The issue of ultra-wide-band (UWB) technology’s possible interference with the Global Positioning System (GPS) signal has become nothing short of a can of worms. We’ve followed this issue intently for several months (see September 2000, page 4, and February 2001, pages 20 and 28) because of its importance to safe air navigation. Over recent months, we’ve seen the issue mushroom to become a brouhaha of unreasonable deadlines, competing study results, and no clear resolution.
I’ll try to bring you up to date (as of April 1). You may recall that several manufacturers of UWB devices, lead by Alabama-based Time Domain, want the U.S. Federal Communications Commission (FCC) to establish criteria that permits the operation of low-power UWB devices without license or the need for frequency coordination. In other words, UWB would be allowed to trespass into restricted spectral bands, including that used by GPS (below 2 GHz). Time Domain claims UWB will impact GPS no more than millions of devices already co-existing with GPS.
The FCC has been quite receptive to Time Domain’s side of the argument–in part because of UWB’s considerable potential (which it has, including for aviation) but also, no doubt, because of the Alabama companies heavy-handed lobbying effort. But before the FCC could amend its rules on UWB, studies had to be conducted.
Time Domain financed its own study. Produced by the University of Texas, the study’s results were subsequently assessed by the Johns Hopkins University Applied Physics Lab (JHU/APL), also on Time Domain’s nickel. Meanwhile, the National Telecommunications and Information Administration (NTIA), the U.S. federal spectrum watchdog, conducted its own study of UWB’s impact on GPS.
In mid-March, the JHU/APL ignited a fire storm among GPS advocates when, after its assessment, it announced that, "Based on this report and inputs from other organizations, JHU/APL believes that sufficient information is available for the FCC to establish criteria for regulating UWB emissions."
Time Domain was quick to declare a victory. It fired off a press release that says, "With the release of the JHU/APL and NTIA GPS reports, the FCC now has sufficient data with which to formulate rules to enable the deployment of UWB without risk of harmful interference to critical safety-of-life services. We look forward to the FCC’s timely completion of its rulemaking..."
In truth, the NTIA study did not give UWB a clean bill of health. In fact, the agency determined that high pulse rate UWB sources, operating within existing GPS frequency allocations, could "seriously degrade GPS performance." And Time Domain’s press release ignores a study conducted earlier by Stanford University that comes to a conclusion similar to NTIA’s.
More over, though their chance to view the JHU/APL report was brief, members of RTCA’s Working Group 6 believe they unearthed discrepencies between the University of Texas data and conclusions the JHU/APL derived from that data–for example, with regard to the distance (3 meters) in which UWB could seriously degrade a GPS receiver’s performance.
And GPS is not the only system potentially effected. The behemoth telecommunications and television broadcasting communities also are concerned. Communications giant Qualcomm says tests show UWB "will degrade [mobile] phones to the extent of rendering their operation useless."
Still despite protest from the telecommunications, broadcasting and aviation industries, the relatively small opposition of essentially three companies–Time Domain, XtremeSpectrum and Fantasma–may well come out on top with the FCC rulemaking.
If you don’t find this muddlesome, consider that the aviation industry’s leading magazine, Aviation Week & Space Technology, recently named Larry Fullerton recipient of its Aerospace Laureate award. Fullerton? He’s the founder of Time Domain. Aviation Week says it "did not ignore the issue of the potential interference of UWB with GPS" when making its decision, but feels "a deep obligation...to identify people and technologies with great potential."
That aside, the UWB/GPS issue needs to break from having "dueling studies." Somehow, as one aviation official put it, we "must make sense" of the data collected. Hopefully, the issue requires no more study, but if it does, it is better to error on the side of caution and thoroughness. Then the FCC can establish the criteria in which UWB can operate with no possible interference to GPS. And once that criteria is established, the onus should be on the UWB community to conform to the criteria.
Even the remote possibility that UWB technology could impact the safety of commercial flight could result in something much worse–and deadlier–than the proverbial open can of worms.