Qualcomm and Ericsson revealed on Thursday that they have successfully passed a voice call from an LTE network to a 3G one, paving the way for mobile carriers to begin migrating their voice traffic onto all-IP 4G networks. That’s a big deal because the sooner carriers move their voice and SMS services to LTE, the sooner they can shut down their pokey 2G and 3G networks and establish a mobile broadband continuum across the airwaves.
First some acronyms: the technology Qualcomm and Ericsson successfully trialed is called SRVCC – single-radio voice call continuity – which is a critical step in migrating today’s old-fashioned circuit-switched voice networks to the IP world of VoLTE, or voice over LTE. Today’s LTE networks rely on a standard called CSFB (circuit-switched fallback) to handle voice calls, which is to say they don’t. AT&T LTE network uses CSFB in its phones to detect an incoming call and then shunts the radio down 2G or 3G mode, where Ma Bell’s reliable old voice switches can take over.
CDMA operators like Verizon Wireless don’t even use CSFB. Instead they maintain dual 2G and LTE connections, ensuring you can always receive a call or SMS, but playing havoc with your battery life.
SRVCC will allow operators that use CSFB to gradually introduce VoIP onto their LTE networks because they don’t need worry about what happens when customers leave 4G coverage. When the network decides to convert the call from IP to circuit, it simply switches radio modes, theoretically maintaining a seamless connection all the while.
Verizon won’t be able to take advantage of those capabilities, but it feels it won’t need to by the time it launches VoIP this year or next. It plans to have LTE coverage in so many places, its customers will never have to leave its 4G network unless they travel way out into the boondocks. If a customer does actually leave the LTE network while making a call, that call would drop, but Verizon CTO Tony Melone said that instance would be rare enough that the carrier simply isn’t going to worry about it. In fact, Verizon is so confident of its LTE network’s ubiquity, it plans to launch its first LTE-only phones in 2013, making 2G handover a moot point.
So when will we start seeing these new VoLTE services appear? Sooner than you might think, actually, but not from Verizon or AT&T. Small, feisty MetroPCS will likely be the first North American operator to migrate to VoIP, and with good reason. Its LTE network is limited in capacity compared to its larger competitors, and as soon as it can start handling calls on 4G it can start shutting down its CDMA networks, re-farming their spectrum for LTE. MetroPCS has already moved its SMS traffic to LTE, and CEO Roger Linquist has said it plans to launch VoLTE this quarter