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

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

Todd E. Humphreys, Cornell University Larry Young, JPL Thomas Pany, University FAF Munich

2008 IGS Workshop, Miami Beach FL

IGS Receiver Considerations

Page 2: 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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Opportunity: New GNSS Signals

(Fig. 1 of Wallner et al., "Interference Computations Between GPS and Galileo," Proc. ION GNSS 2005)

Page 3: 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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Overview

IGS receiver characteristics: Ultra, Super, Minimum Commercial Receiver Outlook Software Receiver Outlook Recommendations

Page 4: 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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The Ultra Receiver

Digital Storage Rx

MassStorage

RF Front-End

ReferenceOscillator

ADC

SampleClock

Page 5: 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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The Ultra Receiver

SoftwareCorrelators

TrackingLoops, DataDecoding,

ObservablesCalculations

FFT-basedAcquisition

Software Post-Processing

Digital Storage Rx

MassStorage

RF Front-End

ReferenceOscillator

ADC

Sample

Clock

Digital Storage Rx

MassStorage

RF Front-End

ReferenceOscillator

ADC

Sample

Clock

Digital Storage Rx

MassStorage

RF Front-End

ReferenceOscillator

ADC

Sample

Clock

Digital Storage Rx

MassStorage

RF Front-End

ReferenceOscillator

ADC

Sample

Clock

Page 6: 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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The Super Receiver

Tracks all open signals, all satellites Well-defined, publicly disclosed

measurement characteristics (phase, pseudorange, C/No)

RINEX compliant Completely user reconfigurable, from

correlations to tracking loops to navigation solution

Internal cycle slip mitigation/detection Up to 50 Hz measurements Internet ready; signal processing

strategy reconfigurable via internet Low cost

Page 7: 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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L1 L1

L2 L2

P2 P2

C1 or P1

C1 or P1

2008 20202012 2016

Minimum IGS Receiver Requirements

Page 8: 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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Requirements Considerations

Pseudorange Precision Multipath Errors

L2C/L5 Rollout Timetable 2020 Discontinuation ofCodeless/Semicodeless access

Page 9: 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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Minimum IGS Receiver Requirements

L1 L1 L1 L1

L2 L2 L2 or L5

L2

P2 P2 or C2

P2 or C2 or C5 P2 C2

C1 or P1

C1 or P1

C1 or P1

C1 or P1

L5

C5

?

?

XX

2008 20202012 2016

Page 10: 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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Commercial Receivers Offerings

Topcon NET-G3

Trimble NetRS/NetR5 Septentrio PolaRx3

Leica GRX1200

Page 11: 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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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):

Page 12: 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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Outlook for Commercial Receivers

Good: Market trend is to track

all available signals, all satellites

Internet ready Some vendors offer

increasing reconfigurability

All top vendors provide near-optimal standard tracking

Rugged, stable, reliable platforms

Bad: Some vendors unwilling

to disclose measurement characterization

Problems in past with proprietary output formats (2 year wait!)

Uneven C/N0 reporting on some devices

No support for exotic tracking techniques

Limited reconfigurability IGS has little leverage

Page 13: 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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Software GNSS Receiver

Front End

RF Front-End

ReferenceOscillator

ADC

SampleClock

SoftwareCorrelators

TrackingLoops, DataDecoding,

ObservablesCalculations

FFT-basedAcquisition

FPGA/DSP/CPU

Page 14: 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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Flexibility: Iridium-based Navigation on a Software Receiver Platform

~100-m geolocationerrors

Page 15: 1 Todd E. Humphreys, Cornell University Larry Young, JPL Thomas Pany, University FAF Munich 2008 IGS Workshop, Miami Beach FL IGS Receiver Considerations

15Humphreys, 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, 2006

Supports 72 L1 C/A channels FFT-based acquisition down to C/N0 = 32 dB-Hz Carrier tracking down to C/N0 = 25 dB-Hz Version 2: Dual-frequency (L1/L2C) with improved

scintillation robustness Completely software reconfigurable

Cornell “GRID” Dual-Frequency Software-Defined GNSS Receiver

Cornell GRID Receiver(GNSS Receiver Implementation on a DSP)

Page 16: 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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GNSS Software Receiver at University FAF Munich & IFEN GmbH

L1, L2, L5 front-end 13 MHz bandwidth at each frequency Multiple CPU cores for parallel

processing Tracks all-in-view civil GPS, SBAS,

and Galileo 1 kHz max measurement output rate Completely software reconfigurable

Page 17: 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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JPL’s TOGA Instrument(Time-shifted, Orthometric, GNSS Array)

L1, L2, L5 front-end Electronically-steered antenna array Multiple FPGAs for parallel

processing Buffer memory for near-realtime or

offline processing Completely software reconfigurable

Page 18: 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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Good: Complete

reconfigurability Complete transparency Support for exotic

tracking strategies Theoretical performance

equal or better than commercial receivers

Bad: Only JPL currently

supports P(Y) tracking Have not been

thoroughly evaluated against traditional receivers

Outlook for GNSS Software Receivers

Unknowns: Who will build platforms? Who will maintain software?

ACs? Commercial provider?

Price?

Page 19: 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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Recommendations (1/2)

1. Study the effects of long-delay multipath by comparing (P1,P2) with (C1,C2) measurements from same SV

2. Compare software receiver and traditional receiver performance via signal simulator and field tests

3. Demand from receiver vendors either (1) detailed measurement description, or (2) adoption of a standard measurement technique (e.g., JPL technique)

4. Consider an IGS-sponsored software receiver5. Revise minimum receiver requirements

according to the foregoing schedule6. Any comment on US proposal to discontinue

access to semicodeless P(Y) tracking? If not, then suggest “no comment.”

Page 20: 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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Recommendations (2/2)

7. Any comment on US proposal to discontinue access to semicodeless P(Y) tracking? If not, then suggest “no comment.”

8. Establish an IGS format for exchange of data among software receivers

1. Specify BW and carrier frequency2. Specify sample rate, quantization, type of AGC

used3. Samples must be time tagged with an accuracy

< 10 usec and sample clock must have Allan deviation < 10e-9 for T = 1 to 100 sec (shorter time scales commensurate)

4. Specify IF of sampled data9. Recommend Galileo provide all signals to

science users