DIRECT SEQUENCE CDMA SOFTWARE SIMULATION TESTBED: COMPREHENSIVE METHOD OF ALGORITHM EVALUATION FOR CDMA COMMUNICATION SYSTEMS

Abstract

Spread Spectrum is a modulation technique that spreads a transmit signal ACrOss bandwidth which is much wider than the usual bandwidth required for transmitting the signal. DS-CDMA is a form of Code Division Multiple Access (CDMA) system that Uses the Direct Sequence Spread Spectrum (DS-SS) technique. In this work, we have developed 4 software testbed for simulating a DS-CDMA using a block diagram simulation system built in the Matlab and Simulink environment. The system was successfully implemented While highlighting the important design options and trade-off issues involved in the basic design of a DS-CDMA communication system. This testbed can be used as a veritable tool for teaching and demonstration of the concept of a DS-CDMA system. Apart from this, it cay also be used as a basic design tool for studying the performance of a CDMA communication system under certain system parameters and channel conditions. In our study, we used the Bit Error Rate (BER) as the performance indicator. The results we obtained showed that among the three sequences used as spreading codes, Gold sequences provided the best autocorrelation and cross correlation properties followed by Kassami and Pseudo random sequences in that order. Results of multipath versus single path simulations showed that multipath effect is exploited to an advantage by the use of rake receivers. Finally, the results of single user versus multiuser simulations support the interference rejection property of DS-CDMA systems.