MLSE Multiuser Detection in MC-CDMA Systems Using Sinusoidal Spreading Codes

The paper proposes a new multiuser interference cancellation system in MC-CDMA transmissions. In the proposed system, spreading codes having sinusoidal waveforms are used. It is shown that, by using the spreading scheme, the spreading and multiplexing processes are accomplished by IFFT in the transmitter and FFT in the receiver. Using the unique property of the spreading scheme, the effect of the multiuser interference due to multipath can be limited only between specific combinations of the spreading codes, therefore MLSE by the Viterbi algorithm can reasonably be applied. Simulation results indicate that significant improvement is obtained by the proposed system when compared with conventional MC-CDMA systems using the Walsh codes and MMSEC (minimum mean sequence error combining).