Memory-Based Codes for Uniform Illumination in MIMO VLC

Light emitting diode (LED) based indoor multiple input multiple output visible light communication system has LEDs placed at various positions in the room which are simultaneously used for illumination and communications. In such a system, there should be no human perceivable fluctuations in the intensity of the individual LEDs to avoid user discomfort. In order to achieve the uniformity in illumination, we propose codes under the constraints of constant total transmit power per symbol and constant average transmit power for each individual LED. We show the performance of the proposed codes in terms of various metrics like bit error rate (BER), consistency in illumination, and spectral efficiency with suitable expressions. We also numerically analyze the impact of channel state information (CSI) on BER performance by assuming perfect CSI is not always available but periodically updated at the receiver.