IN4316 IN4316 Wi l S Wi l S IN4316 IN4316 Wi l S Wi l S IN4316 IN4316 -- Wireless Sensor Wireless Sensor NetworksNetworks

IN4316 IN4316 -- Wireless Sensor Wireless Sensor NetworksNetworksNetworksNetworksNetworksNetworks

Koen LangendoenKoen LangendoenPhilipp Philipp GlatzGlatz, , VenkatVenkat IyerIyer

Andreas Andreas LoukasLoukas, , AnreiAnrei PruteanuPruteanu, Matthias , Matthias WoehrleWoehrle

VLSI T d M ’ LVLSI Trends: Moore’s Law

• in 1965, Gordon Moore predicted that transistors would continue to shrink transistors would continue to shrink, allowing:

doubled transistor density – doubled transistor density – doubled performanceevery 18-24 months

Gordon MooreGordon MooreIntel Co-Founder

Bell’s law: d d tievery decade a new generation

)co

mpu

ter)

ople

per

c

0

log

(peo

[Culler:2004]1960 1970 1980 1990 2000 2010

Wireless Sensor NetworksTh b i i The beginning …

Next Century Challenges: Mobile gNetworking for “Smart Dust”

J. M. Kahn,R H KatzR. H. Katz,K. S. J. Pister

(MobiCom 1999)

S t D t @ UC B k lSmart Dust @ UC Berkeley

Advances in digital circuitry will bring us:• ultra low power devices with• ultra low-power devices, with• small form factor, at • very low cost

f t i f li tifostering a new range of applications

d Autonomous sensing and communication in a cubic millimeter

Wi l t kWireless sensor networks

Many, cheap nodes• wireless ⇒ easy to install Transceiver• wireless ⇒ easy to install• intelligent ⇒ collaboration Embedded

Processor

Transceiver

Memory

• low-power ⇒ long lifetime SensorsBattery

Envisioned applicationsFire fighting

Envisioned applicationsUrban warfare

and many moreand many more…Medical

Process industry Agriculture

Th fi t t Sniper detection

The first steps …BTnode rev3

Mica2

• Develop COTS hardware• Develop software (TinyOS)

Imote

• Develop software (TinyOS)• Run experiments Tmote Sky

TNOdes[Vanderbilt 2003]• Prototype applications TNOdes

ATmega128L CPU (8-bit, 8 MHz)• 128 KB FLASH (program)• 4 KB DRAM (data memory)

Great Duck Island

[Vanderbilt, 2003]

ZebraNet

• 4 KB DRAM (data memory)

Chipcon CC1000 radio (868 MHz)• modulation: FSK 76.8 kBaud• output power: -20 to 10 dBm

[UCB, 2002][Princeton, 2004]

WSN hWSN research

51905520 5550

#publications/yearTopics:• self-configuration

3290

4010Constraints:• robustness

self configuration• node localization • low-bitrate communication

1080

1850• limited resources• energy efficiency

• ad-hoc routing• in-network data processing

14 52 86 227566

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

• time synchronization • …

E b kdEnergy breakdown

TNOdesTNOdes

The battery crisis (M ’ l il t i b th )(Moore’s law evil twin brother)

Limited capacity

~2 kcal (per battery)

Slow increase of capacity• ~8% yearly increase (Wh/cm3)8% yearly increase (Wh/cm )• doubles every 9 years

Back to realityBack to realityBack to realityBack to realityBack to realityBack to realityBack to realityBack to reality

C i f tiCourse information

• Goal: – to acquire knowledge and understanding of to acquire knowledge and understanding of

Wireless Sensor Networks, in particular, of how the inherent need for energy-efficient operation requires a new approach to distributed computing.

M• Means:– by reading, presenting, and discussing

f h h state-of-the-art research papers

C t tCourse contents

• Lectures (2x)– wireless communication– ad-hoc + sensor networks

• Seminar (5x)• Seminar (5x)– Medium access control, Localization, Routing,

Systems ProgrammingSystems, Programming

• Darjeeling Lab (1x)– hands-on experience

S i i tiSeminar organization

• Audience– prepare by reading classic papersp p y g p p– submit short summary before class

• Presenters – select a special topic (today)– browse recent literature– propose paper for presentation (-1 week)– prepare Powerpoint slides (-2 days)– present paper + lead discussion– write report (+2 weeks)

Wireless CommunicationWireless CommunicationWireless CommunicationWireless CommunicationWireless CommunicationWireless CommunicationWireless CommunicationWireless Communicationcrash coursecrash coursecrash coursecrash course

Wi l t h l iWireless technologies

1,000 Km100 Km10 Km1 Km100 m10 m1 m

SatelliteSWMWFMMobile SatelliteLinks

SWRadio

MWRadio

FMRadio

MobileTelephony,WLL

WLANsBlueoothIR

Wi l i tiWireless communication

• Error prone, unpredictable medium• Impact on protocol stack• Impact on protocol stack

– medium access controll li ti– localization

– routingRR

Unrealistic assumptions i WSN in many WSN papers

Unit Disk Graph model

B tt hBottom-up approach

• Wireless channel– RF propagation– RF propagation– noise & interference

• Physical layerd l ti– modulation

– coding

Wi l WWireless = Waves

• Electromagnetic radiation• Sinusoidal wave with a

cf =• Sinusoidal wave with a frequency/wavelengthE itt d b i id l t i

λf =

• Emitted by sinusoidal current running through a wire (transmitting antenna)

