A Novel Leakage-based Precoding Scheme for Multi-cell Multi-user MIMO System Downlink

In future wireless cellular system, full frequency reuse is beneficial for higher spectrum efficiency. However, the co-channel interference (CCI) between the cells constrains the system performance seriously. Therefore, precoder design for multi-cell multi-user MIMO system downlink becomes an important part of the research on future mobile communication systems. In this paper, an improved precoding scheme based on signal-to-Leakage-Noise Ratio (SLNR) maximization is proposed for the downlink of multi-cell multi-user MIMO system. In this scheme, whitening filter is used at each receiver for other-cell interference (OCI) suppression，and the influence of whitening filter is considered at the transmitter for precoder design. This proposed precoding scheme can therefore eliminate the multi-user interference (MUI) and the whitened other-cell interference (OCI) simultaneously. Furthermore, a novel QR-decomposition-based algorithm is derived to find the optimized precoding matrix for each user. Using this proposed SLNR precoding scheme, the system sum rate capacity is improved significantly with lower computational loads. Simulation results demonstrate that the proposed SLNR precoding scheme can suppress the impact of the other-cell interference (OCI) efficiently, and is more suitable for multi-cell MIMO communication systems.