Cable TV giants Comcast and Time Warner Cable are in talks with Sprint Nextel and Clearwire about a joint venture that would finally give the cable firms their elusive quadruple play service package, according to a published report.

The report in Wednesday's Wall Street Journal said that Sprint and Clearwire, which have been in talks for months about a joint venture based on WiMAX, are trying to raise at least $3 billion to build a single, nationwide network.

Comcast would invest about $1 billion, the paper said, while Time Warner Cable would contribute $500 million. Cable operator Bright House Networks would invest between $100 million and $200 million in the deal.

Intel and Google are also involved in the talks, the report said.

A WiMAX venture involving the two mobile carriers and three cable firms could fill service and coverage holes for both groups, but in the rapidly changing mobile market both the success of WiMAX and the joint venture are iffy propositions.

WiMAX, a wireless broadband communications technology, is still very much an unknown quantity.

It has emerged quite slowly over the last seven years and faces a variety of competing services such as cellular broadband, WiFi, and LTE, an emerging technology that has the backing of Verizon Wireless.

"But short of buying a wireless carrier, this joint venture is the best wireless option for the cable companies to date," said Tim Farrar, president of Telecom Media and Finance Associates. "However I am not so sure that a quadruple play service involving WiMAX solves the cable operators competitive problems with the telcos," he said.

Facing increasing competition in their pay-TV markets from the phone companies, the cable operators, which offer TV, Internet access, and phone services, have long sought a wireless addition to their service bundles.

AT&T and Verizon, the two largest phone companies, both own or partially own wireless carriers so they can offer four services, which for reasons of price and billing convenience could make them more attractive to consumers.

Taking an equity position in a WiMAX venture gives the cable operators something the phone companies don't have--access to a differentiated wireless data service that could theoretically maintain an Internet connection at 55 MPH.

It may not prove as popular as many hope, but WiMAX adds an important weapon to the cable operators' arsenal that they don't currently own.

"The cable operators could use WiMAX to pick up say a 10 percent share of the wireless market, which at the very least balances the 10 percent share of the video market the phone companies grab," Mr. Farrar said.