The coming data spectrum crunch is a problem that mobile carriers are getting very nervous about, but it looks as if they’ve already found the solution – simply by tapping into the vast reserves of free, open Wi-Fi networks available in coffee shops, shopping malls and other public buildings, they can seriously lighten the load on their overworked wireless networks.

Today, Chicago-based US Cellular becomes the latest carrier to do just that, sealing a deal with Devicescape to piggyback its virtual Wi-Fi network and ease its mobile data burden.

Linking up with Devicescape is a smart move on the part of US Cellular, given that its virtual network has more than 7.8 million access points in the US. Whereas carriers like AT&T are opting to build their own Wi-Fi networks (currently it has 30,000 or so), Devicescape offers a far greater number of access points simply because it doesn’t actually ‘own’ any of them – rather, it crowdsources data from each device that has its software installed, giving it access to millions of open access points around the world.

US Cellular will enjoy big benefits from Devicescape’s service, given that the vast majority of its customers are based in its home city of Chicago. Currently, competition among US Cellular customers for 3G network time is very intense, but the Windy City conveniently has a massive concentration of open Wi-Fi hotspots that Devicescape can tap into to help US Cellular ease its data burden.

Even better for US Cellular is that Devicescape is growing all the time. Its wireless networking software loads a client into each device that uses it – these devices are constantly on the lookout for new open Wi-Fi sources, so that as more and more people subscribe, the network will keep on adding additional Wi-Fi spots.

Devicescape already offers a similar service to a number of other carriers, including Bouygues in France and Intel in the US.