KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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© James P.G. SterbenzITTC
James P.G. Sterbenz
Department of Electrical Engineering & Computer ScienceInformation Technology & Telecommunications Research Center
The University of Kansas
http://www.ittc.ku.edu/~jpgs/courses/mwn
Mobile Wireless NetworkingThe University of Kansas EECS 882Physical Layer & MW Environment
22 August 2011 rev. 11.0 © 2004–2011 James P.G. Sterbenz
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-2
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPhysical Layer and Mobile Wireless Environment
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-3
© James P.G. SterbenzITTC
Physical LayerPhysical Layer Communication
networkCPU
M app
end system
CPU
M app
end system
R = ∞
D = 0
• Physical layer communicates digital information– through a communication channel in a medium– digital bits are coded as electronic or photonic signals
• digital or analog coding
– over a link between nodes (layer 2)
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-4
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPhysical Layer and Mobile Wireless Environment
• EECS 882 is a networking course– but the operation of the network depends on…– characteristics of the communication channels– physical environment
• Therefore– brief non-mathematical introduction to physical layer
details in EECS 865• review for EE folk• important for CS and IT folk to understand why
– discussion of impact of mobility and wireless on network
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© James P.G. SterbenzITTC
Mobile Wireless NetworkingPL.1 Physical Media and Spectrum
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-6
© James P.G. SterbenzITTC
Physical MediaGuided
• Guided media– wire
• twisted pair• coaxial cable• power line
– fiber optic cable
role in communication networks?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-7
© James P.G. SterbenzITTC
Physical MediaGuided
• Guided media– wire
• twisted pair• coaxial cable• power line
– fiber optic cable
traditional Internet & PSTN mostly guided mediaEECS 780 and 881
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-8
© James P.G. SterbenzITTC
Physical MediaUnguided
• Guided media– wire
• twisted pair• coaxial cable• power line
– fiber optic cable
• Unguided media– free space
• radio frequency• optical
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© James P.G. SterbenzITTC
Physical MediaUnguided
• Guided media– wire
• twisted pair• coaxial cable• power line
– fiber optic cable
• Unguided media– wireless free space
• radio frequency• optical
networks with unguided media subject for EECS 882
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-10
© James P.G. SterbenzITTC
Wireless Free SpaceSpectrum
• Spectrum– range of frequencies available for communication
• λf = c ; c = 3×105 km/s
– only some spectrum usable for communicationwhich parts?
[http://www.ntia.doc.gov/osmhome/allochrt.pdf]
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© James P.G. SterbenzITTC
Wireless Free SpaceSpectrum
• Spectrum– range of frequencies available for communication
• λf = c ; c = 3×105 km/s
– RF: radio frequency• frequency determines propagation characteristics
[http://www.ntia.doc.gov/osmhome/allochrt.pdf]
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-12
© James P.G. SterbenzITTC
Wireless Free SpaceSpectrum
• Spectrum– range of frequencies available for communication
• λf = c ; c = 3×105 km/s
– RF: radio frequency– optical
• infrared 800–900 nm = 333–375 THz 41 THz spectrum
why not higher frequencies?
[http://www.ntia.doc.gov/osmhome/allochrt.pdf]
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© James P.G. SterbenzITTC
Wireless Free SpaceSpectrum
• Spectrum– range of frequencies available for communication
• λf = c ; c = 3×105 km/s
– RF: radio frequency– optical– higher frequencies: UV, x-ray, γ-ray, …
• health risks of radiation exposure• frequency beyond current tranceiver technology• propagation problems
[http://www.ntia.doc.gov/osmhome/allochrt.pdf]
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-14
© James P.G. SterbenzITTC
Wireless Free SpaceSpectrum Table
Usage ExamplesPropagationRangeBand
LOS
LOS
LOS
LOS
LOS
LOS
SW
GW
GW
GW
GW
GW
Sight
770–330 nm400– 900THzvisiblevisible
IR
EHF
SHF
UHF
VHF
HF
MF
LF
VLF
VF
ELF
Name Attenuation
300GHz–400THz
30– 300GHz
3– 30GHz
300–3000MHz
30– 300MHz
3– 30MHz
300–3000kHz
30– 300kHz
3– 30kHz
300–3000 Hz
30– 300 Hz
Frequencies
optical comm.1000–770nminfrared
wireless comm.O2, H2O vapor10– 1mmext. high
wireless comm.O2, H2O100– 10mmsuper high
television, cell tel.cosmic noise1000–100mmultra high
television, FM radiotemp, cosmic10– 1 mvery high
transportationdaytime100– 10 mhigh
maritime, AM radiodaytime1000–100 mmedium
