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

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

Great Duck Island: Petrel Monitoring UCB 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

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 of snapping turtles.

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

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.

Aquatic Observing Systems (CENS)

Macroscope in Redwoods SenSys 05 Tolle et al UC Berkeley Intel Research Berkeley

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

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

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

Temporal Distributions

Spatial Distributions

Subtracting Timestamp Mean

One Day in the Life of a Tree

Visualizing Change

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

Performance of the Network: Data Transmitted

Logged Data

Both Logging & Transmission 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

Wildlife Tracking – ZebraNet Asplos 02 Juang et al Princeton

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

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

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

Mobility Model

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

Energy and Weight Measurements

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

Peer to Peer System Design zebraA zebraB

Peer to Peer System Design zebraA zebraB zebraA zebraB

Peer to Peer System Design zebraB zebraA zebraB zebraA

Peer to Peer System Design zebraB zebraA

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

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

Simulation Results: Ideal

Results with Constrained Storage (10 collar days)

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

Energy (unconstrained case; normalized to direct)

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

Summary of Challenges

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

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)

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)