Lattice Reduction Aided Precoding Combined with SDM for Clusters of Correlated Users

We present a lattice reduction (LR) aided preceding scheme combined with spatial division multiplexing (SDM) for clusters of correlated multiple users. Previously, the LR aided precoding schemes are deeply studied to transmit different symbols, simultaneously, to multiple users since it shows superior performance to linear precoding schemes like zero-forcing (ZF) algorithm. However, it has high complexity compared with linear precoding schemes. To resolve it, we exploit the spatial separability between clusters. That is, we apply the LR aided scheme for highly correlated users in a same cluster and to suppress the interferences from other clusters, we apply the ZF algorithm. Furthermore, we also propose a new SDM scheme to maximize the transmit signal to interference and noise ratio, which is formulated by generalized eigenvalue problem. We verify the performance of the proposed schemes by Monte-Carlo simulations and compare the computation complexities of them with the conventional LR aided precoding scheme.