Lucent Technologies has filed suit against Microsoft for patent infringement over technology used in its Xbox 360 game console. The company claims Microsoft is using its patented technology in the Xbox 360's built-in MPEG-2 decoding capability. MPEG-2 is the latest industry standard for encoding video found on DVDs. The lawsuit was filed on March 28 in U.S. District Court in San Diego.

At the center of the dispute is Patent No. 5,227,878, "Adaptive Coding and Decoding of Frames and Fields of Video," issued by the U.S. Patent and Trademark Office to Lucent in 1993.

Lucent and Microsoft have already disputed legally over the same patent. In a previous suit filed in 2003, Microsoft was suing Lucent and was seeking a judgment of noninfringement. A judge had granted summary judgment in Microsoft's favor because of a typographical error in the patent last year.

Since then, Lucent corrected the error with the patent office and received an official patent correction notice. The previous judgement in favor of Microsoft did not stop Lucent from taking separate action against Microsoft.

Before taking its latest legal action, Lucent says it had notified Microsoft of what the company believes was a voluntary infringement of its patent, but did not cease distribution or production of the Xbox 360.

Lucent is seeking unspecified damages from Microsoft and is requesting a jury trial to resolve the suit.

Microsoft released the Xbox 360 game console in the U.S. last November and it is now available in more than 15 countries.