Pairwise Coding for MIMO-OFDM Visible Light Communication

This work proposes a dual pairwise coding (DPWC) technique for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) based visible light communication (VLC) systems. DPWC is a technique designed to mitigate the signal-to-noise ratio (SNR) imbalance created in the received information symbols due to the light emitting diodes' bandwidth limitations and the strong correlation of typical indoor VLC MIMO channels. With singular value decomposition precoding, the MIMO VLC channel is decomposed into independent parallel sub-channels. The DPWC technique is then applied to further improve the system performance by pairing and interleaving OFDM subcarriers and MIMO sub-channels with imbalanced SNR. The error performance of the proposed DPWC technique is investigated in detail via simulation and experimental demonstration. Its effectiveness with different degrees of bandwidth-limitation (data rate) and channel correlation is presented, and the results are compared with other variants of the pairwise coding technique. DPWC provides performance improvement with a significant reduction in the SNR required to achieve a specific bit error rate (BER).