相干光通信系统中的几何概率整形研究  

Geometric Probability Shaping in Coherent Optical Communication System

作　　者：张一尘 陈健[1] 赵梦鑫 周泽海 宋英雄[1] Zhang Yichen;Chen Jian;Zhao Mengxin;Zhou Zehai;Song Yingxiong(Key Laboratory of Specialty Fiber Optics and Optical Access Networks,Shanghai University,Shanghai 200444,China;Shanghai Institute of Advanced Communication and Data Science,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学特种光纤与光接入网重点实验室,上海200444 [2]上海大学上海市先进通信与数据科学研究院,上海200444

出　　处：《光学学报》2023年第19期59-65,共7页Acta Optica Sinica

基　　金：国家重点研发计划(2021YFB2900800);上海市科委项目(22511100902);高等学校学科创新引智计划(D20031)。

摘　　要：为了缩小矩形正交幅度调制(QAM)方式和香农极限的差距,探究高斯信道下的星座整形性能,设计一种应用于卫星间激光通信的几何整形与概率整形相结合的方案。将星座点的判决范围视为圆形,从图形的紧密排列角度出发提出几何整形的思路,再利用编码映射技术使各个星座点概率分布符合麦克斯韦-玻尔兹曼分布。几何整形与概率整形相结合可以进行非常规星座点数的星座设计。在功率限制的前提下,进行了信息熵为3和星座点数为8~13、信息熵为4和星座点数为16~23的仿真和相干光通信系统实验。在仿真理论中,误码率约为5×10-3时,相比常规8QAM和16QAM,矩形QAM分别取得了约1 dB和1.3 dB的增益。同时还进行了8点和16点的几何整形的仿真和实验,相较于矩形QAM,分别有约0.1 dB和0.22 dB的性能提升。Objective Since the establishment of the information theory in 1948,most researchers have focused on narrowing the gap with Shannon-Hartley theorem.The traditional rectangular quadrature amplitude modulation(QAM)is widely used in optical communication.Although this modulation scheme is relatively mature,the rectangular modulation format is still far from reaching the Shannon-Hartley theorem.To bridge the difference between rectangular QAM and Shannon-Hartley theorem,researchers have developed constellation shaping techniques,namely geometric shaping(GS)and probabilistic shaping(PS).These techniques are based on power constraints and designed around conventional points,such as 16QAM,32QAM,and 64QAM.In the case of a Gaussian channel environment,the probability distribution scheme of PS is based on Maxwell-Boltzmann distribution.In this case,it is combined with GS to form geometric PS;however,the geometric PS of conventional points corresponds to its appropriate transmission rate.For example,the 16QAM's geometric probability shaping is suitable for transmitting signals with an entropy of about 3,but it causes performance issues when it is below 3.Additionally,it does not offer any advantage in PS when the entropy of the transmitted signal is above 3.Thus,this article aims to study the geometric PS scheme of unconventional and continuous points.This scheme can flexibly adapt to the channel environment and transmit appropriate information entropy.Methods It is necessary to focus on the PS scheme for GS to design a geometric PS scheme under power constraints.The probability distribution can be obtained from the Maxwell–Boltzmann distribution.This article designs the most compact hexagonal layout scheme in a two-dimensional plane.The distribution of noise in Gaussian channels is uniform in all directions,and thus,the constellation points are considered circles that conform to the noise distribution in Gaussian channels.After selecting a compact layout scheme,power screening is carried out.In power-limited schemes,layo

关 键 词：相干光通信 几何整形 概率整形 星座整形 星间通信 

分 类 号：TN913.7[电子电信—通信与信息系统]