Performance Analysis and Relay Location Research of OFDM Free-Space Optical Communication Systems Under Moderate and Strong Turbulence

Abstract

In this paper, based on the Gamma–Gamma channel model for describing moderate and strong atmospheric turbulence, we study the relay location of serial decode-and-forward relay systems and parallel decode-and-forward relay systems in free-space optical (FSO) communication. According to the orthogonal frequency-division multiplexing modulation (OFDM) and coherent detection demodulation technology, we develop a novel statistical fading channel model for relay FSO systems by incorporating the atmospheric turbulence, pointing errors, and path loss effects. Based on this channel model, we derive the closed-form expression of the outage probability in the FSO serial relay system and parallel relay system, using the Meijer G-function. The serial decode-and-forward relay system with different relay locations and parallel decode-and-forward relay system, which consider different number of links and different relay locations, are simulation analyzed under moderate and strong atmospheric turbulence. The performance of serial relay systems and parallel relay systems in free-space optical communication can be improved by optimizing the relay location.