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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  • apinkel - Thursday, February 2, 2012 - link

    I'm starting to hear more and more about carriers transitioning to VoLTE... which would seem to make a lot of sense for them as it reduces the amount of resources tied up in running a network that has to use multiple techonologies with each requiring it's own frequencies, handset radios, personnel requiring training in multiple technologies for support, etc..

    Which is all good. However I haven't yet heard what the benefits of VoLTE are for the average cellphone user. Possibly better voice quality or battery handset battery life due to the need to only have one radio in the device?
  • A5 - Thursday, February 2, 2012 - link

    It's just something that has to be done so that carriers don't have to maintain their 3G networks forever since all future network techs are going to be IP-only.

    Theoretically carriers could allocate more bandwidth to voice calls to increase call quality, but I imagine most carriers will keep call bandwidth low to increase range. It shouldn't have a significant effect on battery life.
  • metafor - Thursday, February 2, 2012 - link

    Yes. The additional benefit is that eventually, if GSM/CDMA networks are no longer needed, that spectrum could be used for IP-only data transmission instead.
  • apinkel - Thursday, February 2, 2012 - link

    That's my take on it as well.

    Just confirms that I might choose carrier A over carrier B due to their coverage, whether or not they offer 4G data, unlimited data, etc. but there's nothing about VoLTE that would draw me to a specific carrier.
  • dagamer34 - Thursday, February 2, 2012 - link

    HD voice codecs which lead to improved voice quality, even if the other side isn't capable of sending the same quality back.
  • DigitalFreak - Thursday, February 2, 2012 - link

    Considering how much trouble Verizon has been having with their LTE network being down, I don't think I'm ready to trust it with voice as well.
  • rocketbuddha - Thursday, February 2, 2012 - link

    So now will the "Unlimited" Talk and "Unlimited" text also go the way of "Unlimited" data? :D
  • SunLord - Thursday, February 2, 2012 - link

    If I'm not mistaken this is basically what Sprints Network Vision plans having them doing with their network once they convert to LTE on 1900Mhz and transition the CDMA network to 800MHz. After they transition to the 800MHz CDMA network they were planing to roll out LTE on part of it and deploying VoLTE using something like the above to allow VoLTE to CDMA transitions since CDMA signals cover a far larger area then any LTE signal can.
  • bnowrooz - Thursday, February 2, 2012 - link

    To me there is something that doesn't make sense about this specific test and I am guessing it's set up this way to be more favorable to Qualcomm. I put my full logic on my page... sonlte.com

    Seems like VZW and USCellular have taken the lead in VoLTE with Sprint publicly supporting yet we are reading a press release about a WCDMA/LTE SRVCC transition? Is ATT suddenly and/or silently pushing harder than everyone else??

    Just thinking out loud!

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