Habitat monitoring on Great Duck Island Robert Szewczyk Joe Polastre Alan Mainwaring John Anderson David Culler ACM SenSys’04 November 5, 2004

Instruments of science Study of very small –Microbiology –Microscope Study of very large –Astronomy –Telescope Study of very complex –Ecology, sociology,… –Macroscope* *Joël de Rosnay. Le Macroscope. Vers une vision globale. © Editions du Seuil, 1975

Sample environment: Great Duck Island Leach’s Storm Petrel –Nocturnal seabird, relatively unknown –Large nesting habitat on GDI –Interesting behavior patterns Behavioral questions –What are the occupancy patterns during the nesting season? –How do these patterns correspond to chick’s success? Ecology questions –What environmental factors make for a good nest? How much can they vary? –What environmental changes occurs in the burrows and their vicinity during the breeding season?

Life science research Methodology –Spatial sampling of habitat – sampling rate driven by biologically interesting phenomena, non-uniform patches »Characterize the climate inside and outside the burrow »Collect detailed occupancy data from a number of occupied and empty nests –Augment the sensor data with deployment notes (e.g. location, burrow depth, soil consistency, vegetation data) –Validate a sample of sensor data »Expensive, non-scalable modality Benefits –Larger data sets »Spatial and temporal –Near real-time access to data –Easier sharing, more analysis

Computer science research Methodology –Engineering exercise –Design, implement and evaluate the system »Sensor boards, packaging, »Iterate as necessary –Stress simplicity »Application cycle: sleep, sense, transmit »Tree-based multihop routing as needed »Basic application control – ping, calibration, change sampling rates Benefits –long lifetime –unattended operation –connectivity in real places –harsh conditions

GDI ’03 deployment 2 nd generation deployment 150+ motes –Single hop star topology –Multi hop network –4 month lifetime

Initial biological results John Anderson et al. Microhabitat monitoring in Leach’s Storm Petrels. American Ornithologists Union / Society of Canadian Ornithologists Annual Meeting, August –Burrow climate – large buffering effect, temperature varies no more than 2°C over a 24 hour period –Surface climate – typical variation of 10°C over a 24 hour period; buffering varies by habitat type. Burrow Temperatures (cool and uniform) Surface Temperatures (warmer and variable)

Outline Habitat monitoring vision System architecture –Overview –Node design –Sensor network patch –Base station 2003 deployment analysis Lessons learned & conclusions

System architecture Site WAN Link Client Data Browsing and Processing Base station Verification Network Single Hop Network Multi Hop Network Internet Gateway Sensor Patches Transit Network

Node requirements Size –motes need to fit in burrows Power –Low power consumption on the device –High capacity battery –Stable supply Packaging –provide adequate protection for electronics or proper conditions for sensors Node reliability Data interpretation challenges –Sensor calibration –Occupancy data interpretation – need sophisticated processing of sensor data and/or ground truth data –Metadata and experiment design– sensor location & conditions *Martha Baer. The Ultimate on-the-fly network. Wired Magazine, 11.12, Dec *

Miniature weather station Sensor suite –Sensirion humidity + temperature sensor –Intersema pressure + temperature sensor –TAOS total solar radiation sensor –Hamamatsu PAR sensor –Radiation sensors measure both direct and diffuse radiation Power supply –SAFT LiS02 battery, ~1 2.8V Packaging –HDPE tube with coated sensor boards on both ends of the tube –Additional PVC skirt to provide extra shade and protection against the rain

Burrow occupancy detector Sensor suite –Sensirion humidity + temperature sensor –Melexis passive IR sensor + conditioning circuitry Power supply –GreatBatch lithium thionyl chloride 1 Ah battery –Maxim 5V boost converter for Melexis circuitry Packaging –Sealed HDPE tube, emphasis on small size

GDI ’03 patch network Single hop network deployed mid-June –Rationale: Build a simple, reliable network that allows »HW platform evaluation »Low power system evaluation »Comparisons with the GDI ’02 deployment –A set of readings from every mote every 5 minutes –23 weather station motes, 26 burrow motes –Placement for connectivity –Network diameter 70 meters –Asymmetric, bi-directional communication with low power listening – send data packets with short preambles, receive packets with long preambles –Expected life time – 4+ months »Weather stations perform considerably better than burrow motes – their battery rated for a higher discharge current

