An Iterative Method for Code Acquisition Using DOA Estimation and Beamforming

Abstract:
This paper introduces a method used for code synchronization in direct sequence spread spectrum (DS/SS) systems when the receiver is equipped with a smart antenna followed by the matched filter (MF). The presented method first estimates the direction-of-arrival (DOA) of the DS-signal, then performs beamforming, and finally makes synchronization decision based on the maximum output of the MF. Because the amount of data needed in DOA estimation depends on the prevailing signal-to-noise ratio (SNR), the proposed method operates iteratively. The method starts by collecting a piece of data for DOA estimation. Due to the inaccurate DOA estimation, the main beam of the radiation pattern may be steered to erroneous direction and code acquisition may be failed. After a fail more data is collected and the accuracy of DOA estimate improves. This process is repeated until DOA and delay estimation succeeds. The results show that it is advantageous to start by collecting only a small amount of data for DOA estimation because the shortest mean acquisition times are achieved in that case.