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

Sensor Network Applications for
Environmental Monitoring
Carla Ellis
SAMSI 11-Sept-07
Survey of Deployments
• Two in detail: Redwoods and ZebraNet
• Others
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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)
Mica2Dot hardware, GPS,
Solar cells on the backs of
snapping turtles.
"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.
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 10
• 33 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
Temporal Distributions
Spatial Distributions
Subtracting Timestamp Mean
Subtracting Timestamp Mean
One Day in the Life of a Tree
One Day in the Life of a Tree
Visualizing Change
Visualizing Change
Outliers & Battery
• Once battery
voltage falls,
temperature reading
goes bad
• Opportunity to
automatically reject
outliers
Performance of the Network:
Data Transmitted
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, heartrate, 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
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zebraB
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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
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)