相干光OFDM的时间同步算法研究
发布时间：2018-08-24 10:05
【摘要】：光正交频分复用(OOFDM)因其频谱利用率高,同时对光纤色度色散(CD)和偏振模色散(PMD)容忍性比较强,使OOFDM成为近些年来国内外研究的热点。在相干光正交频分复用系统(CO-OFDM)中,接收端通过ADC采样变为数字信号,可以在后端通过色散补偿、信道估计、载波频偏估计和相位恢复等数字信号处理技术,自适应的去除传输过程中的色度色散、偏振模色散、收发机之间的频率偏差和相位噪声等因素的影响。偏振复用相干光正交频分复用(PDM-CO-OFDM)系统将偏振复用技术与CO-OFDM技术结合,可以使信道传输速率成倍增加,从而提升了信道容量。CO-OFDM系统对同步比较敏感,所以对CO-OFDM系统中的同步进行研究有着重要的意义。本论文主要是对CO-OFDM系统中的符号定时同步算法和采样时钟同步算法进行分析和研究。一、本文首先对CO-OFDM系统的研究背景进行了简单的阐述,概括描述了CO-OFDM传输技术和同步技术在国内外的研究进展。对CO-OFDM系统的整体结构,工作原理和关键技术进行了深入的研究。通过采用VPI光学仿真软件和MATLAB搭建了56 Gb/s的CO-OFDM单模光纤系统的仿真平台。在仿真平台中,I/Q调制模块,整个光纤链路,还有接收机的相干接收模块,主要通过在VPI软件中进行搭建和模拟,从而保证整个系统的信道条件的准确性。二、主要通过理论分析和仿真三个经典的符号定时算法：SchmidlCox算法、MinnLetaief算法和ParkCheon算法,并对三种算法在CO-OFDM仿真系统下的性能进行了对比研究。在此基础上,引入了恒包络零自相关序列(CAZAC),从而利用chu序列特性,对算法进行了优化,通过仿真验证,证明该算法在定时估计有着很高的精度。为了实现符号的精同步,从而对基于频域导频的符号同步算法进行了研究,通过仿真分析,证明优化后的算法具有精确的补偿效果。三、本文还研究了CO-OFDM系统的采样频偏同步算法,采用导频估计出频率偏差,采用基于数字锁相环的采样频偏同步算法,并对该算法开环和闭环的情况下进行分析和仿真,表明该算法使系统性能得到了明显的提升。
[Abstract]:Optical orthogonal Frequency Division Multiplexing (OFDDM) (OOFDM) has high spectral efficiency and strong tolerance to optical fiber chromatic dispersion (CD) and polarization mode dispersion (PMD), so OOFDM has become a hot topic in recent years. In the coherent optical orthogonal frequency division multiplexing (CO-OFDM) system, the receiver is converted into a digital signal through ADC sampling, and digital signal processing techniques such as dispersion compensation, channel estimation, carrier frequency offset estimation and phase recovery can be used at the back end. The effects of chrominance dispersion, polarization mode dispersion, frequency deviation and phase noise between transceiver and transceiver are eliminated adaptively. Polarization multiplexing coherent optical orthogonal frequency division multiplexing (PDM-CO-OFDM) system combines polarization multiplexing technology with CO-OFDM technology, which can double the channel transmission rate and increase the channel capacity. CO-OFDM system is more sensitive to synchronization. So it is of great significance to study synchronization in CO-OFDM system. In this paper, the symbol timing synchronization algorithm and the sampling clock synchronization algorithm in CO-OFDM system are analyzed and studied. Firstly, the research background of CO-OFDM system is briefly described, and the research progress of CO-OFDM transmission technology and synchronization technology at home and abroad is described briefly. The whole structure, working principle and key technology of CO-OFDM system are studied deeply. The simulation platform of 56 Gb/s CO-OFDM single mode optical fiber system is built by using VPI optical simulation software and MATLAB. In the simulation platform I / Q modulation module the whole fiber link and the receiver coherent receiver module are built and simulated in VPI software to ensure the accuracy of the channel conditions of the whole system. Secondly, three classical symbolic timing algorithms, namely: SchmidlCox algorithm, Minn Letaief algorithm and ParkCheon algorithm, are analyzed and simulated theoretically, and the performance of the three algorithms in CO-OFDM simulation system is compared. On this basis, the zero-autocorrelation sequence (CAZAC), of constant envelope is introduced to optimize the algorithm by using the characteristics of chu sequence. The simulation results show that the algorithm has a high precision in timing estimation. In order to realize the precision synchronization of symbols, the symbol synchronization algorithm based on frequency-domain pilot is studied. Through simulation analysis, it is proved that the optimized algorithm has accurate compensation effect. Thirdly, the sampling frequency offset synchronization algorithm of CO-OFDM system is studied in this paper. The frequency deviation is estimated by pilot, and the sampling frequency offset synchronization algorithm based on digital phase-locked loop is adopted. The algorithm is analyzed and simulated under the condition of open loop and closed loop. It shows that the performance of the system is improved obviously by this algorithm.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53
