Multiuser receivers for MC-CDMA MIMO systems with space–time block codes

In this paper, we examine the multiuser detection for quasi-synchronous multi-carrier code-division multiple-access (MC-CDMA) multiple-input multiple-output (MIMO) systems with space–time block codes (STBC). Considering Alamouti's STBC scheme which involves two transmit and multiple receive antennas, the Hermitian persymmetric-like property of the received signal is derived first. The forward–backward averaging technique and weighting analysis are then proposed for the blind constrained minimum output energy (CMOE), subspace-based and diagonal loading (DL)-based CMOE receivers. The forward–backward averaging technique, which uses twice the equivalent STBC blocks to design the multiuser receivers, reduces the bit-error-rate (BER) tremendously for the compared receivers. Besides, the weighting analyses are performed in which half of the computational cost is saved in the calculation of weight vectors. Finally, numerical simulations are given to evaluate and demonstrate the superiority of the multiuser receivers with forward–backward averaging technique and the correctness of weighting analyses.