Simulation performance of a quantized log-likelihood sequential detector for PN code acquisition in the presence of data modulation and Doppler shift

The problem of initial acquisition of data modulated spread-spectrum PN codes in low signal-to-noise ratio (SNR) conditions using a variable-dwell time serial search synchronizer controlled by a sequential detector is addressed. The effect of carrier and code rate Doppler frequency offsets on the acquisition characteristics of three kinds of sequential detector was assessed by means of a Monte Carlo computer simulation, and their performances were compared. The detectors examined are: the ideal log-likelihood sequential detector; the quantized log-likelihood sequential detector; and the biased square law sequential detector. These were analyzed in the presence of Doppler shift and data modulation at two values of bias, namely, the normalized Wald's (1947) optimum bias and a nonoptimum bias.<
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