deployment of wisden: in a real environment - four seasons building deployment of wisden: in a real...
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Deployment of Wisden: Deployment of Wisden: In a real environment - Four Seasons BuildingIn a real environment - Four Seasons Building
Results from Deployment:Results from Deployment: Wisden can deliver Time-synchronized data ReliablyWisden can deliver Time-synchronized data Reliably
The Performance of a Wireless Sensor The Performance of a Wireless Sensor Network for Structural Health MonitoringNetwork for Structural Health Monitoring
Jeongyeup Paek, Nupur Kothari, Krishna Chintalapudi, Sumit Rangwala, Ramesh GovindanEmbedded Networks Laboratory, USC – http://enl.usc.edu
Introduction:Introduction: Wisden, A Multi-hop Wireless Data Acquisition System for SHM Wisden, A Multi-hop Wireless Data Acquisition System for SHM
Overview of Wisden Goal
Deployment Setup•10 motes in 90’x180’ area on the fourth floor of Four Seasons Building•Four nodes co-located with the wired instruments•Tri-axis, with 50Hz sampling rate for each channel•0.5 packets/second transmission rate
Deployment Experiences•High packet loss rate – delivery rate as low as 37.6% for some links•Multi-hop network – path lengths up to 4 hops •Frequent route changes – increased delay for packet loss recovery•Ambient noise – including human movements and interferences with other wired/wireless devices•Ease of deployment – half an hour of deployment time
UCLA – UCR – Caltech – USC – CSU – JPL – UC MercedUCLA – UCR – Caltech – USC – CSU – JPL – UC Merced
Center for Embedded Networked SensingCenter for Embedded Networked Sensing
• Reliable TransmissionApplication layer NACK mechanismHop-by-hop and end-to-end loss recovery over self-configured tree topology
• Data CompressionRun-length encoding for silence suppression
• Data SynchronizationLight-weighted approachSynchronize data at the base station
Techniques and Software
ReferencesReferences• 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, J. Wallace and Daniel Whang, submitted to 2nd European Workshop on Wireless Sensor Networks (EWSN 2005)
• FeaturesTime-synchronized data delivery from multiple sensor nodesReliable data delivery over multiple hops with tolerable latenciesEase and flexibility of deployment
• HardwareMica2 motes as sensor nodesTri-axis accelerometers with sensing range of ±2.5gVibration card for high quality sensing (16bit ADC)
• Evaluation of a sensor network data acquisition system for SHMBased on actual deployment of Wisden in the Four Seasons Building forced vibration test.
Results•Wisden can deliver time-synchronized vibration data over multi-hop network
Captured correct time and magnitude of the vibrations
•Wisden can capture the dominant frequency response of the structureWith some loss of high frequency components
•Insufficient reliability and occasional high-latency observed This was due to a software bug in Wisden
Problems found from the test•Lossy Run-length Encoding
Loss of high-frequency components of data
•Time synchronizationAdjusting time may introduce delay itself
•Software bug in WisdenCounter wrap-around problem caused slow retrieval of data
Test at Seismic Test Structure•Reliability of 99.3% achieved with tolerable latencies•Correctly captured the dominant modes of the structure•Software bug was fixed