Multi-user Visible Light Communication Systems with Precoded SM and SPPM

In this paper, we propose a new precoded multi-user (MU) multiple-input multiple-output (MIMO) optical orthogonal frequency division multiplexing (OOFDM) aided visible light communication (VLC) system. Optical spatial modulation (OSM) and spatial pulse position modulation (SPPM) are utilised for providing uniform indoor illumination and high speed data transmissions. Both OSM and SPPM exploit the index of data streams for carrying additional information bits, while the multi-user interference (MUI) occurring between different user equipments (UEs) is mitigated by the MIMO precoder. The performances of the proposed VLC system using OSM and SPPM are evaluated and compared, which demonstrate that the OSM-aided system is capable of achieving high data rates at sufficiently high signal-to-noise ratios (SNRs), while the SPPM-aided system has a higher bandwidth efficiency at low SNRs, despite the fact that its attainable peak data rate is lower than that of the SPPM counterpart.