Huawei last week announced it had assisted China Mobile in successfully demonstrating international HD voice and video calls between China Mobile VoLTE trial networks in Chengdu and Hangzhou and a South Korea LTE network.  Interconnection between LTE networks is the next checkmark in the wireless world's move to all IP networks.

In the demonstration, a Voice over LTE (VoLTE) call and several video calls were made between China Mobile's TD-LTE network and the unnamed South Korean FD-LTE network. Huawei provided a multimedia conferencing system in Chengdu to bridge the calls between three cities in two locations.

China Mobile expects to have VoLTE available for commercial use by the end of 2014.  The demonstration showed TD-LTE services can interoperate and roam across international boundaries to FD-LTE networks.  China Mobile is working to partner with a number of companies to continue to accelerate TD-LTE "internationalization."

Earlier this year, China Mobile and Huawei conducted the first TD-LTE based eSRVCC (enhanced Single Radio Voice Call Continuity) test and the first national TD-LTE VoLTE network on China Mobile's network. It should be no surprise that the two companies are working together on wireless solutions given Huawei's presence in Asia and China.

LTE roaming, especially on the data side, is one of the few areas where carriers can expect to make money. International rates continue to fall year after year, with carriers starting to offer various flat rate daily and monthly calling plans.  Roaming data plans billed by the packet or on a daily/weekly/monthly "pass" will add money to the bottom line

Interoperability on LTE networks is also necessary  for seamless, end-to-end HD voice calling.  Currently, carriers with larger HD voice deployments are starting to setup call exchanges between their subsidiaries, such as Orange's announced HD voice call exchange between Moldova and Romania.

Larger international carriers believe there's money to be made from IPX (IP eXchange) services, enabling mid-sized and smaller wireless carriers to exchange seamless HD voice and LTE data roaming.  BT International , iBasis, Telstra, and TeleSonera have all announced IPX services.  BT has been especially earnest in predicting HD voice transcoding will make it money and HD voice intercarrier calls will provide profits for both it and the participating carriers.

LTE, however, is the future.  As carriers turn up new LTE networks and shut down older 2G and 3G networks for spectrum re-farming, LTE interoperability isn't optional.  Expect to see more IPX interoperability announcements out of Europe and Asia in the months to come.