The Federal Communications Commission (FCC) is running tests in Seattle to determine the extent of spectrum interference between next-generation Wi-Fi systems and cellular phone networks.

The FCC is planning an auction of spectrum in the 2155MHz to 2180MHz band, but has made a provision that the winner sets up a free wireless broadband service.

Mobile phone companies contend that such a system would interfere with their own services and degrade the signals they send. 3G provider AT&T has also objected to WiMax services on competition grounds.

T-Mobile, which has been particularly vocal in its objections to the plans, claims that its own tests have shown serious degradation to its networks.

The FCC has agreed to carry out tests to examine the issue. The organisation will look at the potential of WiMax services to interfere with cellular signals and will also examine whether shielding could fix any problems.

"We are pleased that the FCC has decided to travel to Seattle for interference testing. This is an important development," T-Mobile said in a written response to the FCC announcement.

"We are convinced that the FCC will learn that its proposed rules are not viable because of the impact on existing wireless providers in the neighbouring spectrum bands.

"We hope we can then move forward towards a set of rules that will maximise the use of all affected spectrum bands for broadband, and that enables alternative solutions."