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 asynchronoustimer powered on

• 100 mW power consumption– Processors, radio,

typical sensor load• 30 uW power

consumption– All components

asleep

Atmega103 Microcontroller

TR 1000 Radio Transceiver4Mbit External Flash

51-Pin I/O Expansion Connector

Power Regulation MAX1678 (3V)

DS2401 Unique ID

8 Analog I/O8 Programming

Lines

SP

I B

us

CoprocessorTransmission Power Control

Hardware Accelerators

Digital I/O

Motes

MICA2

• Crossbow 3rd 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. 1.0 - improved network stack, debugging• Wireless remote programming*• 512 Kb serial flash

MICA2DOT

• Crossbow 3rd 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

AccelerometerLightSensor

TemperatureSensor

Sounder Magnetometer

Ad hoc networking

• Autonomous nodesself-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 <identity, depth, data> when parent is known

• At start, Base Station knows it is at depth 0• It send out <Base ID, 0, **>

• Individuals listen for minimum depth parent

0

 

 

1

1

 

 2

2

 3

 

• A one byte transmission uses the same energy as approx 11000 cycles of computation.

• Lithium Battery runs for 35 hours at peak load and years at minimum load.

Active Idle Sleep

CPU 5 mA 2 mA 5 μA

Radio 7 mA (TX) 4.5 mA (RX) 5 μA

EE-Prom 3 mA 0 0

LED’s 4 mA 0 0

Photo Diode 200 μA 0 0

Temperature 200 μA 0 0Panasonic CR2354

560 mAh

Power breakdown

Duty Cycle Estimated Battery LifeFull Time Listen 100% 3 DaysFull Time Low_Power Listen 100% 6.54 DaysPeriodic Multi-Hop Listening 10% 65 DaysNo Listen (no Multi-hop) 0.01% Years

Battery Lifetime for sensor reporting every minute

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

More Info.

• http://www.tinyos.net/

• http://webs.cs.berkeley.edu/

• www.xbow.com

• http://mail.millennium.berkeley.edu/pipermail/tinyos-help

• http://nescc.sourceforge.net/