Time Synchronization in Wireless Sensor Networks

Accurate time synchronization is crucial for many applications of Wireless Sensor Networks. Extensive research is performed on this topic, however, there are some aspects of time synchronization which still require attention. In this thesis we investigate aspects of the network which influence the accuracy of packed based time synchronization in Wireless Sensor Networks. The network of four nodes that are capable of wireless communication is constructed. Each node consists of Arduino Mega board with ATMEGA2560 micro-controller and RZ502 Accessory Kit with AT86RF230 radio chip. Three time-stamp exchange models are implemented on this network to synchronize the clocks and and compared with each other. The estimation of the synchronization parameters is done using Least Square estimators. Phase offset, frequency offset and communication delay are required to be estimated during the synchronization. From basic time-stamp exchange scheme, only sender-receiver model enables the estimation of the communication delay. The global synchronization leads to more accurate synchronization compared to the pair-wise synchronization. Based on the constructed setup, the aspects which influence the accuracy of time synchronization are identified: clock stability, clock resolution, time-stamping moment, physical layer property, communication aspects, synchronization time, number of synchronization messages, synchronization interval, time-stamp exchange model and synchronization algorithm. The requirements on these aspects are derived from the demand on the accuracy of the synchronization.Circuits and SystemsMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc