Instead of Interference Testing, DOT Should Focus on Pushing Compromise, LightSquared Says

The Transportation Department could make better use of its time and efforts encouraging LightSquared and the major GPS makers to resolve their disagreements on power levels and on steps GPS manufacturers could take to address overload, LightSquared said in an FCC filing posted Thursday in docket 12-340. It included comments LightSquared submitted earlier in the week with the DOT regarding the agency's draft test plan for studying interference between LightSquared's proposed wireless broadband network and GPS devices. LightSquared has been critical of that test plan (see 1510210022). In the latest DOT comments, it said DOT's proposed metric of 1 dB change in noise floor "is misguided because it fails to measure what the expert agency and Congressionally-designated spectrum regulator -- the Federal Communications Commission -- considers when it evaluates 'harmful interference': the ultimate impact of adjacent-band activity on the performance of the device." Arguments that ITU recommendations support such a benchmark are wrong because many recommendations "begin with user-measurable criteria and then derive interference levels," LightSquared said. Some recommendations referring to 1 dB noise floor relate to in-band interference, not adjacent band, and none of them applies the 1 dB specification for adjacent-band signal effects on GPS, it said. No one has shown a strong correlation between device performance and 1 dB desensitization, and even if such correlation existed, LightSquared's proposed testing would show it, it said. LightSquared also rejected GPS Innovation Alliance arguments that the DOT doesn't necessarily need detailed RF front-end information on the devices to be tested, saying it agreed with GPSIA that dwell time should be a component of testing, but it should be at least three minutes.