Cablevision  said it plans to build a mesh Wi-Fi network in its coverage area to  offer customers free wireless Internet access outside the home.

The announcement made Thursday came just two days after Comcast, Time Warner Cable, and Bright House said they were backing a wireless broadband network (see Tech Consortium Bids $14.5B on WiMAX).

The announcements underscore cable operators’ urgent need to embrace mobile connectivity at a time when not just voice and data but TV, their core product, is now available via mobile broadcast.

“If they are thinking long term, they have to find ways to better incorporate both the Internet and mobile in their long range plans,” said Tim Farrar, president of Telecom Media and Finance Associates. (see Will Google and cable Firms Rejuvenate WiMAX?)

Cable operators have struggled with whether they should build their own mobile networks or partner with mobile carriers in the rapidly changing wireless market.

A consortium of cable operators and Sprint Nextel purchased licenses to a swath or wireless spectrum in 2006 to unveil mobile networks.

And earlier that year, a group of cable operators signed a deal with Sprint through which the cable firms would resell Sprint’s mobile services. Both efforts have fallen well short of their goals.

Cablevision’s Wi-Fi network will cost the Bethpage, New York-based cable and entertainment firm $300 million or $100 for each of its 3 million customers in New York, New Jersey, and Connecticut.

The company said the cost of the deployment will be lowered by the fact that the Wi-Fi equipment will not require separate facilities. It will be built on Cablevision’s existing network.

Cablevision, which has been testing the service in a handful of markets, will deploy the network across its coverage area over the course of the next two years.

“This Wi-Fi value proposition will enhance our services and cement our relationship with our customers for the long haul,” said Thomas Rutledge, Cablevision’s chief operating officer.   

A mesh Wi-Fi network would allow Cablevision’s Internet access subscribers to get online wirelessly both inside and outside the home, in places such as parks and restaurants using their laptops and phones.

Customers will be able to do things like make cheap phone calls via voice-over-Wi-Fi, which could ultimately be an issue for Cablevision which sells phone service.

But, Mr. Rutledge said, customers using their Internet access to make cheap phone calls is nothing new to Cablevision which has seen firms such as Vonage build phone businesses on cable modems.