Research On Time Synchronization Algorithm In Wireless Sensor Networks

Wireless sensor networks (WSN) compose with large populations of wirelessly sensor nodes, capable of computation, communication, and sensing. Accurate time synchronization is a base and critical component to many applications of WSN. In most of previous time synchronization algorithms, common nodes often synchronize their clocks to a reference(or root) node's, which is easily disturbed by incidental events (e.g. circuit's invalidation or root node's damage). In the paper, IATS (Improved Average Time Synchronization) algorithm, which synchronizes all the nodes'clock to their average, is presented based on the improvement of the ATSP. There are three main creative ideas in this thesis which are listed as follows:First of all, ROS(Receiver-Only Synchronization) approach is adopted in IATS, which aims at minimizing the number of message transmissions and the energy consumption necessary for global time synchronization.Secondly, a diffusion-based method is used in IATS, which maximizes the number of synchronizing nodes based on the ROS approach and spreads the local time synchronization to the entire network for network-wide time synchronization.Thirdly, The IATS allows neighboring nodes to relatively synchronize with each other by estimating relative clock offsets and skews. Maximum Likelihood estimators (MLE) are derived for both clock offset and skew estimation under Gaussian distributed delays. The joint clock offset and skew correction mechanisms significantly decrease the period of time synchronization, which is an important factor in the energy consumption required for global synchronization.The novel ideas and methods in the dissertation have been studied and verified through theoretic analysis and simulations,which have showed the feasibility.