A Group-Blind MMSE Multi-User Detector Based on Subspace Tracking for MC-CDMA Uplink

In the multicarrier code division multiple access (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. In this paper, we present a novel semi-blind adaptive MMSE multi-user detector based on subspace tracking for MC-CDMA systems in such scenarios. We develop an modified MMSE detector which can combat the performance deterioration induced by eigenvalues estimation errors. Moreover, the proposed method exploits the orthogonal projection approximation subspace tracking (OPAST) algorithm for adaptive subspace estimation. This proposed detector makes use of the spreading sequences of all known users to suppress the intracell interference, while suppresses the intercell interference using the modified MMSE detector. Simulation results demonstrate that the proposed semi-blind multi-user detector offers substantial performance gains over the blind multi-user detection and the traditional semi-blind method in a MC-CDMA uplink environment.