ZTE announced it is “helping” China Mobile deploy voice over LTE (VoLTE) services over the operator’s commercial TD-LTE in Guangzhou province as a precursor to wider nationwide rollout.

Based on a newly-built IMS platform, Chinese supplier ZTE is deploying an enhanced version of SRVCC (single radio voice call continuity), which allows LTE users to maintain voice calls when moving out of LTE coverage and onto 2G and 3G networks.

Enhanced SRVCC, or eSRVCC, reduces latency times when the switch between networks is made.

4G smartphones with Qualcomm’s Snapdragon 800 processors were recently used to demonstrate the system.

“The successful demonstration of the VoLTE service speeds up the development of the entire industry ecosystem,” said Sha Yuejia, vice president of China Mobile.

China Mobile added that the “successful VoLTE deployment” was completed using network systems and terminals from different vendors, therefore showing the feasibility of eSRVCC for all of China Mobile’s networks.

China Mobile, understandably, is also keen to champion VoLTE internetworking between TD-LTE and the more widely-deployed FDD version of the 4G technology.

Last November, Huawei said it had assisted China Mobile in a successful demonstration of international HD voice and video calls between VoLTE trial networks in Chengdu and Hangzhou, and the LTE FDD network of an unnamed South Korean operator.

Both Huawei and ZTE are well-placed to scoop up VoLTE contracts in in their domestic markets following the recent award of China’s first batch of 4G licences.

In July last year, Huawei claimed that in cooperation with China Mobile it conducted the world’s first TD-LTE based eSRVCC handover test.

ZTE, by contrast, claims it leads the industry globally in deploying VoLTE services on 4G TD-LTE networks.

The same month as Huawei was conducting eSRVCC handover on TD-LTE networks, ZTE said it was cooperating with Qualcomm to conduct a VoLTE test using commercial terminals in China Mobile’s lab.

In December 2013, ZTE completed calls over TD-LTE VoLTE between Guangzhou and Tianjin.

The same month, Hong Kong operator CSL “soft” launched VoLTE services on equipment provided by ZTE. CSL is expected to launch full commercial VoLTE services in the first half of 2014.

South Korea is the world’s most advanced VoLTE market with operators SKT, KT and LG Uplus each offering the service.

Last September, courtesy of Samsung’s SHANNON222 modem chipset (embedded in an LTE-Advanced variant of the Galaxy S4 now available in South Korea) the South Korean manufacturer said customers using the device (on SRVCC-enabled networks) will be the first in the world to take advantage of the call handover technology on a commercial basis.