Yadegar- e- Imam Khomeini (RAH) Shahr-e-Rey, Islamic Azad University
iIslamic Azad University, Yadegar-e-Imam Khomeini (RAH) Shahre- Rey Branch, Tehran, Iran
In this paper, an asymptotic estimating technique to detect direct sequence spread spectrum (DSSS) signals using modified frequency domain fourth-order cumulant is proposed. Based on 2-D slices fourth-order cumulant, an efficient algorithm is proposed to solve the problem of complex computation and huge processing time. The method of fourth-order cumulant in frequency domain can achieve detection probability above 50% at SNR -25dB. In this paper, we strongly decrease processing time and complexity of computations that it makes this method appropriate for employing in the DSSS detection systems. This method only requires to store a row vector while ignoring all the low and diagonal elements and therefore the required memory is highly reduced. In addition, as it uses two-line search strategies (predictor and corrector) to obtain a new iterative point, the spectral properties of the diagonal updating scheme is improved, and rapid convergence property is gained. Also, this method estimates carrier frequency and symbol rate simultaneously in the online processing. Simulation results and computation analysis indicate that processing time of the proposed method is decreased about 30% with respect to the commonly used fourth-order cumulant methods.