Performance Comparison Between Spatial Multiplexing and Spatial Modulation in Indoor MIMO Visible Light Communication Systems

Spatial multiplexing (SMP) and optical spatial modulation (OSM) are two important technologies for indoor multiple-input multiple-output (MIMO) visible light communications (VLC). In this paper, we compare the performance of SMP and OSM systems which are operated with typical configurations in an indoor scenario. Both systems transmit data using asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) as the modulation scheme. It is shown that in order to achieve the same data rate with the SMP, the OSM has to employ large constellations which become impractical when either the number of luminaires or the constellation size of the SMP is greater than four. Simulation results are presented for both MIMO systems using four luminaires as transmitters and a receiver configured with three different front-ends. These receivers include a conventional nonimaging receiver, a prism-based receiver and an aperture-based receiver. The BER results demonstrate that SMP outperforms OSM in terms of both the size of the region in which a receiver can achieve low BER and the BER at typical receiver positions.