BT Group is turning to its own broadband subscribers to help crack a nut that many governments and service providers have struggled with: Widespread Wi-Fi access.

The U.K.'s biggest broadband provider will equip about 2 million subscribers' broadband routers with software from Fon Technology that lets them share part of their Internet bandwidth with the other Fon "members" nearby. BT hopes subscribers will take advantage of the free offer and make Wi-Fi available in many suburban areas, complementing the hotspots and central-city hot zones BT has built around the country.

Fon provides special Wi-Fi routers and software that let people create two separate networks: a secure one for their own use and an open one for anyone within range. Anyone who does this becomes a member of the Fon "community" and can access the Internet on any other member's public connection. The company already has deals with carriers in its native Spain as well as France, the U.S. and other countries, in which subscribers can share their connections. The arrangement with BT offers Fon's biggest potential customer base yet.

Any subscriber with BT's Home Hub premium router, currently about half the carrier's customers, can opt in to the service at no cost. Users can sign up and get a firmware download immediately, and next week BT will roll out the firmware to all the Home Hubs and users will just have to opt in, said Jon Hurry, director of Internet services at BT Retail.

Service providers and municipalities have searched for ways to provide widespread outdoor Wi-Fi access, in many cases for free. The hopes of municipalities in the US faded considerably after EarthLink came to the same conclusion some other municipal wireless providers had reached and demanded cities become "anchor tenants" to help pay for its networks. Meanwhile, lower profile vendors such as Meraki Networks have enlisted consumers in efforts to proliferate Wi-Fi.

BT has covered the central districts of 12 UK cities with paid Wi-Fi and provided about 2,000 hotspots in places such as hotels and restaurants. Its broadband subscribers have free access to those. The carrier chose Fon because it was the quickest way to get public Wi-Fi up and running in other locations, complementing the existing deployments, and at no cost, Hurry said. The carrier's ambition is to have hundreds of thousands of BT subscribers opt in to the service, he said. BT made an undisclosed investment in Fon earlier this year and has a seat on its board, according to Hurry.

The piece of a customer's broadband connection that will become available to other Fon members is relatively small, at 512K bps (bits per second) out of a BT broadband connection that can be as fast as 8M bps, but outpaces the minimum 300K bps free service Google wanted to offer on EarthLink's San Francisco network. People should be able to use those connections for Internet access, gaming, VOIP (voice over Internet Protocol) and other applications on any Wi-Fi device, according to Fon.