On the performance of MU-MIMO indoor visible light communication system based on THP algorithm

Multiple input and multiple output (MIMO) technique offers advantage of high data rate parallel transmission for indoor visible light communication (VLC) systems. As multiple decentralized user terminals are generally employed in typical indoor environment, the main difficulty for multi-user MIMO indoor VLC systems lies in the separation of data for different user terminals. We have proposed a linear precoding multi-user (MU) MIMO indoor VLC system to eliminate multi-user interference (MUI), by utilizing block diagonalization (BD) algorithm. However, nonlinear Tomlinson-Harashima precoding (THP) algorithm is generally considered as much better scheme in a practical MIMO system. Besides, channel capacity based on THP algorithm is better than that of BD precoding algorithm. Therefore, in this paper, we utilize THP optimization scheme to eliminate MUI in MU-MIMO indoor VLC system. The performances of conventional THP algorithm and THP optimization scheme in VLC systems are investigated. In addition, based on the limitation analysis of THP algorithm in VLC system, optical detectors with different fields of view (FOV) are utilized to further improve system performance. Numerical simulation results show that nonlinear precoding based on THP algorithm can achieve better BER performance than that with linear BD precoding.