中文摘要：

时间同步是研究多跳ad hoc无线网络的重要问题，例如无线传感器网络，许多具体应用需要传感器节点本地时钟的同步，要求各种程度的同步精度。无线传感器网络设备的一些固有属性，例如能量的限制、存贮、计算和带宽。与节点分布的高密度结合，使传统的时间同步算法不适合于这些网络。因此，越来越多的研究集中在设计适合于无线传感器网络的时间同步算法。首先回顾了时间同步的问题和无线传感器网络时间同步的需要，然后详细介绍了针对无线传感器网络设计的基本的时间同步算法，最后对各种算法进行了比较分析，并指出了下一步的研究方向。

英文摘要：

Time synchronization is an important issue in multihop ad hoc wireless networks such as sensor networks. Many applications of sensor networks need local clocks of sensor nodes to be synchronized, requiring various degrees of precision. Some intrinsic properties of sensor networks, such as limited resources of energy, storage, computation, and bandwidth, combined with potentially high density of nodes make traditional synchronization methods unsuitable for these networks. Hence, there has been an increasing research focus on designing synchronization algorithms specifically for sensor networks. This article reviews the time synchronization problem and the need for synchronization in sensor networks, then presents the basic synchronization methods explicitly designed and proposed for sensor networks, finally compares and analyses these synchronization methods, and indicates the research directions in the future.