Emerging Challenges: Mobile Networking for Smart Dust Joseph M. - - PowerPoint PPT Presentation

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Emerging Challenges: Mobile Networking for Smart Dust Joseph M. - - PowerPoint PPT Presentation

Emerging Challenges: Mobile Networking for Smart Dust Joseph M. Kahn, Randy Howard Katz and Kristofer S. J. Pister Presented by: Patrick Gemme Overview Focus Hardware Challenges Technology Applications Related


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Emerging Challenges: Mobile Networking for “Smart Dust”

Presented by: Patrick Gemme

Joseph M. Kahn, Randy Howard Katz and Kristofer S. J. Pister

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Worcester Polytechnic Institute 2

Overview

  • Focus
  • Hardware
  • Challenges
  • Technology
  • Applications
  • Related Project
  • Conclusions
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Worcester Polytechnic Institute 3

Focus

  • Large scale network of Wireless

sensors are becoming more and more plausible

  • Networking and application layers

are needed to make such a system usable.

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Worcester Polytechnic Institute 4

Hardware

  • Can now integrate sensing, communication, and power

supply into an inch-scale device. (off-the-shelf)

  • 3 technologies leading this advance:

– Digital circuitry – Wireless communications – Micro ElectroMechanical Systems (MEMS)

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Worcester Polytechnic Institute 5

Key Challenges

  • Must consume extremely low power
  • Must communicate at average bit rates

measured in kilobits p/sec

  • Must operate in high volumetric densities
  • How?

– Needs ad hoc routing – Media Access solutions

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Worcester Polytechnic Institute 6

Smart Dust mote

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Worcester Polytechnic Institute 7

Energy

  • Total Stored energy is on the order of 1 J

– If that is consumed continuously over a day, then the dust mote power consumption cannot exceed roughly 10mW

  • Solar cells could gain about 1 J per day in the sun
  • Energy-optimized microprocessors user about 1

nJ per 32-bit instruction

– Bluetooth burns about 100nJ per bit transmitted – – Picoradios Picoradios target 1nJ/bit –which will allow billions of

  • perations per Joule
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Worcester Polytechnic Institute 8

Ultra-low power: RF or Optical

  • RF cons:

– Extremely short-wavelength transmission – Energy Issues

  • Difficult to reduce to such low power consumption
  • Optical Cons:

– Line-of-sight needed (within a few tens of degrees)

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Worcester Polytechnic Institute 9

Optical Pros

  • High antenna gain can be achieved with

very low power

  • A base-station can decode simultaneous

transmissions with Space-division multiplexing

  • Passive optical transmission

– No optical power needed

  • Corner-Cube Retroreflector (CCR)
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Worcester Polytechnic Institute 10 Achieves several kilobits per second over hundreds of meters in full sunlight At night it should extend to at least a kilometer

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Worcester Polytechnic Institute 11

Line-of-sight?

  • Receiver is fairly omni-directional (forget about it)

1. With one CCR a mote has about a 10% chance

  • f being able to transmit to BTS

– Equip it with several CCRs

2. Distribute an excess number of motes (expecting many to not be able to communicate) 3. Steer the Beam in the right direction

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Worcester Polytechnic Institute 12

MAC protocol

  • Sensor-MAC (S-MAC)
  • Etiquette Protocol
  • CSMA for Sensor Networks
  • Z-Mac
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Worcester Polytechnic Institute 13

Passive and Broadcast-oriented techniques

  • A single wide beam from BTS can

simultaneously probe many dust motes

  • Motes transmit in short-duration burst signals

– similar to cell phones

  • BTS grants channels to requesting nodes
  • There are as many channels as resolvable

pixels at the BTS

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Worcester Polytechnic Institute 14

Applications

  • Used to record data for meteorological,

geophysical or planetary research

  • Environments where wired do not work
  • (semiconductor processing chambers, rotating machinery,

wind tunnels, anechoic chambers)

  • Biological:
  • Measure movements, habits, and environments of insects

and small animals

  • Military:
  • (passage of vehicles, perimeter surveillance, chemicals)
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Worcester Polytechnic Institute 15

Operate in Ensembles

  • Sensors can specialize in certain signatures and

combine for more useful information

– A change in temperature may not mean much – A change in sound level probably doesn’t tell us enough – Movement could mean many things

  • The combined array through P2P could determine

that a vehicle just pulled up with at least 2 men

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Worcester Polytechnic Institute 16

Why is Ad hoc needed?

  • The centralized/passive scheme is most power

efficient way to communicate.

  • Line-of-sight (again)

– The mote will have to use Ad hoc if line-of-sight to BTS is not possible – Requires 4 phase handshake

  • Standard routing algorithms like RIP, OSPF, and

DVRMP assume bidirectional and symmetric links

– New routing algorithms must be able to deal with unidirectional and/or asymmetric links

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Worcester Polytechnic Institute 17

Related Projects

  • Factoid Project at Compaq Palo Alto Western

Research Laboratories

  • Wireless Integrated Network Sensors

(WINS) Project at UCLA

  • Ultralow Power Wireless Sensor Project at

MIT

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Worcester Polytechnic Institute 18

Summary and Conclusions

  • “Smart Dust” has described an inexpensive way

to setup small low power sensors which can communicate to a central BTS and/or each other

  • Attacked the line-of-sight issue with 3 possible

solutions

  • Opened up leads into 3 main future work focuses

1. New routing algorithm to deal with unidirectional 2. A p2p collision avoidance scheme to deal with dynamic networks 3. A Beam-steering algorithm