Semiblind maximum-likelihood multiuser detector for MC-CDMA systems via sphere decoding

Multicarrier code-division multiple-access (MC-CDMA) has emerged as a promising candidate for future wireless communication systems. A novel multiuser detection scheme for multiuser MC-CDMA systems is proposed in this paper. In particular, a new joint detection method based on sphere packing lattice decoding and semiblind channel estimation is presented in this paper. After modelling an MC-CDMA system as a sphere packing lattice, a low-complexity maximum-likelihood (ML) detection, sphere decoding algorithm, is applied to jointly detect all users. The impacts of channel estimation errors are studied by incorporating a semiblind subspace based channel estimation in the receiver. The selection of search radius for sphere decoding is also investigated. Simulation results demonstrate the superior performance of the semiblind receiver compared to the conventional receivers for MC-CDMA and its robustness to channel estimation errors.