Comcast reportedly is investing $1.05 billion in the WiMAX wireless joint venture, which is valued at $12 billion, and will sell the service as a premium product for customers seeking fast online connections outside their homes or in cars.

Other investors, including Google Inc., are putting an additional $2.2 billion into the new venture - for a total financial investment of $3.2 billion.

Sprint and Clearwire will contribute wireless spectrum that will create a national footprint for the wireless product, sources say, and the WiMAX technology for the venture.

WiMAX is considered a fourth-generation wireless technology with Internet speeds similar to a cable modem. The technology is expected to be a competitive threat to services such as WiFi Philadelphia.

Comcast, the nation's largest cable company, has said it would like a wireless component in its product offerings of video content, wireline phone and home-based Internet if the market for wireless develops. It expects customers eventually to ask for a wireless option, though they have not yet done so. It is not clear when the service would be available.

Sprint, which is developing WiMAX through its Xohm unit, will have a majority interest in the new joint-venture company, which will be called Clearwire. But Comcast and other cable companies will have strategic control of the new product within their franchise areas, the sources say.

A Sprint spokeswoman declined to comment late yesterday. Clearwire, which is based in Kirkland, Wash., and was founded by Craig O. McCaw, did not return phone calls.

Sprint is struggling financially. Speculation has focused on a German telecom company buying it, or in Sprint divesting its Nextel unit.

Besides Comcast, other investors include Intel Corp., which is investing $1 billion, and Web search-engine giant Google, which is investing $500 million.

Time Warner Cable is investing $550 million and Bright House Networks L.L.C., another cable company, $100 million. A Bellevue, Wash., private-equity firm, Trilogy Equity Partners, is putting in $10 million.

Both AT&T Inc. and Verizon Communications Inc. spent billions of dollars on new spectrum for wireless services in a government auction earlier this year, putting pressure on cable companies to develop a competitive alternative.