A modified leakage-based transmit filter design for multi-user MIMO systems

This paper proposes a modified definition of signal-to-leakage-plus-noise ratio (SLNR) as a criterion for linear transmit filter design in Multi-user MIMO systems. The proposed metric incorporates receiver structures into the precoder design, which can potentially exploit unused receive signal subspaces in cases where the available eigenmodes are not fully transmitted. The improvement in terms of the degrees of freedom of the precoder is also elaborated. In addition, an iterative precoding algorithm is proposed and is studied with two linear receivers, namely the matched filter (MF) and the minimum mean square error (MMSE) receivers. Simulation results show that the proposed scheme outperforms the conventional SLNR scheme and can achieve further improvement with an MMSE receiver, at the expense of increased computational complexity and slow convergence rate. Moreover, the proposed scheme is shown to reduce its form to the conventional scheme when full-eigenmode transmission is assumed.