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by voodoomagicman
5236 days ago
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It sounds like it is not so cut and dry. From the article: Michael Marcus, who worked at the FCC for 25 years and is now a consultant on wireless technology and spectrum policy, writes that cellular base stations have been "allowed next to the GPS band since 2003" under FCC policy, yet GPS makers "paid little attention to the fact that GPS would be having a new neighbor with much stronger signals in some places than the original MSS [mobile satellite services] signals." Marcus, who does some consulting work for LightSquared, further writes that the "GPS industry has not pressed the filter manufacturers for the latest technology," and "as a result many GPS receivers have a lingering vulnerability to strong adjacent band signals that results from GPS manufacturers ignoring policy changes made in the US almost a decade ago." |
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cellular base stations have been "allowed next to the GPS band since 2003"
The FCC started allowing an "Ancillary Terrestrial Component (ATC)" specifically to supplement areas where satellite signals may have dead zones due to, say, dense urban areas. This would also be a low-power signal. It was put in place for things like Sirius/XM satellite radio to have acceptable performance in urban areas.
ATC is intended to (1) be a small supplement to a satellite-based service and (2) have a comparably low-power signal to the signal provided by the satellites.
Once LightSquared came along and got waivers so that (1) their whole 'satellite' spectrum could be terrestrial, and (2) could run much higher powered terrestrial stations (power levels similar to cellular towers) the amount of power they were radiating for their network eclipsed the weak signals GPS units depend on to function. The design and filtering for GPS units is fine for the adjacent spectrum to be used for similar systems/services as allocated (until the last 18 months).