Estimation of spread spectrum parameters using fourth-order statistic for a DSSS signal

Direct sequence spread spectrum (DSSS) signals are now widely used for secure communications, as well as for multiple accesses. Since the transmission uses Pseudo-random (PN) sequence to spread the spectrum, the power spectral density of a DSSS signal can be below the noise level. Hence, parameter estimation of a DSSS signal is difficult and necessary. In this paper, estimations of a DSSS signal's spread spectrum parameters using a higher-order statistic are investigated. Two kinds of parameters, PN sequence period and chip rate, are estimated. Since one dimensional slice of the fourth-order moment of Gaussian white noise is zero, while that of the DSSS signal contains information of the PN sequence, estimation algorithms are proposed. Analyzing the received signal's fourth-order moment, there are periodic peaks and triangle waves near the peaks. The location of peaks and triangle wave width are used to estimate PN sequence period and chip rate. Simulation results indicate that these methods can provide good estimation performances even at -17 dB SNR.