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
1 – REAL network requirements, problems and solutions

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

5. Scientific Motivation
Methodology
Characterize the climate inside and outside the burrow
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

6. Scientific Motivation
Problems
Seabird colonies are very sensitive to disturbances
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

7. Field Stations Great Duck Island James San Jacinto Mountains Reserve
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
General Requirements
Internet access
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)
1 – need for remote intercations support
2 – explain (p2.b.2)

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

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

11. Sensor Nodes Computational Module Mica Platform
Atmel Atmega 103 micro 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
IR sensor and thermistor and photo resistor to detect cloud cover
IR sensor: detect occupancy, measure temp of nearby object (bird in nest)

13. Power Management Sensor Node Power Limited Resource (2 AA batteries)
Estimated supply of 2200 mAh at 3 volts
Each node has 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:
Is it worthwhile to implement compression?

15. Gateway Function Hardware
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. Base Station Base Station Laptop: Coordinates the sensor patches
Provides database service
Connects to the Internet:
Great Duck Island: Two-way satellite
James Reserve: T1 line
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 and retasking 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 10 mA
Equals one complete days energy
Virtual Machine based retasking:
Only small parts of the code needs to be changed
Network can be reprogrammed once per day of all 9 months if no other task is done

20. Conclusion Paper conclusion Future
Two small scale sensor networks deployed at Great 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
So far only mild challanges – low data rates and not really extreme environment

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

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