“There is no practical way to mitigate the potential interference at this time”, says the NTIA in a letter to FCC Chairman Julius Genachowski about LightSquared’s 1.5 GHz LTE terrestrial network interference to GPS receivers. LightSquare had been granted a conditional waiver to allow its wholesale customers to offer terrestrial-only service, but that waiver was conditioned on all GPS interference concerns being resolved before LightSquared could launch commercial service.
LightSquared may of course be right about the very relaxed requirements on GPS receivers. Cutting corners in receiver design saves a few bucks, but makes the receivers very sensitive to strong nearby signals – even if they are out-of-band and otherwise in perfect accordance with regulations. This is, unfortunately the situation in many bands. Incumbant, traditional users of the spectrum (e.g. TV, Radar, GPS) have “squatters rights” and may have their receivers protected even if these were designed ages ago and with no thought of adjacent band services. Is it time to not only regulate “out-of-band emission” but also “out-of-band reception”, i.e. stipulating lower limits on receiver performance ?
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