相干光OFDM的時間同步算法研究
發(fā)布時間：2018-08-24 10:05
【摘要】：光正交頻分復用(OOFDM)因其頻譜利用率高,同時對光纖色度色散(CD)和偏振模色散(PMD)容忍性比較強,使OOFDM成為近些年來國內外研究的熱點。在相干光正交頻分復用系統(tǒng)(CO-OFDM)中,接收端通過ADC采樣變?yōu)閿底中盘?可以在后端通過色散補償、信道估計、載波頻偏估計和相位恢復等數字信號處理技術,自適應的去除傳輸過程中的色度色散、偏振模色散、收發(fā)機之間的頻率偏差和相位噪聲等因素的影響。偏振復用相干光正交頻分復用(PDM-CO-OFDM)系統(tǒng)將偏振復用技術與CO-OFDM技術結合,可以使信道傳輸速率成倍增加,從而提升了信道容量。CO-OFDM系統(tǒng)對同步比較敏感,所以對CO-OFDM系統(tǒng)中的同步進行研究有著重要的意義。本論文主要是對CO-OFDM系統(tǒng)中的符號定時同步算法和采樣時鐘同步算法進行分析和研究。一、本文首先對CO-OFDM系統(tǒng)的研究背景進行了簡單的闡述,概括描述了CO-OFDM傳輸技術和同步技術在國內外的研究進展。對CO-OFDM系統(tǒng)的整體結構,工作原理和關鍵技術進行了深入的研究。通過采用VPI光學仿真軟件和MATLAB搭建了56 Gb/s的CO-OFDM單模光纖系統(tǒng)的仿真平臺。在仿真平臺中,I/Q調制模塊,整個光纖鏈路,還有接收機的相干接收模塊,主要通過在VPI軟件中進行搭建和模擬,從而保證整個系統(tǒng)的信道條件的準確性。二、主要通過理論分析和仿真三個經典的符號定時算法：SchmidlCox算法、MinnLetaief算法和ParkCheon算法,并對三種算法在CO-OFDM仿真系統(tǒng)下的性能進行了對比研究。在此基礎上,引入了恒包絡零自相關序列(CAZAC),從而利用chu序列特性,對算法進行了優(yōu)化,通過仿真驗證,證明該算法在定時估計有著很高的精度。為了實現符號的精同步,從而對基于頻域導頻的符號同步算法進行了研究,通過仿真分析,證明優(yōu)化后的算法具有精確的補償效果。三、本文還研究了CO-OFDM系統(tǒng)的采樣頻偏同步算法,采用導頻估計出頻率偏差,采用基于數字鎖相環(huán)的采樣頻偏同步算法,并對該算法開環(huán)和閉環(huán)的情況下進行分析和仿真,表明該算法使系統(tǒng)性能得到了明顯的提升。
[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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN929.53
，
本文編號：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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN929.53
，
本文編號：2200483
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