Abstract:

he multiple input multiple output free space optics (MIMO-FSO) system model is analyzed under the Gamma-Gamma distribution channels and pulse position modulation (PPM). The SER calculating formula of single input single output (SISO)-PPM systems is derived firstly, then as a benchmark, under the cases of both independent with identical distribution (IID) and independent with different distributions(IDD), the average slot error rates (SER) of MISO-PPM, SIMO-PPM and MIMO-PPM systems are derived respectively. Simulations of the average SER performances of these systems are done. The simulation results show that, under GammaGamma distribution, the average SER is indeed improved in MIMO systems. When SER is at 10^-4, the average SER of the MIMO-PPM system with  M=2 and N=2 is improved by about 50 dB and 65 dB under IID and IDD respectively. In practical designs, M and N are enough to set to 3 or 4 respectively. The obtained conclusion is significant to the analysis and design of FSO systems.