A self-synchronizing method for asynchronous code acquisition in band-limited spread spectrum communications

Abstract

This paper addresses the problem of initial synchronization of pseudo-noise code. A new code acquisition technique for spread-spectrum communication systems using band-limited chip waveforms is presented. Unlike conventional power detector based on testing the estimated maximum of the ambiguity function, the devised detector exploits a fast parabolic interpolation, running on three estimated ambiguity samples in the neighborhood of the coarse estimate. Performance analysis is carried out in comparison with conventional detector. Mathematical expressions for the probability of false alarm and detection are derived. They are numerically evaluated, under operating settings, by a reduced Tayloriquests expansion up to the second order. The theoretical results, substantiated by computer simulations, have evidenced that the devised method is well suited for asynchronous spread-spectrum communications. In particular, the acquisition performance depends on the actual offset between the received and the reference code waveforms, which are randomly distributed (in chip-asynchronous systems) within one sampling period. In fact, the parabolic interpolation technique outperforms the conventional detector for a wide range of code offsets because it is able to self-synchronize the testing variable around the true offset.