On the performance of selective transmission based DF FSO system with generalized M-distributed turbulence

This paper investigates the error performance of the decode-and-forward (DF) based free space optical (FSO) communication system utilizing subcarrier intensity modulation (SIM) for binary phase-shift keying (BPSK) signalling in generalized M-distributed atmospheric turbulence. The M-distribution is a generic statistical model which unifies several existing distributions used for atmospheric turbulence induced fading. The exact closed-form expression of the average bit error rate (BER) is derived for selective transmission based DF FSO system using independent and non identically distributed (i.n.i.d) optical links. Moreover, we analytically obtain the diversity order of the considered set-up for various distributions (e.g. gamma-gamma distribution, K-distribution, and negative exponential distribution), characterized by the generalized M-distribution model. It is shown by the simulations that the selective relaying based DF protocol provides maximum possible diversity in all the considered fading environments.