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In all the hoohah I never read a simple line like this: "Rather, most GPS devices are incapable of filtering out signals from adjacent frequencies—particularly when those signals are many times stronger than the signals GPS devices are supposed to receive. LightSquared chalks this up to a failure on the part of GPS makers, and this is at least partly true."
In true ArsTechnica style, a great article
>This doesn't mean LightSquared signals would travel outside their allotted spectrum. Rather, most GPS devices are incapable of filtering out signals from adjacent frequencies—particularly when those signals are many times stronger than the signals GPS devices are supposed to receive.
Incidentally, this is exactly the reason Iran was able to capture the American advanced spy drone recently. The drones are fully automated and remote controlled in flight. But the level of latency needed at the critical takeoffs and landings require that a ground based GPS unit be present relatively close by to finesse these portions of the flight so as not to risk a crash. It is believed that the Iranians used a ground based GPS signal that simply overpowered the signal that the drone was expecting from the US localized source. They then sent new landing coordinates to the drone, which thought it was responding to the correct signal.
It seems to me that all parties are at fault. The GPS industry should have been working hard to develop filters since there was a "for rent" sign above their patio on the adjacent empty lot. The FCC should have put an asterisk on that 'for rent' sign with some fine print that read: "*you have to let the neighbors use this patio." And finally, Lightsquared should have done due diligence in their planning of this network. I would have to imagine that potential issues regarding GPS interference would have surfaced pretty early. Sure they might be 'in the right', but that doesn't matter so much when you are dealing with government. They could probably get some judges to side with them, but the time and money would probably be better spent in finding an alternate spectrum.
It's a damn shame. I'd like to see this network realized.