Just as the number of Bluetooth device users passed the billion mark, a lawsuit threatens the momentum of the short-range wireless technology.

A Washington state organisation has sued Nokia, Samsung Electronics, Panasonic of North America and Matsushita Electrical Industrial Co for making and selling Bluetooth products that infringe on at least one patent.

The Washington Research Foundation (WRF), a non-profit organisation that helps Washington state universities and research institutes commercialise technologies and also helps fund research at such organisations, filed the suit on 21 December in the District Court for the Western district of Washington.

The legal action comes as a surprise to some members of the Bluetooth Special Interest Group (SIG), which was created to control and protect the technology behind the standard. The companies that belong to the Bluetooth SIG (numbering more than 6,000) agree to license their relevant patents to other members without cost, said Anders Edlund, marketing director for the Bluetooth SIG. The group has done its own legal investigations to ensure that companies can build Bluetooth products without infringing on patents. "It seems to have worked so far, so this lawsuit was kind of a surprise," he said.

The WRF claims that at least one of its patents related to radio frequency receivers is used in the Bluetooth standard.

That patent was filed in August 2003 and granted on 3 October 2006. The first version of the Bluetooth specification was approved in 1998 and several updates have passed since.

While Broadcom, a mobile-phone chip maker, licenses patents from WRF, CSR, a UK chip maker that supplies Nokia and the other defendants, doesn't, the WRF said.

The WRF asks the court to forbid the companies from importing or selling the relevant Bluetooth products in the US and also asks for damages for historical infringement.

The Bluetooth SIG hasn't had the chance to take a close look at the suit yet to determine if it thinks the claims are valid, according to Edlund. "Obviously any legal issue with the technology is a concern to us," he said.

These types of lawsuits, launched by companies that claim they have technology essential to existing standards, aren't completely uncommon, according to Stefan Svedberg, a Bluetooth SIG board member and an executive with Telefonaktiebolaget Ericsson. "The set-up of the SIG is something that would minimise this risk but it's not a surprise that there might be some parties like this out there," he said.