Lecture 8: Wireless Sensor Networks
Announcement Midterm EXAM : 5:00 – 6:15 pm March 28
(Thursday)
Midterm project report due 4/4 (Email submission) No class on 4/4 due to Chancellor's Inauguration “we ask that all classes be cancelled
beginning at 12:30 for the remainder of the day. Classes will resume on Friday morning, April 5, 2013” – Provost
Project Presentation on April 9
Sensor Node Hardware Two main components
Sensor Board
Base (Processor + Transceiver)
Base + Sensor Board(s) = Sensor Node
Sensor Board Light
Ultraviolet IR Visible Light Color sensors
Magnetic Sound
Ultrasound Accelerometer Temperature Pressure Humidity Touch sensors
2.25 in Microphone
Accelerometer
Light
TemperatureSounder
Magnetometer
1.25 in
Sensor Node Hardware
Power UnitPower Unit ANTENNAANTENNA
Sensor ADCSensor ADCProcessorProcessor
MemoryMemoryTransceiverTransceiver
SENSING UNITPROCESSING UNIT
Properties of wireless sensor networks
Sensor nodes (SN) monitor and control the environment Nodes process data and forward data via radio Integration into the environment, typically attached to other
networks over a gateway (GW) Network is self-organizing and energy efficient Potentially high number of nodes at very low cost per node
SN
GWSN
SN
SNSN
SN SN
SN
SNSN
SN
GW
GW
GW
Bluetooth, TETRA, …
Ethernet
SN
GPRS WLAN
ALARM!
ALARM!ALARM!
ALARM!
Wireless Sensor Networks (WSN)• Commonalities with MANETs
– Self-organization, multi-hop– Typically wireless, should be energy efficient
• Differences to MANETs– Applications: MANET more powerful, more
general WSN more specific
– Devices: MANET more powerful, higher data rates, more resources WSN rather limited, embedded, interacting with environment
– Scale: MANET rather small (some dozen devices) WSN can be large (thousands)
– Basic paradigms: MANET individual node important, ID centric WSN network important, individual node may be dispensable, data centric
Sensor Motes Timeline
Mica“Open
Experimental Platform”
WeC“Smart Rock”
Rene’“Experimentation”
Dot“Scale”
Spec “Mote on a chip”
Telos“Integrated Platform”
Mica2Dot
Mica2
200620062005200520042004200320032002200220012001200020001999199919981998
IMote
MicaZ
Stargate 2.0&
IMote2
Stargate
20072007
SunSpot
Promising applications for WSNs Machine and vehicle monitoring
Sensor nodes in moveable parts Monitoring of hub temperatures, fluid levels …
Health & medicine Long-term monitoring of patients with minimal
restrictions Intensive care with relative great freedom of movement
Intelligent buildings, building monitoring Intrusion detection, mechanical stress detection
Environmental monitoring, person tracking Monitoring of wildlife and national parks Cheap and (almost) invisible person monitoring Monitoring waste dumps, demilitarized zones
… and many more: logistics (total asset management, RFID), telematics …
CodeBlue: WSNs for Medical Care
NSF, NIH, U.S. Army, Sun Microsystems and Microsoft Corporation
Motivation - Vital sign data poorly integrated with pre-hospital and hospital-based patient care records
Reference: http://www.eecs.harvard.edu/~mdw/proj/codeblue/
Wearable Patient Monitoring Application (ECG) Through Wireless Networks
Wearable Resilient Electrocardiogram (ECG) networked sensor device used for patient monitoring
Wireless ECG medical sensorSoftware GUI interface
Sensor Networks: Research AreasReal-World Integration
– Gaming, Tourism– Emergency, Rescue– Monitoring, Surveillance
Self-configuring networks– Robust routing– Low-power data aggregation– Simple indoor localization
Managing wireless sensor networks– Tools for access and programming– Update distribution
Long-lived, autonomous networks– Use environmental energy sources
Routing in WSNs is different
No IP addressing, but simple, locally valid IDs
Example: directed diffusion Interest Messages
Interest in sensor data: Attribute/Value pair Gradient: remember direction of interested node
Data Messages Send back data using gradients Hop count guarantees shortest path
Sink
TTDD: A Two-tier Data Dissemination Model for Large-scale Wireless Sensor Networks
A Sensor Network Example
Assumptions
Fixed source and sensor nodes, mobile or stationary sinks
Nodes densely applied in large field
Position-aware nodes, sinks not necessarily
Once a stimulus appears, sensors surrounding it collectively process signal, one becomes the source to generate the data report
Sensor Network Model
Source
Stimulus
Sink
Sink
Mobile Sink
Excessive PowerConsumption
Increased WirelessTransmissionCollisions
State MaintenanceOverhead
Goal, Idea
Efficient and scalable data dissemination from multiple sources to multiple, mobile sinks
Two-tier forwarding model Source proactively builds a grid structure
Localize impact of sink mobility on data forwarding
A small set of sensor node maintains forwarding state
Grid setup Source proactively divide the plane into αXα
square cells, with itself at one of the crossing point of the grid.
The source calculates the locations of its four neighboring dissemination points
The source sends a data-announcement message to reach these neighbors using greedy geographical forwarding
The node serving the point called dissemination node
This continues…
TTDD Basics
Source
Dissemination Node
Sink
Data Announcement
Query
Data
Immediate DisseminationNode
TTDD Mobile Sinks
Source
Dissemination Node
Sink
Data Announcement
Data
Immediate DisseminationNode
Immediate DisseminationNode
TrajectoryForwarding
TrajectoryForwarding
TTDD Multiple Mobile Sinks
Source
Dissemination Node
Data Announcement
Data
Immediate DisseminationNode
TrajectoryForwarding
Source
Trajectory Forwarding
Conclusion TTDD: two-tier data dissemination Model
Exploit sensor nodes being stationary and location-aware
Construct & maintain a grid structure with low overhead
Proactive sources Localize sink mobility impact
Infrastructure-approach in stationary sensor networks Efficiency & effectiveness in supporting mobile
sinks
The Future of WSNs Fundamental requirements today only
partially fulfilled Long life-time with/without batteries Self-configuring, self-healing networks Robust routing, robust data transmission Management and integration
Think of new applications Intelligent environments for gaming … <your idea here>
Still a lot to do… Integration of new/future radio technologies Cheap indoor localization (+/- 10cm) More system aspects (security, middleware, …) Prove scalability, robustness Make it cheaper, simpler to use
Already today: Flexible add-on for existingenvironmental monitoring networks
Major References TTDD: http://portal.acm.org/citation.cfm?
id=1160112
“ A survey on sensor networks”http://www-net.cs.umass.edu/
cs791_sensornets/papers/akyildiz2.pdf
Routing techniques in wireless sensor networks: A Survey
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1368893&userType=inst
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