Inter-carrier interference self-cancellation for CI/MC-CDMA system

Multi-carrier code division multiple access (MC-CDMA) has been considered as a strong candidate for next generation wireless communication system due to its excellent performance in multi-path fading channel and simple receiver structure. Carrier Interferometry code for MC-CDMA (CI/MC-CDMA) provides better BER performance, less peak to average power ratio (PAPR) and higher design flexibility than conventional MC-CDMA systems employing Hadarmard-Walsh spreading code. However, like all the multi-carrier transmission technologies such as orthogonal frequency division multiplexing (OFDM), the inter-carrier interference (ICI) produced by the frequency offset between the transmitter and receiver local oscillators or by Doppler frequency shift due to high mobility causes significant bit error rate (BER) performance degradation in CI/MC-CDMA system. In this paper, we apply the ICI self-cancellation scheme previously proposed for OFDM system to orthogonal CI/MC-CDMA system to reduce ICI effect and improve BER performance. Unlike the traditional ICI self-cancellation scheme for OFDM which reduces the ICI at the price of lowing the transmission rate and reducing the bandwidth efficiency, we introduce a second set of orthogonal CI codes to maintain the throughput. Simulations of different leveled modulations over AWGN channel and multi-path fading channel confirmed the effectiveness and efficiency of the proposed self-embedded ICI cancellation scheme for CI/MC-CDMA system where significant BER performance gain has been observed when ICI is present.