Multiple-LED Complex Modulation Schemes for Indoor MIMO VLC Systems

Abstract

In this paper, two complex modulation schemes suited for use in multiple-input multiple-output (MIMO) visible light communication (VLC) systems are proposed and their performance investigated. The proposed schemes are quadrature spatial modulation (QSM) and dual mode index modulation (DMIM) with a dual-LED complex modulator (DCM) used as the basic building block (termed as DCM block) to transmit complex modulation symbols. The proposed schemes, referred to as QSM-DCM and DMIM-DCM schemes, do not require Hermitian symmetry operation to transmit complex modulation symbols. The proposed schemes are shown to achieve enhanced rates and good performance in indoor MIMO VLC settings. Compared to spatial modulation DCM (SM-DCM) scheme known in the recent literature, the proposed schemes achieve significantly better performance. Results show that, at a bit error rate of 10<sup>−5</sup>, performance gains up to 10.2 dB and 7.4 dB can be achieved using the proposed QSM-DCM and DMIM-DCM schemes, respectively. Also, the spatial performance investigation indicates that the proposed schemes outperform the SM-DCM scheme for most of the receiver locations across the room.