Sensor Network Applications for Environmental Monitoring

1. Sensor Network Applications for Environmental Monitoring Carla Ellis SAMSI 11-Sept-07

2. Survey of Deployments • Two in detail: Redwoods and ZebraNet • Others • Great Duck Island • TurtleNet • James Reserve Forest • Volcanos & earthquakes • Aquatic observing systems • Localization, real-time tracking

3. Great Duck Island: Petrel MonitoringUCB • Goal: build ecological models for breeding preferences of Leach’s Storm Petrel • Burrow (nest) occupancy during incubation • Differences in the micro-climates of active vs. inactive burrows • Environmental conditions during 7 month breeding season • Inconspicuous Operation • Reduce the “observer effect” • Unattended, off-the-grid operation • Sensor network • 26 burrow motes deployed • 12 weather station motes deployed (+2 for monitoring the insides of the base station case) Burrow Occupancy Detector

4. TurtleNet (Corner, Umass) "Wetness" is a measure of current in the water sensor. This graph shows that the turtle came out of the water to sun itself for only brief periods and went back into the colder water. Mica2Dot hardware, GPS, Solar cells on the backs ofsnapping turtles.

5. James Reserve Forest (CENS) • Heterogeneous • Robotics • Imaging • Full motion cameras • In nesting boxes • Time lapse images • Microclimate array& soil moisture

6. Volcano Monitoring (Welsh, Harvard) • Motes with seismic sensors deployed on active volcano in Ecuador • Science dictates: high fidelity during events, large spatial separation, time synchronization. • Nature of the application allows triggered data collection rather than continuous.

7. Aquatic Observing Systems (CENS)

8. Macroscope in RedwoodsSenSys 05 Tolle et al UC Berkeley Intel Research Berkeley

9. Dense temporal and spatial data collection 44 days from Apr 27 to Jun 10 33 sensor nodes Sampling every 5 minutes Temperature, relative humidity, PAR Deployment Up a Tree

10. Mica2Dot node from Crossbow 4MHz processor 433 MHz radio, 40 Kbps 512 KB Flash Sensors Packaging Sensor Node Platform & Package

11. TASK Software • Duty cycling – node on 4 sec every 5 min • Time synchronization • Tree route discovery between gateway and nodes • TinyDB data collection and querying • Data logging in Flash as backup

12. Temporal Distributions

13. Temporal Distributions

14. Spatial Distributions

15. Subtracting Timestamp Mean

16. Subtracting Timestamp Mean

17. One Day in the Life of a Tree

18. One Day in the Life of a Tree

19. Visualizing Change

20. Visualizing Change

21. Once battery voltage falls, temperature reading goes bad Opportunity to automatically reject outliers Outliers & Battery

22. Performance of the Network:Data Transmitted

23. Performance of the Network:Data Transmitted

24. Logged Data

25. Both are good – compensate for the other’s failures Flash running out of space but transmissions continue Transmissions stopped but Flash retains those data points Both Logging & Transmission

26. Wildlife Tracking – ZebraNetAsplos 02 Juang et al Princeton

27. Long-term & wide ranging zebra herd migration tracking Associated with data on feeding behavior, heart-rate, body temp. Biological Goal

28. Why a Wireless Sensor Network Approach? • Traditional radio collars – coarse grain information • Sensor nodes (GPS), not networked – usually must retrieve collar to download stored data • Satellite tracking – high energy costs, low bitrate

29. A Day in the Life of a Zebra • Social structure can be exploited • Plains zebra form tight-knit harems (1 male, multiple females). Collar 1 individual and track the group • Sometimes form loose herds of multiple harems, often at watering holes • Drink water on a daily basis • Mostly moving 24 hours a day

30. Mobility Model

31. Collar Design GPS samples every 3 minutes Detailed activity logs for 3 min every hr 1 year of operation 3-5 lb weight limit

32. Energy and Weight Measurements

33. Vandalism is a problem for deploying an array of fixed antennas or base stations Base station sporadically available Drive-by Mobile Base Station

34. zebraA 10101 11101 10001 10001 10000 zebraB 10010 11111 10001 10000 Peer to Peer System Design

35. zebraA 10101 11101 10001 10001 10000 zebraA 10101 11101 10001 10001 10000 zebraB 10010 11111 10001 10000 zebraB 10010 11111 10001 10000 Peer to Peer System Design

36. zebraA 10101 11101 10001 10001 10000 zebraA 10101 11101 10001 10001 10000 zebraB 10010 11111 10001 10000 zebraB 10010 11111 10001 10000 Peer to Peer System Design

37. zebraA 10101 11101 10001 10001 10000 zebraB 10010 11111 10001 10000 Peer to Peer System Design

38. Implications of Collar Design • GPS provides precise synchronized clock • For avoiding short-range network collisions • Assume 5 days battery life between recharging • Need 13.5AH to sample (6KB/day), search for peers (6hr/day), search for base station (3 hr/day), and transmitting 640KB of data. • 640KB Flash = 300 days of data compressed, 110 days uncompressed • Need to accommodate redundancy of data stored from other nodes

40. Homing Success Rate • Fraction of data successfully delivered to base station (goal to eventually get 100% data reported) • Simulation study (single radio): • Flooding protocol – share data with everyone encountered • History protocol – send to “best” peer discovered based on their previous success in delivering to base • Direct protocol – not peer-to-peer, just to base

41. Simulation Results: Ideal

42. Results with Constrained Storage(10 collar days)

43. Results with Constrained Bandwidth (12kps) Short-range, flooding best Long-range, history best

44. Energy (unconstrained case; normalized to direct)

45. Final Design Choices • Storage viewed as effectively infinite • 2 radios: • one short-range, do flooding • other long-range, direct

46. Summary of Challenges

47. Energy in battery powered nodes. • Constrain lifetime of nodes, if not recharged • Energy harvesting, weight of solar collectors • Duty cycling necessary -> clock synchronization • Data delivery • Missing data • Connectivity • Routing issues • Unsynchronized duty cycles • Collisions • Dead nodes • Outliers • Calibration of sensors

48. Hierarchy, heterogeneity, mobility • Robotics, actuation • Packaging • Weather effects = dead nodes • Weatherproofing – gets in the way of sensors • How to deal with massive amounts of data • Infrastructure • System behavior monitoring • Interactive remote control (retasking)

49. Breakouts • Form 3 or 4 ad hoc multi-disciplinary groups (outside comfort zone: mix ECE+stat+CS+bio) • Discuss one of two topics • Research question you might address with Duke Forest data • Research study you might design from scratch, its requirements and challenges. • Report back at end of class (elect a spokesperson)