Time Synchronization in Wireless Sensor Networks: A Survey

Time synchronization is a critical piece of infrastructure for any distributed system. Wirelesssensor networks have emerged as an important and promising research area in the recent years. Timesynchronization is important for many sensor network applications that require very precise mapping of gatheredsensor data with the time of the events, for example, in tracking and vehicular surveillance. It also plays animportant role in energy conservation in MAC layer protocols. The paper studies different existing methods,protocols, significant time parameters (clock drift, clock speed, synchronization errors, and topologies) to achieveaccurate synchronization in a sensor network. The studied Synchronization protocols include conventional time syncprotocols (RBS, Timing-sync Protocol for Sensor Networks -TPSN, FTSP), and other application specificapproaches such as all node-based approach, a diffusion-based method and group sync approaches aiming atproviding network-wide time. The goal for writing this paper is to study most common existing time synchronizationapproaches and stress the need of a new class of secure-time synchronization protocol that is scalable, topologyindependent, fast convergent, energy efficient, less latent and less application dependent in a heterogeneous hostileenvironment. Our survey provides a valuable framework by which protocol designers can compare new andexisting synchronization protocols from various metric discussed in the paper. So, we are hopeful that this paperwill serve a complete one-stop investigation to study the characteristics of existing time synchronization protocolsand its implementation mechanism in a Sensor network environment.