Lucent Technologies has filed suit against Microsoft for patent infringement over technology used in its Xbox 360 game console.

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 (USPTO) to Lucent on July 19, 1993, according to court papers filed by the company in U.S. District Court in San Diego. Lucent, which is in the process of merging with Alcatel SA, filed the papers on March 28.

Lucent 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.

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

This is not the first time Lucent and Microsoft have sparred legally over the 5,227,878 patent. In a previous suit filed in 2003, the tables were turned, with Microsoft suing Lucent in an effort to seek a judgment of noninfringement, according to court papers. The company was successful; a judge last year granted summary judgment in Microsoft's favor because of a typographical error in the patent.

Lucent has since corrected the error with the USPTO and received an official patent correction notice, according to last week's filing. Although Microsoft was awarded a judgment in the previous case concerning the same patent, the judgement in that case did not bar Lucent from taking separate action against Microsoft in the future, Lucent said in court papers.

Before taking its latest legal action, Lucent notified Microsoft of what it believes is "willful' infringement of its patent, but did not cease distribution or production of the Xbox 360, according to papers filed by Lucent.

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

Neither Lucent nor Microsoft responded to requests for comment on Tuesday.