As testing continues into whether LightSquared will interfere with GPS signals, Qualcomm has filed the results of its own initial cellphone testing with the FCC. Of course, LightSquared is depending on Qualcomm as its principal supplier of chipsets and developer of the GMSA/S-EVDO air interface for its satellite services, so it might have been expected that Qualcomm would confirm the position asserted by LightSquared supporters, that cellphones won’t need to use filters to prevent interference with their A-GPS location chips. However, in fact Qualcomm has come to the initial conclusion that “additional rejection of 30dB may be required” and that the current filters used in its A-GPS chipsets may need to be upgraded, in view of how close the upper part of the LightSquared downlink band (the Phase 0 spectrum at 1550-1555MHz) is to the GPS band. Given that most people agree that the interference problem will likely be much worse for other types of GPS receivers, this is not an encouraging result for LightSquared.
LightSquared may therefore be unable to use the Phase 0 spectrum unless receiver standards are imposed on GPS receivers, as the FCC suggested in its recent 2GHz ruling, which indicated that “incumbent users…must use receivers that reasonably discriminate against reception of signals outside their allocated spectrum”. However, Inmarsat indicated yesterday that on April 25, it signed an amendment to its Cooperation Agreement with LightSquared, and received an additional payment of $40M to accelerate the clearing of the Phase 1A spectrum (i.e. to free up the additional 2x5MHz block at the bottom of the L-band, which under the original agreement would have been made available sometime between February and November 2012). Thus it appears that even LightSquared may be acknowledging that the top part of its frequency band will be largely unusable for the foreseeable future, unless and until receiver standards are imposed on the GPS community, requiring a multi-year program of equipment upgrades and recertification, with all of the additional costs and delays that would imply.