Packet arrival interval (PAI)-based time synchronization

Abstract

Recently, in the fields of network measurement and distributed control, synchronization accuracy of better than microsecond order is required. For highly accurate time synchronization, the skew (the variation of the clock rate) and the queuing delay in the packet switching network constitute problems. In this paper, Packet Arrival Interval-based time synchronization (PAI) is proposed. In the proposed system, based on the fact that the average arrival interval of the synchronized packets broadcast accurately at a certain interval is less likely to be affected by the queuing delay, the clock rate is accurately estimated. Also, the one-directional delay from the master to each client can be calculated accurately from prior knowledge of the constituent elements of the LAN. Wide-range synchronization is possible if the master is synchronized to GPS. An experiment confirms that synchronization accuracy of better than microsecond order can be realized even in the presence of cross traffic with a channel use rate of about 80%. In addition, the present system can be used even with small nodes such as a sensor network. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(11): 12–24, 2007; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecja.20402