WIRELESS CARRIERS SAY FCC UWB REPORT ISN'T ADEQUATE
FCC staff report on ultra-wideband (UWB) testing brought criticism from some wireless carriers who said it wasn’t rigorous enough to be basis for rulemaking (CD Oct 23 p2). Comments on report were due Nov. 22, and several respondents questioned FCC’s testing methods and whether they adequately analyzed interference issues associated with UWB and GPS, especially as they related to E-911 systems.
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“Hair dryers and electric drills are not UWB devices, and RF [radiofrequency] noise levels in the FCC’s server room and an automobile factory tell the Commission nothing about whether UWB devices will interfere with an assisted-GPS E-911 call,” Cingular said. “The study is no more than a snapshot of what is occurring at a certain location, on a certain date, and at a certain time,” company said. Qualcomm said it had conducted its own ambient noise measurements and results “differ markedly” from FCC study by showing ambient noise in indoor environments wasn’t above UWB emission limits.
FCC report said ambient noise levels in certain environments were well above emission limits for UWB -- in GPS spectrum, up to 3,000 times greater than interference threshold that was used as basis for UWB limits at some outdoor test sites.
Nascent UWB industry said report showed some UWB limits could be relaxed. Time Domain said report demonstrated that FCC UWB limits were “extremely conservative.” It said report also showed electrical and electronic devices radiate in restricted bands were at levels above those established for UWB devices. “These emissions, and not thermal noise, establish a limit of performance for many systems in many common environments, especially indoors,” Time Domain said. “There is no evidence to show that the existing levels of emissions pose any realistic threat of harmful interference to services in the restricted band.”
XtremeSpectrum said FCC report provided “conclusive evidence” that UWB couldn’t affect GPS reception for indoor E-911. It said: “Permitted UWB emissions are not only safe in these environments, but in most cases will be completely undetectable.” Ground Penetrating Radar Industry Coalition (GPRIC) said GPR emission limits should be raised to Part 15 general limits and FCC should eliminate rule keeping UWB bandwidth below 960 MHz.
Cingular said report was “too little, too late” and validated need for conservative UWB limitations. FCC report also showed “more rigorous approach is needed to fully understand the characteristics of interference as well as noise,” it said. RF Metrics said report didn’t provide sufficient description of measurement system nor of measurement technique to allow independent analysis of measurement results. Company said measurements needed to resolve some issues weren’t collected. “These inconsistencies, coupled with a lack of explanatory information, are enough to render the measurement results inconclusive,” RF Metrics said. FCC report shouldn’t be used to justify rulemaking, it said.
Sprint said result of proceedings was of “critical importance” to users of GPS band, but of only “marginal importance” to UWB developers. “The enormous effort that wireless carriers and public safety agencies are undertaking to deploy Phase II E-911 service will be of little value if UWB interference prevents customers from even originating 911 calls and/or prevents carriers from providing to public safety agencies the location accuracy that their networks are capable of supporting,” Sprint said. It also said that Time Domain’s “TAG device” didn’t meet Rule 15 requirements.