Nanyang Technological University
In downlink multiuser Multiple-Input Multiple-Output (MIMO) systems, Block Diagonalization (BD) is a practical linear pre-coding scheme which achieves the same Degrees of Freedom (DoF) as the optimal linear/nonlinear pre-coding schemes. However, its sum-rate performance is rather poor in the practical SNR regime due to the transmit power boost problem. In this paper, the authors propose an improved linear pre-coding scheme over BD with a so-called "Effective-SNR-enhancement" technique. The transmit covariance matrices are obtained by firstly solving a power minimization problem subject to the minimum rate constraint achieved by BD, and then properly scaling the solution to satisfy the power constraints.