Sunday, February 20, 2011

GPS FUD – Part 2

Now the USAF is apparently weighing in on the GPS/LightSquared controversy.  This is a little more significant. As I mentioned in my previous post, DoD would be one of the leaders of the torchlit pitchforking if LightSquared’s system does interfere with GPS signals. And if this system does interfere, it will be shut down – one upstart satellite owner doesn’t have the juice to fight all the other users of GPS.

Seriously, look at what happened to broadband over power lines. Notice that we don’t have it and probably never will (outside of the home). Interfering with other people’s spectrum is Not Done, at least not by private parties. (The Russian Woodpecker would be a governmental counterexample).

Incidentally, this is one of those cases where I think that governmental interference in the operation of radio transmission might be justified. As near as I can tell, the proposed system is not deliberately operating outside its own spectrum; rather that the laws of physics cause undesirable interference. This interference could (theoretically) be filtered out. The GPS manufacturers appear to be upset because their cheaper systems don’t have the capability to filter (having been designed in a period in which the LightSquared spectrum was only being used for satellite-to-surface communication). The principles by which this interference will happen are evidently well-known, so the cheap receivers are depending entirely on there never being a (relatively) powerful terrestrial transmitter in a position to generate such interference. I don’t know if that’s a reasonable assumption in a pure free-market spectrum allocation. Initial allocation of spectrum was done on both an ad-hoc basis and one taking into account certain physical constraints (for example certain spectra are unsuitable for certain uses due to atmospheric properties, and especially well-suited for others). The LightSquared frequencies are evidently not economically unsuitable for terrestrial operation.

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