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Evolution and Sustainability of a Wildlife Monitoring Sensor Network

Evolution and Sustainability of a Wildlife Monitoring Sensor Network. Vladimir Dyo , Stephen A. Ellwood†, David W. Macdonald†, Andrew Markham‡ Cecilia Mascolo §, Bence P´asztor §, Salvatore Scellato §, Niki Trigoni ‡, Ricklef Wohlers ‡, Kharsim Yousef §

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Evolution and Sustainability of a Wildlife Monitoring Sensor Network

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  1. Evolution and Sustainability of aWildlife Monitoring Sensor Network Vladimir Dyo, Stephen A. Ellwood†, David W. Macdonald†, Andrew Markham‡ Cecilia Mascolo§, BenceP´asztor§, Salvatore Scellato§, NikiTrigoni‡, RicklefWohlers‡, KharsimYousef§ Dept. of Computer Science and Technology, University of Bedfordshire, UK §Computer Lab, University of Cambridge, UK †Wildlife Conservation Research Unit, Dept. of Zoology and ‡Computing Laboratory, University of Oxford, UK

  2. Introduction • Sensor network deployment to reality gradually • Wildlife tracking • Collect unprecedented(無先例)granularity data • Maintain period > deployment period • Idealistic selling point in WSN • Low effort maintenance • Self-reconfiguration

  3. Wildlife monitoring application • Badgers 獾 • 寒帶動物 • Nocturnal夜行 animal • Group life • Often visit latrines and sett • Zoologist wants to know • Movement • Social interaction • Disease

  4. Overview • Active RFID • Tmote Sky sensor • Temperature • humidity • Solar powered gateway • 3G sink gateway • Mobile sink

  5. Heterogeneous network

  6. Initial system design • Sensing • Environmental monitoring • Badger monitoring • Data collection • Compression • Routing

  7. Environmental monitoring • Tmote Sky • Data-loggers • Network nodes • SHT-71 sensor • 1m height • One buried 30cm underground (temp.) • Sample/5min • hot-melt glue and heat-shrink is the best solution • Current consumption ~30uA

  8. Badger monitoring • Commercial 433MHz active RFID tag • Small enough that animal could bear (40x20x3mm) • Reliable • Inexpensive • Potted in epoxy resin • Mount on collar • Tag range 0~30m

  9. Badger monitoring • RFID detection node • RFID reader + Tmote Sky • RS232, regulator • 12V 18Ah battery • Powered up 10s • 26 sets at setts and latrines • Record • Tag Id , Reader ID • Serial NO., RSSI, checksum • Two communication system • Ground communication : extended communication range, high BW • Tracking :consistent antenna orientation, receiver sensitivity

  10. Data collection • Compression and local range • 1 Mb flash memory • Simple delta compression • 25% compression factor • Routing • Shortest path routing • Update table/30 min

  11. Evolution stage1 • Problem • High power consumption of the RFID reader • Heavy communication load around fixed gateway • Improvement • Adaptive sensing • Delay-tolerant data collection

  12. Adaptive sensing • 12V 18Ah battery support only 1 week • Duty cycle, 30s on within 330s => 9% • Adaptive duty cycle B: daily budget of active time(s) E: expected number of sightings N: equal time slots • Weighted function • O:actural number of sighting

  13. Simulation • Duty cycle 9%, B=7454 sec • Comparison with • Always on • Fixed duty cycle • Always on • 76707 encounter • 100% duty cycle • Fixed duty cycle • 7773 encounter • 9% • Adaptive • 46214 encounter(60%) • 5%

  14. Deployment evaluation • Real deployment • 833 hrs in July • Always on • 76707 encounter • 100% duty cycle • Fixed duty cycle • 7201 encounter • 9% • Adaptive • 54568 encounter(73%) • 8.2%

  15. Delay Tolerant data collection • Priority • Class 1 • Urgent latency, a few hours max • Unusual event • Network status • Forwarded to 3G router • Class 2 • Badger visits • forwarded to frequently visited node for opportunistic collection • Class 3 • Raw sensor data • No latency constrains, delay of weeks • Direct download

  16. Node priorities • Node priorities • Based on frequency expected to be visited by mobile sink • Class 1 • 3G router • Class 2 • Mobile sink visit at least every 3 days • Class 3 • Remaining nodes

  17. Evaluation • 24 RFID for 20 days • Half of time distributed, centralized • P1: 30min/2hr, P2:15min/3days • Centralized • All data forwarded to 3G gateway • Distributed • Forwarded to the nearest node

  18. results • Centralized exhibit 46% duty cycle

  19. Evolution stage 2 • Problem of Tmote Sky • Radio range • Usable • Power • Time • cost

  20. Design new node

  21. New node • RJ-485 RFID reader => OEM board • Trigger an interrupt on microcontroller when read a tag instead of maintain the clock for UART • Turn on time <100ms, 96mW when active • 2G SD memory for 40 yrs V.S. 1 week • Flexible connect to additional device (sensor)

  22. Duty cycle revisited • 9%, 30/330s =>1/11s • Higher encounter(89%) and efficiency • 5% duty cycle

  23. Deployment result

  24. Data collection revisited • Communication range: 50m => 1km • Fewer mobile sink visit: • 1week =>2 week=>2month • All nodes have one-hop connectivity • Node priorities collapsed • DTN improved little • Plan to scale-up network cover large area

  25. Network maintenance • VHF V.S. GPS V.S. RFID • VHF • Analogue device, can’t track number of IDs • 1 person to 1 animal, cost 2,030USD for 28 days • GPS • GPS perform poorly in woodland

  26. Network maintenance • 74 tag and 26 detection nodes costs 4440+7800=12240 USD • Human resource • 2 PhD + 2 post-doctoral, work for 3 yrs • Summary of cost

  27. Data analysis • Mar.09~Jun.10 • 29 million valid detection data • Badge Movement All locations setts latrines

  28. Badger co-location All locations setts latrines

  29. Conclusion • Maintenance cost • Not be a afterthought • Software and hardware interaction • Before SW optimization consider HW limit • Rapid initial prototyping and deployment • Observation and improvement • Gradual versus step-change improvements • Testing new component over a long period • Continuous interaction with domain scientists • Understand the need of the user, then design

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