A Research On The Parameters Estimation Algorithm Of DSSS Signal In Non-cooperative Communication

In the background of non-cooperative communication, the third part needs to do signal parameters estimation to demodulate the information. The study of this thesis focuses on the estimation algorithms of spread spectrum signal parameters, including two kinds spread spectrum signals:the conventional direct sequence spread spectrum(DSSS)signal and the WCDMA satellite signal.This thesis is based on the practical project. Firstly, we discuss the pre-processing procedure:including the down sampling, digital down convert, interpolation, ect; The pre-processing is used to convert the received signal to the standard format that required by the estimation algorithms.As to direct sequence spread spectrum(DSSS) signal, the parameters that need to be estimated are:carrier frequency, chip rate, pseudo-code period, pseudo-code. In the estimation of the carrier frequency, we study on the cyclic spectrum algorithm which has excellent performance of anti-noise, and thus can estimate the carrier frequency of DSSS signal even in low SNR. In the estimation of chip rate, we study on the wavelet algorithm in which we take advantage of the wavelet transformation’s feature that sensitive to time sudden change and excellent denoising performance. In the estimation of pseudo-code period, we study on the classic signal spectrum reprocessing algorithm and another algorithm which is based on time domain correlation, do comparison of the performance of these two algorithm and summarize the application situation. Finally, in the estimation of pseudo-code, we study on the eigenvalue decomposition algorithm. Besides, we also use the Independent Component Analysis algorithm to do blind separation and estimate the target user’s pseudo-code and the information sequence in DS-CDMA system.As to WCDMA-S signal, because of the similarity between WCDMA-S signal and WCDMA signal, we take the WCDMA signal as an example to discuss the parameter estimation of WCDMA-S. By comparing the transmitter structure between WCDMA signal and the conventional DSSS signal can be found that the algorithm for estimating carrier frequency and chip rate can be general used for both signals, which have nothing to do with the type of spread spectrum signal. In the end, we do research on the scrambling code estimation algorithm:the algorithm based on the WCDMA signal generation protocol, convert the problem of estimation scrambling code to the problem that estimate one m sequence’s initial state. The simulation shows that the algorithm has the ability of anti-interference and anti-multipath.