Performance evaluation of spread-spectrum code acquisition system using four-state Markov process

A direct sequence serial search acquisition scheme based on the assumption that there are two adjacent in-phase states (H/sub 1/ cell) in the code position uncertainty region, on which the received pseudorandom noise (PN) code and the local despreading PN code signal is coarsely aligned, is presented. To utilize both cells, the test statistic is composed of the observation on the couple of adjacent cells by the given type of the detector and the acquisition process is modeled by a four-state Markov chain. As an application of this general approach, the non-coherent matched filter detector acquisition of BPSK direct sequence spread-spectrum signals over an additive white Gaussian noise (AWGN) channel is analyzed. The mean acquisition time is evaluated for various values of system parameters. The comparisons with that of the conventional cell-by-cell serial search acquisition system show that at almost the same cost a significant improvement can be achieved and a much more robust mean acquisition time performance against the change of the threshold or the signal-to-noise ratio per chip (SNR/chip) can be reached.