Pointing Error Effects on Performance of Amplify-and-Forward Relaying MIMO/FSO Systems Using SC-QAM Signals Over Log-Normal Atmospheric Turbulence Channels

In this work, we analyze pointing error effects on performance of Amplify-and-Forward (AF) relaying multiple-input multiple-output (MIMO) free space optical (FSO) communication system employing subcarrier quadrature amplitude modulation (SC-QAM) signal over log-normal distributed atmospheric turbulence channels. We study the pointing error effect by taking into account the influence of beam-width, aperture size and jitter variance on the average symbol error rate (ASER), which is derived in closed-form expressions of MIMO/FSO and SISO/FSO systems. In addition, the number of relaying stations is taken into account in the statistical model of the combined channel including atmospheric loss, atmospheric turbulence and pointing error. The numerical results show that by combining AF relaying stations and MIMO/FSO configurations, the link length can be extended due to the transmitted power is reduced accordingly to the amplifier gain. Moreover, performance of AF relaying MIMO/FSO systems is better than that of AF relaying SISO/FSO systems at the same link length.