A semi-blind multiuser detection based on a subspace constrained RLS algorithm for MC-CDMA uplink

In this paper, a new semi-blind multiuser detection based on a subspace constrained RLS algorithm is proposed for multicarrier code division multiple access (MC-CDMA) systems. In the MC-CDMA uplink, the base station receiver has the knowledge of the spreading sequences of all the users within the cell, but not that of the users from other cells. By imposing linear vector constraints on the multiuser detector, the proposed semi-blind detection can efficiently suppress the intracell interferers, while mitigating the intercell interferers based on the mean output energy (MOE) principle. A subspace constrained RLS algorithm is proposed to obtain the MOE weight vector adaptively. To reduce the computational complexity, an improved projecting approximation subspace tracking with deflation (PASTd) algorithm is proposed to calculate the signal subspace. Numerical results show that the performance of the proposed semi-blind detector is much better than the RLS-based MOE blind multiuser detection.