基于中继协作的FSO通信系统模型性能分析

发布时间：2018-08-26 10:59

【摘要】：自由空间光(Free Space Optical,简称FSO)通信是一种新型的无线通信技术,因其具有保密性好、频谱自由、通信容量大和安装便捷等优点被研究人员广泛关注。在解决“最后一公里”问题和应急通信方面很有发展前景。然而,自由空间光通信是以光为载波,在开放的自由空间中传输信号的,所以很容易受到天气等因素的影响,其中大气湍流是影响无线光通信系统性能的关键因素之一。由大气湍流引起的光强闪烁、相位偏移等效应会严重影响自由空间光链路的传输性能。因此,深入研究大气湍流对光通信系统的影响机理和抑制方法很有必要。另外,由光的传播特性可知,单链路的自由空间光通信系统不适宜长距离通信,为了增大通信系统的通信距离和覆盖范围,论文从中继协作的角度出发,基于指数韦伯(Exponentiated Weibull,简称EW)的FSO链路衰落模型,研究了混合RF/FSO中继系统和全光中继FSO/FSO系统在不同的大气湍流情况和不同的接收机尺寸下的中断性能,具体内容如下:(1)为了解决Log-normal和Gamma-Gamma信道衰落模型的单一适用性,基于Rayleigh-EW信道衰落模型提出中继协作RF/FSO通信系统。通过对指数韦伯分布型FSO链路中断概率的数值模拟,重点分析了该混合RF/FSO通信系统在不同大气湍流强度下的影响。同时,也推导了系统在高信噪比下的中断概率的渐进表达式,并对系统的分集度进行了分析。(2)为了增大光通信系统的通信距离和覆盖范围,提出了一种对称式的中继协作FSO/FSO自由空间光通信系统,系统采用增益可变的全光中继,并使用副载波调制,重点研究了指数韦伯大气湍流信道下自由空间光通信的中断性能。具体地,首先,基于指数衰落分布推导出了端对端信噪比的累积分布函数,然后得出系统的中断概率表达式,进而分析了高信噪比下中断概率的渐进性能和分集度。最后,通过仿真对比分析了RF/FSO通信系统和FSO/FSO中继系统的中断概率。
[Abstract]:Free space optical (Free Space Optical, (FSO) communication is a new type of wireless communication technology, which is widely concerned by researchers because of its advantages of good confidentiality, free spectrum, large communication capacity and convenient installation. In solving the "last kilometer" problem and emergency communication is very promising. However, optical communication in free space is transmitted in open free space with light as carrier, so it is easy to be affected by weather and other factors, among which atmospheric turbulence is one of the key factors that affect the performance of wireless optical communication system. The effects of intensity scintillation and phase shift caused by atmospheric turbulence will seriously affect the transmission performance of free space optical links. Therefore, it is necessary to study the influence mechanism and suppression method of atmospheric turbulence on optical communication system. In addition, according to the characteristics of optical propagation, the single link free space optical communication system is not suitable for long distance communication. In order to increase the communication distance and coverage of the communication system, this paper starts from the angle of relay cooperation. Based on the FSO link fading model of exponential Webb (Exponentiated Weibull, (EW), the interrupt performance of hybrid RF/FSO relay system and all-optical relay FSO/FSO system under different atmospheric turbulence conditions and different receiver sizes is studied. The main contents are as follows: (1) in order to solve the single applicability of Log-normal and Gamma-Gamma channel fading model, a relaying cooperative RF/FSO communication system based on Rayleigh-EW channel fading model is proposed. Based on the numerical simulation of the outage probability of exponential Weber distributed FSO link, the influence of the mixed RF/FSO communication system on different atmospheric turbulence intensity is analyzed. At the same time, the asymptotic expression of the outage probability in high SNR is derived, and the diversity of the system is analyzed. (2) in order to increase the communication distance and coverage of the optical communication system, A symmetric relaying cooperative FSO/FSO free space optical communication system is proposed. The system adopts all-optical relay with variable gain and uses subcarrier modulation. The interruption performance of free space optical communication in exponential Webb atmospheric turbulence channel is studied emphatically. Specifically, the cumulative distribution function of end-to-end signal-to-noise ratio is derived based on exponential fading distribution, and then the expression of system interrupt probability is derived, and then the asymptotic performance and diversity of interruption probability under high SNR are analyzed. Finally, the outage probability of RF/FSO communication system and FSO/FSO relay system is analyzed by simulation.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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