Wireless Sensor Networks Karishma Babu Kenneth Kinion 4 December 2007

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

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

Overview Mesh network features Three components for this network: 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

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

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

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

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

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

Milestone 2: Goals Obtain Simple Sensor Data Alternatives 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

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

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

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

Milestone 3: Results

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

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

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

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

Milestone 5 Modified code:

Milestone 5 Results Before After

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

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

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

Thank You Questions?