I've glanced at the same doc, got a slightly different take from it. The higher precision devices are actually receiving data in LightSquared's licensed band (by having more receive bandwidth, they get better accuracy), on purpose. This is not the GPS devices' band to use, so IMO tough luck on them. (If you like analogies, it's like carving out a block of unassigned IPs for yourself, and then complaining when someone is actually assigned those IPs and wants to use them).
The one band they tested is the one that is further away, and therefore easier for devices to reject. They claim it's not a problem for "over 99% of devices" when they are at full power there. They concede that operation the the higher frequency band (that LightSquared has licensed) would cause trouble for "a significant portion of legacy devices."
The root cause of most of the problem (not the part where ultra-precision receivers use bands that aren't theirs) is that the GPS receivers expected things in neighbouring bands to remain quiet, when there was no guarantee that such would happen. This assumption made for easier and cheaper designs for them, and now all this hardware is out there that is susceptible to the interference.
Right. I might've done a bad job describing my take on the report, because I agree with all that.
It's also worth noting that LightSquared is offering to provide circuitry -- which they claim to have already developed -- to any device manufacturers that want to filter LightSquared's signal.
Regardless, I'm not yet seeing a single thing anywhere in this part of the report that would lead me to conclude that they're proposing something that "defies physics".
The "defies physics" part would be a filter that is physically impossible to implement. As you need sharper roll-off of your filter (more rejection of out-of-bands, and sooner), you start making sacrifices and attenuating the signals in your passband as well. GPS already needs very sensitive receivers, and attenuating the signals more than they already are could make them unusable. ("Oh!" you say, "just put more amplifiers behind the filter!" Well, no, at that point the signal is inderminable from thermal noise, which you will amplify just the same. And you can't put one in front of the filter, because then the LightSquared signals don't get filtered out and they interfere...)
Without seeing the specs they are being asked to hit, I can't speak to the challenges of realizing these filters.
And just to be clear, there is no way for LightSquared to use their upper band and not interfere with the ultra-precision stuff that's effectively squatting there. There's no happy compromise in that situation, but as I implied earlier, I have little sympathy for the guys who weren't playing by the rules.
Ok, because the implied situation in the article is the LightSquared is pooping all over the GPS spectrum and then selling licences to manufactures for their spiffy new GPS service which happens to work much better than old GPS now.
Nope, more like GPS guys built a luxury spa in the middle of a farming area, and are complaining that LightSquared is pooping all over the field they [edit: they=LightSquared] just purchased upwind, which has been wildflowers that spa patrons could trespass through on on illicit trails until then. And LightSquared is saying "guys if you make this simple wall on your own property, the poop smell won't blow that far."
And to bring my analogy one step further, the GPS guys are saying "that wall is too difficult to build." [I cannot speak to how hard that wall is to build.]
The one band they tested is the one that is further away, and therefore easier for devices to reject. They claim it's not a problem for "over 99% of devices" when they are at full power there. They concede that operation the the higher frequency band (that LightSquared has licensed) would cause trouble for "a significant portion of legacy devices."
The root cause of most of the problem (not the part where ultra-precision receivers use bands that aren't theirs) is that the GPS receivers expected things in neighbouring bands to remain quiet, when there was no guarantee that such would happen. This assumption made for easier and cheaper designs for them, and now all this hardware is out there that is susceptible to the interference.