Data Centric Sensor Networks

最近的技术进步导致了传感器网络的出现，它将小型、低功耗的传感器和执行器与有限的车载处理和无线通信能力集成在一起。这种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：大量低成本的轻型无线设备分散在一个地理区域，形成一个监视和通信网络。它的主要功能是定位和跟踪该地区的异常声音。这些无线设备配备了声学传感器，可以定位声波。它们必须动态组织起来，并在允许控制器采取必要行动的时间范围内传达位置信息，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。这是如何在不可靠的无线自组织网络上有效地协调和控制传感器的关键技术挑战，也是本方案的重点。具体地说，研究人员提出了一个集成框架，其中可以设计一个全面的解决方案，通过一组组件解决方案来实现目标。然后，研究人员建议沿着以下五个研究途径开展工作：设计一个统一的框架来设计传感器网络的有效性，并对其有效性进行推理：研究人员综述了几种以数据为中心的应用场景，面向应用的传感器网络，定义了传感器网络中信息传播的抽象问题，并确定了一组需求和目标。然后，研究人员将所需的功能配置到层内/层间的模块中，并绘制出它们的功能依赖图。在这个统一的框架下，人们可以设计特定于某一层的协议，而不会忽略它们与其他层协议的交互和兼容性。此外，跨层问题可以被识别和适当地解决。分层簇的形成和路由：由于以数据为中心的传感器网络的独特特性，研究人员认为以分层簇结构形式的拓扑结构提供了最大的性能好处。此外，由于各种传感器收集的信息可能是相关的、冗余的和/或不同性质的，这种结构有助于传感器数据的消化。研究人员建议开发并严格证明其最优化的去中心化集群形成方案，该方案捕捉并利用这些独特的特征。研究人员还将对移动路由器/基站进行运动控制，以有效恢复网络分区和/或缓解通信瓶颈。拓扑控制和功率管理：研究人员结合分层簇形成方案，考虑如何进行功率管理，以保持网络连通性，优化空间网络重用，减轻MAC级干扰。这是通过以下方式实现的：(1)在没有事件时关闭非中继节点的传感器；以及(Ii)设计用于在传感器不均匀分布时设置(一组)最小传输功率的策略。在此途径中的一些任务将在严格的理论基础下执行。用于及时传播延迟敏感数据的MAC设计：研究人员解决了几个媒体接入问题：(I)如何缓解媒体竞争以提高短期和长期吞吐量公平性，(Ii)如何在MAC中结合基础良好的调度策略以实现簇内/簇间的临时QOS，使用MOTES的经验研究：为了验证设计并对整体性能进行实证研究，研究人员将利用微型无线传感器MOTES，并构建传感器网络试验台。由于Motes的处理和通信能力相当有限，研究人员将Motes与MOPS/520 PC104板集成在一起。这是通过在PC板上连接Mote的串行外围接口(最初用于Motes中的Atmega 163处理器和外围设备之间的同步数据传输)来实现两板之间的数据传输。研究人员还将使用PC104板上的声卡和麦克风来模拟声传感器的行为。有了这样的传感器网络试验台，研究人员将能够实现和实验所提出的协议和算法。研究人员计划模拟国土监视，声音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 Out-of-date information is of no use, as the object that was tracked may no longer be in the vicinity when the information is received.This presents a key technical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.