基于FSO的星地协作系统中断概率的性能分析

Performance Analysis of Outage Probability of Satellite-terrestrial Cooperative System Based on Free-space Optical

针对卫星信道的衰落特性和阴影效应,分析了基于自由空间光(Free-Space Optical,FSO)通信的星地协作系统的中断概率性能。在卫星至无人机(Unmanned Aerial Vehicle,UAV)间采用RF信道,并采用解码-转发(Decode-and-Forward,DF)模式;在无人机至目的节点(地面用户)采用FSO信道。利用双状态的Lutz模型表述陆地卫星移动通信链路(Land Mobile Satellite,LMS),并引用Gamma-Gamma分布表述由大气湍流引起的光信号强度的波动。推导了星地协作系统的中断概率的闭环表述式,并利用MATLAB进行仿真。仿真结果表明,阴影效应的时间对传输信号的质量有重要影响。当陆地FSO链路处于较恶劣的大气湍流环境时,LMS信道状态对系统的总体性能影响甚少。

Focusing on the fading and shadowing effect in satellite channel,outage probability of Satellite-Terrestrial Cooperative System based on FSO is analyzed in this paper. The RF channel is used between satellite and relay(Unmanned Aerial Vehicle),which is performed under consideration of the decode-and-forward(DF)relaying protocol. The FSO channel is assumed for relay-destination link. The land mobile satellite link is described by two-state Lutz’s model. The Gamma-Gamma distribution is used to model. The Gamma-Gamma distribution is used to model the intensity fluctuations of the optical signal caused by atmospheric turbulence. The closed-form expression of outage probability is derived. The analytical expression of the outage probability was verified with the MATLAB simulation. Simulation result shows that the time-share of shadowing determines the quality of the signal transmission. Then LMS channel state has a minor impact on the overall system performance when the terrestrial FSO link is under the influence of harmful atmospheric turbulence conditions.