1 Todd E. Humphreys, Cornell University Larry Young, JPL Thomas Pany, University FAF Munich 2008 IGS Workshop, Miami Beach FL IGS Receiver Considerations.

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<ul><li><p>Todd E. Humphreys, Cornell University Larry Young, JPL Thomas Pany, University FAF Munich</p><p>IGS Receiver Considerations2008 IGS Workshop, Miami Beach FL</p></li><li><p>Opportunity: New GNSS Signals(Fig. 1 of Wallner et al., "Interference Computations Between GPS and Galileo," Proc. ION GNSS 2005)</p></li><li><p>OverviewIGS receiver characteristics: Ultra, Super, MinimumCommercial Receiver OutlookSoftware Receiver OutlookRecommendations</p></li><li><p>The Ultra Receiver</p></li><li><p>The Ultra Receiver</p></li><li><p>The Super ReceiverTracks all open signals, all satellitesWell-defined, publicly disclosed measurement characteristics (phase, pseudorange, C/No)RINEX compliantCompletely user reconfigurable, from correlations to tracking loops to navigation solutionInternal cycle slip mitigation/detectionUp to 50 Hz measurementsInternet ready; signal processing strategy reconfigurable via internetLow cost</p></li><li><p>Minimum IGS Receiver Requirements2008202020122016</p><p>L1L1L2L2P2P2C1 or P1C1 or P1</p></li><li><p>Requirements ConsiderationsPseudorange Precision Multipath Errors L2C/L5 Rollout Timetable 2020 Discontinuation ofCodeless/Semicodeless access </p></li><li><p>Minimum IGS Receiver RequirementsXX2008202020122016</p><p>L1L1L1L1L2L2L2 or L5L2P2P2 or C2P2 or C2 or C5P2 C2C1 or P1C1 or P1C1 or P1C1 or P1L5C5??</p></li><li><p>Commercial Receivers OfferingsTopcon NET-G3 Trimble NetRS/NetR5 Septentrio PolaRx3 Leica GRX1200 </p></li><li><p>Sample Responses to QuestionnaireMeasurement intervals defined? Tracking loop parameters configurable or disclosed? Firmware updates deliverable via internet? Baseband software available for licencing? Recommended receiver and approximate list price (no antenna): </p></li><li><p>Outlook for Commercial ReceiversGood:Market trend is to track all available signals, all satellitesInternet readySome vendors offer increasing reconfigurabilityAll top vendors provide near-optimal standard trackingRugged, stable, reliable platformsBad:Some vendors unwilling to disclose measurement characterizationProblems in past with proprietary output formats (2 year wait!)Uneven C/N0 reporting on some devicesNo support for exotic tracking techniquesLimited reconfigurabilityIGS has little leverage </p></li><li><p>Software GNSS ReceiverFront End</p><p>RF Front-EndReference OscillatorADCSample ClockSoftwareCorrelatorsTrackingLoops, DataDecoding,ObservablesCalculationsFFT-basedAcquisitionFPGA/DSP/CPU</p></li><li><p>Flexibility: Iridium-based Navigation on a Software Receiver Platform~100-m geolocationerrors</p></li><li><p>Cornell GRID Receiver(GNSS Receiver Implementation on a DSP)Supports 72 L1 C/A channelsFFT-based acquisition down to C/N0 = 32 dB-HzCarrier tracking down to C/N0 = 25 dB-HzVersion 2: Dual-frequency (L1/L2C) with improved scintillation robustnessCompletely software reconfigurable</p><p>Humphreys, T. E., B. M. Ledvina, M. L. Psiaki, and P. M. Kintner, Jr., "GNSS receiver implementation on a DSP: Status, challenges, and prospects," Proc. 2006 ION GNSS Conf., Institute of Navigation, 2006Cornell GRID Dual-Frequency Software-Defined GNSS Receiver</p></li><li><p>GNSS Software Receiver at University FAF Munich &amp; IFEN GmbHL1, L2, L5 front-end13 MHz bandwidth at each frequencyMultiple CPU cores for parallel processingTracks all-in-view civil GPS, SBAS, and Galileo1 kHz max measurement output rateCompletely software reconfigurable</p></li><li><p>JPLs TOGA Instrument(Time-shifted, Orthometric, GNSS Array) L1, L2, L5 front-endElectronically-steered antenna array Multiple FPGAs for parallel processingBuffer memory for near-realtime or offline processingCompletely software reconfigurable</p></li><li><p>Outlook for GNSS Software ReceiversGood:Complete reconfigurabilityComplete transparencySupport for exotic tracking strategiesTheoretical performance equal or better than commercial receiversBad:Only JPL currently supports P(Y) trackingHave not been thoroughly evaluated against traditional receiversUnknowns:Who will build platforms?Who will maintain software? ACs?Commercial provider?Price? </p></li><li><p>Recommendations (1/2)Study the effects of long-delay multipath by comparing (P1,P2) with (C1,C2) measurements from same SVCompare software receiver and traditional receiver performance via signal simulator and field testsDemand from receiver vendors either (1) detailed measurement description, or (2) adoption of a standard measurement technique (e.g., JPL technique)Consider an IGS-sponsored software receiverRevise minimum receiver requirements according to the foregoing scheduleAny comment on US proposal to discontinue access to semicodeless P(Y) tracking? If not, then suggest no comment.</p></li><li><p>Recommendations (2/2)Any comment on US proposal to discontinue access to semicodeless P(Y) tracking? If not, then suggest no comment.Establish an IGS format for exchange of data among software receiversSpecify BW and carrier frequencySpecify sample rate, quantization, type of AGC usedSamples must be time tagged with an accuracy &lt; 10 usec and sample clock must have Allan deviation &lt; 10e-9 for T = 1 to 100 sec (shorter time scales commensurate)Specify IF of sampled dataRecommend Galileo provide all signals to science users</p><p>I know that we who aspire to being academics should hew to theory and not get too excited about devices, but Ill confess that I get excited about this box, and I devoted a great deal of time to developing it while at Cornell. Its capable even compared to receivers who use dedicated GPS processing chips, and its flexibility means that it can be tailored for use in novel GPS-based applications. </p><p>You can think of it as a powerful platform for ionospheric, etc, research</p></li></ul>


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