Analytical Performance Evaluation of Turbo Coded SIMO TF-Domain Spreaded MC-DS-CDMA Wireless Communication System over Nakagami Fading Channel

In this paper an analytical model of a MC-DS-CDMA with TF-domain spreading for wireless communication system with spatial diversity considering channel fading, Doppler shift, multi-access interference (MAI) along with AWGN channel is presented. The analysis presents a novel approach to the development of an analytical expression of signal to interference plus noise ratio (SINR) considering fading and Doppler shift of SISO (single input single output) system. The analysis is also extended to the SIMO (single input multiple output) system considering maximal ratio combining (MRC) scheme and a probability density function (pdf) of output of MRC receiver is proposed. The system performance is evaluated in terms of average bit error rate (BER) at the output of MRC receiver by averaging the conditional BER over the proposed pdf of the SINR. The system performance is evaluated for traditional BPSK modulation as well as different types of M-ary PSK modulation. Analytical expression of the conditional bit error rate of the system with Turbo encoding-decoding is also presented and comparison of BER performance of the system with and without turbo coding is computed. Analysis shows that applying spatial diversity significantly improves BER performance of the system. It is shown in numerical result that increasing number of receiver antenna or increasing number of orthogonal subcarriers at transmitter side makes 8-ary PSK modulation a better choice than 4-ary PSK modulation in terms of transmitted power and as a result spectral efficiency of transmitted signal gets improved. Finally applying turbo code improves BER performance several degrees better than without turbo coding with less number of receiver antenna and less amount of transmitted power.