This kind of stuff always annoys me. One of the interesting things would be a &#x27;home designed&#x27; cell system based on using unlicensed spectrum in the TV white spaces. Then you could build a system where a phone only answered a tower which sent out an ident frame which was cryptographically signed by a trusted key. And the response would be encrypted with that trusted key as well so only the cell tower could decrypt it. That and an VOIP back haul network and you&#x27;re closer.<p>Its on my list of projects to look at with SDR, but sadly I am no Fabrice Ballard (who no doubt has already built such a system as a proof of concept and then tossed it away)