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What is a Wireless Sensor Network (WSN)?

What is a Wireless Sensor Network (WSN)? An autonomous , ad hoc system consisting of a collective of networked sensor nodes designed to intercommunicate via wireless radio . Motivation. Questions What environmental factors make for a good nest? How much can they vary?

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What is a Wireless Sensor Network (WSN)?

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  1. What is a Wireless Sensor Network (WSN)? An autonomous, ad hoc system consisting of a collective of networked sensor nodes designed to intercommunicate via wireless radio.

  2. Motivation • Questions • What environmental factors make for a good nest? • How much can they vary? • What are the occupancy patterns during incubation? • What environmental changes occur intheburrows and their surroundings duringthe breeding season?

  3. Motivation • Problems • Seabird colonies are very sensitive to disturbances • The impact of human presence can distort results by changing behavioral patterns and destroy sensitive populations • Repeated disturbance will lead to abandonment of the colony • Solution • Deploy a sensor network

  4. GDI Network Services • Power management • Communications • Re-tasking • Node management

  5. GDI Requirements • Internet access • Hierarchical network • Sensor network longevity • Operating off-the grid • Management at a distance

  6. GDI Requirements • Inconspicuous operation • System behavior • In-situ interactions • Sensors and sampling • Data Archiving

  7. Great Duck Island Project

  8. Patch Network Sensor Patch Gateway (low power) Transit Network Client Data Browsing and Processing Base-station (house-hold power) Base-Remote Link Internet Data Service GDI Sensor Network Sensor Node (power)

  9. Mica Sensor Nodes • Single channel, 916 Mhz radio for bi-directional radio @40kps • 4MHz micro-controller • 512KB flash RAM • 2 AA batteries (~2.5Ah), DC boost converter (maintain voltage) • Sensors are pre-calibrated (±1-3%) and interchangeable Left: Mica II sensor node 2.0x1.5x0.5 cu. In. Right: weather board with temperature, thermopile (passive IR), humidity, light, accelerometer sensors, connected to Mica II node

  10. Power Management • Sensor Node Power • Limited Resource (2 AA batteries) • Estimated supply of 2200 mAh at 3 volts • Each node has 8.128 mAh per day (9 months) • Sleep current 30 to 50 uA (results in 6.9 mAh/day for tasks) • Processor draws apx 5 mA => can run at most 1.4 hours/day • Nodes near the gateway will do more forwarding 75 minutes

  11. LAN WAN (satcast) sensor networks Base Station • Gateways are connected to base station through transit network. • Wide area connectivity is brought to base station instead of of each node. • Locations of such habitat is remote so WAN connection is wireless (e.g. two way satellite)

  12. Communication • Routing • Routing directly from node to gateway not possible • Approach proposed for scheduled communication: • Determine routing tree • Each gate is assigned a level based on the tree • Each level transmits to the next and returns to sleep • Process continues until all level have completed transmission • The entire network returns to sleep mode • The process repeats itself at a specified point in the future

  13. Routing network

  14. Graphic Adaptive Fidelity (GAF) • Conserve the energy identifying nodes that are equivalent from routing perspective and then turning of unnecessary node. • Simulation of GAF suggests that network lifetime increases proportionally to node density

  15. SPAN • A power sharing technique for multiple ad hoc networks that reduces energy consumption. • Node makes a local decision to whether to sleep or to join fore wording backbone. • Decision is based on an estimate of how many of its neighbors will benefit it being awake and the amount of energy available to it.

  16. Network Re-tasking • Initially collect absolute temperature readings • After initial interpretation, could be realized that information of interest is contained in significant temperature changes • Full re-programming process is costly: • Transmission of 10 kbit of data • Reprogramming application: 2 minutes @ 10 mA • Equals one complete days energy • Virtual Machine based re-tasking: • Only small parts of the code needs to be changed

  17. Virtual Machine Based Network Re-tasking • Allows complex program to be very small. • Code is broken up into capsules of 24 instructions. • Allows large program to be frequently reprogrammed in an energy efficient manner.

  18. Sensed Data Raw thermopile data from GDI during 19-day period from 7/18-8/5/2002. Show difference between ambient temperature and the object in the thermopile’s field of view. It indicates that the petrel left on 7/21, return on 7/23, and between 7/30 and 8/1

  19. Health and Status Monitoring • Monitor the mote’s health and the health of neighboring motes • Duty cycle can be dynamically adjusted to alter lifetime • Periodically include battery voltage level with sensor readings (0~3.3volts) • Can be used to infer the validity of the mote’s sensor readings

  20. Conclusion • Paper conclusion • Applied wireless sensor networks to real-world habitat monitoring • Two small scale sensor networks deployed atGreat Duck Island and James Reserve (one patch each) • Future • Develop a habitat monitoring kit

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