IEEE1588高精度時間同步於行動裝知實現與應用

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。

關鍵字

適應性卡爾曼濾波器；精確時間協議；時間同步；虛擬時鐘

並列摘要

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

並列關鍵字

adaptive Kalman filter ； precision time protocol ； time synchronization ； virtual clock

參考文獻

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4. D.L. Mills, Modelling and analysis of computer network clocks. 1992, Electrica l Engineering Department.

8. HomeKit. Available from: https://developer.apple.com/homekit/.

10. D.L. Mills, Network Time Protocol Version 4 Reference and Implementation

國際替代計量

IEEE1588高精度時間同步於行動裝知實現與應用

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