Study On Lightweight Time Synchronization Method For Large Scale Ad Hoc Network

Among various research interests in Wireless Sensor Networks (WSNs), time synchronization has received much increasing attention. Time synchronization is necessary in many WSNs aspects such as data fusion application, node sleeping and waking up, node localization, and node scheduling mechanism and so on. Exiting time synchronization protocols for large scale Ad Hoc network do not balance time synchronization precision and network overhead for time synchronization, so we propose Lightweight Time Synchronization Protocol (LTSP) for large scale Ad Hoc network.With the summary of WSNs, time-stamping and packet delay, this thesis compares current time synchronization protocols in WSNs. Utilizing the scheduling scheme to optimize source utilization; LTSP achieves nodes’ synchronization in WSNs with less collisions. To low the network overhead for time synchronization, LTSP adopts one way time synchronization message exchange mechanism. And there is a new definition of UNIT_OFFSET for measuring son’s time offset from its parent. By updating the value of UNIT_OFFSET, time synchronization accuracy is improved. At the same time, UNIT_OFFSET prevents time synchronization accuracy from node’s power-on delay. Physical tests and network simulations show that LTSP meets the requirement of nodes’synchronization in WSNs applications.On the base of nodes’ synchronization, this thesis proposes adaptive synchronization period scheme. In the improved LTSP, son’s time synchronization accuracy will be fed back to its parent to adjust the synchronization period. With the given time synchronization accuracy, improved LTSP makes the time synchronization period longer, decreases the network overhead for time synchronization. Simulations present that improved LTSP can flexibly adjust time synchronization period and effectively reduce energy consumption for time synchronization.