11 M ar 2 01 5 Generalized Spatial Modulation in Indoor Wireless Visible Light Communication

Abstract—In this paper, we investigate the performance of generalized spatial modulation (GSM) in indoor wireless vi sible light communication (VLC) systems. GSM usesNt light emitting diodes (LED), but activates onlyNa of them at a given time. Spatial modulation and spatial multiplexing are special cases of GSM with Na = 1 and Na = Nt, respectively. We first derive an analytical upper bound on the bit error rate (BER) for maximu m likelihood (ML) detection of GSM in VLC systems. Analysis and simulation results show that the derived upper bound is very tight at medium to high signal-to-noise ratios (SNR). The channel gains and channel correlations influence the GSM performanc e such that the best BER is achieved at an optimum LED spacing. Also, for a fixed transmission efficiency, the performance of GSM in VLC improves as the half-power semi-angle of the LEDs is decreased. We then compare the performance of GSM in VLC systems with those of other MIMO schemes such as spatial multiplexing (SMP), space shift keying (SSK), gene ralized space shift keying (GSSK), and spatial modulation (SM). Ana lysis and simulation results show that GSM in VLC outperforms the other considered MIMO schemes at moderate to high SNRs; for example, for 8 bits per channel use, GSM outperforms SMP and GSSK by about 21 dB, and SM by about 10 dB at10 BER.