Telefónica’s German subsidiary has demonstrated the seamless transfer of telephone calls from an LTE network to a 3G mobile network, using technology called Single Radio Voice Call Continuity standard (SRVCC).
The breakthrough, the first time such a test been successfully performed by a network operator, was simulated in a laboratory environment.
While there has been recent progress with VoLTE technology, particularly in South Korea and the US, LTE networks are still unable to handover a VoLTE voice call to 2G or 3G when moving out of LTE coverage.
Instead, they fall back to a legacy 2G/3G network whenever voice calls are made or received out of the coverage.
However, the successful SRVCC test, which breaks the voice call into data bits before transmitting across the network, is a “significant landmark” according to Telefónica CTO Enrique Blanco.
The company used handsets and network components from at least six different manufacturers as part of the test.
“This is an important step in the evolution of voice support and will provide the many operators now running 3G networks with a simplified upgrade path to 4G,” Chris Nicoll, lead analyst, Wireless Networks at Analysys Mason told Mobile Europe.
“As much as we focus on data services, people not only want to make phone calls, they absolutely demand reliability for their voice service. Being able to offer SVCC means better battery life for devices, potentially less cost as well.”
Telefónica said future benefits as a result of this service could include HD video calls, chat applications and “other rich-media services”.
However, key challenges including device support and sufficient LTE network coverage still remain as operators roll-out of VoLTE services, said Nicoll.
“Network coverage is needed to keep from dropping back to 3G constantly. Devices need specific upgrades for VoLTE which are not just software downloads, and then the operator needs sufficient numbers of these devices in the network so that calls are VoLTE to VoLTE, and the network hardware support, gateways, signalling controllers, need to be proven,” he added.
According to Jeremy Green, principal analyst in Industy Communications and Broadband at Ovum, there is no advantage in being a first-mover in VoLTE.
“It’s a peculiar fix to put something in that really ought to have been in there in the first place, that they hadn’t thought about clearly,” he said.
“However, this will give other operators comfort that they won’t have to do anything wild and whacky to enable voice calls on LTE, which is the main purpose, as it allows customers to make telephone calls, essentially.”
Huawei and T-Mobile ran successful test calls demonstrating VoLTE call continuity using the Enhanced Single Radio Voice Call Continuity (eSRVCC) specification, which is an enhanced version of SRVCC in October 2012.
The test calls were carried out at T-Mobile Austria and and Huawei’s Innovation Center in Vienna, using test devices running Qualcomm’s Snapdragon S4 processor MSM8960 chipset.