Performance Analysis of Serial and Parallel Amplify-and-Forward Relaying Coherent OFDM FSO System over Exponential Weibull Atmospheric Turbulence Channel

This paper proposes a coherent orthogonal frequency division multiplexing (OFDM) free space optical (FSO) communication system model consisting of parallel channel state information (CSI)-assisted amplify-and-forward (AF) relays over Exponential Weibull (EW) atmospheric attenuation channel. Using quadrature amplitude modulation (QAM) as a subcarrier mapping mode for OFDM signals. Considering the joint effects of path loss, pointing errors and atmospheric turbulence, the closed-form expressions of the Meijer G form of moment generating function (MGF), probability density function (PDF), and cumulative distribution function (CDF) are derived. Using these results, the closed-form expressions for the lower bounds of the outage probability and the symbol error rate (SER) of the proposed system are derived using Meijer’s G-function. In addition, the influence of atmospheric turbulence intensity, number of subcarriers, mapping coefficient and other important factors on outage performance and SER are analyzed by simulations. The simulation results show that the relaying technology can increase the link range and improve the performance of the FSO communication systems.