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

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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).