Wireless Sensor Networks for Habitat Monitoring

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Wireless Sensor Networksfor Habitat Monitoring

• Alan Mainwaring1
• Joseph Polastre2
• Robert Szewczyk2
• David Culler1,2
• John Anderson3
• 1 Intel Research Laboratory at Berkeley
• 2 University of California, Berkeley
• 3 College of the Atlantic

2
Introduction

• Application Driven System Design, Research, and
  Implementation
• Parameterizes Systems Research
• Localization
• Calibration
• Routing and Low-Power Communications
• Data Consistency, Storage, and Replication
• How Can All of these Services and Systems Be
  Integrated into a Complete Application?

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Great Duck Island

• Breeding area for Leachs Storm Petrel (pelagic
  seabird)
• Ecological models may use multiple parameters
  such as
• Burrow (nest) occupancy during incubation
• Differences in the micro-climates of active vs.
  inactive burrows
• Environmental conditions during 7 month breeding
  season

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Application
gt 1000 ft
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Sensor Network Solution
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Outline

• Application Requirements
• Habitat Monitoring Architecture
• Sensor Node
• Power Management
• Sensor Patch
• Transit Network
• Wide Area Network and Disconnected Operation
• Sensor Data
• System Analysis
• Real World Challenges

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Application Requirements

• Sensor Network
• Longevity 7-9 months
• Space Must fit inside Small Burrow
• Quantity Approximately 50 per patch
• Environmental Conditions
• Varying Geographic Distances
• Inconspicuous Operation
• Reduce the observer effect
• Data
• As Much as Possible in the Power Budget
• Iterative Process

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Application Requirements

• Predictable System Behavior
• Reliable
• Meaningful Sensor Readings
• Multiple Levels of Connectivity
• Management at a Distance
• Intermittent Connectivity
• Operating Off the Grid
• Hierarchy of Networks / Data Archiving

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Habitat Monitoring Architecture
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Sensor Node Mica

• Hardware
• Atmel AVR w/ 512kB Flash
• 916MHz 40kbps Radio
• Range max 100 ft
• Affected by obstacles, RF propogation
• 2 AA Batteries
• Operating 15mA
• Sleep 50mA
• Software
• TinyOS / C Applications
• Power Management
• Digital Sensor Drivers
• Remote Management Diagnositcs

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Sensor Node Power Management

• AA Batteries have 2500 mAh capacity
• Mica consumes 50mA in sleep 1.2 mAh/day

Mica Expected Lifetime
Node Activity Days Years
Mica Always On 7 0.1
Mica Always Sleeping 2081 5.7
Expected Lifetime (days)
Number of Operating Hours per Day
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Sensor Node Power Management
Operation nAh
Transmitting a packet 20.000
Receiving a packet 8.000
Radio Listening for 1ms 1.250
Operating Sensor for 1s (analog) 1.080
Operating Sensor for 1s (digital) 0.347
Reading a Sample from the ADC 0.011
Flash Read Data 1.111
Flash Program/Erase Data 83.333

• Target Lifetime 7-8 months
• Power Budget 6.9mAh/day
• Questions
• What can be done?
• How often?
• What is the resulting sample rate?

Operation Operating Time per Day Duty Cycle Sample Rate
Always Sleep 24 hours 0 0 samples/day
mCPU on 52 minutes 3.61 0 samples/day
Radio On (Listen) 28 minutes 1.94 0 samples/day
Sample All Sensors 21 minutes 1.45 630 samples/day
Transmit Samples 20 minutes 1.38 600 samples/day
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Sensor Node Mica Weather Board

• Digital Sensor Interface to Mica
• Onboard ADC
• Designed for Low Power Operation
• Individual digital switch for each sensor
• Designed to Coexist with Other Sensor Boards
• Hardware Enable Protocol to obtain exclusive
  access to connector resources

