Performance analysis of a MC-CDMA system with spatial diversity over nakagami fading channel

Abstract

The new information age is paving its way forward with high demand of wireless communication systems. New services such as data and video require achieving reliable highspeed transmissions even in high mobility scenarios. Multicarrier code-division multiple access (MC-CDMA) is a transmission technique which combines advantages of both codedivision multiple access (CDMA) and orthogonal frequency-division multiplexing (OFDM). In this thesis, we consider a wireless system with MC-CDMA with orthogonal subcarrier multiplying with OFDM after converting the high data bit stream to low data parallel streams. Spatial diversity is considered in the receiving end with multiple antenna and Rake receiver. Analysis is carried out to find out the expression of the receiver output with Maximal Ratio Combining (MRC) technique considering a Nakagami-m fading channel. Performance analysis includes the effect of Multiple Access Interferences (MAI), Inter Carrier Interferences (ICI) and in presence of Additive White Gaussian Noise (AWGN). The expression of the Signal to Interference and Noise Ratio (SINR) is derived for a MC-CDMA system considering the above limitations. Analysis is also carried out to find the expression for the MAI and instantaneous SINR and the probability density function of the SINR at the output of maximal ratio combiner. The analysis is then extended to MC-CDMA system with Rake Receiver. The performance results are evaluated numerically in terms of SINR and BER considering several parameters like number users, number of subcarriers, code length of a sub-channel, bit rate, number of rake fingers and number of receiving antennas. The results show that there is a significant improvement in SINR and BER performance considering rake receiver and number antennas at the receiver. For a given performance level and a given system BER, optimum system design parameters are determined from the analytical results.