Performance of direct sequence spread spectrum techniques for high rate communications in the high frequency band.

Abstract

For the last decade or so, major development in the fields of Large Scale Integration and Digital Signal Processing have revived the interest in the HF skywave channel (3-30 MHz) and more particularly in the use of wideband signalling to either increase the transmission rate or to improve the system efficiency. This thesis is aimed at the performance estimate of a wideband HF communication system using direct sequence spread spectrum. In this study, an HF channel model referred to as the Ionospheric Parameter Model is implemented in software and used to simulate a variety of channel conditions. BER performance for a communications systems transmitting at a rate of 2400 bits per second is estimated through 'Monte-Carlo' simulations. More specifically, direct sequence spread spectrum combined with a RAKE receiver implementation is evaluated under quiet and disturbed ionospheric conditions. Performance is compared for different processing gains and levels of multipath diversity. Finally, performance obtained with the addition of block coding and convolutional coding with and without interleaving is provided.