DF Relayed QAM or DBPSK FSO Links with Generalized Pointing Errors Over Mixture Gamma Turbulence Channels

The performance of serially DF relayed QAM or BDPSK FSO systems with generalized pointing errors over turbulence channels is investigated in this work. The turbulence-induced fading of the received optical signal is studied through the mixture Gamma distribution, which represents an accurate model for the description of the irradiance fluctuations at the receiver of an FSO link while, at the same time, it reduces significantly the mathematical complexity of the expressions used for the description of composite channels with turbulence along with pointing errors induced fading. Mathematical expressions of the average BER for differential binary PSK and QAM schemes are derived and the corresponding numerical results are presented.