Wireless Sensor Networks for Habitat Monitoring

1. Wireless Sensor Networks for Habitat Monitoring Alan Mainwaring, Joseph Polastre, Robert Szewczyk, and David Culler, June 2002 Presented by Team 8: Feng Kai and Michael Thomsen, September 2004

2. Outline • Habitat monitoring • Network Requirements • System Architecture • Hardware and Design • Results

3. Why? • Why are we interested in Habitat Monitoring? • Focus attention on a REAL network • Some problems have simple concrete solutions, while others remain open research areas • Application driven approach separates actual problems from potential ones, and relevant issues from irrelevant ones • Collaboration with scientists in other fields helps define broader application space as well as scientific requirements

4. Scientific Motivation • How much can they vary? • What are the occupancy patterns during incubation? • What environmental changes occurs intheburrows and their vicinity duringthe breeding season? • Questions • What environmental factors make for a good nest?

5. Scientific Motivation • Collect detailed occupancy data from a number of occupied and empty nests • Validate a sample of sensor data with a different sensing modality • Augment the sensor data with deployment notes (e.g. burrow depth, soil consistency, vegetation data) • Try to answer the questions based on analysis of the entire data set • Methodology • Characterize the climate inside and outside the burrow

6. Scientific Motivation • Solution • Deployment of a sensor network • The impact of human presence can distort results by changing behavioral patterns and destroy sensitive populations • Repeated disturbance will lead to abandonment of the colony • Problems • Seabird colonies are very sensitive to disturbances

7. Field Stations • Great Duck Island • Almost 1 km2 (237 acre) remote island • Coast of Maine • Large Breeding colonies of Leech’s Storm Petrels and other seabirds • James San Jacinto Mountains Reserve • Small 0,1 km2 (29 acre) ecological preserve • Near Idyllwild, California(about 100 km east of LA) • Studying nest boxes, and ecosystems over time

8. Application Requirements • Hierarchical network (local networks over longer distances) • Sensor network longevity (at least 9 months) • Operating off-the-grid (battery or solar cells) • Remote management (personnel just available 2-3 months) • Inconspicuous operation (should not disrupt natural processes or behaviors under study) • System behavior (stable, predictable and repeatable behavior) • In-situ interactions (during deployment and maintenance) • Sensors and sampling (light, temperature, IR, humidity, pressure) • General Requirements • Internet access

9. Patch Network Sensor Node (power) Sensor Patch Gateway (low power) Transit Network Client Data Browsing and Processing Base-station (house-hold power) Base-Remote Link Internet Data Service System Architecture

10. Sensor Nodes • Sensor Nodes • Separated into two logical components: • Computational module (MICA) • Sensing Module (Weather board) • Sensor nodes communicate andcoordinate with one another • Battery powered • Small (5 x 3.8 x 1.25 cm3) • Mechanically robust • Weather-proofed (but ventilatedto avoid data distortion)

11. Sensor Nodes • Computational Module • Mica Platform • Atmel Atmega 103 micro controller @ 4 MHz • 512 kb Flash memory • 916 MHz, 40 kbps radio • 2 AA batteries w/boost converter

12. Sensor Nodes • Sensor Module • Mica Weather Board • Temperature • Photoresistor • Barometric pressure • Humidity • Passive IR (Thermopile) • Designed to coexist with other sensor boards • Low variation when interchanged with other sensors of same model

13. Power Management • Sensor Node Power • Limited Resource (2 AA batteries) • Estimated supply of 2200 mAh at 3 volts • Each node has 8.128 mAh per day (9 months) • Sleep current 30 to 50 uA (results in 6.9 mAh/day for tasks) • Processor draws apx 5 mA => can run at most 1.4 hours/day • Nodes near the gateway will do more forwarding 75 minutes

14. Power Management • Compression • Does the compression require more power than transmission? • Even if it does it may be worthwhile to compress if data must pass through many nodes • 2 - 4 times reduction by combining: • Delta compression and • Standard compression algorithm:

15. Gateway • Function • Relay sensor patch network data to base station • Coordinate the activity within the sensor patch • Provides additional computation and storage • Gateway to base station distance apx 100 m • Hardware • Strong-Arm based embedded system (CerfCube) • Runs an embedded version of Linux • Compact Flash memory • 2.5 W supplied by solar cells and lead-acid battery inches

16. Connects to the Internet: • Great Duck Island: Two-way satellite • James Reserve: T1 line • Laptop: • Coordinates the sensor patches • Provides database service Base Station Base Station

17. The Gizmo • In situ Interaction (Planned) • PDA-sized device • Communicate directly with the sensor patch • Direct communication to the mote • Provides fresh readings • Interactively control the network (sampling rates, power management etc) • Useful during initial deployment andretasking of the network

18. Communication • Routing • Routing directly from node to gateway not possible • Approach proposed for scheduled communication: • Determine routing tree • Each gate is assigned a level based on the tree • Each level transmits to the next and returns to sleep • Process continues until all level have completed transmission • The entire network returns to sleep mode • The process repeats itself at a specified point in the future

19. Network Retasking • Network Retasking • Initially collect absolute temperature readings • After initial interpretation, could be realized that information of interest is contained in significant temperature changes • Full reprogramming process is costly: • Transmission of 10 kbit of data • Reprogramming application: 2 minutes @ 10 mA • Equals one complete days energy • Virtual Machine based retasking: • Only small parts of the code needs to be changed

20. Conclusion • Paper conclusion • Two small scale sensor networks deployed atGreat Duck Island and James Reserve (one patch each) • Results not evaluated • No calibration was done, development of auto-calibration procedure suggested • Future • Develop a habitat monitoring kit

21. Problems • 2002 Deployed Network • No new science about petrel breeding behavior, many insights into how to build sensors that would yeild that science • Base Station laptop must run unattended (problem with unscheduled system reboots (mostly fixed)) • Temperature Sensors: • Measured temperature inside the enclosure, rather than ambient temperature • Good correlation with Cost Guard measurements on cloudy days • Batteries: • Only operational down to 2.5 V (expected down to 1.6V)

22. Problems • 2002 Deployed Network • Rain affecting the humidity sensor and short-circuiting the battery

23. Additional References • R. Szewczyk, J. Polastre, A. Mainwaring, D. Culler: ”Lessons from a Sensor Network Expedition”, UC Berkerly, Jan 2004 • J. Polastre: ”Design and Implementation of Wireless Sensor Networks for Habitat Monitoring”, Research Project, 2003 • www.greatduckisland.net

24. Burrow, Ground, D-Cell, 2002 Ground 2003 Network • New design • Lithium battery based • New enclosure