自适应温度补偿无线传感器网络时间同步方法

Adaptive temperature compensation time synchronization method for wireless sensor network

时间同步是多智能体网络协同工作的基础,具有重要意义。低成本无线传感器网络节点时钟易受到环境因素的影响,导致节点时间同步误差增大,网络信道负载增加。针对上述问题,提出了一种低时钟再同步周期、自适应温度补偿的无线传感器网络时间同步方法。首先,基于双向通信时间同步模型,提出了温度补偿的节点频移量动态估计模型;然后,采用Almon函数加权求和的方式对温度和频移量数据进行融合,解决数据采样率不匹配和模型维度高的问题;其次,为进一步提高时间同步精度,采用Kalman滤波器对频移量和相移量估计值进行滤波,并采用系统状态后验估计值对节点本地时间进行补偿;最后,参照IEEE 802.15.4标准对时间同步精度的要求,设计了一种失效风险最小化的再同步决策函数,最大限度提高节点再同步周期,减少信道负载。在高低温箱、室内和室外3种环境下进行实验以验证所提的方法。试验结果表明,与洪泛时钟同步协议(FTSP)时间同步协议相比,自适应温度补偿的时间同步(ATCTS)算法平均时间同步误差降低了97.4%,室外环境下平均时间同步周期为324 min。

Time synchronization is the foundation for the cooperative work of multi-agent networks and has great significance. The clock of a low-cost wireless sensor network node is subject to the influence of the environment factors, which leads to the increasing of the node time synchronization error and network channel overhead. Aiming at this problem, a novel network time synchronization method with low clock re-synchronization interval and adaptive temperature compensation for WSNs is proposed. Firstly, a node frequency shift dynamic estimation model with temperature compensation is proposed based on the two-way message exchange time synchronization model. Then, the Almon function weighted summation method is adopted to fuse the temperature and frequency shift data, and solve the problems of data sampling rate un-matching and high model dimension;next, in order to further improve the time synchronization accuracy, a Kalman filter is used to filter the estimation values of the frequency shift and phase shift, and the system state posteriori estimation value is used to compensate the node local time. At last, an adaptive re-synchronization decision function with minimized failure risk is designed according to the time synchronization accuracy requirement of the IEEE 802.15.4 standard, which improves the node re-synchronization interval and decreases the channel overhead to the maximum extent. Experiments in high, low temperature chamber, indoor and outdoor environments were conducted to verify the proposed method. The experiment results show that compared with that of FTSP time synchronization protocol, the average time synchronization error of the proposed ATCTS method is reduced by 97.4%, and the average time synchronization interval is 324 minutes in outdoor environment.