一种基于休眠机制的网络时间同步协议

Network Time Synchronization Protocol Based on Sleeping Mechanism

时间同步技术是网络系统正常运行的基础。为了降低能耗,无线传感器网络(WSN)需要采用周期性休眠机制。针对目前WSN时间同步协议较少考虑网络节点的休眠问题,提出了一种适用于采用休眠机制的WSN时间同步协议。该协议包括递增序列号(ISN)机制和时钟校正机制。ISN同步机制能够在唤醒休眠节点的同时,将各网络节点同步到一致的时间点。随后,各节点利用本地时钟与参考节点时钟间的时钟漂移差值,对本地时钟进行校正。基于硬件平台的测试表明,该协议能够以较低的同步成本达到较高的同步精度;与传统时间同步协议相比,协议的执行不再受节点休眠状态影响,并且节点的唤醒过程与时间同步相结合,减少了同步消息的交换量;此外,协议中的时钟校正机制还可有效延长再同步周期。该协议还为众多基于时间同步的应用,如网络通信协议、时分多址(TDMA)调度及节点定位等,奠定了必要的基础。

Time synchronization technique provides the basis for the normal operation of network system. To save energy, the wireless sensor network（WSN） usually has to adopt sleeping mechanism. At present,the sleeping mechanism for network nodes does not be considered in the time synchronization protocol for WSN. Aiming at this problem,the time synchronization protocol based on sleeping mechanism which is suitable for WSN is proposed. The protocol includes an incremental serial number （ISN） synchronization mechanism and a clock correction mechanism. The ISN mechanism is able to synchronize a set of network nodes to consistent time points while waking them up. Then the network nodes will correct their local clocks in accordance with the time drift between their clock and that of the reference node. According to the experiment based on the hardware test platform, the proposed protocol is able to reach a high synchronization precision with relatively low cost; compared with traditional time synchronization protocols, the execution of the proposed protocol will not be affected by the sleeping state of the node, and the wake - up process of the node is combined with time synchronization, thus the amount of synchronization messages exchanged is reduced, and the resynchronization period can be effectively extended by the clock correction mechanism of the protocol. Meanwhile,the proposed protocol will also be the cornerstone for many applications based on time synchronization, such as network communication protocols, time division multiple access （TDMA） scheduling and node positioning, etc.