INTERNATIONAL JOURNAL OF APPLIED ENGINEERING RESEARCH, DINDIGUL Volume 1, No 4, 2011 © Copyright 2010 All rights reserved Integrated Publishing Association REVIEW ARTICLE ISSN  09764259 691 A Comparative Study of Time Synchronization Protocols in Wireless Sensor Networks Gopal Chand Gautam, Teek Parval Sharma Department of Computer Science & Engineering National Institute of Technology Hamirpur, (H.P.), INDIA tipugautam@gmail.com ABSTRACT Due to the recent innovations in the arena of wireless technologies, it is feasible to deploy inexpensive tiny disposable and low power devices throughout the physical space for the measurement of physical environments like temperature, pressure, humidity etc. These small devices are known as sensor nodes and their deployment is termed as wireless sensor network (WSN). Sensor nodes have resource constraints in terms of storage capacity, battery power and processing capabilities. Wireless sensor network was originally developed for military applications but later it has come for the public uses. Wireless sensor networks are useful for the military application, medical application, environmental monitoring, traffic control, industrial monitoring etc. All the proposed applications of wireless sensor networks involve monitoring sensor readings and communicating events to the other network nodes, or sinks. The deductions made during data fusion are sensitive to the time at which an event occurred at each node. These applications require partial or full time synchronization; therefore it is important that message exchanged by the sensor nodes for data fusion must be time stamped by each sensor’s local clock. In this paper we survey various time synchronization protocols and compare quantitative and qualitative various synchronization protocols. Keywords: Time synchronization, wireless sensor network, Data fusion, Clock drift, offset. 1. Introduction In Wireless Sensor Networks (WSNs) (Akyildiz 2002) the technological improvement has made these lowpower devices very cost effective. Sensor nodes are capable of gathering information, processing, and communication. Information gathering is done by actual sensors, such as measuring the temperature, air pollution, pressure, etc. (HofmannWellenhof 2001, Hill 2001, He 2006, Haenselmann 2006). Wireless Sensor Networks forms the network without any infrastructure (Sivrikaya 2004, Li 2007, Lasassmeh 2010), it is a special type of adhoc network where the wireless nodes work collectively to form a network. These devices are designed in such a way that they can work well in a harsh environmental and geographical conditions i.e where difficult to go or live. The wireless sensor network is being used in various applications such as health for tracking and monitoring doctors inside a hospital, military for monitoring forces, equipments and ammunition and environmental applications such forest fire monitoring, water quality monitoring, habitat monitoring and earthquake detection (Mainwaring 2005, Rhee 2009). In WSNs the purpose of the nodes is to sense the environment for an event and communicate data to the sink or base station. To identify the correct event time, these nodes must be synchronized among themselves and with universal time i.e with the global time. Therefore, time synchronization is significant aspect in wireless sensor networks. The performance of