Performance evaluation of serial-search strategies for the acquisition of DS/CDMA signals

Search strategies for initial synchronization of direct sequence (DS) spread spectrum communication systems are compared, modelled and implemented using MATLAB then tested in the presence of additive white Gaussian noise (AWGN) and narrowband interference. The performance of these search strategies, namely, offset-z-search strategies and expanding alternate search strategies, in terms of the mean value of the search length is evaluated for different probabilities of detection. A truncated Gaussian probability phase distribution is assumed (as a priori information about the correct phase) and the performance of these search strategies is tested for different standard deviations (σ) of the phase. A novel search strategy, namely the offset-z3, based on the offset z-search strategy is introduced. Among all search strategies investigated the non-uniform expanding alternate (NUEA) search strategy is found to perform best at high probability of detection. However, for a more peaked phase distribution, the offset-z3-search strategy is shown to offer better performance at low probability of detection. Outcomes of the simulated system support trends predicted by theory for the performance of different search strategies.