PERFORMANCE COMPARISON OF VARIOUS SHORT CODES IN DIRECT SEQUENCE SPREAD SPECTRUM (DS/SS) SYSTEM

Abstract

A spread spectrum system is largely categorized by its coding scheme,the type of code depend on its length, and its chip-rate all define the overall system parameters. In order to improve the system's spreading capability it is necessary to alter the coding arrangement. This paper compares the performance of the direct sequence spread spectrum (DS/SS) system-baseband QPSK modulation with various types of short codes: Barker ,Walsh,Hadamard,Kasami ,M-sequence and Gold code by measuring the probability of error (Pe) and shows the autocorrelation and crosscorrelation of these code in presence of Rayleigh Fading (Flat Fading) channel and Additive White Gaussian Noise (AWGN) channel.The results were shown the probability of error (Pe) for Barker code was 3.817 x10-5 at 20dB signal- to-noise ratio (SNR), so the best choice in short code DS/SS system was Barker code,in addition to it had good autocorrelation and crosscorrelation functions.Also the results were shown the probability of error (Pe) for Gold code was 3.13x10-3 at 20dB signal- to-noise ratio (SNR), so the worst case in DS/SS system was Gold code.