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

A direct sequence serial search acquisition scheme based on the assumption that there are two adjacent in-phase states (H₁ cells) 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 utilise both H₁ cells, the test statistic is composed of the observation on the couple of adjacent cells by a given type of detector and the acquisition process is modelled by a four-state Markov chain. As an application of this general approach, the noncoherent matched filter detector acquisition of BPSK direct sequence spread-spectrum signals over an additive white Gaussian noise channel is analysed. 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, an improved acquisition performance can be achieved and a more robust mean acquisition time performance against the variation of the threshold can be reached. The proposed scheme can be employed to replace any conventional cell-by-cell PN sequence serial search scheme, provided that the decision variable is changed correspondingly