An Adaptive Threshold Technique for Fast PN Code Acquisition in DS-SS Systems

This paper presents an efficient technique to considerably reduce pseudonoise (PN) code acquisition time by adjusting threshold values, depending on the pre-estimated correlation energy in direct-sequence spread spectrum (DS-SS) systems. The proposed technique utilizing a threshold generation mode (TM) prior to a search mode is employed to a conventional double-dwell serial-search algorithm, and the TM determines the threshold values of both search and verification modes, depending on its correlation energy. We present a mathematical model of the proposed scheme to analyze it with respect to the mean code acquisition time in synchronous code-division multiple-access (CDMA) systems such as Third-Generation Partnership Project 2 (3GPP2) under a Rayleigh-fading channel. Numerical results show that the proposed method can reduce the mean code acquisition time by more than 60% and compensate for the performance degradation in high signal-to-noise ratios (SNRs) with no increase in hardware costs, compared with the conventional algorithm that adopts a soft-decision technique.