John W. Cox senior editor Network World

Basically, you're then outside the range of the data network and you don't have a connection.

For some enterprise users, this shortcoming -- that Xohm right now just covers 3/4 of one city -- is a problem. But for others, who move within the Xohm network's coverage, it won't be.

Xohm says that it's working toward enabling Xohm subscribers to "roam" to 3G when they move outside of Xohm coverage, presumable to Sprint's 3G network. But to do that, their mobile devices will have to have a 3G radio. It seems unlikely that would be a seamless roaming, but I could be wrong.

They seem to be also working toward roaming between different WiMAX networks, which might be interesting, given that the economics of WiMAX make it relatively cheap to deploy in small areas. There may be a crop of regional and local WiMAX-based networks rising, which will at least have interoperability with any WiMAX client. I'm not sure what else would have to be done at the backend among different WiMAX providers.