Charles Tytler

 Pseudo-satellites:  Ground-based transmitters of GPS signals  Augment GPS  Applications:  Indoor GPS  Mining, Caves  Underground/Underwater Surveying  Differential GPS

 The largest difficulty in pseudolite installation  A common problem for CDMA systems Illustration of distance from pseudolite and its effect on signal tracking

 Pseudolites use PRN codes  Pulsing Scheme in simulation defined by RTCM SC-104  Pulse Duration = 1/11 C/A Code Period  90.91µs (93 Chips)  Every 10 th period transmits 2 pulses  Pulse Duty Cycle = 10%  Entire PRN code received in 10 periods PURPOSE:  Allows pseudolite to transmit at high power without blocking out signals from satellites

 White Noise: -141dBW  Satellite signals: -160dBW

 Pseudolite signal tracking with all four transmitting  Takes up approximately 40% of the signal  Cross-correlation plots  Correlation vs. Time delay  Each peak represents a PRN code match for a code period  Peaks should occur every 1ms Simulated for 20ms and sampled at 12MHz

1 Pseudolite 2 Pseudolites 3 Pseudolites 4 Pseudolites

 Since satellite signals are overpowered by pseudolite pulses  Better to have zero input than interfering pulses  Receiver “blanks” all input when it detects saturation  Would need modification to GPS receivers

Pseudolite Blanking Applied

 Use of multiple pseudolites in isolated areas such as open pit mining is very practical  Pseudolite configurations should be investigated  Allow use of multiple pseudolites by local users  Limit interference to other nearby receivers  Cost effective techniques for both hardware and software implementation of pseudolite blanking

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