First LTE to WCDMA voice call handover completed by Qualcomm and Ericsson

For some time now, one of the biggest problems with LTE is the lack of support for traditional mobile phone services like voice calls, text messages, multimedia messages, and various other systems implemented on traditionally circuit-switched systems. Without a system to handle traditional phone services, LTE cannot replace current 2G and 3G networks.

Fortunately, a solution has been devised. VoLTE (voice over LTE) adds the necessary framework to support traditional phone services through the data network. However, there’s just one problem: There is no practical way to hand over calls from 3G to LTE and back. Until now. Last week, Qualcomm and Ericsson announced that they have successfully implemented and tested SRVCC (Single Radio Voice Call Continuity) for WCDMA and LTE. This means that any UMTS network (sorry, Veri on and Sprint) can now support voice calls from LTE and have them transfer over to WCDMA when the phone goes out of range of LTE. It also means that the phone can transfer the call back to LTE when the phone comes back in range.

Up until this point, there were two ways that voice calls were supported on LTE phones: active dual-mode operation and CSFB (circuit-switched fallback). CDMA2000 operators (Veri on, Sprint, MetroPCS, Cricket, and so on) traditionally use active dual-mode operation, but UMTS networks use CSFB instead. CSFB essentially kicks the phone off LTE when traditional phone services are being used and then flips back to LTE when the phone is done with them. It is not a very elegant solution, but it works well because UMTS 3G networks support both voice and data at once anyway.

Support for SRVCC for VoLTE will become available initially with LTE phones using the Snapdragon S4 MSM8960 multi-mode modem chip. LTE phones using the MSM8960 will likely arrive either at the end of the first half of this year or in the beginning of the second half of this year. I also expect other modem chip makers like ST-Ericsson and Motorola to offer it in the second half of this year as well.

This is a big step. With the successful usage of SRVCC, network operators that were hesitant to deploy LTE because of the lack of voice call handover will now be much more willing to deploy. Emerging markets, in particular, really need this technology. Now that it’s ready, we should see a huge surge in LTE deployments in Europe, Latin America, and Asia. Soon, the whole world will be connected through LTE.

First LTE to WCDMA voice call handover completed by Qualcomm and Ericsson