smart dust --- hardware for wireless sensor networks
Post on 10-Jun-2015
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Distributed Systems Group
Chair of Computer Science IV
RWTH Aachen University
http://ds.cs.rwth-aachen.de
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Martin Jansen
Smart Dust
Hardware forWireless Sensor Networks
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Agenda
1. Introduction1.1. Use Cases1.2. Requirements1.3. Hierarchies
2. Hardware implementations2.1. Intel Mote2.2. Telos2.3. eXtreme Scale Mote
3. Summary
1. Introduction
• Wireless Sensor Networks are also called „Smart Dust“
• „[N]etworks of interconnected computing devices deeply embedded into the physical environment (...) providing detailed instrumentation of many points over large spaces, both natural and artificial.“
• The nodes of a sensor network are called Motes.
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1.1 Use Cases: Environmental monitoring
• Outdoor deployments
• Situated in hostile environments and remote areas• Mountain regions• Sea• Primeval forests• Antarctica• Sahara
• Measuring e.g. temperature or humidity
• Monitoring animals
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1.1 Use Cases: Surveillance
• Important topic these days
• Different targets for surveillance:• Monitoring cars on roads to avoid recurring traffic
jams
• Monitoring people• Airports, train stations
• Stadiums
• Public places
• Battle fields
• Recognising motion
• Taking images
• Recording voice
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1.1 Use Cases: Industrial Monitoring
• Monitoring complex or expensive equipment• Detect upcoming machine failures• Harvest performance data• Tell engineers when maintenance is necessary
• Deployments spread across huge facilities like refineries or nuclear power plants
• Motes situated indoor and outdoor
• Measuring• Vibration• Temperature• Water level• Pressure• ...
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1.2 Requirements
Based on these use cases, requirements can be deduced:
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1.2 Requirements
Based on these use cases, requirements can be deduced:
• Energy Efficiency• Long lifetime is important in all use cases• Replacing batteries usually
• too expensive or time-consuming• not possible at all
• Strategy for saving energy:• Keeping motes in sleep phase for most of their
lifetime• Waking them up regularly in order to collect data
• Not applicable in all cases
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1.2 Requirements
• Pricing• Deployments can become huge:
• Thousands of motes on a battlefield• Thousands of motes monitoring complex factories• Hundreds of thousands of motes embedded into
a brigde‘s concrete during construction
• Thus motes must be cheap• Price drops when demand rises
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1.2 Requirements
• Physical Robustness• Especially important in outdoor deployments• Protection against vandalism• Protection against the environment
• Heat• Low temperature
• Precipitation• Humidity
• „Camouflage“• Unobtrusive colours
• Avoid sun reflection
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1.2 Requirements
• Upgrading-Robustness• Reprogramming manually not desirable
• Motes support being upgraded wirelessly• Faulty upgrades may render motes unusable
• Resetting manually not desirable• Demand for autonomous reset system
• When upgrade failed, reset the mote to a known-good software revision
• This revision is stored in a write-protected storage on the mote
• Saves time in research & experimentation
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1.2 Requirements
• Size• Motes need to be small and unobtrusive• Battery size needs to be considered• External antennas increase size but also increase networking range
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1.2 Requirements
• Networking• On the one hand: High transfer rates and good ranges are required• On the other hand: Energy is scarce
• Trade-off between high-traffic and energy-efficiency needed
• Capability of routing around failed nodes
• Possible technologies:• Radio (low bandwidth, little energy)• Bluetooth (higher bandwidth, more energy)
• Wireless LAN (high bandwidth, a lot of energy)
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1.3 Hierarchies (Type 1)
Depending on its performance data, a mote belongs to one of the following categories:
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1.3 Hierarchies (Type 1)
Depending on its performance data, a mote belongs to one of the following categories:
• Specialised Sensing Platforms• Single-chip solution• Support only simple sensors• Small network ranges, max. 50 Kb/s• Very little storage < 10 KB
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1.3 Hierarchies (Type 1)
Depending on its performance data, a mote belongs to one of the following categories:
• Specialised Sensing Platforms• Single-chip solution• Support only simple sensors• Small network ranges, max. 50 Kb/s• Very little storage < 10 KB
• Generic Sensing Platforms• Constructed with off-the-shelf components• Often support sensing and being proxy for specialised sensing motes• Maximum bandwidth of 100 Kb/s• Up to 0.5 MB of storage
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1.3 Hierarchies (Type 1)
• High-bandwidth Sensing Platforms• High-bandwidth sensor interfaces• Suitable for video or audio sensors• Increased CPU power, more memory (permanent and volatile)• High-bandwidth networking, e.g. using Bluetooth
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1.3 Hierarchies (Type 1)
• High-bandwidth Sensing Platforms• High-bandwidth sensor interfaces• Suitable for video or audio sensors• Increased CPU power, more memory (permanent and volatile)• High-bandwidth networking, e.g. using Bluetooth
• Gateway Platforms• Collect and store data from other motes• Make the data accessible from the outside
• Database interfaces• Web-based interfaces
• Several MB of RAM• Fast networking, e.g. IEEE 802.11 WLAN
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1.3 Hierarchies (Type 2)
Motes can also be categorised based on how they work:
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1.3 Hierarchies (Type 2)
