Sensors: Smart RF Antennas for Reliable and Real-Time Sensor Networks

由传感器节点组成的无线传感器网络，通过节点间的协作进行信息收集和分析，已成为多个领域的重要平台。该领域的研究兴趣日益增长，包括设备、通信、网络协议和有限程度的应用程序。为了使传感器网络成为其目标应用的可行平台，需要考虑不同层之间的交叉交互。例如，路由协议应该利用传感器配备能够进行功率优化的智能天线这一事实。拟议研究的新奇是多方面的。我们建议设计一个传感器节点，它集成了基于射频（RF）的通信设备，MAC层和容错和实时中间件的创新思想。集成节点将用于构建传感器网络，并评估网络的性能，成本，鲁棒性，简单性和灵活性的权衡。不确定性将是传感器网络在真实的世界部署中不可否认的事实。不确定性将源于环境变化（例如，缺少视线通信），节点可变性（例如，比预期更快地消耗电池）、业务可变性（例如，由于感兴趣的事件的频繁发生而高于预期的感测到的数据业务）和攻击者引起的可变性（例如，恶意入侵者对物理信道的干扰）。在我们的研究中，我们建议在节点中提供内置的支持，以容忍不同维度的不确定性。我们提出了几种新颖的低功耗操作模式的基础上，我们提出的智能天线的特点，在射频通信设备。我们提出的传感器节点将能够不仅仅是容忍不确定性，但利用不确定性，以其优势。我们建议利用有限的移动性的情况下，它导致一个节点的邻居在一个狭窄的频带对齐。在这种情况下，天线可以从全向工作模式切换到低功率的单向工作模式，传感器节点的自适应性将是其设计中的另一个重要驱动因素。传感器节点应通过易于使用的机制，在面对不确定性时进行重新配置。在我们提出的节点中，一个通用的自适应线程将被构建在所有三个层次上，在每一层以及层之间的交叉交互中，将考虑自适应性或灵活性与性能、成本和简单性之间的权衡问题。例如，在通信设备层，成本的关键权衡将是突出的，因为昂贵的天线阵列可以提供我们所需的灵活性，但其成本对于传感器节点来说是不可行的。系统软件层的适应性将集中在按需执行任务上，例如只有在发生感兴趣的事件时才激活传感器。中间件层面的适应性将集中在调整通信和计算以调整节点提供的容错和实时服务质量。拟议的研究包括三个关键任务：（i）在电气小节点上构建多样化和智能的RF硬件，这将使更强大和更低功耗的操作成为可能。这里解决的关键问题将是方向性，电磁小尺寸，和吸引力之间的权衡辐射整形和成本和复杂性;（ii）建立MAC和网络机制，可以利用RF硬件提供的灵活性，并提供挂钩的中间件。MAC层和网络层将平衡资源成本与性能之间的权衡，并根据应用需求进行优化;（iii）构建一个中间件层，优化容错和实时要求的操作，并平衡这些标准对成本和性能的影响。本研究的一个重要目标是开发具有新技术的传感器节点，并建立一个具有移动性的传感器网络试验床。该试验台将作为一个直观和有吸引力的传播研究成果的工具。这种普及研究的趋势遵循了合作PI Rosenberg的早期经验，他在Purduecampus上开发和部署了位置感知无线服务（如打印服务），以供社区广泛使用。研究结果将通过出版物和会议演示传播到RF，网络和中间件研究社区。这个项目将有助于教学和培训研究生和本科生谁是实施技术和执行测试平台的开发和评估。研究结果可以被纳入PI和co-PI教授的几门研究生和本科生课程（i-FaultTolerant System Design，即网络高级课程，即分布式参数系统。

Wireless networks of sensor nodes cooperating among themselves for information gathering and analysisare becoming an important platform in several domains. The area has seen growing research interest indifferent layers - devices, communication, network protocols and to a limited extent, applications. Forsensor networks to become viable platforms for the large class of applications it is being targetedtowards, there is the need to consider the cross-interaction between the different layers. For example, thefact that the sensors are equipped with smart antennas capable of power optimization should be utilizedby the routing protocols. The novelty of the proposed research is manifold. We propose to design asensor node that integrates innovative ideas for the radio frequency (RF) based communication device,the MAC layer, and a fault-tolerant and real-time middleware. The integrated node will be used in buildinga sensor network and evaluating the network for tradeoffs of performance, cost, robustness, simplicity,and flexibility.Uncertainty will be an undeniable fact of life with sensor networks in their real world deployments. Theuncertainty will stem from environmental variability (e.g., lack of line of sight communication), nodevariability (e.g., faster drainage of battery than expected), traffic variability (such as, higher than expectedsensed data traffic due to frequent occurrence of the event of interest) and attacker induced variability(e.g., jamming of the physical channels by a malicious intruder). In our research, we propose to providein-built support in the nodes to tolerate the uncertainty in the different dimensions. We propose severalnovel low power modes of operation based on the features of our proposed smart antenna in the RFcommunication equipment. Our proposed sensor node will be capable of not simply tolerating uncertainty,but exploiting the uncertainty to its advantage. We propose to make use of limited mobility in case itcauses the neighbors of a node to be aligned in a narrow band. In such a situation, the antenna can beswitched from its omni-directional mode of operation to a lower power unidirectional mode.Adaptivity of the sensor node will be another important driving factor in its design. The sensor nodeshould lend itself to reconfiguration in the face of uncertainty through easy to use mechanisms. In ourproposed node, a common thread of adaptivity will be built in at all the three levels under investigation.The issues of trade-off between adaptivity or flexibility and performance, cost, and simplicity will beconsidered for each layer as well as for the cross-interaction between layers. For example, at thecommunication device layer, the key tradeoff against cost will feature prominently since expensiveantenna arrays can provide the flexibility we require, but at a cost infeasible for the sensor nodes.Adaptivity at the system software level will focus on performing tasks on an as-needed basis, such asactivating the sensor only when there is an event of interest. Adaptivity at the middleware level will focuson adjusting the communication and computation to tune the fault -tolerance and real-time quality ofservice provided by the node.The proposed research comprises three key tasks: (i) Building diverse and intelligent RF hardware onelectrically small nodes, which will enable more robust and lower power operation. The key issuesaddressed here will be directionality, electromagnetically small size, and tradeoff between attractiveradiation shaping and cost and complexity; (ii) Building MAC and networking mechanisms which canleverage the flexibility provided by the RF hardware and provide hooks to the middleware. The MAC andnetwork layers will balance the tradeoffs of resource cost against performance and optimize it based onthe application requirements; (iii) Building a middleware layer that optimizes the operations for fault-tolerance and real-time requirements and balances these criteria against the cost and performanceimpact.Broad Impact in Technology and Teaching: An important goal of the research is to develop sensornodes with the new technology and create a sensor network testbed with the nodes equipped withmobility. The testbed will serve as an intuitive and attractive vehicle for disseminating the researchresults. This trend of popularizing research follows the earlier experience of the co-PI Rosenberg who hasdeveloped and deployed locality aware wireless services (such as, printing services) on the Purduecampus for widespread community use. The research findings will be disseminated to the RF, network,and middleware research community through publications and conference presentations. This project willhelp in teaching and training the graduate and undergraduate students who are implementing thetechniques and performing the testbed development and evaluation. The research results may beincorporated in several graduate and undergraduate courses taught by the PI and the co-PIs (i-FaultTolerant System Designlt, ieAdvanced Course in Networkingl., ieDistributed Parameter Systemslr).