Google and Apple don't have major booths on the floor of the CES trade show, but they are very much on the minds of their competitors.

Among those competitors are Microsoft and Yahoo, which separately announced ambitious plans for their mobile technology in 2008. Among the 2,700 other vendors at the show, both companies also have large displays at the trade show, including special tents outside the Las Vegas Convention Center.

Microsoft Chairman Bill Gates in his keynote speech on Sunday said about 20 million devices that use the Windows Mobile operating system will ship in 2008, double the number of 2007. Significantly, he said Windows Mobile devices outsell Apple's iPhone and the BlackBerry from Research In Motion.

Yahoo Monday announced the Mobile Developer Platform to allow developers to build mobile applications, or widgets, as well as the third generation of its Yahoo Go software, a mobile gateway.

Despite comparisons of Yahoo with Google, Yahoo's Ojas Rege, vice president of global mobile products, said that the company is not interested in building a mobile phone operating system similar to what Google and other companies are doing with the Android initiative.

"We're not building a mobile OS or a phone," Rege said in an interview. "That's too limited of an approach. We're going after [building software for] billions of phones."

Yahoo also intends to continue developing mobile advertising formats and campaigns in the coming year, Rege said.

During his speech, Gates also described ways that voice commands will increasingly be used in mobile devices, replacing button pushes that are commonly used today. Scott Rockfeld, group marketing manager for Windows Mobile, said voice-enabling technology from Tellme Networks Inc., which Microsoft acquired last spring, will increasingly be used in the Windows Mobile operating system.

Apple, meanwhile, does not participate in CES and has its own major conference, Macworld, coming Jan. 14 in San Francisco, but the company has a small iPod booth in the lobby of the Hilton Hotel adjacent to the major show areas.

Google, meanwhile, does not plan any major announcements at the show, although a spokeswoman said Google officials would be in attendance.