In multiple-input multiple-output (MIMO) indoor visible light communication (VLC) systems, the elements of the channel matrix can be highly correlated which is a cause for degraded bit error performance. Imaging receiver techniques can resolve the spatial correlation in VLC channels because of the increased spatial resolution possible in imaging receivers. In this paper, we investigate the performance of MIMO modulation schemes using imaging receivers that employ an imaging lens above the receiving plane to focus the energy from the transmitting LEDs onto the receiving plane. Hemispherical lens and fish-eye lens for imaging are considered in the study. The MIMO modulation schemes considered include spatial multiplexing, generalized spatial modulation, quad-LED complex modulation, and dual-LED complex modulation. Analytical and simulation results show that imaging receivers can provide significant performance gains compared to nonimaging receivers. We analytically capture the high SNR performance of the modulation schemes with nonimaging and imaging receivers by computing the normalized minimum distance of the received signal set. Simulation results validate the analytical results. Using this distance measure, we study the spatial distribution of the best performing modulation scheme with nonimaging and imaging receivers.
© 2018 IEEEPDF Article