An improved detection technique for direct-sequence code acquisition in a Rayleigh fading mobile channel

A novel differentially coherent (DC) detection scheme for rapid code acquisition is proposed for a direct-sequence (DS) spread-spectrum system in a nonselective Rayleigh fading mobile channel. The scheme processes the received signal at baseband by a complex differential decoder and, then, performs a coherent partial correlation of the differentially-decoded (DD) output and the DD version of a local DS code to form the detection statistic. Its detection performance is analyzed based on a central-limit-theorem type of argument, and verified by extensive simulation. Parallel acquisition systems employing the DC detector and the conventional noncoherent I-Q detector are compared by mean acquisition time performance. It is shown that the DC acquisition system significantly outperforms the noncoherent I-Q acquisition system