，
本文编号：2200483
[Abstract]:Optical orthogonal Frequency Division Multiplexing (OFDDM) (OOFDM) has high spectral efficiency and strong tolerance to optical fiber chromatic dispersion (CD) and polarization mode dispersion (PMD), so OOFDM has become a hot topic in recent years. In the coherent optical orthogonal frequency division multiplexing (CO-OFDM) system, the receiver is converted into a digital signal through ADC sampling, and digital signal processing techniques such as dispersion compensation, channel estimation, carrier frequency offset estimation and phase recovery can be used at the back end. The effects of chrominance dispersion, polarization mode dispersion, frequency deviation and phase noise between transceiver and transceiver are eliminated adaptively. Polarization multiplexing coherent optical orthogonal frequency division multiplexing (PDM-CO-OFDM) system combines polarization multiplexing technology with CO-OFDM technology, which can double the channel transmission rate and increase the channel capacity. CO-OFDM system is more sensitive to synchronization. So it is of great significance to study synchronization in CO-OFDM system. In this paper, the symbol timing synchronization algorithm and the sampling clock synchronization algorithm in CO-OFDM system are analyzed and studied. Firstly, the research background of CO-OFDM system is briefly described, and the research progress of CO-OFDM transmission technology and synchronization technology at home and abroad is described briefly. The whole structure, working principle and key technology of CO-OFDM system are studied deeply. The simulation platform of 56 Gb/s CO-OFDM single mode optical fiber system is built by using VPI optical simulation software and MATLAB. In the simulation platform I / Q modulation module the whole fiber link and the receiver coherent receiver module are built and simulated in VPI software to ensure the accuracy of the channel conditions of the whole system. Secondly, three classical symbolic timing algorithms, namely: SchmidlCox algorithm, Minn Letaief algorithm and ParkCheon algorithm, are analyzed and simulated theoretically, and the performance of the three algorithms in CO-OFDM simulation system is compared. On this basis, the zero-autocorrelation sequence (CAZAC), of constant envelope is introduced to optimize the algorithm by using the characteristics of chu sequence. The simulation results show that the algorithm has a high precision in timing estimation. In order to realize the precision synchronization of symbols, the symbol synchronization algorithm based on frequency-domain pilot is studied. Through simulation analysis, it is proved that the optimized algorithm has accurate compensation effect. Thirdly, the sampling frequency offset synchronization algorithm of CO-OFDM system is studied in this paper. The frequency deviation is estimated by pilot, and the sampling frequency offset synchronization algorithm based on digital phase-locked loop is adopted. The algorithm is analyzed and simulated under the condition of open loop and closed loop. It shows that the performance of the system is improved obviously by this algorithm.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53
，
本文编号：2200483
本文链接：https://www.wllwen.com/kejilunwen/wltx/2200483.html
