基于记忆多项式的Volterra混合均衡器设计与研究  

Design and Study of Memory Polynomial⁃based Volterra Hybrid Equalizer

作　　者：贾科军[1] 雷蕾 蔺莹[1] 余彩虹[2] JIA Kejun;LEI Lei;LIN Ying;YU Caihong(School of Computer and Communication,Lanzhou University of Technology,Lanzhou 730050,China;School of Electronic Electrical Engineering and Physics,Fujian University of Technology,Fuzhou 366000,China)

机构地区：[1]兰州理工大学计算机与通信学院,兰州730050 [2]福建工程学院电子电气与物理学院,福州366000

出　　处：《光通信研究》2024年第3期36-44,共9页Study on Optical Communications

基　　金：国家自然科学基金资助项目(61461026);甘肃省科技计划资助项目(22JR5RA276,22JR5RA274,23YFGA0062,2022A⁃215);兰州理工大学博士科研启动项目(061903)。

摘　　要：【目的】发光二极管(LED)的非线性特性导致可见光通信(VLC)系统的误码率(BER)性能恶化,特别是在具有较高峰均功率比(PAPR)的光正交频分复用(O⁃OFDM)系统中。基于Volterra级数的单级均衡器可以处理LED非线性高阶失真,且延时较小。但是求解传统Volterra级数需要多重积分运算,基于Volterra级数的均衡器实现复杂度高,且单级均衡器存在误差累积,因此均衡抑制效果有限。【方法】首先,针对传统Volterra级数计算复杂度高的问题,只保留Volterra级数中各阶非线性项和内核系数的高阶幂级数项,提出了基于记忆多项式的Volterra级数(MPVS)。相比于传统Volterra级数降低了计算复杂度,同时考虑了当前时刻的所有输入信号,提高了非线性系统建模的精度。然后,设计基于记忆多项式的Volterra(MPV)均衡器和基于记忆多项式的Volterra判决反馈均衡器(MPV⁃DFE),对于单级MPV⁃DFE,若判决部分一个码元判断错误,那么这种错误会连续成串出现,导致整个码元序列受到影响。文章提出将MPV和MPV⁃DFE两个非线性均衡器级联构成混合后均衡器(MPV+MPV⁃DFE)。MPV均衡器对LED非线性失真信号一级均衡,可以抑制一部分非线性失真,从而减少MPV⁃DFE码元判断错误。再经过MPV⁃DFE二次均衡,可以更好地抑制残留的非线性失真。【结果】最后,采用蒙特卡洛BER仿真方法验证系统设计的有效性。结果表明:与单级MPV均衡器、线性级联非线性混合均衡器(LMS+MPV-DFE)相比,在4阶正交幅度调制(QAM)非对称限幅光OFDM(ACO⁃OFDM)系统BER为10^(-4)时,所提混合均衡器分别可以获得大约7和2 dB的信噪比增益。【结论】MPV均衡器实现简单,且将两级非线性均衡器级联设计混合均衡器可以更好地抑制LED非线性失真。【Objective】The non⁃linear characteristics of Light Emitting Diodes(LEDs)contribute to the degradation of Bit Error Rate(BER)performance in Visible Light Communication(VLC)systems,particularly in Optical Orthogonal Frequency Division Multiplexing(O⁃OFDM)systems with high Peak⁃to⁃Average Power Ratio(PAPR).A single⁃stage equalizer based on the Volterra series can handle the high⁃order non⁃linear distortions of LEDs with low latency.However,solving the traditional Volt⁃erra series necessitates multiple integration operations,resulting in the high implementation complexity of the Volterra⁃based equalizer.Additionally,the single⁃stage equalizer accumulates errors with limited performance improvements.【Methods】Firstly,to address the issue of high computational complexity in the traditional calculations of the Volterra series,a proposition is made to retain only the high⁃order power series terms of the various nonlinear terms and kernel coefficients within the Volterra series.This approach,known as the Memory Polynomial⁃based Volterra Series(MPVS),not only reduces the computational complexity compared to the traditional Volterra series but also enhances the accuracy of nonlinear system modeling by considering all input signals at the current moment.Subsequently,the design of channel equalizer considers the Memory Polynomial⁃based Volterra(MPV)equalizer and the Memory Polynomial⁃based Volterra Decision Feedback Equalizer(MPV⁃DFE).For a single⁃stage MPV⁃DFE,if an error occurs in the decision part leading to an incorrect symbol decoding,this error tends to manifest as a consecutive series of errors,thereby impacting the entire symbol sequence.To mitigate this,a proposal is made to cascade the two non⁃linear equalizers,MPV and MPV⁃DFE,forming a hybrid equalizer called MPV+MPV⁃DFE.The MPV equalizer performs a primary equalization on the LED's nonlinear distortion signal,effectively suppressing a portion of the non⁃linear distortions and thereby reducing symbol decoding errors

关 键 词：可见光通信 发光二极管非线性 沃尔泰拉级数 混合后均衡器 

分 类 号：TN929.12[电子电信—通信与信息系统]