Blind synchronization, estimation of data symbol, spread sequence, and generator polynomial in direct sequence spread spectrum systems

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.