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Sensor Node Mica Weather Board
Sensor Accuracy Interchange Max Rate Startup Current
Photo N/A 10 2000 Hz 10 ms 1.235 mA
I2C Temp 1 K 0.2 K 2 Hz 500 ms 0.150 mA
Pressure 1.5 mbar 0.5 10 Hz 500 ms 0.010 mA
Press Temp 0.8 K 0.24 K 10 Hz 500 ms 0.010 mA
Humidity 2 3 500 Hz 500 ms 0.775 mA
Thermopile 3 K 5 2000 Hz 200 ms 0.170 mA
Thermistor 5 K 10 2000 Hz 10 ms 0.126 mA
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Sensor Node Packaging

• Parylene Sealant
• Acrylic Enclosures

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Sensor Patch Network

• Nodes
• Approximately 50
• Half in burrows, Half outside
• RF unpredictable
• Burrows
• Obstacles
• Drop packets or retry?

• Transmit Only Network
• Single Hop
• Repeaters
• 2 hop initially
• Most Energy Challenged
• Adheres toPower Budget

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Transit Network

• Two implementations
• Linux (CerfCube)
• Relay Mote
• Antennae
• No gain antenna (small)
• Omnidirectional
• Yagi (Directional)
• Implementation of transit network depends on
• Distance
• Obstacles
• Power Budget
• Duty cycle of sensor nodes dictates transit
  network duty cycle

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Transit Network

• Renewable Energy Sources
• CerfCube needs 60Wh/day
• Assuming an average peak of 1 direct sunlight
  hour per day
• Panel must be 924 in2 or 30 x 30 for a 5 x
  5 device!
• A mote only needs 2Wh per day, or a panel 6 x 6

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Base Station / Wide Area Network

• Disconnected Operation and Multiple Levels of
  State
• Laptop
• DirecWay Satellite WAN
• PostgreSQL
• 47 uptime
• Redundancy and Replication
• Increase number of points of failure
• Remote Access
• Physical Access Limited

• Keep state all areas of network
• Resiliency to
• Disconnection
• Network Failures
• Packet Loss
• Potential SolutionKeep Local CachesSynchronizat
  ion

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Sensor Data Analysis
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Sensor Data Analysis
Outside Burrow
Inside Burrow
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System Analysis

• Power Management Goals
• Calculated 7 months, expect 4 months
• Battery half-life at 1.2V

• Predictable Operation
• Observed per node constant throughput, loss
• 739,846 samples as of 9/23, network is still
  running

Battery Consumption at Node 57
Packet Throughput and Active Nodes
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Real World Experiences

• System and Sensor Network Challenges
• Low Power Operation (low duty cycle)
• Affects hardware and software implementation
• Multihop Routing
• Allows bigger patches
• Route around physical obstacles
• Must have 1 operating duty cycle
• In Situ Retasking/Reconfiguration
• Let biologists interactively change data
  collection patterns
• Not Implemented due to conservative energy
  implementation
• Lack of Physical Access
• Remote management
• Disconnected operation
• Fault tolerance
• Reliance on other people and their networks
• Physical Size of Device
• Affects microcontroller selection, radio,
  practical choice of power sources

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Real World Experiences

• Failures
• Extended Loss of Wide Area Connectivity
• Unreliable Reboot Sequence in Windows
• Solderless Connections Fail (expansion/contraction
  cycles)
• Node Attrition (Petrels are not mote neutral)
• Environmental Conditions (50km/hr gale winds
  knock over equipment)
• Lack of post-mortem diagnositics

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Conclusions

• First long term outdoor wireless sensor network
  application
• Application driven sensor network design
• Defines requirements and constraints on core
  system components (routing, retasking, fault
  tolerance, power management)

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Backup Slides
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Mote 18 Outside
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Mote 26 Burrow 115a
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Mote 53 Burrow 115b
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Mote 47 Burrow 88a
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Mote 40 Burrow 88b
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Mote 39 Burrow 84