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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/
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