Until now, the way voice has worked on handsets with a 4G LTE air interface has been, well, interesting. That is to say, thus far all voice calls haven't been over 4G LTE but conventional circuit-switched (as opposed to packet-switched) 2G or 3G networks like CDMA2000 1x in 3GPP2 land, or WCDMA/GSM in 3GPP land. For example, on Verizon LTE the handset has a second radio always camping 1x for voice and SMS, and on AT&T LTE the handset falls back from LTE to WCDMA for the voice transaction. This is CSFB - Circuit-Switched FallBack. LTE deployments thus far have focused primarily on data connectivity for a variety of reasons, and further logistical hurdles like emergency call support has made VoLTE effectively only possible in 3GPP Release 9.
Following their first quarter earnings announcement (and quiet period), Qualcomm is lifting the veil on news of a successful SR-VCC (Single Radio Voice Call Continuity) call which took place December 23, 2011 on an Ericsson test network using a Snapdragon S4 MSM8960 SoC. This marked the first successful trial of a VoLTE call which originated in the VoIP/IMS packet-switched domain handing over to WCDMA's circuit-switched domain. While this news is effectively a technology demonstration on a test network, this is just one more sign that the dual baseband cellular architecture (and associated power draws) we've talked about already is on its way out this upcoming year. With the appropriate software updates to radio access hardware, sufficient carrier testing, and the appropriate baseband support, it's looking like 2012 might be the year we finally get handsets with VoLTE enabled out of the box.
The Ericsson device and a demonstration network will be on display at MWC 2012, and we're looking forward to seeing VoLTE in action.
Source: Qualcomm
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