A Research Of Time Synchronization Protocol Based On Dynamic Topology In Large Scale Wireless Sensor Networks

With the development of wireless sensor networks with huge scale,traditional time synchronization protocols cannot satisfy the requirement of the precision of time synchronization of wireless sensor networks.A time synchronization protocol based on dynamic topology and broadcast selection(DTBS)is designed in this thesis to solve problems including serious synchronization error accumulation in multi-hop effectively,the change of wireless network topology,and the difference between stability of different nodes.Synchronous information of node is not forwarded by fixed route in this protocol,node chooses the best parent-node which has more stable performance and fewer synchronization hops to synchronize time to restrain accumulation of synchronization error by multi-hop forwarding.The parent-node is chosen afresh in every synchronization circle to keep most nodes being synchronized with root node when the wireless network topology changes.In the process of broadcast selection,the node is determined as the poor node which has clock abrupt swinging many times,the qualification of sending synchronous information is cancelled,but the node can still receive synchronous information from other nodes.Nodes with stable performance are selected as high-quality nodes by setting threshold,synchronous information of high-quality nodes can be forwarded to ensure the time synchronization precision and decrease traffic of the network at the same time,thus the energy consumption is less than others.Large scale feasibility testing is verified on NS2 simulation platform,the testing data shows the feasibility of DTBS protocol in large scale wireless sensor networks.