GPS World, January 2013

expert advice the lessons learned see below were understandably from the perspective of a party which was unable in this particular instance to achieve the goals desired by their sponsors This failure was for reasons of basic spectrum policy conflicts between GNSS applications and those mooted to become transcendent mobile high speed data for consumer and industrial applications Lee depicted the lack of a requirement in history for regulation of receiver standards as opposed to transmitter standards to the inability to anticipate the crowded spectrum for example his statement that spectrum was regarded as free and minimizing interference was the key objective a burden placed on the transmitters Now that spectrum is seen as scarce and underutilized in many U S government applications and inadequately conserved in many civil applications the concept of receiver standards for avoiding interference and the use of advanced filterand antenna technology in receivers as well as in transmitterswould enable easier less confrontational and more lucrative use of this 21st century El Dorado Parenthetically Pierre de Vries University of Colorado and a member of the FCCs Technical Advisory Committee and others recently testified to a House of Representatives panel recommending that harm claim thresholds be established with which to manage the trade offs between intrinsic receiver protection requirements and transmitter power distribution so that instead of just adding the specification requirement to receivers a flexible system approach be adopted They noted that it was very difficult to anticipate the receiver design needs for all applications The failure to understand the requirements of precision GNSS receivers and the simplistic concept of fences was a large driver in the collision between LightSquared and GNSS Now that spectrum is seen as scarce and underutilized in many U S government applications and inadequately conserved in many civil applications the concept of receiver standards for avoiding interference and the use of advanced filterand antenna technology in receivers as well as in transmitterswould enable easier less confrontational and more lucrative use of this 21st century El Dorado Lees lessons learned summary is Upper 10 candidate for ground augmentation The upper 10 MHz 1545 1555 MHz of spectrum was originally allocated to LightSquared through its acquisition of TerraSat During the 2012 conflict months LightSquared publicly abandoned operating in the Upper 10 Question sound alternatives for this band Including as a good GNSS guard band Consider sub microwatt uses for short range augmentation such as Department of Transportation Intelligent Transport Systems ITS TWG findings Given very low effective isotropically radiated power EIRP ample compatibility with precision GPS nearby Precision GPS 82 dBm worst case Upper 10 susceptibility 1 dB C N O 1 uW EIRP transmitter is about 13 dB below at 1 meter Seems suitable for high availability in urban areas provides urban in fill redundancy such as ITS At 100 mETER range Signals 135 dBm incident power at an ITS receiver antenna Band continues as a space to earth downlink shared with geostationary Earth orbit mobile satellite services including carriage of GPS GNSS corrections OmniSTAR StarFire Lee contested the FCC chairmans assertion that the LightSquared GPS matter was an anomaly saying instead that it was foreseeable However foreseeable anomalies such as singularities exist in predictions of scientists I believe that this anomaly was clearly foreseeable but a hedgefund mentality financial engineering and a long held attitude toward GPS in the FCC were the drivers of these benighted decisions The gold rush is still on for finding underutilized spectrum Some systems including GNSS utilize bandwidth that needs protection for purposes other than the usual communications requirements It is vital to honor the homesteads of GNSS and protect the noise floors Receiver standards must be considered very carefully because communications receivers and high precision GNSS receivers are very different systems Scientific Subjects Some presentations grouped under this topic are available in ION publications from GNSS 2012 Atom Interferometry Mark Kasevich of Stanford presented his paper on precision navigation sensors based upon atom interferometry While application of these sensors in general awaits many highly difficult engineering advancements the outcome would be a great boon to navigation were the outcome comparable to the evolution of chipscale atomic clocks GPS World January 2013 www gpsworld com 14