SIM/SM-aided free-space optical communication with receiver diversity

In this paper, we propose subcarrier intensity-modulation (SIM)/spatial modulation (SM)-aided free space optical communications with receiver diversity. Using computer simulation, the performances of the proposed SIM/SM scheme are investigated and compared with those of the conventional SIM scheme in an additive white Gaussian noise (AWGN) channel and in outdoor applications with lognormal atmospheric channels. The error performances are also mathematically analyzed in the AWGN channel for spectral efficiency of 2 bits/s/Hz in order to validate the simulation results. Numerical results show that the proposed SIM/SM scheme can outperform the conventional SIM for both channels with various spectral efficiencies. We also demonstrate that, by employing multiple receivers, the deleterious effect of scintillation on the proposed SIM/SM scheme has been further ameliorated. Furthermore, our proposed SIM/SM scheme with the receiver diversity gets more resistant to turbulence-induced fading, when the spectral efficiency and the number of receivers are increased.