A Practical Implementation of IEEE 1588-2008 Transparent Clock for Distributed Measurement and Control Systems

This paper addresses issues with time synchronization using the IEEE 1588-2008 for distributed measurement and control systems. A practical implementation of the transparent clock is presented with the overall system architecture and detailed operation of each building block. To verify the submicrosecond accuracy using the implemented devices, an experimental setup that was analogous to a practical distributed system has been built. Measured results from the experiment show that the time error is limited below 30 ns for nodes that were connected by three switches. It is remarkable that the results are observed in spite of large packet queuing delays that were introduced by a traffic generator. The discussion on sources of time error that was outlined here provides technical considerations to designing IEEE 1588 systems.

I. Introduction

Synchronization has been an important issue in various applications. In particular, in distributed measurement and control systems, the overall performance greatly depends on the synchronization accuracy between each node over the network. As a means of providing robust cost-effective time synchronization for the distributed systems, the IEEE 1588 [1] specifies the precision-time protocol (PTP). Recent research effort has been focused on applying the IEEE 1588 to practical measurement and control systems [2]–[4]. The fundamental idea of the IEEE 1588 is very close to that of the network-time protocol (NTP) [5] based on packet exchanges, but the target accuracy is much higher (on the order of submicroseconds) [6]. By taking timestamps on the boundary of the physical layer for each network interface, the time error can be reduced below 100 ns for a very simple experimental setup.