Clock synchronization for wireless sensor networks with multiple external time references

Pao Yue-kong Library Electronic Theses Database

Clock synchronization for wireless sensor networks with multiple external time references


Author: Chow, Wing-tuen
Title: Clock synchronization for wireless sensor networks with multiple external time references
Degree: M.Sc.
Year: 2007
Subject: Hong Kong Polytechnic University -- Dissertations.
Sensor networks.
Wireless communication systems.
Department: Dept. of Computing
Pages: xi, 104 leaves : ill. ; 30 cm.
Language: English
InnoPac Record:
Abstract: Using peer-to-peer routing protocols, devices in a wireless sensor network (WSN) are capable of performing data collection without any external infrastructure, in areas that may be either ineffective or near impossible for humans to reach. The research presented here focuses on the issue of clock synchronization in WSNs, specifically addressing networks that include multiple external time references as well as mobile nodes. Clock synchronization is an essential network operation that provides the timestamps required for maintaining the chronological ordering of events, along with the management of time-sensitive applications. A series of protocols are designed to address the important issues concerning clock synchronization in a WSN with the presence of multiple external time references. To achieve the most accurate clock synchronization possible throughout a WSN, these protocols dictate an individual sensor's decisions that involve the supporting mechanisms of clock synchronization, primarily decisions regarding network topology set-up and network topology maintenance. These protocols include the Network Topology Set-up Protocol (NTSP), the Clock Synchronization with External Time References (CSETR) protocol, the CSETR protocol with mobile nodes (CSETR-M), the Parent Switching Protocol (PSP), and the Tree Switching Protocol (TSP). A WSN model and a node mobility model were developed and utilized in conducting performance studies, in which the results of WSN simulations were analysed to determine the network conditions for which of the protocols are most effective. The metrics analysed include node density, range, number of packets, duration of synchronization, and accuracy of synchronization. Studies concerning NTSP focused on the impacts of transmission range and node density on both network traffic and set-up latency. CSETR studies focused on clock accuracy and latency in determining the network conditions under which CSETR is most effective. CSETR-M studies focused on the degree of mobility and its impact on clock synchronization and network traffic. The relationships between network neighbourhood size, latency, and accuracy, as well as their effects on network communication are observed. Initial performance study findings helped to lay the foundations for the designs of PSP and TSP. Both PSP and TSP produce a marginal improvement on clock synchronization efficiency as measured by clock accuracy, while with PSP, clock synchronization efficiency is strongly affected by the degree of node mobility.

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