South Korea’s largest mobile operator, SK Telecom, announced that it has successfully tested interoperability between a 5G Non Standalone (NSA) Core developed by Samsung Electronics and 5G base stations made by Nokia and Ericsson.

The test took place at the company’s 5G testbed located in its Bundang office building.

SK has been working closely with global mobile operators—including AT&T and Orange—to develop interfaces for interoperability between diverse multivendor 5G network equipment.

AT&T, which plans to launch its mobile 5G service in the next few weeks, revealed last month that it is using technology from Ericsson, Nokia and Samsung to build its nationwide 5G network. SK Telecom last month also announced that it’s using those same three vendors. Samsung is supplying the core, while Nokia and Ericsson are supplying the base stations for SK.

The 5G NSA Core used in SK’s interoperability trial was specially developed by SK Telecom and Samsung Electronics. Theoretically, the 5G NSA standard allows for operators to deploy 5G network by adding 5G features to the existing LTE core equipment. SK Telecom said it has decided to also deploy new 5G NSA Core to further enhance both the stability and quality of its 5G service.