On the BER performance of FSO links with multiple receivers and spatial jitter over gamma-gamma or exponential turbulence channels

Free-space optical (FSO) communication systems attract significant research and commercial interest due to their high performance characteristics along with their compact size, ease of deployment and the license-free spectrum that they use. Nevertheless, the time-varying characteristics of the atmosphere -which is the propagation path of the optical signal, and its variable composition of scatterers and absorbent matter, can cause significant distortions in the signal quality at the receiver. Thus, in this work we investigate the performance of an FSO link using receivers' spatial diversity scheme and optimal combining reception. The performance assessment is carried out by means of the average bit error rate metric for some of the most widely used modulation formats on wireless optical links taking into account the atmospheric turbulence modeled either by the gamma-gamma or the negative exponential distribution model in conjunction with the pointing errors effect. More specifically, new closed-form mathematical expressions for the estimation of the average bit error rate are derived and could be easily used for the designing and implementation of the wireless optical links. The corresponding numerical results are presented along with the simulation ones and finally the outcomes' conclusions are discussed.