Channel Estimation and Physical Layer Security in Optical MIMO-OFDM based LED Index Modulation

In this paper, we propose a new and low-complexity channel estimation algorithm for the generalized LED index modulation (GLIM), recently proposed for visible-light communication systems based on multi-input multi-output (MIMO) and orthogonal frequency-division multiplexing (OFDM). For this scheme, denoted by GLIM-OFDM, we investigate the bit-error rate (BER), the mean-square error (MSE) of channel estimation, as well as the Cramer-Rao bound on the latter. Furthermore, we present a novel physical layer security (PLS) technique for the GLIM-OFDM scheme using precoding at the transmitter assuming it has the channel state information (CSI) between the LEDs and a legitimate user, but no knowledge of the CSI corresponding to eavesdroppers. The efficiency of the proposed PLS technique is demonstrated through numerical results.