DS-CDMA performance with maximum ratio combining and antenna arrays in Nakagami multipath fading

Abstract

The indoor wireless communication (IWC) channel is very hostile to a DS-CDMA signal and therefore effective techniques are needed to enhance the system performance and capacity. By implementing antenna arrays, diversity schemes or a combination of antenna arrays and diversity techniques, the receiver can discriminate between users by their temporal signatures, spatial signatures and also make use of the statistic independence of the received signal. In this study we are interested in IWC performance and therefore the channel model is assumed to be Nakagami distributed. At the receiver an array of M antennas is used to discriminate between the users based on their spatial diversity. The fading process at each of the antenna elements are statistically dependent and further improvements can be realized by making use of the independent fading characteristics of the received signal. To make use of this statistical independent information, the performance of a P branch maximum ratio combining (MRC) receiver is also considered. We further investigate the performance of a combination of P clusters of M antennas separated by the coherence bandwidth of the channel, thereby making use of both forms of spatial diversity. A comparison of the three schemes (antenna arrays, MRC diversity and a combination of antenna arrays and MRC diversity) under equal complexity conditions are made under multipath fading conditions. It is shown that the performance and capacity of a MRC diversity receiver, under the given assumptions, outperforms the other two methods.