Data Centric Sensor Networks

最近的技术进步导致了传感器网络的出现，这些传感器网络集成了小型、低功耗的传感器和执行器，具有有限的机载处理和无线通信能力。这种类型的传感器网络的一个例子是机场、桥梁和公共建筑的国土安全：大量低成本的轻量级无线设备分散在一个地理区域内，形成一个监控和通信网络。其主要这些无线设备配备了声学传感器，可以定位声波。它们必须动态地组织自己，并在一定的时间范围内传达位置信息，以便控制器采取必要的行动，即使在传感器设备空间分布不佳、无线/声学干扰和恶意破坏的情况下也是如此。过时的信息是没有用的，因为当接收到信息时，被跟踪的对象可能不再在附近。这提出了在协作交战中如何在不可靠的无线ad hoc网络上有效地协调和控制传感器的关键技术挑战，并且是本提议的焦点。具体地，研究者们提出了一个综合框架，在这个框架中，一个综合的解决方案可以被设计成一组组件解决方案来实现预定目标。然后，研究者们提出了沿着以下五项研究的任务途径：一个统一的框架，设计和推理的有效性，传感器网络：研究人员调查几个应用场景的数据为中心，面向应用的传感器网络，定义一个抽象的问题，在传感器网络中的信息传播，并确定一组要求和目标。然后，研究人员将所需的功能配置到层内/跨层的模块中，并计算它们的功能依赖性。在这个统一的框架下，可以设计特定于一个层的协议，而不会忽略它们与其他层协议的交互和兼容性。此外，可以识别并适当解决跨层问题。分层集群形成和路由：由于以数据为中心的传感器网络的独特特性，研究人员认为，分层簇结构形式的拓扑结构提供了最大的性能优势。此外，由于各种传感器收集的信息可能是相关的，冗余的，和/或不同的质量，这种结构有助于传感器数据的分类。研究人员建议开发并严格证明其最优性，一种分散的集群形成方案，该方案可以捕获和利用这些独特的特征。研究人员还将对移动的路由器/基站进行运动控制，以有效地恢复网络分区和/或缓解通信瓶颈。拓扑控制和电源管理：研究人员考虑，结合层次聚类形成方案，如何进行功率管理，以保持网络连通性，优化空间网络重用，这是通过（i）在没有事件时关闭不是中继节点的传感器;及（ii）制订策略，（一套）当传感器不均匀分布时，最小的传输功率。同样，这一途径中的任务将在严格的理论基础上进行。MAC设计延迟敏感数据的及时传播：研究人员解决了几个介质访问问题：（i）如何减轻介质争用，以提高短期和长期吞吐量公平性，（ii）如何在MAC中结合良好的调度策略，以实现集群内/集群之间的时间QoS，以及（iii）如何在涉及实时消息时权衡吞吐量和延迟。为了验证设计并实证研究整体性能，研究人员将利用微型无线传感器Motes构建传感器网络测试平台。由于尘埃在处理和通信能力方面相当有限，研究人员将把Mote与MOPS/520 PC 104板集成在一起，这是通过在PC板上附加一个Mote并使用Mote的串行外设接口来实现的（最初用于Motes中的Atmega 163处理器与外围设备之间的同步数据传输）用于两块板之间的数据传输。研究人员还将通过使用PC 104板上的声卡和麦克风来模拟声学传感器行为。有了这样的传感器网络测试平台，研究人员将能够实施和实验所提出的协议和算法。研究人员计划模拟本土监控，其中声学传感器可以为观看闭路电视的警卫提供线索。

Recent technological advances have led to the emergence of sensor networks that integrate small, low-power sensors and actuators with limited on-board processing and wireless communication capabilities.An example of this type of sensor networks is homeland security at airports, bridges, and public buildings: a large number of low cost lightweight wireless devices is scattered in a geographic region and form a surveillance and communication network.Its major function is to locate and track unusual sounds in the region.These wireless devices are equipped with acoustic sensors and can locate a sound wave.They have to organize themselves dynamically, andconvey the location information within a time frame that allows the controller to take necessary action, even in the case of poor spatial distribution of sensor devices, wireless/acoustic interference, and malicious destruction. Out-of-date information is of no use, as the object that was tracked may no longer be in the vicinity when the information is received.This presents a key technical challenge in cooperative engagement how to effectively coordinate and control sensors over an unreliable wireless ad hoc network and is the focus of this proposal.Specifically, the researchers propose an integrated framework in which a comprehensive solution can be designed with a set of component solutions to achieve the targeted goals.Then the resesarchers propose to carry out tasks along the following five research avenues:A unified framework for designing, and reasoning the effectiveness of, sensor networks: the researchers survey several application scenarios of data-centric, application-oriented sensor networks, define an abstract problem for information dissemination in sensor networks, and identify a set of requirements and objectives. Then, the researchers configure the required functionalities into modules in/across layers, and figure in their functional dependency.Under this unified framework, one can design protocols specific to a layer without negligence of their interaction, and compatibility, with protocols in other layers.Also, cross layer issues can be identified and appropriately addressed.Hierarchical cluster formation and routing: Due to the unique characteristics of data-centric sensor networks, the researchers believe topology in the form of hierarchical cluster structure offer the greatest performance benefits.Also, as the information collected by various sensors may be correlated, redundant, and/or of different qualities, this structure facilitates digests of sensor data. The researchers propose to develop, and rigorously prove its optimality of, a decentralized cluster formation scheme that captures and utilizes these unique characteristics. The researchers will also exercise motion control of mobile routers/base stations to effectively recover network partition and/or to relieve communication bottlenecks.Topology control and power management: The researchers consider, in conjunction with the hierarchical cluster formation scheme, how to exercise power management so as to maintain network connectivity, optimize spatial network reuse, and mitigate MAC-level interference.This is achieved by (i) powering off sensors that are not relay nodes when there are no events; and (ii) devising strategies for setting (a set of) minimal transmission powers when sensors are not evenly distributed.Again tasks in this avenue will be carried out with a rigorous theoretical base.MAC design for timely dissemination of delay-sensitive data: The researchers address several medium access issues: (i) how to mitigate medium contention to improve short-term and long-term throughput fairness, (ii) how to incorporate well-grounded scheduling policies in MAC to achieve temporal QoS within/between clusters, and (iii) how to tradeoff throughput for delay when real-time messages are involved.Empirical study with the use of Motes: To validate the design and to empirically study the overall performance, the researchers will leverage the tiny wireless sensors, Motes, and construct a sensor network testbed. As Motes are rather limited in their processing and communication capability, the researchers will integrate Motes with MOPS/520 PC104 boards.This is realized by attaching a Mote to the PC board and use the Mote's serial peripheral interface (originally for synchronous data transfer between the Atmega 163 processor in Motes and peripheral devices) for data transfer between the two boards.The researchers will also simulate acoustic sensor behaviors by using the sound cards and microphone on the PC104 board.With such a sensor network testbed in place, the researchers will be able to implement and experiment with the proposed protocols and algorithms. The researchers plan to simulate homeland surveillance where acoustic sensors can give clues to guards who watch close circuit TVs.