Constrained Optimization of Coincidence Detector Parameters for GPS Acquisition

Acquisition of code division multiple access (CDMA) signals can be carried out using fixed or variable dwell times. The choice of acquisition strategy is a trade-off between performance and computational complexity, and a number of variable parameters (number of dwells, dwell lengths and thresholds) must be carefully designed. In this work, the performance of a variable dwell time coincidence detector is analysed in terms of its mean time to verify the acquisition of Global Positioning System (GPS) L1 C/A signals. A new expression for the variance of the coincidence detector dwell time is derived. A general framework for the optimisation of dwell parameters for the coincidence detector is outlined. Both immediate- and non-immediate reject cases are analysed and compared to the fixed dwell time single dwell strategy, which is, itself, a special case of the coincidence detector. Case-specific numerical optimisation results are illustrated across a range of signal-to-noise ratios and general rules-of-thumb for the best choice of parameters are highlighted.