GPS CDMA Link Analysis

The GPS uses direct sequence spread spectrum (DSSS-CDMA) for the C/A code transmissions at a chip rate of 1.023 Mcps using BPSK modulation. The C/A code transmissions are 1023 chip PRN sequences, formed into 37 Gold codes (unique for each satellite) using BPSK. At any given time, assume that 10 GPS satellites are visible, where 4 are closer than the remaining 6 at greater range. The navigation solution selects the 4 strongest signals, and assume the following: Downlink Budget for C/A code Satellite EIRP 27.0 dBW Path loss: -187 dB (4 closest GPS) -189 dB (6 remaining GPS) Receiving antenna gain +1.0 dB Lsys: -2.5 dB CIA code Rc: 1.0230 Mcps Receiver noise bandwidth: 2.0 MHz (allows extra BW for Sat Doppler) Receiver Noise Temp: 150 K Assuming an ideal correlation receiver, output signal-to-noise (SNR) ratio = = dB The Rb of the despread GPS CIA code signal (@ receiver output) Hz The GPS uses direct sequence spread spectrum (DSSS-CDMA) for the C/A code transmissions at a chip rate of 1.023 Mcps using BPSK modulation. The C/A code transmissions are 1023 chip PRN sequences, formed into 37 Gold codes (unique for each satellite) using BPSK. At any given time, assume that 10 GPS satellites are visible, where 4 are closer than the remaining 6 at greater range. The navigation solution selects the 4 strongest signals, and assume the following: Downlink Budget for C/A code Satellite EIRP 27.0 dBW Path loss: -187 dB (4 closest GPS) -189 dB (6 remaining GPS) Receiving antenna gain +1.0 dB Lsys: -2.5 dB CIA code Rc: 1.0230 Mcps Receiver noise bandwidth: 2.0 MHz (allows extra BW for Sat Doppler) Receiver Noise Temp: 150 K Assuming an ideal correlation receiver, output signal-to-noise (SNR) ratio = = dB The Rb of the despread GPS CIA code signal (@ receiver output) Hz