IEEE1588 Based High Precision Time Synchronization Implementation and Application for Mobile Systems

隨著時代的進步,人們以往對於桌上型電腦的依賴漸漸 的轉移到 了 行 動 裝 置 上面,智慧型平板、智慧型手機成為人們隨身攜帶的必需品。而行動裝置的優 勢 在 於機器與人和機器與機器之間的高度互動性,與雲端技術的配合,造就了新的生活、 娛樂和工作模式。然而隨著互動性的提升,精確時間的需求也隨之提升。本論 文 在 基於 IEEE1588 標準之上,建立一套可以在行動裝置上運行的高精度時間同步機 制。 IEEE 1588 標準定義了精確時間協定(Precision Time Protocol, PTP)的相關準則, 其主要目標為達成區域網路系統各節點的時間同步。透過網路封包的交換,各節點 互相交換時間戳記的資訊,經由演算可以得到從時鐘(Slave Clock)相對於主時鐘 (Master Clock)的時間相位誤差。進一步藉由時鐘約束演算法(Clock Discipline Algorithm)將從時鐘同步於主時鐘。 本論文建立了一套虛擬時鐘的架構,藉此避免介入行動裝置的作業系統,並提 供了一個可以在行動裝置上運行的區域型時鐘同步方案。 虛擬時鐘的 同 步 演 算 法 主要有三大部分。第一部分採用了精確時間協定開放程式(Precision Time Protocol daemon, PTPd),量測從時鐘節點與主時鐘節點間的時間相位誤差量。第二部份透 過卡爾曼濾波器估測從時鐘相對於主時鐘的實際相位誤差 ,並且經由 系 統 時 鐘 與 虛擬時鐘的平行架構量測同步環境上的雜訊統計量值,藉 此調整系統 的 估 測 與 控 制參數,達到適應性的功能。第三部分透過鎖相迴路與比例-積分型控制器完成時 鐘的同步控制。經由行動裝置上實際測試證實本系統提供 了一個穩定 且 高 精 度 的 時鐘同步。With the progress of the times, the dependency on desktop computers by people now is gradually shifted to mobile devices. Smart phones and tablet computers more and more popular. Mobiles devices bring a new type of life to people. People can use mobile devices to communicate to other people or other smart devices, also people can interact with smart mobile devices. Aglobal standard time for mobile devices to follow bacomes a basic issue. So a high precision time synchronization method is needed. In this paper, we design and implement a clock synchronization system for mobile devices. It is based on IEEE1588 precise time protocol. The IEEE1588 protocol defines the information and rules for precision time protocol (PTP). It can measure the clock offset between two devices by the exchange of time network packets. We build a virtual clock so that the operating system of mobile devices will not be invaded. IEEE1588 precision time protocol, clock state estimator and controller are used to implement clock synchronization system. First we use IEEE1588 precision time protocol to measure the clock offset between devices. Second we use the Kalman filter to estimate the clock state. Also, the parameters of the Kalman filter are adjusted by clock noise estimators. And third we adjust the clock frequency and control the clock phase by a proportion-integral controller. Experimental results show that our system provides good clock synchronization performances for mobile devices誌謝................................................................................................................................ i 摘要............................................................................................................................... ii Abstract ........................................................................................................................ iii 目錄...............................................................................................................................iv 圖目錄..........................................................................................................................vii 表目錄...........................................................................................................................ix 第一章序論 .................................................................................................................... 1 1.1 研究動機 .................................................................................................. 1 1.2 研究方向 .................................................................................................. 1 1.3 論文架構 .................................................................................................. 1 第二章背景知識 ............................................................................................................ 3 2.1 時間訊號 .................................................................................................. 3 2.1.1 連續時間訊號模型.......................................................................... 3 2.2 時間頻率穩定度分析 .............................................................................. 4 2.2.1 冪次定律雜訊...................................................................................... 4 2.2.2 標準差(Standard Deviation)............................................................. 5 2.2.3 亞倫偏差(Allan Deviation) .............................................................. 5 2.2.4 修正型亞倫偏差(Modified Allan Deviation) .................................. 6 2.2.5 時間偏差(Time Deviation) .............................................................. 7 2.3 電腦時鐘系統簡介 .................................................................................. 8 2.3.1 時鐘系統架構.................................................................................. 8 2.3.2 Unix時鐘......................................................................................... 9 2.3.3 Unix時鐘改良時鐘---NTP時鐘................................................... 10 2.4 智慧型行動裝置 .................................................................................... 11 2.4.1 智慧型行動裝置簡介.................................................................... 11 2.4.2 智慧型行動裝置目前與未來之發展............................................ 11 2.4.3 智慧型行動裝置作業系統介紹(iOS) ........................................... 13 2.5 目前於智慧型行動裝置之時間同步 .................................................... 14 2.5.1 網路時間協定(Network Time Protocol, NTP) .............................. 14 2.5.2 智慧型行動裝置上之時間同步效能量測.................................... 15 第三章高精度時間同步於智慧型行動裝置之實現.................................................. 18 3.1 時間同步演算法概述 ............................................................................ 18 3.2 時間同步演算法架構 ............................................................................ 18 3.3 虛擬時鐘系統 ........................................................................................ 20 3.3.1 系統架構........................................................................................ 21 3.3.2 系統實作........................................................................................ 23 3.4 IEEE 1588 高精度時間協定 .................................................................. 25 3.4.1 精確時間協定介紹........................................................................ 25 3.4.2 精確時間量測................................................................................ 26 3.5 精確虛擬時間同步軟體 ........................................................................ 30 3.6 卡爾曼濾波器 ........................................................................................ 33 3.6.1 時鐘數學模型................................................................................ 34 3.6.2 狀態估測........................................................................................ 35 3.7 適應性時間校正演算法 ........................................................................ 38 3.8 時鐘控制演算法 .................................................................................... 41 第四章實驗結果 .......................................................................................................... 44 4.1 實驗環境架設 ........................................................................................ 44 4.2 時間同步實驗結果 ................................................................................ 45 4.2.1 以傳統卡爾曼濾波器進行時鐘狀態估測之時間同步................ 45 4.2.2 以適應性卡爾曼濾波器進行時鐘狀態估測之時間同步............ 49 4.3 同步實驗穩定度分析 ............................................................................ 52 第五章iOS時鐘同步應用開發................................................................................... 55 5.1 應用介紹 ................................................................................................ 55 5.1.1 反應時間量測................................................................................ 55 5.1.2 心臟病撲克牌遊戲........................................................................ 57 5.2 iOS應用程式架構 .................................................................................. 61 5.2.1 應用程式運作流程........................................................................ 61 第六章結論與未來展望 .............................................................................................. 63 6.1 結論 ........................................................................................................ 63 6.2 未來展望 ................................................................................................ 6