maritimedaytime10– 1kmlow
submarineatmos. noise100– 10kmvery low
voice tel., modem1000–100kmvoice
home automation10– 1Mmext. low
WavelengthDescription
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© James P.G. SterbenzITTC
Wireless Free SpaceCommunication and Radar Bands
• Communication band designations– UHF, VHF, and SHF bands subdivided– ITU-T B.15 and ITU-R V.431-7– IEEE Std. 251
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-16
© James P.G. SterbenzITTC
Wireless Free SpaceCommunication and Radar Bands
television, p2p radio1000–300mm300MHz–1GHzUHF
cordless and mobile phones, satellite300–150mm1–2GHzUHFL
SHF
PSTN relay, satellite, WLAN75– 40mm4–8GHzC
satellite links40– 25mm8–12GHzX
satellite links25– 17mm12–18GHzKu
satellite, µwave links17– 10mm18–27GHzK
satellite, WMAN10– 7.5mm27–40GHzKa
Usage ExamplesRangeBand
future27–.77µm110–300GHzmm
W
V
S
VHF
Name
75–110GHz
40–75GHz
2–4GHz
30– 300MHz
Frequencies
future40– 27µm
emerging WLAN, WMAN7500– 40µmEHF
WLAN, WPAN, WMAN, satellite150– 75mm
television, FM radio10– 1 mVHF
WavelengthPartition
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© James P.G. SterbenzITTC
Wireless SpectrumAllocation
• Spectrum allocationwhat is it?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-18
© James P.G. SterbenzITTC
Wireless SpectrumAllocation
• Spectrum allocation – how to partition among:– application
• broadcast radio, television, data communication, etc.
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-19
© James P.G. SterbenzITTC
Wireless SpectrumAllocation
• Spectrum allocation – how to partition among:– application
• broadcast radio, television, data communication, etc.
– user sector• consumer, business, government, military
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-20
© James P.G. SterbenzITTC
Wireless SpectrumAllocation
• Spectrum allocation – how to partition among:– application
• broadcast radio, television, data communication, etc.
– user sector• consumer, business, government, military
– assignees• entity that is allowed to transmit into spectrum• service providers and/or end users
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© James P.G. SterbenzITTC
Wireless SpectrumAllocation: Governance
• Governance of spectrum allocation• International
– ITU-R: International Telecommunication –Radio Sector www.itu.int/ITU‐R
– began as International Telegraph Union in 1865– now agency under UN mandate
• incentive for UN members to play nice
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-22
© James P.G. SterbenzITTC
Wireless SpectrumAllocation: Governance
• Governance of spectrum allocation• International
– ITU-R: International Telecommunication –Radio Sector www.itu.int/ITU‐R
• National: government agency or appointee– US FCC – Federal Communications Commission
www.fcc.gov
– UK Ofcom – Office of Communicationswww.ofcom.org.uk
– India TRAI – Telecom Regulatory Authority of India www.trai.gov.in
– etc.
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© James P.G. SterbenzITTC
Wireless SpectrumRegulation
• Regulations for transmission within allocation– determined and enforced by governing bodies
• Parameters for allowed communication, e.g.– transmission power– field strength– interference parameters
• transmission energy permitted outside allocation
– geographic limits– date and time restrictions
• e.g. AM radio clear channel interference
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-24
© James P.G. SterbenzITTC
Wireless SpectrumEnforcement
• Enforcement of transmission regulations– enforcement by national entity– e.g. US FCC EB (enforcement bureau) www.fcc.gov/eb
• Can cause international tension– e.g. former border blasters
• e.g. XETRA-AM (Mighty 690) in Tijuana Mexico• now US-Mexico treaty coordinates AM transmission
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© James P.G. SterbenzITTC
Wireless SpectrumLicensing
• Licensed spectrum– most frequency bands require license to transmit– generally issued by national authority (FCC, Ofcom, etc.)
• e.g. broadcast TV, radio, amateur radio, GMRS• e.g. mobile telephony
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-26
© James P.G. SterbenzITTC
Wireless SpectrumLicensing
• Licensed spectrum– most frequency bands require license to transmit– generally issued by national authority (FCC, Ofcom, etc.)
• e.g. broadcast TV, radio, amateur radio, GMRS• e.g. mobile telephony
– some unlicensed bands do not require license to transmit• e.g. US CB (citizen band), FRS (family radio system)• e.g. ISM for cordless telephones and wireless LANS
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© James P.G. SterbenzITTC
Wireless SpectrumLicensing
• Licensed spectrum– most frequency bands require license to transmit– generally issued by national authority (FCC, Ofcom, etc.)
