Differential Evolution Assisted MUD for MC-CDMA Systems Using Non-orthogonal Spreading Codes

In this paper, receiver optimization techniques are being investigated into a Differential Evolution (DE) assisted Multiuser Detection scheme for a synchronous, MC-CDMA system. In multiuser detection, the induced multiple access interference (MAI) makes the detection very inefficient and critical. However, the proposed system is less vulnerable to this issue in MC-CDMA communication. In this proposed scheme, for sake of attaining frequency diversity gain, Orthogonal Frequency Division Multiplexing (OFDM) has been used. That is, same signal is transmitted over different sub-carrier frequencies and these sub-carrier frequencies being adequately separated in frequency domain, do not interfere with each other and hence end of the day capacity is added up. Moreover, the role of Walsh (orthogonal but less practical) and Gold spreading sequences (non-orthogonal) which are more practical in nature, is also investigated and the results are demonstrated for different number of users communicating at the same time. The proposed scheme can perform sufficiently well with very low computational complexity compared to the optimum maximum likelihood (ML) detection scheme with increasing users.