mobile networking for smart dust

7/29/2019 Mobile Networking for Smart Dust

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Emerging Challenges: Mobile

Networking for Smart Dust

Naveen Gupt a

200301040


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Outline Introduction

Off the Shelf Technology

What is Smart Dust

Vision

Smart Dust Technology

RF versus Optical Corner Cube Retro Reflector

Active Transmitter


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INTRODUCTION

THREE KEY TECHNOLOGIES

Digital Circuitry Wireless Communications

Micro Electro Mechanical Systems

In each area, advance in hardwareTechnology, design led to reduction insize, power consumption and cost.


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OFF THE SHELF TECHNOLOGY


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What is Smart Dust

Large scale Networks of wirelesssensors of various applications

The three key capabilities of smart dustare:

Sensory Capabilities

Processing Capabilities

Communication Capabilities


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Vision

Smart Dust will be small enough toremain suspended in air, buoyed by aircurrents, sensing and communicationfor hours or days on end.


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Smart Dust Technology


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Integration MEMS (Micro-Electro-Mechanical Systems)

Sensors

Semi Conductor laser diode MEMS beam-steering Mirror

Corner-Cube Retro reflector

Optical Receiver

Signal Processing and Control Circuitry

Power Source based on thick film batteries

Solar Cells


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CHALLENGE To incorporate all these functionalities in a

cubic millimeter volume.

The total energy stored in the order of 1Joules.

Power Consumption cannot exceed over10microWatts.


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RF versus Optical RF radio frequency

MHz hundreds of GHz -> 1mm 100s meters

wavelength Technologies:

Bluetooth

Cell phones (GSM, CDMA, etc.)

RFID

Optical 100THz 1PHz -> 0.3 - 1.6 micro wavelength

Lasers and LEDs


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Radio Frequency Pros

Well developed technologies

Multiplexing techniques: TDMA, FDMA, CDMA.

Does not require line of sight

Not much affected by the environment

Cons

Antenna size (has to be at least of thewavelength)

Complex circuitry (modulation/demodulation,bandpass filters, etc.)

Energy consumption (approx. 100nJ/bit)


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Optical (1/2) Pros

Low energy consumption (


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Optical (2/2)

BTS (Base Transceiver Station)

Compact imaging receiver- decode thesimultaneous transmissions from a largenumber of dust motes at differentlocations within in the receiver field of

view


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Corner-Cube Retro reflector To supply signals without

any power

It comprises threeperpendicular mirrors ofgold-coated polysilicon

CCR includes anelectrostatic actuator-deflects on of the mirrorsat kilohertz rates.


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CCR Passive Optical (1/2)

Directional

CTS body diagonal happens to directlyto the BTS

Emerging More CCRS Omnidirectional


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CCR - Passive Optical (2/2) BTS contains a laser whose beam illuminates

an area containing dust nodes

Modulated beam contain Downlink data +commands to wake up and Query

Analysis show that this uplink achievesseveral kbps + hundreds of meter in fullsunlight

Design is simple


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Design of Free-Space Optical

Network


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Smart dust act ive t ransmit t er

Incorporates a laser, lens and a MEMsteering mirror

Peer Peer Communication

Trade off between bandwidth and range

1mrad transmission

Data rate of approx. 5Mb/sec

Energy consumption depends on distanceand detector size


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Base Station Architecture

Mirror

Camera Lens

Beam

Mirror

PolarizingBeam Splitter

PlateFilter

LaserExpander Smart

dust


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Smart dust act ive

transmitter

~25nJ/bit1m2500km

~10nJ/bit1cm25km

~20pJ/bit0.1mm25m

Energyconsumption

Detector areaDistance

~25nJ/bit1m2500km

~10nJ/bit1cm25km

~20pJ/bit0.1mm25m

Energy

consumptionDetector areaDistance


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Mobile Networking Challenges

Line of Sight Requirement

Link Directionality

Trade offs Between Bit rate, Distanceand Energy per bit


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Line of Sight Requirement (1/2)

Optical communication requires photons from thetransmitter reach the receiver photons travel in

straight lines

Specular reflections

Diffuse reflections Feasible only when ActiveTransmitters are used over short distances (probably 1m) Note : Cannot work with passive communication ,very small SNR


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Line of Sight

Requirement(2/2)

Dust Mote can communicate with theBTS via Multi hop Routing

Mote Density should be high

Multi hop routing increase latency


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Link Directionality(1/2)General

Motes are unaw are of neighbours locat ion

Base st ation can disseminate location informat ion t o motes

Passive links

A corner cube retro-r eflector angle of acceptance is 10-20

Placing mu lt iple corner cubes Placing t he corner cube and t he receiver on a MEM

mount signal maximization

I ncrease mote densit y high probability forcommunication w it h at least some mot es in t he area of

interest


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Link Directionality(2/2)Act ive links Mote receiver is omni direct ional w it hin a hemisphere

Enables mote at t ention w it hout aiming No source ident if ication

Making t he receiver di rect ional (by adding a lens) andconnect ing its directionalit y t o the transmit ter w illenable comm unicat ion autom at ically t o the source Requires aiming

Solved by increasing the densit y of motes I n a stati c syst em, ident ifi cat ion could be saved in m ote

memory Difference betw een receiver and transmit t er angular

spreads leads to non-reciprocal link ing


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Mobile Networking Opportunities

Parallel Read Out

Demand Access


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THANKS FOR YOUR

CO-OPERATI ON

mobile networking for smart dust

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