A group of vendors is celebrating this week after demonstrating WiMAX interoperability at a WiMAX Forum public "plugfest" in Beijing, China.

Five vendors-Aperto Networks, Axxcelera Broadband Wireless, Redline Communications, Sequans Communications and Wavesat-were involved in the WiMAX interoperability demo using TDD-based base stations and customer premise equipment. The plugfest event provided equipment suppliers with the chance to test and inter-work their respective pre-certified products and equipment in advance of final certification.

For network operators, interoperability means they eventually can expect more options and lower costs, says Manish Gupta, vice president of marketing and alliances at Aperto. He and other vendors say the event, which included demonstrations of video and data, marks an important milestone for the WiMAX industry.

And while much has been made of WiMAX as a data-only technology, that's not so, Gupta says. In fact, "we believe that voice over IP is the killer app for WiMAX," he says.

Milpitas, Calif.-based Aperto targets service providers of all kinds, including mobile operators, fixed wireline, cable and wireless ISPs. With customers in 65 countries using its WiMAX-class, or pre-certified, equipment, the company also serves some non-traditional service providers, like the Netherlands' Enertel, which started in the cable and energy business in 1994 and now offers data, IP VNP, VoIP and other wireless and wired telecom services.

As for WiMAX's advantages in developing countries, the buildout cost savings vs. DSL may be obvious, but that's not the only desired place of deployment, Gupta points out. Urban areas in the United States, including New York City, are deploying Aperto's gear as well.

For now, the company is sticking with the fixed version of WiMAX. "Our view is the true mobility part of WiMAX is about two years away," Gupta says.

In August, Aperto shipped its WiMAX product portfolio to the Cetecom certification labs in Malaga, Spain, and it expects to have full certification in the next few weeks.