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Sensor networksOpportunities for theory

The future

Sensor Networks and the Future of Networked

Computation

James AspnesYale University

February 16th, 2006

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

http://find/http://goback/

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Why wireless sensor networks?

Question: If a tree falls inthe forest, how do we hearit?

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

http://find/http://goback/

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Why wireless sensor networks?

Question: If a tree falls inthe forest, how do we hearit?

Answer: nail a sensor to

every tree.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

The central dogma of sensor networks

Distributed sensing is necessary to detect rare, localizedevents.

Abundant sensors must be cheap.Short-hop radio is the obvious communication mechanism.

The more computation we can do in the network itself, theless communication we need.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

R i l

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Classical networks

Classical networks are made of big, expensive devices:

Routers.

Wires (or equivalent fixed point-to-point connections).

Power cables running to the routers.

Network administrators standing next to the routers.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

R ti l

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Sensor networks

Sensor networks are made of small, cheap devices:

Sensors.Short-distance radio broadcast.

Weak power sources: batteries, solar cells, RF antennas.

No network administrators!

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

Rationale

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Sensor networks

Sensor networks are made of small, cheap devices:

Sensors.Short-distance radio broadcast.

Weak power sources: batteries, solar cells, RF antennas.

No network administrators!

Every feature of sensor networks is likely to become typical of mostnetworked computing devices.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

Rationale

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Where we are evolving from

Existing sensor network applications.

Weather stations.Networks of strain gauges on ships.

Ecological sensor networks.B-52-launched tank detectors.

Active RFID chips.

Mostly used for inventory tracking.Many are writable.

Some already can record temperature extremes or suddendrops.

New hardware technologies like proximity interconnect andchip-based networks.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

Rationale

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Sensor networksOpportunities for theory

The future

RationaleClassical networksSensor networksThe presentThe future

Where we are evolving to

Sensors/RFID chips that talk to each other.

Computers without wires.

Cheap sensors everywhere.

Long view: smart molecules?

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

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Sensor networksOpportunities for theory

The future

Classic network problems revisitedNew problemsNew models

Classic network problems revisited

Consensus, leader election, clock synchronization withsevere resource constraints.

New geographical routing algorithms that require no externalconfiguration and respect sensors limitations.

Internet-scale problems on much smaller scales.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

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Sensor networksOpportunities for theory

The future

Classic network problems revisitedNew problemsNew models

Data aggregation

The central problem in sensor networks.

Still an active area of research.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

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Sensor networksOpportunities for theory

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Classic network problems revisitedNew problemsNew models

Localization

How do we know where oursensors are?

Triangulation/trilateration.

NP-hard in the worst case.

Good algorithms for densenetworks.

Error propagation still needswork.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

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Sensor networksOpportunities for theory

The future

Classic network problems revisitedNew problemsNew models

Mobility

Controlled mobility creates a need for planning.Uncontrolled mobility requires tolerance of a rapidly-changingnetwork structure (or maybe no consistent network structure).

Details: see previous talk.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

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Sensor networksOpportunities for theory

The future

Classic network problems revisitedNew problemsNew models

Security

How do we keep dumb sensors from being hijacked or misused?

Controversy over adding RFID tags to US passportsexemplifies issues of control.

Most RFID and sensor network applications rely on physicaldistance to limit access.

Such reliance may not be reasonable as sensors become

ubiquitous.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

S k Cl i k bl i i d

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Sensor networksOpportunities for theory

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Classic network problems revisitedNew problemsNew models

New models

Population protocols model collections of very weak devicesusing networks of finite-state automata.

Unstructured case is now very well understood.Bounded-degree networks are in principle equivalent toLINSPACE Turing machines.Speedy algorithms are still needed.

Can we build continuous models that are good approximations

to discrete physical systems?Battery life, geographical constraints, and sensor unreliabilityneed to be incorporated into models at a fundamental level.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

S t k

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Sensor networksOpportunities for theory

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The future

There are many morebacteria than people (even

by weight).The same economicssuggests we can expectmany more tiny computersthan big ones.

Sensor networks are thevanguard of this revolution.

0 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 01 1 1 11 1 1 11 1 1 11 1 1 11 1 1 11 1 1 11 1 1 11 1 1 1ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

Sensor networks

http://find/http://goback/

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Sensor networksOpportunities for theory

The future

The future

There are many morebacteria than people (even

by weight).The same economicssuggests we can expectmany more tiny computersthan big ones.

Sensor networks are thevanguard of this revolution.

ToNC workshop, February 16th, 2006 Sensor Networks and the Future of Networked Computation

http://find/http://goback/