New Detection Methods of DS-CDMA Signal at Lower SNR

DS-CDMA in the modern civil and military communications is widely used. Due to its low power spectral density, the DS-CDMA signal always floods in the background noise, bringing difficulties to the signal’s reconnaissance. Therefore, DS-CDMA signal detection has attracted attention of researchers. In this paper, the fourthorder moment chip ( ( ) τ , 0 , 0 4x m ) of DS-CDMA signals is derived, against the background of Gaussian white noise, and get the conclusion that ( ) τ , 0 , 0 4x m can suppress Gaussian white noise. In order to reduce the estimation error of ( ) τ , 0 , 0 4x m , the quadratic fourth-order moment chip is proposed and finally two detection methods based on the quadratic fourth-order moment chip of DS-CDMA are proposed. Experimental results show that the detection performance of the methods is better than that of the double frequency method, spectrum-reprocessing method and cepstrum method. When the false alarm probability is 1%, the detection probability of presented methods reaches above 90% at SNR -22dB.