Link Quality of a RF-assisted Relayed FSO System under Turbulence, Pointing Error and Fading

Link quality of a free-space-optical (FSO) link depends on atmospheric turbulence severity and pointing error due to optical beam misalignment. To improve reliability of a FSO link, an intermediate relay node may be used. The overall link quality may be further improved by using an additional radio-frequency (RF) link assisting the relay, as described in this paper. For assessing the link quality, we have considered three metrics, namely, probability of outage, average bit error rate and ergodic capacity. Analytical expressions for these three metrics have been found which contains easily computable Meijer’s G functions and the numerical results are verified through Monte Carlo simulations. The turbulence in FSO links is modelled with Málaga distribution whereas the fading in the RF link is modelled with Rayleigh distribution. For the FSO relay node a decode-andforward (DF) relaying protocol is assumed.