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Wireless Sensor Networks

Karishma Babu Kenneth Kinion. Wireless Sensor Networks. 4 December 2007. Introduction. Wireless sensor networks - wireless network consisting of spatially distributed sensors to cooperatively monitor physical or environmental conditions GOAL

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Wireless Sensor Networks

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  1. Karishma Babu Kenneth Kinion Wireless Sensor Networks 4 December 2007

  2. Introduction • Wireless sensor networks - wireless network consisting of spatially distributed sensors to cooperatively monitor physical or environmental conditions • GOAL • To implement and study a Real Time Sensor Network using mica2 motes • Demonstrate wireless connectivity between base station and sensor board • Show successful reads of sensor values • Develop algorithm for decreasing power usage

  3. Introduction • Wireless sensor network features • small-scale sensor nodes • limited power • node mobility • dynamic network topology • large scale deployment • resilient and pervasive • Wireless sensor network applications: • Military applications eg: Battlefield surveillance • Environment and habitat monitoring • Healthcare applications • Home Automation • Traffic Control

  4. Overview • Mesh network features • Multihop routing for scalable range extension • Self-configuration – network formed without intervention • Self-healing – nodes added and removed dynamically • Dynamic routing – adaptively determine route • Three components for this network: • MIB510 – programmer, PC interface • MPR400 – wireless interface and mote processor • MTS310 – 6-sensor data acquisition board

  5. Background • MICA2 – module for enabling low-power wireless sensor networks; 868/916 MHz transceiver • Crossbow provides three essential components for wireless sensor network development using Mica2 motes • RS-232 Gateway – communicates with PC software; allows nodes to be programmed one at a time • Transceiver – communicates with sensor board, other transceivers • Sensor board – includes accelerometer, light, pressure, temperature, and humidity sensor Sensors Gateway Transceiver

  6. Background • Each transceiver powered by 2 AA batteries • Mica2 Motes loaded with TinyOS and TinyDB • Use PC to insert SQL-like queries into Sensor Network • Each Mica2 Mote must have sensor board attached • Java-based GUI runs on PC • C programs compiled, then loaded onto mote • PC Development Environment: Cygwin used for... • building applications for the Motes • programming the motes from PC • launching Java-based network analysis tools • Surge – GUI for displaying network topology

  7. Milestones • Milestone 1: Install TinyOS and communicate with mica2 mote • Milestone 2: Demonstrate simple setup-report and display sensor values using one remote mote • Milestone 3: Determine maximum reporting rate and observe corresponding energy drain • Milestone 4: Develop algorithm for Event-Driven Reporting • Milestone 5: Implement Event-Driven Sensor Reporting using NesC

  8. Milestone 1: Goals • Install TinyOS and communicate with mica2 mote • install TinyOS on laptop • Windows PC • 1 GB free space on hard drive required • Hardware verification performed on motes • Blink application compiled and executed on motes • TinyOS 1.1.0 features: • TinyOS and associated tools (sample programs)‏ • NesC programming language • Use of Cygwin as the development environment • Java tools for monitoring motes with base station

  9. Milestone 1: Results • TinyOS installed with difficulty • Windows XP support, but installation on Vista fails • Set desired frequency by modifying .h files • 915.998 kHz • Ran hardware verification tests • toscheck – TinyOS verification • MicaHWVerify – mote hardware verification • TOSBase – radio verification • Compiled Blink application and programmed mote to demonstrate setup

  10. Milestone 2: Goals • Obtain Simple Sensor Data • Query Constructor • compile TinyDB and load onto mote; PC connected to base station inserts SQL-like queries into sensor network • run TinyDB Java application on PC • Perform simple data acquisition test • Display network topology • Alternatives • Read sensor network over serial port and obtain readings using Oscilloscope, OscilloscopeRF applications • Display network topology using Surge GUI

  11. Milestone 2: Results • Used query constructor to measure light vs. time Light off of sensor Light shines on sensor Finger over sensor Finger not over sensor

  12. Milestone 2: Results • Obtained sensor network topology – base station and one remote mote

  13. Milestone 3 • Obtain the maximum reporting rate of the Mica2 motes • Mica2 motes have a default transmit rate of once every 8 seconds • Query Constructor • Determine maximum reporting rate by changing the interval after which the sensor transmits information • Max reporting rate interval- 128 ms • Alternative • Reporting rate can also be changed by changing initial_timer_rate in Surge.h

  14. Milestone 3: Results

  15. Effect of Reporting Rate • Energy Drain • Each transceiver powered by 2 AA batteries • Default transmission power - 1mW • Alternatives • Statistics window: test how reporting rate affects quality and yield • User Interface, Xlisten :PC based tool to view sensor data

  16. Milestone 4:Event-driven Reporting Algorithm • Send messages only when necessary • What defines necessary? • Threshold vs. change-based • Threshold – target value • Change-based – target change from previously reported value • Hysteresis necessary in both cases

  17. Milestone 4:Event-driven Reporting Algorithm • Read sensor values regularly • Report on change • Hysteresis – important to reduce reporting due to “noise” • Remember the previously REPORTED value (not the previously READ value)‏ • Report when newly read value exceeds hysteresis value with respect to previously reported value

  18. Milestone 5 • Modified Oscilloscope application • Easily read and plot reported values • Proof of concept only • Original code:

  19. Milestone 5 • Modified code:

  20. Milestone 5Results Before After

  21. Additional Milestone: Multihop Mesh Networking • Need for multihop networking • Unreliable ad-hoc networks; node failure & node mobility • Challenges: Minimize use of energy • Surge multihop routing networking application • Implementation uses shortest path first algorithm with single destination node (root) and two way link estimation • Route decision and Data movement functionality spilt up

  22. Precautions/Issues • Installation Issues: • Administrator privileges required • Need to uninstall older versions before installing newer ones • Configuration difficult with Windows Vista OS • Tools difficult to figure out • Compile in correct base radio frequency otherwise radio communication will fail • If battery voltage <3.0 V, flash memory may not be reprogrammed correctly • Programming statements should be consistent with new MakeRules • While programming using node addresses, do not use reserved values, TOS_BCAST_ADDR (0xffff) & TOS_UART_ADDR(0x007E)‏ • While programming a mica2 mote always switch off the battery switch • Mote programming difficulties - flash verification errors, programmer not responding • Performance affected by nearby sources of interference

  23. Future Work • Data acquisition from multiple sensors incorporating Surge routing protocol • Exposure to WSN simulator - TOSSIM

  24. Thank YouQuestions?

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