On the Performance of Multiuser CDMA System Using Separate Channel Streams

Abstract

Code Division multiple access (CDMA) is a spread spectrum multiple access technique with the advantages of efficient bandwidth utilization, flexible cell planning and capacity. Although CDMA itself is 3rd generation scheme, some of its variants are expected to be used in conjunction with the upcoming 5th generation technologies to enhance the network capacity. In many simulation models, a single channel is used to transmit the composite CDMA signal. This model is not suitable for practical scenarios where each user's signal is passed through different channel undergoing various channel degradations. In this paper, a multiuser CDMA system model is proposed in which the data from each user passes through different channel prior to aggregation at the base station. The performance of the system is analyzed under various channel qualities. Depending upon the SNR, channels are categorized as Best, Medium and Worst. The performance of the system in terms of Bit Error Rate (BER) is investigated under several combinations of channel qualities. Both the orthogonal and nonorthogonal spreading codes are used for comparison under different channel qualities.