摘要
针对自由空间光(FSO)通信系统易受大气湍流效应影响的问题,为降低系统在饱和湍流情况下的误码率(BER),并且考虑到实际工程中需要在有限信噪比(SNR)下得到最大的分集增益,需要对系统的分集性能进行研究,以得到分集增益与SNR和系统链路数量等参数的关系。文章选择采用多输入多输出(MIMO)技术,设计了基于正交振幅调制(QAM)的MIMO-FSO通信系统,分析了系统在负指数分布信道模型下的性能表现,推导出系统的BER计算公式与分集增益相关参数(如分集阶数(DO)、分集阶数增量(IDO)和收敛速度(SOC)等)的闭式表达式,并利用数学软件Matlab进行仿真实验,通过蒙特卡洛仿真来验证所推导公式的准确性。仿真结果表明,MIMO技术在不增加发射功率和接收孔径面积的情况下,可以大幅度降低FSO通信系统的BER,且在饱和湍流信道下,系统链路数量越多或湍流强度越低时,DO随SNR增长到理论最大值的速度越快。MIMO技术有效地抑制了大气湍流对系统的负面影响,大幅提高了系统性能。在条件允许的情况下,尽量使用多的发射机和接收机可以使得系统在有限SNR下获得的分集增益更高,但是也需要考虑到实际工程中的部署成本和安装难度来选择合适的链路数量。
Free Space Optical(FSO)communication systems are easily affected by atmospheric turbulence effects.In order to reduce the Bit Error Rate(BER)of the system under saturated turbulence condition,and considering the requirement of maximum diversity gain under limited Signal Noise Ratio(SNR)in practical engineering,it is necessary to study the diversity performance of the system to obtain the relationship between diversity gain and parameters such as SNR and system link number.This article uses Multiple-Input-Multiple-Output(MIMO)technology to design a MIMO-FSO system based on Quadrature Amplitude Modulation(QAM).The performance of the system in a negative exponential distribution channel model is analyzed,and the BER calculation formula and closed form expressions of diversity gain related parameters(such as Diversity Order(DO),Incremental Diversity Order(IDO),and speed of convergence(SOC))are derived.Simulation experiments are conducted using mathematical software such as Matlab to verify the accuracy of the derived formula through Monte Carlo simulation.The simulation results show that MIMO the technology can significantly reduce the BER of FSO systems without increasing the transmission power and receiving aperture area.Moreover,in saturated turbulent channels,when the number of system links increases or the turbulence intensity decreases,the diversity order increases to the theoretical maximum with the SNR at a faster rate.The MIMO technology effectively suppresses the negative impact of atmospheric turbulence on the system and significantly improves system performance.When conditions are satisfied,using more transmitters and receivers can achieve higher diversity gain in the system under limited SNR.However,it is also necessary to consider the deployment cost and installation difficulty in actual engineering to choose the appropriate number of links.
作者
李璞
汤璇
徐景
陈阳
LI Pu;TANG Xuan;XU Jing;CHEN Yang(School of Communication and Electronic Engineering,East China Normal University,Shanghai 200241,China)
出处
《光通信研究》
2023年第5期23-29,共7页
Study on Optical Communications
