Wireless Sensor Networks Based On MICA Platform Wei Zhou Sep 8, 2004

Overview and Goals Big Idea: Ubiquitous sensing How? –Necessarily “cheap” This is the military / commercial. Cheap is relative. –Necessarily small (more survivable, low profile, etc.) –Necessarily many (economies of scale, higher measurement granularity, lower power comms, etc.) –Necessarily robust Common case: no maintenance

Roadmap $$ + Network Embedded Systems Technology Program

Hardware Development Circle

Design Analysis Integrate sensors, computation and communication in single unit –Basic board has radio, processor, memory –Sandwich sensor boards in layers –“Just like the rock…great cleavage” Open-source hardware/software concept –Software is TinyOS (TOS) –Hardware design and Intel networking technology is licensed to Crossbow Modular design allows fast development

Mote Design: MICA Three low-power modes –Idle: Processor is turned off –Power Down: Everything but the watch-dog is turned off –Power Save: Only asynchronous timer powered on 100 mW power consumption –Processors, radio, typical sensor load 30 uW power consumption –All components asleep Atmega103 Microcontroller TR 1000 Radio Transceiver 4Mbit External Flash 51-Pin I/O Expansion Connector Power Regulation MAX1678 (3V) DS2401 Unique ID 8 Analog I/O 8 Programming Lines SPI Bus Coprocessor Transmission Power Control Hardware Accelerators Digital I/O

Motes

MICA2 Crossbow 3 rd generation wireless sensor Design changes to MICA: Processor now offers standalone boot-loader New radio (Chipcon 1000) –500 to 1000 ft. range, 38.4 Kbaud –Better noise immunity, linear RSSI –FM modulated (vs Mica AM) –Digitally programmable output power –Built-in Manchester encoding –Software programmable freq. –hopping within bands Tiny OS v improved network stack, debugging Wireless remote programming* 512 Kb serial flash

MICA2DOT Crossbow 3 rd generation wireless sensor Similar feature set to MICA2 Degraded I/O capabilities: 18 pins vs. 51 pins –6 analog inputs, digital bus, serial or UART Integrated temperature and battery voltage sensors, status LED Battery is 3V coin cell instead of AA x 2 25 mm diameter, 6 mm height Compatible with MICA2

Sensor Board Placement 2.25 in 1.25 in Microphone Accelerometer Light Sensor Temperature Sensor SounderMagnetometer

Ad hoc networking Autonomous nodes self-assembling into a network of sensors Sensor information propagated to central collection point Intermediate nodes assist distant nodes to reach the base station Connectivity and error rates used to infer distance Routing Tree Link Connectivity

Ad hoc networking Each node needs to determine it’s parent and its depth in the tree Each node broadcasts out when parent is known At start, Base Station knows it is at depth 0 It send out Individuals listen for minimum depth parent

A one byte transmission uses the same energy as approx cycles of computation. Lithium Battery runs for 35 hours at peak load and years at minimum load. ActiveIdleSleep CPU5 mA2 mA5 μA Radio7 mA (TX)4.5 mA (RX)5 μA EE-Prom3 mA00 LED’s4 mA00 Photo Diode200 μA00 Temperature200 μA00 Panasonic CR mAh Power breakdown

Sample tradeoffs

Operating system: TinyOS Tiny Microthreading Operating System –Tiny - 4k OS + program memory limit –Microthreading - processor directly handles almost all data (radio, sensors, etc.) –OS - allows platform for future development convenient abstractions for hardware Designed to do the job fast and then turn off everything allowed Open source

What is TinyOS TinyOS is an event-based operating environment designed to work with embedded network sensors Designed to support concurrency intensive operations required by network sensors with minimal hardware requirements TinyOS was initially developed by the U.S. Berkeley EECS department

Design Considerations Make best use of most constrained asset: battery power Network self-configuration –Manage complexity, respond to unplanned events Sensor self-configuration –“Glue and go” Real-time –Limited buffering available Network robustness and maintenance –Multiple points of failure, self-healing ability

Sample Application: Tiny DB Imposes SQL-like querying ability on nodes Treats distributed network like a database (!) Allows specification of which data should be sent, update rate, etc. Filters and aggregates before displaying on PC screen (Java interface) Saves bandwidth and power by allowing nodes to only transmit requested data Graphical query-builder Download self-configuring runtime to motes, no C coding

Potential applications at ISU Building various monitor-and-alarm systems –Monitor-and-alarm testbed for power systems Accelerometer Extremely sensitive sensor (Voltage, Current, etc.) Interface with control system –What device you have? Is it possible to integrate it with MICA to make a monitoring system? Testing new research ideas –Data integration/dissemination –Information delivery/routing –Localization –Sensor network security –More…

MICA Motes Conclusion Sensor Hardware –Cheap, publicly-available, modular, integrated, power- efficient, extensible, tiny Sensor Software –Free, open-source, modular, abstract, power-efficient, extensible, small Cost –Potentially cheap enough for densely deployment –Expected $1 for each radio board in NEXT generation

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