• Induces current in receiving antenna

El t ti Electromagnetic waves

• Propagation in vacuum

El t ti Electromagnetic waves

• Free-space loss– due to surface area increase– due to surface area increase

2

⎟⎞

⎜⎛GG λ

d

⎟⎠⎞

⎜⎝⎛4

=d

GGPP RTTR πλ

Al k F ii Also known as Friis free space formula

A t b iAntenna basics

Isotropic Dipole High gain directional

0 dB 2 2 dB 14 dB0 dBi 2.2 dBi 14 dBi

ldirectionaPG =Antenna gain:isotropicP

GAntenna gain

dB d f i ddB and friends

• dB (Decibel)D t th diff b t t l ls– Denote the difference between two power levels

– (P2/P1)[dB] = 10 * log10 (P2/P1)

• dBm (dB milliWatt)– Denote the power level relative to 1 mW– P[dBm] = 10 * log10 (P/1mW)

• dBi (dB isotropic)dB (dB sotrop c)– Denote the gain a given antenna has, as compared

to a theoretical isotropic (point source) antenna

A t di ti i thAntenna radiation in theory

Vertical Whip Antenna, 1/4 Wave

azimuth

zy y

elevation

x

[htt // f f / f / l t i l/ t tt ht ][http://www.rfcafe.com/references/electrical/antenna_patterns.htm]

A t di ti i tiAntenna radiation in practice

Distortion:

[htt // f /]

• metal objects• electronics

[http://www.mwrf.com/]• polarization

Wi l T i i I iWireless Transmission Impairments

• Attenuation (free space loss, directionality)• Noise (thermal + impulse)• Noise (thermal + impulse)• Objects

– reflection (+ scattering + diffraction)– absorption– refraction absorrption

R fl ti lti th di t tiReflections ⇒ multipath distortion

• Propagation along multiple paths leads

Ceiling

TX RXmultiple paths leads to self interference

• Unlike attenuation

TX RX

Obstruction

• Unlike attenuation and noise, multipath cannot be handled by

Floor

R i d Si lcannot be handled by increasing the send power

Time

Received Signals

C bi d R ltpower Combined Results

Time

R fl ti h d iReflections ⇒ shadowing

shadowshadowshadowshadowareaareaTXTX

l bj hi ld h b hi d i• A large object shields the area behind it• As for multipath, shadowing cannot be p g

handled by increasing the send power

P ti lPropagation loss

Attenuation = path loss p+ shadowing + multipath

Fading depends– location– frequency– time

[G. Janssen, ET4358]

P th l E tPath-loss Exponents

2

⎟⎠⎞

⎜⎝⎛4

=d

GGPP RTTRλ

• Depends on environment:⎠⎝ 4 dπ

p– Free space 2– Urban area cellular 2.7 to 3.5– Shadowed urban cell 3 to 5– In building LOS 1.6 to 1.8

Ob d b ld 4 6– Obstructed in building 4 to 6– Obstructed in factories 2 to 3

Ph i l lPhysical layer

• Encoding information as waves– modification of a carrier signal– modification of a carrier signal– high frequency: low loss, small antennas

tM d l ti• Modulation– digital to analog conversion (and back)

l d f h– options: amplitude, frequency, phase

Di it l d l tiDigital modulation

• Amplitude Shift Keying (ASK):– very simple

1 0 1

y p– low bandwidth requirements– very susceptible to interference

• Frequency Shift Keying (FSK):– needs larger bandwidthg

• Phase Shift Keying (PSK):– more complexmore complex– robust against interference

Mote EvolutionMot E o ut on

Ph i l l t h iPhysical layer techniques

• Handling noise– channel coding– channel coding

Handling fading• Handling fading– location: antenna diversity

f h i d t OFDM – frequency: hopping, spread spectrum, OFDM, UWB

time: (retransmissions; link layer and up)– time: (retransmissions; link layer and up)

Ch l diChannel coding

• Forward Error Correction (FEC)– add redundant information at sender– add redundant information at sender– coding gain vs. overheads (code rate, processing)

• Types– block codes (BCH, Reed-Solomon)– convolution codes (Viterbi, Turbo)

• Error bursts• Error bursts– interleaving (at the expense of latency)

R di Bl k DiRadio Block Diagram

Coding Modulation Antenna

DemodulationDecoding Antenna pathloss

R di i t fRadio interface

• Data– Serial Peripheral Interface (SPI) Bus– Serial Peripheral Interface (SPI) Bus

CPU Radio

• Controlfi ti (f h l t )

CPU Radio

– configuration (freq. channel, etc.)– TX/RX mode (half duplex)

/ ff ( l d )– power on/off (sleep modes)

Wi l S N t kWireless Sensor Networks

• Technology push– “Smart Dust: autonomous sensing and Smart Dust autonomous sensing and

communication in a cubic millimeter”

• Novel research area • Novel research area – focus on energy efficiency

• Hostile wireless environment– channel basics (RF propagation & interference)p p g– physical layer (modulation & coding)

H kHome work

• Check out info on Blackboard

• Register with the CPM submission system– send {Name student nr NetID} tosend {Name, student nr, NetID} to

Koen Langendoen <k.g.langendoen@tudelft.nl>K L g .g. g @ f .

– try account aty

http://cpm.ewi.tudelft.nl/