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The Performance of a Wireless Sensor Network for Structural Health Monitoring Jeongyeup Paek, Nupur Kothari, Krishna Chintalapudi, Sumit Rangwala, Ramesh Govindan Embedded Networks Laboratory, USC Sep. 24. 2004
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Overview of Wisden
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Wisden A wireless multi-hop sensor network based data acquisition system for structural health monitoring Features Time-synchronized data delivery from multiple sensor nodes Reliable data delivery over multiple hops with tolerable latencies Ease and flexibility of deployment
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Wisden (cont’) Hardware Mica-2 mote Vibration card : 4-channel, 16-bit ADCs Accelerometer : tri-axis (-2.5g ~ 2.5g) Reliability Application layer NACK mechanism Hop-by-hop and end-to-end loss recovery over self-configured tree topology
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Wisden (cont’) Data Compression Lossy run-length encoding for silence suppression Required to handle the large data volume Data Synchronization Calculate residence time of a packet within each node Time-stamp data at the base station (possibly with GPS)
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Four Seasons Building
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Four Seasons Building and Eccentric mass shaker
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Wisden deployment Setup 10 motes in 90’ X 180’ area on the fourth floor of the building Four nodes co-located with the wired instruments Tri-axis, with 50Hz sampling rate for each channel 0.5 packets/sec transmission rate
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Deployment experiences High packet loss rate Delivery rate as low as 37.6% for some links Multi-hop network Maximum of 4-hop paths Frequent route changes Increased delay for packet loss recovery Ambient noise Human movements, power generator Interference with other wired/wireless devices
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Results
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Results (cont’)
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Problems Lossy Run-length compression Loss of high-frequency components of data Time-synchronization Adjusting time takes time …with GPS at the base station Software bug Counter wrap-around problem
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Seismic Test Structure Full-scale realistic model of hospital ceiling Located in the civil engineering building at USC
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Results
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Results (cont’)
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Conclusion Our deployments indicate that Wisden can deliver time-synchronized data reliably across multiple hops with tolerable latencies. However, a number of improvements can be made. Lossless compression Time synchronization
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Reference A Wireless Sensor Network for Structural Monitoring, Ning Xu, Sumit Rangwala, Krishna Chintalapudi, Deepak Ganesan, Alan Broad, Ramesh Govindan, Deborah Estrin, In Proceedings of the ACM Conference on Embedded Networked Sensor Systems, November 2004 The Performance of a Wireless Sensor Network for Structural Health Monitoring, Jeongyeup Paek, Nupur Kothari, Krishna Chintalapudi, Sumit Rangwala, Ning Xu, John Caffrey, Ramesh Govindan, Sami Masri, and Daniel Whang, submitted 2nd European Workshop on Wireless Sensor Networks (EWSN 2005)
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