Spreading Sequence Estimation of Direct Sequence Spread Spectrum Signals with Unknown Carrier Offset

In this paper, by absorbing the carrier frequency into the spreading waveform, an efficient algorithm to estimate the spreading sequence of direct sequence spread spectrum (DSSS) signals with unknown carrier offset is proposed. The proposed algorithm is based on the subspace decomposition of covariance matrix. The signal to noise ratio (SNR) of the spreading waveform estimation with unknown carrier offset is improved by signal subspace decomposition, which reduces the difficulty in carrier frequency estimation. Under the stochastic signal model assumption, we also derive the Cramer-Rao lower bound (CRB) of spreading waveform estimators. Simulation results demonstrate the effectiveness of proposed algorithm in lower SNR situations.