A general precoding scheme for multi-user MIMO downlink system with 4 × 4 Quasi-orthogonal space time block codes

In this paper, we concentrate on the downlink precoding scheme for the multi-user MIMO system with 4 × 4 Quasi-orthogonal space time block codes (QSTBC). An iterative precoding scheme based on the signal-to-leakage-noise ratio (SLNR) maximization is proposed. This precoding scheme is general to different QSTBCs. By choosing the complex scalars properly, a simple solution of the optimization problem is achieved and the symbols can be decoded separately at each receiver. Our scheme is more robust to the number of users within the system. By using an iterative optimization approach, it eliminates the co-channel interference (CCI) more efficiently. Simulations demonstrate the performance of our scheme.