Post on 12-Jan-2016
transcript
Challenges & Opportunities in Monitoring of Buildings with Wireless Sensor Networks
Murat Demirbas
University at Buffalo, SUNY
Computer Science & Engineering Dept.
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New Class of Computing
year
log
(p
eo
ple
pe
r c
om
pu
ter)
streaming informationto/from physical world
Number CrunchingData Storage
productivityinteractive
Mainframe
Minicomputer
Workstation
PC
Laptop
PDA
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Ubiquitous computing vision
• Instead of us interacting with the computers in the virtual world, the computers should interact with us in our physical world
• Technology is now available via MEMS, CMOS, CMOS radios
• PC processors are only 2% of all processors: the rest go to
Automotive; Communications; Consumer electronics; Industrial equipment
• Real-world deployments for networked embedded systems have already started:
Environmental monitoring Precision agriculture Asset management Military surveillance
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Wireless sensor networks (WSNs)
A sensor node (mote)
8K RAM, 4Mhz processor magnetism, heat, sound, light, vibration, infrared wireless (radio broadcast) communication up to 100 feet costs ~$10 (right now costs ~$100)
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Real-world deployments of robust WSN
Line In The SandLine In The Sand
• In OSU, we developed a surveillance service for DARPA-NEST
Detect, track, and classify trespassers as car, soldier, civilian LiteS: 100 nodes in 2003, ExScal: 1000 nodes in Dec 2004
Thick Entry Line
A S S E T
1 km
250 m
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Real-world deployments of robust WSN
Redwood monitoring
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Benefits of using WSN
• Ease of deployment
Wireless communication means no need for a communication infrastructure setup
Drop and play
• Low-cost of deployment
Nodes are built using off-the-shelf cheap components
• Fine grain monitoring
Feasible to deploy nodes densely for fine grain monitoring
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TinyOS in a nutshell
• Most popular operating system for WSN
developed by UC Berkeley
• Features a component-based architecture
software is written in modular pieces called components TinyOS provides a component library that includes network protocols,
services, and sensor drivers
• Easy to link components together by “wiring” their interfaces to form larger components
similar to using Lego blocks
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Benefits of using TinyOS
• Separation of concerns
TinyOS provides a proper networking stack for wireless communication & abstracts away the complexity of message transfer, e.g., MAC layer
• Concurrency control
TinyOS provides a scheduler that achieves efficient concurrency control
An interrupt-driven execution model is needed to achieve a quick response time for the events and capture the data
• Modularity
TinyOS’s component model facilitates reuse and reconfigurability; several middleware services are available as well-documented components
Over 500 research groups and companies are using TinyOS
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Middleware services
• Middleware is the software that supports building of complex distributed applications:
Time synchronization Localization Routing Querying Reprogramming Power management
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Challenges in sensor networks
• Energy constraint
• Unreliable communication
• Unreliable sensors
• Large scale networks
• Limited computation power
• Distributed execution
: Nodes are battery powered, each transmission is precious
: Radio broadcast, limited bandwidth, bursty traffic
: False positives
: Algorithms should scale well
: Centralized algorithms inapplicable
: Difficult to debug & get it right
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Monitoring of next generation buildings
• Structural monitoring
• In-door environmental monitoring
• Extreme-events response
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Structural monitoring
• Accelerometer and strain gauges
for monitoring the natural vibration frequencies of a structure under naturally induced or forced vibrations
2micro-g sensitivity & 2g range 1micro-strain sensitivity & 2milli range
• Networking challenges for reliable transmission of the large amount of bursty traffic
Wavelet compression, event thresholding Combination of dimensionality reduction
and scalar quantization: Transform coding
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Open research problems
• Model-based monitoring– This may lead to huge
bandwidth and energy savings– But, we need good models of
the behaviors (e.g., a classification of the behavior to 10 categories?)
• Prioritization of data– Huge bandwidth savings are
possible by deciding which data is more important
– Need help from domain experts
• Lifetime of deployment– Alternative means to power the
nodes
• Lightweight localization – It may be possible to achieve
light-weight (in terms of computational power and communication cost) localization by exploiting domain specific information
• Data mules– Alternative ways of carrying
messages by exploiting the mobility inherent in the system
– E.g., can we use elevators to carry data between floors
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In-door environment monitoring
• Applications:– Control of heating, AC, light
intensity– Monitoring the in-door air
quality
• Querying and wireless reprogramming can put the building in different modes:Night / Holiday / Busy mode
• Standard sensors are available for the job
Open research problems
• Scalability– Hundreds of nodes should be
deployed– Hierarchical management
techniques can be useful
• Integration with 802.11 WAPs and Internet
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Extreme event response
• Alarm should be issued quickly upon detection of fire, explosion, structural strength degradation, or chemical attack
• Using the information gathered, WSN can provide real-time evacuation directions for occupants
• The system can also be useful for enabling rescuers locate survivors under collapsed structures in the aftermath of a collapse
Open research problems
• Timeliness & dependability guarantees are needed– Formal methods can be helpful
• The number of false-positives should be kept at an acceptable level for deployment
• Intuitive interfaces
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Concluding remarks
• Interdisciplinary collaboration between CSE and CE is needed
CSE effort should be guided by the context provided by CE that answer the questions what to sense?, where to sense?, when to sense?
Depending on the answers to the questions such as What level of accuracy is acceptable?, Which events are of interest and which are ignorable?, and What are the right places for deployment?, CSE researchers can fine-tune the performance and lifetime of the wireless monitoring systems
• Security and privacy issues should also be addressed before real deployments