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