Virtual addressing is a pretty commonly-used thing these days in all sorts of data networks. I wouldn't get too worried about it, the stations with the clash would figure it out, perhaps using one of the -1 -2 type identifiers to keep from confusing the little stupid $40 boxes, if there's not already something in the standard that tells those boxes how to react to such things.
Imagine if you will, the 10,000 foot view of all of this. Once the broadcasters are digital, most of them have some amount of spare capacity (many are broadcasting "sub-channels" with weather or other useless information they don't get paid well for) on what are basically the widest-area data transmitters in existence, besides satellites. And they're easier to deploy too. We've already seen where the cellular industry has done: 2-way radio features Video broadcast features (from very "TV like" transmitters) What's to stop some smart folks from utilizing that excess bandwidth on the HDTV transmitters for other purposes? Perhaps some Public Safety folks would like having a 40KW "remote base" for their digital HT's to listen to traffic on? The possibilities once they're digital, are virtually endless if the right big-money businesspeople and engineers can sit down at a table and figure it out as to how everyone gets paid, who builds what, and how it integrates. Take data from the trunking controller running a P-25 network, and feed it out the 40KW UHF transmitter in a format that an ATSC receiver goes "huh?" and ignores on a sub-channel, encrypt it, and you've got one hell of a big transmitter for a voted system... The hurdles are less technical and more regulatory and "territorial" than anything. Get the right people working together, and you'd have one hell of a 2-way radio system. Think big, the country needs such "ground-breaking" ideas right now... to heck with "Whitespace" and the resulting mess of going unregulated, just piggy-back on the broadcasters. All you need is a standard way to stuff data into their unused bandwidth at their transmitter sites. If it gets popular, you could always put up another "TV" transmitter in an area to handle the excess load. It's "just data"... at some point along the chain. But it's data with BIG transmitters that cover a LOT of ground -- a very useful asset in any system designer's arsenal. Put the right business model, design engineering, and hard work around it -- and you've got yourself a really useful and innovative way to reach mobile voice/data users. Nate WY0X
