Performance of multicarrier CDMA with dual spreading in Nakagami-m frequency offset fading channels

In general, Multicarrier systems are very sensitive to carrier frequency offset (CFO) which generates intercarrier interference (ICI) resulting in performance degradation. However, by using frequency diversity in multicarrier DS-CDMA system, the effect of ICI caused by CFO can be significantly reduced. This can be achieved in Time-Frequency (TF) domain spreading MC DS-CDMA system which employs both time and frequency (TF) domain spreading or hybrid spreading. In this paper, the performance of TF-domain spread MC-DS-CDMA system over Nakagami-m fading channels is evaluated and investigated with varying CFO, number of users, number of subcarriers, and Signal-To-Noise-Ratio (SNR). The probability of bit error rate (BER) of TF-domain spread MC-DS-CDMA is derived using the standard Gaussian Approximation (SGA) approach for different values of m parameter. Numerical evaluation of the analytical expression of BER reveals that a high capacity and BER performance improvement are achieved for TF-domain spread MC-DS-CDMA system over the performance of multicarrier CDMA (MC-CDMA) system which spreads the signal in the frequency domain only. The simulation results show excellent agreement with the analysis.