湍流与相位噪声联合影响下的16QAM自适应概率整形  

16QAM Adaptive Probability Shaping Under Combined Influence of Turbulence and Phase Noise

作　　者：陈丹[1] 艾菲尔 王睿[1] 赵沛岩 Chen Dan;Ai Feier;Wang Rui;Zhao Peiyan(School of Automation and Information Engineering,Xi'an Key Laboratory of Wireless Optical Communication and Network Research,Xi'an University of Technology,Xi'an 710048,Shaanxi,China)

机构地区：[1]西安理工大学自动化与信息工程学院,西安市无线光通信与网络研究重点实验室,陕西西安710048

出　　处：《光学学报》2023年第24期171-180,共10页Acta Optica Sinica

基　　金：国家自然科学基金(62371390);陕西省重点研发计划(2023-YBGY-039,2020GY-036);西安市高校院所人才服务企业项目(GXYD14.21);陕西省教育厅一般专项科研计划(22JK0339)。

摘　　要：考虑大气湍流及电解调模块相位噪声对光通信系统性能的影响,基于低密度奇偶校验(LDPC)编码设计了一种自适应概率整形(PS)的实用自由空间光通信编码调制方案,实现以比特度量解码速率为目标函数的速率自适应,采用启发式算法求解M元正交幅度调制(M-QAM)信号星座点概率质量函数(PMF)分布的最优问题。结果表明:在弱湍流与相位噪声的联合影响下,概率整形正交幅度调制(PS-16-QAM)在最优概率分布下的比特度量解码速率比均匀分布16-QAM下更逼近香农容量。当湍流强度一定时,相位噪声增大对低信噪比下选取的PS分布影响更大,当前向纠错译码前的误码率为10-2时,提出的PS方案与均匀分布编码调制系统相比最高可获得4.8 dB的整形增益。Objective When a laser is transmitted in the atmosphere,atmospheric turbulence causes random fluctuations in the received light intensity,which seriously affects the performance of the free space optical(FSO)system.At the same time,the phase noise introduced by the electrolytic modulator module in the M-th quadrature amplitude modulation(MQAM)FSO system can cause the signal phase to shift,leading to degradation of demodulation performance and an increase in system error rate.Therefore,it is crucial to design a high-performance adaptive transmission scheme that can alleviate the severe degradation of optical signal transmission caused by atmospheric channels.The atmospheric turbulence effect in atmospheric channels is a slow fading process compared with high-speed coded modulation systems.By mapping the constellation points in the outer circle of the constellation map to a position close to the constellation origin with a certain probability and rules and sending and transmitting the mapped constellation points,probability shaping(PS)is achieved.Therefore,it is feasible to optimize the source distribution of the MQAM encoding FSO system and achieve adaptive adjustment of the transmitter signal constellation distribution based on channel conditions.In summary,we propose an adaptive PS system model in atmospheric channels that considers the combined effects of Gamma-Gamma turbulence and phase noise.This scheme can effectively improve the capacity of FSO communication links with QAM and suppress the impact of atmospheric turbulence on FSO systems.Methods We consider the comprehensive impact of atmospheric turbulence and phase noise of the electrolytic modulation module on the performance of optical communication systems. A model describing the combined effects of phase noise and atmospheric turbulence is constructed using Tikhonov distribution and Gamma-Gamma turbulence model. By iteratively searching through the particle swarm optimization algorithm in the heuristic algorithm, we obtain the optimal probability distr

关 键 词：光通信 自由空间光通信 湍流衰落 相位噪声 概率整形 速率自适应 

分 类 号：TN929.1[电子电信—通信与信息系统]