SE40 Meeting on Pseudolites JRC test results 04-05 July 2011

Conclusion and Future Work Outline Previous Results Saturation Loss Model Experimental Setup Results Conclusion and Future Work

Previous Results Experiments on Commercial Receivers - conducted mode - pulsed and continuous pseudolite signals - measurements and position domain analysis (results published in “Impact of Pseudolite Signals on Non-Participating GPS Receivers”, JRC Scientific and Technical Report) Scoping Study on Pseudolites Investigation of pseudolite technology and applications (published as JRC Scientific and Technical Report)

Impact on Non-participating Receivers 4/14 Assess the pseudolite impact on non-participating receivers: + theoretical analysis: development of a model able to predict the loss caused by pseudolite signals + experimental analysis: Hardware and software simulations Experiments using RF signals in conducted and radiated mode Software based and hardware commercial receivers GPS and GALILEO + use of commercial pseudolites - Space System Finland (SSF)

Theoretical Analysis: Model Assumptions 5/14 Theoretical model capable of predicting the impact of pulsed pseudolite signals on non-participating receivers. Signal Conditioning ADC ADC working in saturation mode Ideal and very slow AGCs: the AGC gain is constant Down-conversion Filtering AGC Loss computed at the correlator output (impact of the despreading process) Complex Correlator Output Local Carrier Local Code

Theoretical Analysis: Receiver Losses 6/14 Account for: Quantization effects: ADC and AGC Pulse duration Spectral separation between pseudolite and GNSS signals Simulation results supporting the theoretical analysis Pulse duty cycle Quantization loss ADC: number of bits AGC gain

Receiver Losses: Results 7/14 Theoretical results supported by “field tests” (simulation of RF pseudolite signals) Experiments using commercial hardware receivers Good agreement with theoretical results Residual differences due to lack of information on the commercial Rx (black box): number of bits, AGC type, ...

Experimental Setup (I/II) 8/14 Experiments in Anechoic Chamber Up to three GPS PLs Space Systems Finland GPS + Galileo Constellation simulator Spirent Communications Two commercial receivers GPS + Galileo: Simulated Experiments: Single PL: continuous Single PL: pulsed 3 PLs: pulsed Anechoic Chamber GPS Pseudolites SSF Receivers: Javad: Survey GPS+Galileo u-Blox: High Sensitivity GPS

Experimental Setup (II/II) 9/14 Fixed PL – Rx geometry maintained throughout tests ~ 5 m between PL and Rx antennas Tx power and/or pulse duty cycle was varied Baseline performance  simulator run with all PLs switched off Performance metric  C/N0 loss for satellite signals relative to baseline PL Antennas Rx Antenna

Impact of Pulsed PL (I/II) 10/14 Single PL – Pulse Duty Cycle (PDC) ~ 9.35 % Constant geometry – Transmit power increased by 3 dB every 5 minutes C/N0 loss in non-participating receivers averaged over all satellites Notes: Galileo less affected  impact of spectral separation coefficients Javad receiver shows greater loss than u-Blox  impact of receiver bandwidth and, potentially, bit-depth

Impact of Pulsed PL (II/II) 11/14 “Ideal” loss model: (loss incurred with no quantization effects) SSC – Spectral separation coefficient P/N0 – Effective PL power to noise density ratio “ideal” model  loss gets worse with increasing P/N0 In practice  Saturation limits loss N.B.  The “better” the receiver (larger BW, more bits) the worse the effect of the pulsed PL

Continuous vs. Pulsed 12/14 Continuous case: Receivers had difficulty tracking as PL C/N0 increased Continuous case: additional losses due to compression by AGC Advantages of pulsing apparent from the results Lines  Continuous PL Markers  Pulsed PL Note: u-Blox shows greater losses for continuous PL  due to ability to track weaker signals Javad fails to track most GPS signals when P/N0 > 54 dB-Hz

Multiple Pulsed Pseudolites 13/14 For this test  PLs configured to operate in pulsed mode Power levels high  receivers operate in saturation Pulse duty cycle varied in range 2 to 9 % Aggregate duty cycle up to 3 times these values Note: At PDC ~ 4%  loss is similar to single PL with PDC of 9% u-Blox experiences marked increase in losses for larger PDC Effect of AGC?

Conclusion and Future Work 14/14 Conclusions Developed a loss model to account for quantization effects For the same effective P/N0, continuous mode PLs induce greater losses than pulsed mode PLs Due to capture of the AGC Radiated-mode test-bed confirms conducted-mode results Future Work Further analysis of these results – particularly multiple PL case Improve model to account for non-ideal AGC (i.e. consider the impact of the pulsed PL on the AGC) Further testing Acknowledgement JRC thanks Space Systems Finland for the generous loan of the pseudolites used in these tests.