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.
Time synchronization, wireless sensor network, Data fusion, Clock drift, offset
