Performance improvement of MC-DS-CDMA system through ICI cancellation and modified duobinary coding scheme

Multi-carrier direct sequence code division multiple access (MC-DS-CDMA) is an attractive candidate for fourth generation (4G) wireless communication systems due to its high spectral efficiency, large system capacity and high flexibility in data rate. Multi-carrier systems are very sensitive to carrier frequency offset (CFO) caused by oscillator instabilities or by Doppler shifts, which leads to loss of orthogonality among the subcarriers resulting in intercarrier interference (ICI). ICI causes reduction of signal amplitude at the filter output and degrading the system performance. In this paper an effective method that combats the effect of intercarrier interference (ICI) through conjugate cancellation (CC) and modified duobinary coding scheme is proposed. Simulation results show that the proposed method gives better carrier to interference ratio (CIR) and bit error rate (BER) performance than the conventional CC scheme, without reducing bandwidth efficiency or increasing system complexity.