Performance analysis of an FFT based fast acquisition GPS receiver

The performance of a parallel/serial FFT based acquisition unit for weak signal GPS processing is analysed. Parallel search in the code delay domain is implemented via FFT correlation. Frequency domain search is performed in a serial fashion. A catastrophic false alarm model is assumed, i.e. once a false alarm is declared there is no return to the search state. System performance is measured in terms of the probability of detection and the mean time to the first "Hit" event. The system is modelled as a Markov chain and the flow graph method is used to determine system performance. Signal effects, including code and carrier Doppler and data modulation, are considered. Results are compared with Monte Carlo simulation for a simplified signal model (Doppler rate, local oscillator drift and quantisation effects are ignored). Optimisation of a subset of the receiver parameters is considered as a demonstration of the utility of the results.