Blind synchronization, estimation of data symbol, spread sequence, and generator polynomial in direct sequence spread spectrum systems
Youngho Jo, Dapeng Oliver Wu · 2008
Secure transmission of information over hostile wireless environments is desired by both military and civilian parties. Direct-sequence spread spectrum (DS-SS) is such a covert technique resistant to interference, interception and multipath fading. Identifying spread-spectrum signals by an unintended receiver (or eavesdropper) without a priori knowledge is a challenging problem. To address this problem, we first search the start position of a data symbol in the spread signal (for synchronization); our method is based on maximizing spectral norm of a covariance matrix, which achieves smaller estimation error than the existing method of maximizing Frobenius norm. After synchronization, we remove information symbols by a cross-correlation based method, and identify the spread sequence by a matched filter. The proposed identification method is less expensive and more accurate than the existing methods. We also propose a zigzag searching method to identify a generator polynomial that reduces memory requirement and is capable of correcting polarity errors existing in the previous methods. Our simulation results validate the effectiveness of our proposed method.