Variable dwell-time code acquisition for direct sequence spread spectrum systems on multipath fading channels

Variable-dwell time code acquisition based on multiple-dwell or sequential linear test is investigated for direct-sequence spread spectrum systems on time-varying multipath Rayleigh fading channels. Not like the case of conventional additive white Gaussian noise channels, the channel memory incurred by multipath fading renders the exact analysis of the acquisition systems extremely difficult, if not impossible. A novel method is developed to evaluate the mean acquisition time of the acquisition systems to any desired accuracy. The effects of multipath fading are evaluated, and comparisons are made between the multiple-dwell and sequential linear tests. Numerical results show that multipath fading may result in 1-4 dB loss in performance, and the sequential linear test can outperform the multiple-dwell test by a margin of 1-2.5 dB. The analytical results are verified by computer simulations.