Semi-Blind Multiuser Detection Based on Subspace Constrained LMS for MC-CDMA Uplink

In this paper, a new semi-blind multiuser detection algorithm based on subspace constrained least mean-squared (LMS) is proposed for multicarrier code division multiple access (MC-CDMA) uplink system. This proposed detector makes use of the spreading sequences of all known users to impose multiple constraints on the minimum output energy (MOE) multiuser detection so that the interference within the cell can be suppressed. A subspace constrained LMS 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 developed for adaptive signal subspace estimation. Computer simulations show that the performance of the proposed semi-blind multiuser detection is significantly superior to that of the LMS-based blind multiuser detection