GDI 2003: status report

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GDI 2003 status report

• Robert Szewczyk
• Joe Polastre
• Alan Mainwaring
• David Culler
• NEST Retreat, Jan 15, 2004

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Outline

• GDI
• Mote design
• Networking improvements
• Infrastructure redesign
• Conclusions

Analysis
Design
Deployment
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Scientific motivation Leachs Storm Petrel

• Questions
• What environmental factors make for a good nest?
  How much can they vary?
• What are the occupancy patterns during
  incubation?
• What environmental changes occurs in the burrows
  and their vicinity during the breeding season?
• Methodology
• Characterize the climate inside and outsize the
  burrow
• Collect detailed occupancy data from a number of
  occupied and empty nest
• Spatial sampling of habitat sampling rate
  driven by biologically interesting phenomena,
  non-uniform patches
• Validate a sample of sensor data with a different
  sensing modality
• Augmented the sensor data with deployment notes
  (e.g. burrow depth, soil consistency, vegetation
  data)
• Try to answer the questions based on analysis of
  the entire data set

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Application architecture
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Sensor node evolution
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Sensor node GDI 02

• Mica platform
• Atmel AVR w/ 512kB Flash
• 916MHz 40kbps RFM Radio
• Range max 100 ft
• Affected by obstacles, RF propogation
• 2 AA Batteries, boost converter
• Mica weather board one size fits all
• Digital Sensor Interface to Mica
• Onboard ADC sampling analog photo, humidity and
  passive IR sensors
• Digital temperature and pressure sensors
• 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
• Packaging
• Conformal sealant acrylic tube

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GDI 02 population

• 43 distinct nodes reporting data between July 13
  and November 18
• Heavy daily losses
• Between 3 and 5 daily

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Redesign directions

• Node-level issues that need resolving
• Size motes were too large to fit in many
  burrows
• Application specific packaging minimize size of
  burrow package, base the system around mica2dot
• Packaging did not provide adequate protection
  for electronics or proper conditions for sensors
• Waterproof plastic packaging to protect
  electronics
• Design to provide both shielding and exposure to
  sensors
• Node reliability
• Power consumption boost converter not
  particularly useful
• Eliminate boost whenever possible, use stable
  voltage lithium cells
• Data interpretation challenges
• Sensor calibration
• Occupancy data interpretation need more
  sophisticated processing of sensor data and/or
  ground truth data
• Better metadata sensor location conditions

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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 Ah _at_ 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

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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

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GDI 03 weather mote population
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GDI 03 burrow mote population
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Patch network GDI 02

• Single hop transmit-only network
• 43 nodes, about 25 above ground, the rest in
  burrows
• Repeater network add an extra hop to improve
  connectivity into burrows
• Ran out of energy before it made any difference
• Sampling rates 1 set of samples from every node
  every 70 seconds
• A compromise between response time (and ease of
  deployment) and expected power management
  behavior
• Application logic sense (fix time), send,
  sleeep(fix time)
• Expected that CSMA MAC backoff will effectively
  desynchronize all nodes

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GDI 02 deployment
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Software architecture advances

• Bi-directional communication with low-power
  listenting
• 1 duty cycle
• Parameter adjustment and query
• Sample rate changes, sensor status queries
• Improved power management scheme
• Fine granularity through StdControl interface
• 10 uA sleep mode, 30 uA with running Timer.

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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

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Packet yields
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GDI 03 deployment
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GDI 03 Multihop network

• Motivation
• Greater spatial reach
• Better connectivity into burrows
• Implementation
• Alec Woos generic multihop subsystem
• Low power listening tradeoff channel capacity
  for average power consumption
• Contrast with TASK approach Alecs multihop
  component but with duty cycling on a loosely
  synchronized network
• 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

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Packet Yield
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Topology stability
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Parent-child link distribution
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Parent-child link longevity distribution
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GDI 02 base station

• Requirements
• Disconnected operation
• Remote management
• Automatic restart
• Redundancy
• Implementation
• 2 laptops, each with a direct serial connection
  to a transit network (via GenericBase)
• Asymmetry one of the laptops acting as a
  gateway/firewall
• Limited inside network
• Replicated but independent PostgreSQL servers
  provide resiliency against laptop crashes
• Limited remote admin capability remote desktop,
  ssh
• How do you reboot a system 3000 miles away
• Satellite connection
• DirecWay WAN
• Uptime 47

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GDI 03 Base Station

• More sophisticated networking structure
• Dual laptops with PostgreSQL
• Dual base stations (Mica2 EPRB)
• But one logs single hop the other logs multihop
• Cross logging of the data
• Vastly improved remote access
• Remote wakeonlan
• Web enabled power strip
• Ubiquitous POE
• VPN for direct access from authorized networks
• Extensible schema to accommodate new sensor
  modalities and query types, compatibility with
  TASK
• Main stumbling block
• Power, power, power
• Lack of redundancy on the transit net
• Minor HW issues outdoors is harsh

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Occupancy measurements GDI 02
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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 mimicsthe architecture of
  the sensornet
• Sample a 15 sec video/audio clipevery 5 minutes
• 6 GB worth of data so far

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Occupancy data evaluation status

• PIR data from website used for finding occupied
  burrows
• Saturated sensor outputs
• Video data analysis underway
• Entry/exit events
• Automatic video analysis

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Analysis from biology side
Temperature and humidity distributions
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Temperature and humidity in different habitats
Weather stations
Burrow motes
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Climate data
Weather stations
Burrow motes
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Climate data day-to-day variations,meadow
Weather stations
Burrow motes
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Conclusions

• Another iteration on the design, deploy, analyze
  cycle
• 50 node single hop network, 100 node multi hop
  network
• 4.5 months of operation June 8 October 20
• 436 thousands weather station observations
• 234 thousands burrow mote observations
• Improvements in the network quality
• Longevity, reliability, features, power
  management, data quality
• Room for much more improvement ease of
  packaging, robustness
• Data analysis
• Biologists are engaged
• Video analysis for occupancy corroboration under
  way

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QA

• Thank You!
• http//www.greatduckisland.net

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Gateway node design

• GDI 02 implementations
• Linux CerfCube 802.11b
• Generic Base x 2 omni-directional antenna to
  receive from patch directional antenna to xmit
  to base station
• Power requirements
• CerfCube 30x30 solar
• Mote-based 6x6 solar
• Reliability
• Side effects transit network transmissions
  will affect the transmissions in the patch

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Gateway node design

• GDI 03 design keep elements that worked
• Keep a mote-based system
• Use different frequencies on patch and transit
  networks to eliminate interference different
  frequencies for single and multihop networks
• Asymmetrical bi-directional communication on
  single hop network exploit low power listening
  always-on gateways
• Symmetrical bi-directional communication in the
  multihop network
• Storage and processing
• Keep it simple
• No storage, processing, aggregation, etc.
• Big disadvantages removes a layer that could
  buffer packets in case of transient failure
  elsewhere in the system (e.g. base station down)