Clock Synchronization in Sensor Networks for Civil Security

Wireless sensor networks are widely deployed in security surveillance applications. Since most of these applications depend on having a common notion of time among the sensors, performing fine-grained clock synchronization is highly desirable. Most of the existing time synchronization approaches mainly focus on improving clock precisions and reducing energy consumption, while ignoring the effect of faults and attacks on system performance. In this thesis we show the importance of fine-grained clock synchronization and implement two of the most well-known synchronization schemes proposed in the literature. We compare these approaches considering the precision, cost and fault tolerance. Our implementations tolerate node failures and adopt newly joint nodes to the network. We also use the synchronized time to avoid message collisions by emulating TDMA-based scheduling in the synchronization protocol. Finally we describe some of the existing attacks against clock synchronization protocols and some of the possible solutions.