An efficient multiple user access over the wireless channel necessitates a communication system design that can overcome the adverse impact of multipath propagation such as Inter Symbol Interference (ISI) and Multiple Access Interference (MAI). This being the objective, a Multi-Carrier Code Division Multiple Access (MC-CDMA) communication system is discussed in this paper. MC-CDMA, being a combination of Direct Sequence Code Division Multiple Access (DS-CDMA) and Orthogonal Frequency Division Multiplexing (OFDM), converts a frequency selective fading channel into multiple flat fading channels, thereby mitigating Inter Symbol Interference (ISI). To overcome the effect of Multiple Access Interference (MAI), Multi-User Detection (MUD) receiver has been suggested. The performances of Blind Successive Interference Cancellation (BIC) technique is compared with Matched Filter (MF) receiver and Block-based Minimum Mean Square Error (BMMSE) receiver by simulating the entire system. The BIC is a MUD technique that uses knowledge of the desired user’s signature sequence and his timing to estimate his information. This is done by executing interference cancellation in a successive manner, starting from the most dominant component and successively canceling the weaker ones. The simulation results show that the BIC scheme outperforms conventional MF receiver and BMMSE receiver.

Multi-Carrier Code Division Multiple Access (MC-CDMA) (Yee et al., 1993; Chatterjee et al., 2003; Antonia et al., 2005; and Shang-Ho et al., 2006) is a promising candidate to the challenge of providing high data rate wireless communication. It is a combination of two distinct techniques namely OFDM (Richard and Ramjee, 2002) and CDMA. MC-CDMA system combines features of these two technologies to provide a communication system that has the advantages of both. MC-CDMA can have synergistic effects, such as enhancement of robustness against frequency selective fading and high scalability in possible data transmission rate. While DS-CDMA spreads in the time domain, MC-CDMA applies the same spreading sequences in the frequency domain. While the performance of MC and DS-CDMA is identical in an additive white Gaussian noise (AWGN) channel, MC-CDMA has been shown to outperform DS-CDMA in multipath channels. In a DS-CDMA system, a single fade or interferer can cause the entire link to fail, but in an MC-CDMA system, only a small percentage of sub-carriers gets affected. MC-CDMA system is considered to be one of the candidates, as a physical layer protocol for 4G mobile communications, because 4G systems require high scalability and adaptability in the possible transmission rate and the MC-CDMA has the potential.

MC-CDMA is a digital modulation technique where a single data symbol is transmitted at multiple narrowband sub-carriers, with each sub-carrier encoded with a phase offset of 0 or  based on the signature sequences. This modulation scheme is also a multiple access technique in the sense that different users use the same set of sub-carriers but with different signature sequences that are orthogonal to the code of all other users. Thus, it is essential to point out that there exist two levels of orthogonality. While the sub-carrier frequencies are orthogonal to each other, the signature sequences are also orthogonal to each other. Firstly, an OFDM system is used to provide a number of orthogonal carriers, free from ISI. The narrowband sub-carriers are obtained by using Binary Phase Shift Keying (BPSK) modulated signals (Simon, 1998), each at different frequencies, which at base band are at multiples of a harmonic frequency.

Telecommunications Journal, Inter Symbol Interference, ISI, Multiple Access Interference, MAI, Multi-Carrier Code Division Multiple Access, MC-CDMA, Multi-User Detection, MUD, Orthogonal Carriers, Inter-Chip-Interference, ICI, Urban Environment, Minimum Mean Squared Error, MMSE, Frequency Selectivity.