Asymptotic bit error rate analysis of free space optical systems using spatial diversity

Free space optical (FSO) communication is used to provide very high speed network connection to end users, especially the last mile users thereby enabling cost-effective, fast and secure internet service to them. But the single input single output (SISO) connection is highly hampered by the atmospheric turbulence and pointing error of the link. As a solution to this problem, the spatial diversity technique can be used to improve the communication service. The bit error rate (BER) analysis for the received signal to noise ratio (SNR) is analyzed in this paper to study the performance improvement over the SISO case for the system over the generalized atmospheric turbulence channel known as the Málaga turbulence channel. A new expression for the BER in terms of the beta function is derived and the diversity gain and coding gain are obtained from the same.