PAM-DMT光无线通信检测与同步技术研究

发布时间：2018-06-29 05:31

本文选题：可见光通信 + 脉冲幅度调制-离散多音　；参考：《东南大学》2017年硕士论文

【摘要】：脉冲幅度调制-离散多音(Pulse Amplitude Modulation-Discrete MultiTone,PAM-DMT)是一种典型的应用于LED(LightEmittingDiode,LED)可见光通信(Visible Light Communication,VLC)系统的光正交频分复用(Optical-Orthogonal Frequency Division Multiplexing,O-OFDM)方案。本文主要研究了基于PAM-DMT的VLC系统中检测与同步技术,设计了一个基于时域分集合并办法的高性能选择检测算法,并且提出了基于PAM-DMT接收信号对称特性的盲符号定时同步算法以及基于高效黄金分割搜索法的采样时钟频率偏差估计方法。首先,本文对传统射频(Radio Frequency,RF)通信系统中正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术以及VLC系统中强度调制/直接检测(Intensity Modulation/DirectDetection,IM/DD)方式进行了介绍,引出了适用于IM/DD方式的O-OFDM技术,分析了三种典型的O-OFDM方案,即直流偏置光正交频分复用(Direct Current Biased Optical OFDM,DCO-OFDM)、非对称截断光正交频分复用(Asymmetrically Clipped Optical OFDM,ACO-OFDM)和PAM-DMT。经过对这三种方案的理论研究与性能分析,选择了基于PAM-DMT的VLC系统作为本文研究的系统模型。然后,研究了基于PAM-DMT的高性能选择性检测算法的设计问题。回顾了传统检测方案并且分别介绍了基于时域和频域的分集合并检测办法。为了解决分集合并的检测方法中存在的符号矩阵估计精度不高的问题,提出了一种基于时域分集合并办法的选择性检测算法。与频域分集合并检测算法相比,该算法的计算复杂度要小得多。此外,仿真结果表明,该算法可以进一步改善系统的检测性能。接着,设计了基于PAM-DMT的VLC系统中的符号定时同步方案。分别对基于训练序列的定时同步方案和盲定时同步方案进行了探讨和总结,给出了基于PAM-DMT接收信号本身固有的结构特性设计的盲符号定时同步算法。对该定时同步算法进行了仿真,并且与基于训练序列的定时同步算法进行了性能比较。仿真结果表明,在高信噪比(Signalto Noise Ratio,SNR)下,该定时同步方案可以获得与基于训练序列的定时同步方案相同的正确定时性能。最后,提出了基于PAM-DMT的VLC系统中的采样时钟频率同步方案。分析了采样时钟频率偏差的基本理论及其对系统性能造成的影响,建立了包含采样时钟频率偏差因子的系统模型。设计了基于一维搜索方法(黄金分割法)的采样时钟频率偏差因子的估计算法。仿真结果表明,该算法可以高效地对采样时钟频率偏差因子进行估计,此外,利用得到的高精度的估计值还可以实现对采样时钟频率偏差的有效补偿,完成对系统的采样时钟频率的同步。
[Abstract]:Pulse Amplitude Modulation-Discrete Multitone (PAM-DMT) is a typical optical orthogonal Frequency Division Multiplexing (OFDM) scheme for visible Light Communication (VLC) systems. In this paper, the detection and synchronization technology in VLC system based on PAM-DMT is studied, and a high performance selective detection algorithm based on time-domain diversity combination is designed. A blind symbol timing synchronization algorithm based on the symmetry of PAM-DMT received signals and a sampling clock frequency offset estimation method based on efficient golden section search are proposed. Firstly, this paper introduces the orthogonal Frequency Division Multiplexing OFDM (OFDM) technology in the traditional Radio Frequency Division Multiplexing (RF) communication system and the intensity Modulation / Direct Detection (IM-DD) method in VLC system. Three typical O-OFDM schemes, Direct current Biased Optical OFDMOFDM (DCO-OFDM), Asymmetrically clipped Optical OFDM ACO-OFDM and PAM-DMTs, are analyzed. The VLC system based on PAM-DMT is selected as the system model after the theoretical research and performance analysis of the three schemes. Then, the design of high performance selective detection algorithm based on PAM-DMT is studied. This paper reviews the traditional detection schemes and introduces the diversity combination detection methods based on time domain and frequency domain respectively. In order to solve the problem that the precision of symbol matrix estimation is not high in the detection method of diversity merging, a selective detection algorithm based on time-domain diversity combination is proposed. Compared with the frequency domain diversity combination detection algorithm, the computational complexity of this algorithm is much smaller. In addition, the simulation results show that the algorithm can further improve the detection performance of the system. Then, the symbol timing synchronization scheme in VLC system based on PAM-DMT is designed. The timing synchronization scheme based on training sequence and blind timing synchronization scheme are discussed and summarized respectively. A blind symbol timing synchronization algorithm based on the inherent structural characteristics of PAM-DMT reception signal is presented. The timing synchronization algorithm is simulated and compared with the training sequence based timing synchronization algorithm. The simulation results show that the timing synchronization scheme can achieve the same correct timing performance as the training sequence based timing synchronization scheme under high signal-to-noise ratio (SNR). Finally, the sampling clock frequency synchronization scheme in VLC system based on PAM-DMT is proposed. The basic theory of sampling clock frequency deviation and its influence on system performance are analyzed, and a system model including sampling clock frequency deviation factor is established. An estimation algorithm of sampling clock frequency deviation factor based on one dimensional searching method (golden section method) is designed. The simulation results show that the proposed algorithm can efficiently estimate the sampling clock frequency deviation factor, in addition, it can effectively compensate the sampling clock frequency deviation by using the obtained high precision estimation value. Synchronize the sampling clock frequency of the system.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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