSC with pooled MSC Servers, to successfully implement LTE to GSM voice handover.

Hand over delay in the live network environment was measured constantly below 200 ms, far less than the 300 ms for SRVCC defined in 3GPP. This provides excellent user experience with seamless voice over LTE to GSM voice handover.

In addition, in the demonstration Ericsson enabled the Fast Return function on the network side, which allows a quick and direct return from 2G to 4G network within one second after the completion of a call, and ensures advanced user experience. With Fast Return function, it is possible to avoid unreachable paging during inter-RAN cell re-selection when Circuit Switched Fallback (CSFB) and eSRVCC are deployed for improved user experience.

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