Motes can also be categorised based on how they work:
(A) Data collection• Wake up shortly to collect and transmit sensor data
• Remain in sleep phase the rest of the time
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1.3 Hierarchies (Type 2)
Motes can also be categorised based on how they work:
(A) Data collection• Wake up shortly to collect and transmit sensor data
• Remain in sleep phase the rest of the time
(B) Event detection• Monitoring their surroundings for random and ephemeral events all the
time
• Wake up/Sleep procedure not applicable
• Motes can be shut down only partially while monitoring for events
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2.1: Intel Mote
• Developed by Intel Research
• High-bandwidth sensing mote
• Size: 3x3 cm
• Four D-cell batteries
• Bluetooth networking, max. 2.1 Mbit/s
• Scatternet functionality coming with Bluetooth
• Lifetime:
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Sleep duration Network connected Network disconnected
1 hour 2 months 2-3 months
12 hours 3 months 10-12 months
24 hours 3-4 months 12-14 months
1 week 4 months 15 months
1 month 4 months 15-16 months
2.2 Telos
• Developed by UC Berkeley
• Dimensions: 8x3.2 cm (plus batteries)
• Power supply• via two AA batteries• via USB
• Lifetime: 3 years with 1% activity time
• Wideband radio, max. 250 Kb/s
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2.2 Telos
• Sophisticated radio interface:• Encryption of data before sending
• Authentication
• Auto-acknowledgement• Packets not addressed to the mote are not passed to the OS
• Wideband was chosen because it is more stable
• Narrowband radio consumes less energy
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2.2 Telos
• Upgrading-Robustness through watchdog timer• Part of the microcontroller• Independent of the operating system• Resets mote if pulse signals stay away• Golden image stored in write-protected flash storage
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2.2 Telos
• Upgrading-Robustness through watchdog timer• Part of the microcontroller• Independent of the operating system• Resets mote if pulse signals stay away• Golden image stored in write-protected flash storage
• Available for $130
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2.3 eXtreme Scale Mote
• Developed as part of the ExScal project• 10,000 nodes spread over 10 km2
• Lifetime of 1,000 hours• Detect objects and classify them as civilians,
soldiers, and vehicles
• Event detection mote, generic sensing platform
• Dimensions: 8.89 x 8.89 x 6.35 cm
• Two AA batteries
• Narrowband radio, max. 76.8 Kb/s
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2.3 eXtreme Scale Mote
• Event detection with three sensors:• Infrared sensor → warmth• Acoustic sensor → noise• Magnetic sensor → metal
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2.3 eXtreme Scale Mote
• Event detection with three sensors:• Infrared sensor → warmth• Acoustic sensor → noise• Magnetic sensor → metal
• Classification:• vehicle = infrared ∧ acoustic ∧ magnetic
• soldier = infrared ∧ ¬acoustic ∧ magnetic
• civilians = infrared ∧ ¬acoustic ∧ ¬magnetic
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
• Solution: Chained trigger network
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
• Solution: Chained trigger network• Comparable to people‘s behaviour when sleeping
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
• Solution: Chained trigger network• Comparable to people‘s behaviour when sleeping
• Infrared sensor is necessary for all three targetclasses. Keep it active all the time.
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
• Solution: Chained trigger network• Comparable to people‘s behaviour when sleeping
• Infrared sensor is necessary for all three targetclasses. Keep it active all the time.
• Launch other sensors if the infrared sensortriggers.
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
• Solution: Chained trigger network• Comparable to people‘s behaviour when sleeping
• Infrared sensor is necessary for all three targetclasses. Keep it active all the time.
• Launch other sensors if the infrared sensortriggers.
• Collect data, process it and activate radio.Transmit data and „doze“.
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2.3 eXtreme Scale Mote
• Energy saving is a problem because the mote cannot be powered down completely.
• Solution: Chained trigger network• Comparable to people‘s behaviour when sleeping
• Infrared sensor is necessary for all three targetclasses. Keep it active all the time.
• Launch other sensors if the infrared sensortriggers.
• Collect data, process it and activate radio.Transmit data and „doze“.
• Lifetime: 1,000 hours at 6 events/hour
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2.3 eXtreme Scale Mote
• Physical robustness through solid enclosure• Primary field of application: battle field
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2.3 eXtreme Scale Mote
• Physical robustness through solid enclosure• Primary field of application: battle field
• Upgrading-Robustness through grenade timer• Resets the mote regularly
• Even if functioning properly
• Mote are never defunct longer than the timer interval
• More solid than a watchdog timer
• However: Unnecessary resets
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3. Summary
• Requirements: energy-economical, cheap, robust, small
• 4 classes
• 2 modus operandi• Data collection• Event detection
• 3 motes• Intel Mote• Telos• eXtreme Scale Mote
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The End.
• Questions?
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The End.
• Questions?
• Thank you!
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The End.
• Questions?
• Thank you!
• Some images were taken from Flickr.com and require attribution:
• http://flickr.com/photos/halloweenjack/47269493/• http://flickr.com/photos/vanityfailed/325592829/ • http://flickr.com/photos/78169939@N00/229466536/, • http://flickr.com/photos/chrischris/119272930/• http://www.flickr.com/photos/a_mason/27659607/• http://www.flickr.com/photos/ftf/43813301/• http://www.flickr.com/photos/mrflip/36854420/• http://www.flickr.com/photos/illogicnet/111537408/
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