Research On Time Synchronization Technology Of Wireless Ad Hoc Network

Wireless ad hoc network is a kind of mobile communication network composed of several mobile nodes and independent of fixed infrastructure.It has the characteristics of no-center,self-organized,dynamically changing network topology,strong resistance to damage and so on.It has wide application prospects in military and civilian fields.Accurate and efficient time synchronization technology is the guarantee of wireless ad hoc network when it works.Therefore,time synchronization technology is a key issue for wireless ad hoc networks.In this paper,we studied the traditional time synchr-onization technology,and analyzed the principle,advantages,disadvantages and scope of application of master-slave synchronization and mutual synchronization carefully.Among them,master-slave synchronization is suitable for small networks,and mutual synchronization is suitable for large networks.However,traditional time synchronization technology can only achieve synchronization of nodes in a single network.Due to the random movement characteristics of the nodes,they need to be integrated into one network when two or more networks collide,which may cause time out of synchronization.In this paper,We proposed a new algorithm for joining the network strategy to cope with the problem.The new algorithm is based on the master-slave synchronization algorithm,which is reflected in the following two aspects:(1)When a node in the network receives time information of other networks,the melted network flag and the melt timer are set.The nodes receive and transmit signals according to the timing relationship of the original network before the melt timer expires.When the melt timer expires,the nodes should be updated to be IDLE,receive and send signals according to the timing relationship of the new network.(2)In order to ensure the optimal network after the network is integrated,we proposes two different improvement schemes for the nodes of the IDLE state.In the first scheme,the node in the IDLE state receives the time information of other nodes,and updates the node to the synchronization state after the synchronization search time ends.In the second scheme,when the node in the IDLE state receives the time information of the same node twice,and updates the node to the synchronization state.In this paper,we use two different network topology to simulate the synchronization performance and integration performance of the new algorithm.Simulation results show that the algorithm can realize synchronization when several networks are integrated.Furthermore,we compare the two different processing schemes for IDLE state nodes and conclude that under the premise of ensuring the optimal network after the network is integrated,when the node receives the time information of the same node twice,it updates to the synchronization state,and the required integrating time is shorter.