基于OFDM的大气激光通信湍流抑制关键技术研究

文章在分析无线激光通信(FSO)存在两种主要的大气信道问题的基础上,针对激光大气信道问题尤其是在复杂湍流环境下的频率选择性衰落问题和多径效应问题,提出了基于正交频分复用(OFDM)的湍流效应抑制方法,构建了FSO-OFDM系统,研究了该系统的基带模型以及信号的多载波调制与解调方法。分析了无线激光通信中存在复杂湍流环境下的大气信道问题,讨论了大气湍流影响下的平面波激光通信系统模型,建立了大气湍流影响下对数正态湍流通道的高斯光束空间光通信系统模型,推导了光波强度的概率密度函数,研究了利用信噪比概率密度函数分析各种大气湍流效应对系统性能影响的方法;设计了无线光通信系统的OFDM多载波调制方案,构建了FSO-OFDM系统基带模式模型,并基于该模型研究了其信号的调制与解调原理。最后,采用MATLAB编程实现FSO-OFDM系统,对多径干扰下的FSO通信系统进行仿真实验,进行了不同保护间隔下的误码率特性实验,验证了FSO-OFDM系统具有很强的抗多径干扰和频谱选择性衰落能力以及良好的BER性能,可有效解决码间干扰大、链路不可靠的问题,具有非常广泛的应用前景和使用价值。

Research on the key technology of turbulence suppression for atmospheric optical laser communication based on OFDM

Based on the analysis of the two main problems of atmospheric channel in free space optics(FSO),aiming at the problem of laser atmospheric channel especially the problems of frequency selective fading and multipath effect in complex turbulent environment,the suppression method is proposed based on OFDM turbulence effect,the FSO-OFDM system is built,the baseband model of this system and the signal of multi-carrier modulation and demodulation method are studied.First of all,this article systematically analyzes the mechanism of turbulence effect of atmospheric channel,and discusses the model of plane wave laser communication system under the influence of atmospheric turbulence,the space optical communication system model of Gaussian beam of a logarithmic normal turbulent channel is established under the influence of atmospheric turbulence,the probability density function of light intensity is deduced,the methods for analyzing the effects of various atmospheric turbulence effects on system performance using the signal-to-noise ratio probability density function;the OFDM multi-carrier modulation scheme of FSO-OFDM system is designed,the baseband mode model of FSO-OFDM system is constructed,and the modulation and demodulation principle of its signal is studied using this model.Finally,FSO-OFDM system is realized by using MATLAB,and the FSO communication system under the multipath interference is simulated,experiments on bit error rate characteristics under different guard intervals are performed.It is confirmed that the FSO-OFDM system has a strong ability to resist multipath interference and frequency selective fading,as well as good bit error rate(BER)performance.It can effectively solve the problem of intersymbol interference and the reliable link,and has a very broad application prospect and using value.