Abstract—Atmospheric induced-turbulence is the major challenge suffers by the free space optical (FSO) communication systems in practical deployment. To overcome this limitation, cooperative diversity technique is considered as a prominent solution to improve the system performance. In this paper, we present the error performance of a cooperative diversity AF-based mixed FSO/RF system with direct link over induced-fading channels. The FSO link is characterized by Gamma-Gamma distribution while the RF link is subjected to Nakagami-m distribution. Owning to difficulty involves in determining the probability density function (PDF) of the total signal-to-noise ratio (SNR), the moment generating function (MGF) for the total SNR is derived through the lower bound cumulative distribution function (CDF). Utilizing the MGF, the closed-form expression of the average bit error rate (ABER) with a series expansion of the modified Bessel function is then derived for the system. Moreover, the simulation result shows the accuracy of the derived ABER series expression. The effect of atmospheric turbulence under different conditions and the Nakagami-m fading parameter are observed on the ABER of the proposed system. The results also illustrate the effectiveness of the parallel relays in enhancing the system performance against fading effect. 

Index Terms—Cooperative diversity, gamma-gamma distribution, Nakagami-m distribution, moment generating function, average bit error rate

Cite: Kehinde O. Odeyemi and Pius A. Owolawi, "Error Performance of a Cooperative Diversity Mixed FSO/RF System over Gamma-Gamma and Nakagami-M Fading Channels," Journal of Communications, vol. 14, no. 8, pp. 669-675, 2019. Doi: 10.12720/jcm.14.8.669-675