Network concept over UHF white spaces
Microsoft and HarvardUniversity have tested a transmission of signals over "whitespaces," which is part of the radio spectrum that was formerly used by analog television stations and is still used by wireless microphones.
Microsoft has published a paper that explains networking over UHF white spaces and how it differs from conventional Wi-Fi in spatial variation, temporal variation, and fragmentation of the UHF spectrum.
You can read the paper here (PDF) or more technical summary of it at Dailywireless.
Note: The protection of wireless microphones is an unsolved problem.