Sensor Network Applications for Environmental Monitoring

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Sensor Network Applications for Environmental
Monitoring

• Carla Ellis
• SAMSI 11-Sept-07

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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

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Great Duck Island Petrel MonitoringUCB

• Goal build ecological models for breeding
  preferences of Leachs 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
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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.
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James Reserve Forest (CENS)

• Heterogeneous
• Robotics
• Imaging
• Full motion cameras
• In nesting boxes
• Time lapse images
• Microclimate array soil moisture

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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.

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Aquatic Observing Systems (CENS)
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Macroscope in RedwoodsSenSys 05

• Tolle et al
• UC Berkeley Intel Research Berkeley

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Deployment Up a Tree

• 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

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Sensor Node Platform Package

• Mica2Dot node from Crossbow
• 4MHz processor
• 433 MHz radio, 40 Kbps
• 512 KB Flash
• Sensors
• Packaging

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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

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Temporal Distributions
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Temporal Distributions
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Spatial Distributions
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Subtracting Timestamp Mean
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Subtracting Timestamp Mean
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One Day in the Life of a Tree
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One Day in the Life of a Tree
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Visualizing Change
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Visualizing Change
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Outliers Battery

• Once battery voltage falls, temperature reading
  goes bad
• Opportunity to automatically reject outliers

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Performance of the NetworkData Transmitted
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Performance of the NetworkData Transmitted
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Logged Data
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Both Logging Transmission

• Both are good compensate for the others
  failures
• Flash running out of space but transmissions
  continue
• Transmissions stopped but Flash retains those
  data points

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Wildlife Tracking ZebraNetAsplos 02

• Juang et al
• Princeton

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Biological Goal

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

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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

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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

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Mobility Model
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Collar Design
GPS samples every 3 minutes Detailed activity
logs for 3 min every hr 1 year of
operation 3-5 lb weight limit
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Energy and Weight Measurements
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Drive-by Mobile Base Station

• Vandalism is a problem for deploying an array of
  fixed antennas or base stations
• Base station sporadically available

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Peer to Peer System Design
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Peer to Peer System Design
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Peer to Peer System Design
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Peer to Peer System Design
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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

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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

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Simulation Results Ideal
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Results with Constrained Storage(10 collar days)
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Results with Constrained Bandwidth (12kps)
Short-range, flooding best Long-range, history
best
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Energy (unconstrained case normalized to direct)
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Final Design Choices

• Storage viewed as effectively infinite
• 2 radios
• one short-range, do flooding
• other long-range, direct

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

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• 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)

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Breakouts

• Form 3 or 4 ad hoc multi-disciplinary groups
  (outside comfort zone mix ECEstatCSbio)
• 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)