Avistar Communications Corporation reported today that the US Patent & Trademark Office (USPTO) has rejected Microsoft's requests for re-examination of 29 of Avistar's US patents pertaining to audio, video and collaboration technologies.

Nine disputed Avistar patents will, however, be re-examined at Microsoft's request.

Avistar argues that the disputed patents have an early priority date (1993) and have already been examined over a large body of prior art.

"Based on the history of these patents and the USPTO's response this week, Avistar is confident that it will overcome any of the remaining re-examination requests that may be granted," the company stated.

"Avistar patents have industry-wide applicability to audio, video and data unified collaboration products and services."

Paul Carmichael, primary licensing advisor at Avistar, insisted that Microsoft's challenge to Avistar's entire US patent portfolio is without merit.

"We expect that the nine patents that the USPTO has agreed to re-examine at this point will also be validated, and actually strengthened, through this process," he said.