The world’s biggest operator, China Mobile, Japanese market leader NTT Docomo and South Korea’s KT extended their collaboration to include the implementation of international LTE roaming services.

The extension of the relationship to January 2017 will allow the deployment of international LTE roaming to be accelerated in China, Japan and South Korea. This follows the launch of a data roaming service by KT, allowing subscribers to make use of Docomo’s LTE data services when in Japan. The operators originally joined forces in January 2011.

The collaboration has already driven the development of common specifications for international NFC roaming services, created a cross border scheme for Wi-Fi roaming services and provided Japanese mobile content for China Mobile’s Mobile Market portal and KT’s Olleh Market.

The three operators plan to work more closely in the future to develop a range of service areas for users as they move between their respective home markets.

KT’s fellow South Korean operator SK Telecom expanded its LTE roaming services in Japan in September, in cooperation with SoftBank. The company also successfully trialled interworking of 1.8GHz FDD-LTE and 2.6GHz TD-LTE networks with Mobily in Saudi Arabia.

Close collaboration between operators should help overcome the complexity that LTE roaming entails. According to GSMA Intelligence figures, there are currently 230 commercial LTE networks operating worldwide, running on 12 different FDD/TDD frequency bands.

Most deployments are in the 1.8 GHz, 2.6 GHz and digital dividend bands but the dominance of these existing LTE bands is likely to lessen in the medium- to long-term as more countries allocate 4G spectrum and additional bands are introduced.

The amount of LTE bands supported by individual handsets is another complicating factor.