A Novel Cyclic-Moment Based Method for DS-SS QPSK Signal Blind Parameter Estimation

The parameter estimation of Direct sequence spread spectrum (DS-SS) signals with QPSK modulation under non-cooperative conditions is considered. The explicit expressions of both the third- and the fourthorder cyclic-moments of QPSK signals are derived, and the cycle frequency structure corresponding to the secondand fourth-order cyclic-moment of DS-SS (Direct sequence spread spectrum) QPSK signals is deduced. A novel parameter estimation method is proposed by combining the second- and the fourth-order cyclic-moments, which can perform blind parameter estimation without a priori knowledge of pseudorandom sequence and frequency parameters. Moreover, the method which employs onedimensional slices, also avoids multi-dimensional searching. Simulation results are presented to confirm the validity of the method.