GDI ’03 Multihop network Motivation –Greater spatial reach –Better connectivity into burrows Implementation –Alec Woo’s generic multihop subsystem –Low power listening: tradeoff channel capacity for average power consumption The network nodes –44 weather motes deployed July 17 –48 burrow motes deployed August 6 –Network diameter – 1/5 mile –Duty cycle – 2% to minimize the active time (compromise between receive time and send time) –Reading sent to base station every 20 minutes, route updates every 20 minutes. Expected lifetime: 2.5 months –2/3 of nodes join within 10 minutes of deployment, remainder within 6 hours. Paths stabilize within 24 hours

Base station Similar concerns to the sensor network –Remote access and management –Redundancy and replication –Power management –Resiliency against »Power failures »Link failures Solution –Replicated databases on different laptops –Remote power management –Periodic log downloads Mica2-EPRB#2 IBM laptop #1 DB Web power strip Axis 2130 PTZ South Wireless bridge 4-port VPN router and 16-port Ethernet switch Power over LAN midspan DB IBM laptop #2 Mica2-EPRB#2 WWW power strip Southern WAP Satellite router

Outline Habitat monitoring vision System architecture 2003 deployment analysis –Reliability, energy budgets, and lifetime –Initial packet yields –Network topology and dynamics –Performance over lifetime Lessons learned & conclusions

Base station reliability Shutdown for hurricane Isabel Power problemsEnd of field season

GDI 2003: mote lifetimes Met the lifetime target for single hop weather motes, came close on multihop weather motes Burrow motes, particularly in multihop network were a disappointment

Energy breakdown Doesn’t account for forwarding and overhearing, does account for route discovery 56 uW 62 uW 465 uW 14 uW 120 uW Singlehop Average power: 0.7 mW 56 uW 62 uW 930 uW 64 uW 31 uW Multihop Average power: 1.1 mW sleep timer listen transmit sense

First day of deployment

Multihop network over time Weather station deployment Burrow mote deployment

Multihop network dynamics

Multihop tree structure 1/3 of nodes are leaves A few nodes route traffic for majority of the network

Multihop links characteristics 80% of packets delivered over long lived links (stable for more than a day) 80% of the links are short lived (less than a day)

Performance over time

Packet delivery in the multihop network

Outline Habitat monitoring vision System architecture 2003 deployment analysis Lessons learned & conclusions

Occupancy data

Verification network –Difficult to deploy »Power, high bandwidth, limited scale »Maintenance efforts –Time consuming analysis »Brute force video annotations »Certainty of occupancy data Mote-based detection –PIR sensor data unreliable »Sensor railing, environmental damage –Burrow occupancy inferred from ambient temperature and humidity

Lessons learned In the field, things only get worse Experimental discipline matters –Calibration, sensor characterization –Mechanical design –Analysis starts on day 1 »Site survey and deployment augmentation –Ground truth and building of trust in the experimental method –Field tools Design for observability –Only recorded data can be analyzed –Degrade into data logger –Post mortem

Conclusions Network design –Even static networks undergo many changes »Adaptation matters »MintRoute sufficient –No evidence of software crashes in the sensor network »Simplicity rules – no one rebooted motes »Base station required significant attention –Deployment yielded a wealth of data »node reliability, link quality, performance of routing algorithms, load ditribution… »Establish a reference point for future analyses Macroscope vision –John Anderson got unprecedented microclimate data –Wireless sensor networks work »… just barely in 2003 –This is just the beginning –Applications will continue to drive the technology

Thank you! Datasets available at

Energy cost of multihop forwarding

Occupancy measurements GDI ‘03 Calibrated ASIC for conditioning and processing the passive IR signal –0 to 40 deg C range Corroboration of data –Multiple sensor nodes in occupied burrows Verification of data –Co-locate a completely different sensing network with motes –IR-illuminated cameras –Ethernet video servers –Wireless connection to the base station –Verification network mimics the architecture of the sensor net –Sample a 15 sec video/audio clip every 5 minutes –~6 GB worth of data so far… Sensor Patch Power over LAN Midspan IR Burrow Camera #1 IR Burrow Camera #2 IR Burrow Camera #3 ) IR Burrow Camera #4 IR Burrow Camera #5 IR Burrow Camera #6 IR Burrow Camera #7 IR Burrow Camera #8 Axis 2401 Video Server 12VDC, 0.9A network Burrow Camera Configuration Northern WAP Ethernet switch Wireless bridge 12V PoL Active Splitter 110VAC service

Power management evaluation

Packaging evaluation We observed what happens to motes when packaging fails –Battery venting, H2SO3 corroding the entire mote –Need to assemble the package correctly – we failed to create proper indication of a good seal –Majority of packages survived severe weather!