Research On Detection Of PN Code Acquisition Based On Wavelet Transform In DS-CDMA System

The third mobile communication system is built on the basis of ITU IMT-2000 suggestion, and it can work on 2GHz. Meanwhile, the wideband system's rate can get 2Mbit/s and this system use communication pattern of CDMA. As a key technique of the third mobile system, initial synchronism technology is the necessary base of other key technologies. Initial synchronisms of CDMA communication system receiver include PN code sync, symbol sync, frame sync, sync of scramble code, and so on. Because that DS-SS technology is used most widely in the system of CDMA, a great deal of research on method for acquisition of PN code is based on DS-SS. The sync of PN code is divided into two steps generally: The first step is the searching and acquiring of PN code phase (namely, acquisition of sequences) so that the phase error between sending code and receiving code is within 1 bit. The second step is tracking which is on the base of the initial acquisition, so the error of phase is decreased more and sync is keeping. The judgement of PN code acquisition is an important problem of the code sync and the traditional method of it is power detection.At present, wavelet analyzing is a hot task in the field of science and engineering application. It is a mathematic method and developed from Fourier analyzing. Similar to Fourier analyzing, it is a kind of technique in time-frequency. Because of the characteristic of its multire-solution analysis, wavelet is applied in signal de-noising, signal data compressing, diagnosing of machine breakdown and data processing. In this paper the wavelet transform is used in the PN code acquisition of CDMA communication system. Considering the signal characteristic of PN code acquisition, the judgment of code acquisition by wavelet transform is made under AWGN channel of system. It is a try to apply the new tool of signal processing to communication system.This thesis studies the characteristic of acquired signal (namely BPSK signal or QPSK signal) and non-acquired signal (namely white Gaussian noise), The AWGN channel of CDMA system is analyzed. At the same time, The pertinent knowledge of wavelet multire-solution decomposition and a method of wavelet detection which apply on the PN code acquisition is given. In the end, The Matlab simulation results show that this method can be used in AWGN channel, And the relations among , under different SNR is given...