BER ANALYSES OF NORMAL AND MULTIPLE CHIP RATE CODE-DIVISION MULTIPLE-ACCESS SYSTEMS

Abstract

A new technique using multi-fold convolution to model both self and multipath interference has been developed. The algorithm possesses a semi-analysis/semi­simulation characteristic which makes it very efficient and flexible in evaluating any DS/CDMA based system. The BER performance versus the number of active interfering users can be obtained, taking into account of the effects of some very important factors, such as self-interference, multipath fading and correlator receiver. By analysing a normal DS/CDMA system, which models a fully connected communication system or the up-link channel of CDMA mobile cellular, it is found that both self-interference and multipath fading will severely damage the BER performance. Code type selection doesn't show much significance when the number of active users is fairly large or severe multipath fading presents. However, deliberately choosing some proper sequences from a large code family can benefit a small CDMA system. To support multiple data rate and multi-media communications, a multiple chip rate (MCR) CDMA system is proposed and its performance evaluated. The results revealed that MCR/CDMA system can provide a comparable BER performance as a normal CD MA system.