D-sync: Doppler-based time synchronization for mobile underwater sensor networks
D-sync: Doppler-based time synchronization for mobile underwater sensor networks
复制标题
DOI：
10.1145/1868812.1868815
复制
发表时间：
2010-09
期刊：
影响因子：
--
通讯作者：
Feng Lu;Diba Mirza;C. Schurgers
中科院分区：
文献类型：
--
作者：
Feng Lu;Diba Mirza;C. Schurgers
时间同步是水下网络中的一项重要服务，它需要许多功能，如MAC、睡眠调度、定位和传感器事件的时间戳。然而，水下同步存在两个基本挑战，即大的传播延迟和同步过程中节点的大量迁移。虽然现有的水下时间同步解决方案已经提出了解决这些挑战，但它们依赖于重信号，由于能源成本高，这是不可取的。在本文中，我们介绍了一种强大的新方法，该方法结合了物理层信息，即多普勒频移的估计。大的多普勒频移已被确定为水下通信的主要挑战，目前的系统采用复杂的解决方案来估计和跟踪每次数据交换的多普勒频移。虽然这是通信的障碍，但我们将展示多普勒频移包含非常有用的信息，可以用来大大提高时间同步。具体来说，它提供了节点之间相对运动的指示。我们的新协议，称为D-sync，战略性地利用这一特性来解决由于节点移动性造成的时间不确定性。因此，D-sync可以处理大量的移动性，而无需对潜在的运动进行任何假设，也无需大量的信号。仿真结果表明，D-sync在精度和能量方面都明显优于现有的时间同步。
Time synchronization is an essential service in underwater networks, required for many functionalities such as MAC, sleep-scheduling, localization, and time-stamping of sensor events. However, there exist two fundamental challenges to underwater synchronization, namely, large propagation delays and substantial node mobility during the synchronization process. While existing underwater time sync solutions have been proposed to address these challenges, they rely on heavy signaling, which is undesirable due to high energy costs. In this paper, we introduce a powerful new approach that incorporates physical layer information, namely an estimate of the Doppler shift. Large Doppler shift has been identified as a major challenge to underwater communication, and current systems implement sophisticated solutions to estimate and track such Doppler shift for each data exchange. While an impediment to communication, we will show that the Doppler shift contains highly useful information that can be leveraged to greatly improve time synchronization. Specifically, it provides an indication of the relative motion between nodes. Our new protocol, called D-sync, strategically exploits this feature to address the timing uncertainty due to node mobility. As such, D-sync can handle substantial mobility, without making any assumptions about the underlying motion, and without extensive signaling. Simulation results show that D-sync significantly outperforms existing time synchronization both in terms of accuracy and energy.