Noncoherent hybrid parallel PN code acquisition for CDMA mobile communications

Abstract

This paper proposes a noncoherent hybrid parallel pseudonoise (PN) code acquisition scheme for code-division multiple access (CDMA) mobile communication systems and analyzes the effect of multiple access interference (MAI) on the code acquisition performance for Rayleigh and Rician fading channels. The hybrid acquisition scheme combines parallel search with serial search to cover the whole uncertainty region of the input code phase. It has a much simpler acquisition hardware structure than the total parallel acquisition and can achieve the mean acquisition time slightly inferior to that of the total parallel acquisition in the case of severe MAI; on the other hand, it provides the flexibility in the tradeoff between the mean acquisition time and system complexity if no MAI is considered. The closed-form expressions of the detection and false-alarm probabilities and mean acquisition time are derived. Numerical analysis quantifies the severe performance degradation of code acquisition due to both MAI and channel fading, and demonstrates the dependence of the increase of mean acquisition time (due to MAI) on the number of users in the CDMA system, system design parameters, and channel fading statistics.