• e.g. broadcast TV, radio, amateur radio, GMRS• e.g. mobile telephony
– some unlicensed bands do not require license to transmit• e.g. US CB (citizen band), FRS (family radio system)• e.g. ISM for cordless telephones and wireless LANS
unlicensed ≠ unregulated!
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-28
© James P.G. SterbenzITTC
Licensed SpectrumBroadcast Radio and Television
transcontinental broadcast radio2.3 – 26.1 MHzAM short wave
US ch.broadcast television54 – 72 MHz76 – 88 MHz
VHF TV ch. 2–4ch. 5–6
broadcast radio520 – 1610 kHzAM medium wave
512 – 698 MHz698 – 806 MHz806 – 894 MHz
174 – 216 MHz
65.9 – 74 MHz76 – 90 MHz87.5 – 108 MHz
153 – 279 kHz
Frequency Range
ch. 18–51UHF TV ch. 52–69
ch. 70–83
VHF TV ch. 7–13
FM radio
AM long wave
Allocation
phasing outreclaimed
broadcast television
US ch.broadcast television
OIRTJapanInternational
broadcast radio
not USbroadcast radio
NotesTypical Use
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© James P.G. SterbenzITTC
Licensed SpectrumSelected Telephony Bands
1710 – 1755 MHzcdma2000, UMTS
Europe890 – 960 MHz1710 – 1880 MHz
GSM
Americas PCS1850 – 1990 MHzIS-95, GSM
2496 – 2690 MHz
2110 – 2155 MHz
824 – 894 MHz
Frequency Band
LTE-A
cdma2000, UMTS, W-CDMA
AMPS, IS-95, GSM
Allocation
Americas
Notes
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-30
© James P.G. SterbenzITTC
Wireless Free SpaceUnlicensed Spectrum
• Unlicensed spectrum– regulations for use (FCC Title 47 Part 18 and 15.243–249)
• max transmit power (e.g. 1W)• field strength• spread spectrum parameters
– ISM: industrial, scientific, and medical• … 900 MHz, 2.4 GHz, 5.8 GHz, 24GHz …
– UNII: unlicensed national information infrastructure• 5.8 GHz
– may be use by anyone for any purpose (subject to regulations)
problem?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-31
© James P.G. SterbenzITTC
Wireless Free SpaceUnlicensed Spectrum
• Unlicensed spectrum– regulations for use (FCC 15.243–249)
• e.g. max transmit power• e.g. spread spectrum parameters
– ISM: industrial, scientific, and medical• … 900 MHz, 2.4 GHz, 5.8 GHz, 24GHz …
– UNII: unlicensed national information infrastructure• 5.8 GHz
– may be use by anyone for any purpose (subject to regulations)
– interference a significant problem• e.g. 2.4 GHz FHSS cordless phones against 802.11b• e.g. interference among 802.11 hubs in dense environments
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-32
© James P.G. SterbenzITTC
Unlicensed SpectrumISM Bands
802.11ad, millimeter-wave links61.250 ± 0.250 GHz61 GHz
27.120 ± 0.163 MHz27 MHz
40.680 ± 0.020 MHz40 MHz
13.560 ± 0.007 MHz13 MHz
245.000 ± 1.000 GHz
122.500 ± 0.500 GHz
24.125 ± 0.125 GHz
5.800 ± 0.075 GHz
2.450 ± 0.050 GHz
915.00 ± 13.00 MHz
433.92 ± 0.87 MHz
6.78 ± 0.15 MHz
Center & BW Freq
245 GHz
122 GHz
24 GHz
5.8 GHz
2.4 GHz
900 MHz
433 MHz
7 MHz
Band
future
future
Microwave mesh link
cordless phones, WLANs (limited use)
cordless phones, WLANs, WPANs
cordless phones, WLANs (historic)
Europe
NotesTypical Use
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-33
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• ITU allocates and regulates international spectrumproblem?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-34
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• ITU allocates and regulates international spectrum– competing national interests– agreement can be difficult– compromises are frequently poor solutions
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-35
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• ITU allocates and regulates international spectrum• Government agencies allocate and regulate spectrum
problem?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-36
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• ITU allocates and regulates international spectrum• Government agencies allocate and regulate spectrum
– competing business, consumer, and government interests– agreement can be difficult– compromises are frequently poor solutions
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© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use : spectrum within defined area
• government, military, public safety, public interest
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-38
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control : license assignment• comparative bidding
– process: broadcasters and service providers submit proposalsproblem?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-39
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding
– process: broadcasters and service providers submit proposals– problem: fairness (real and perception) and appeals
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-40
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding• lottery
– process: assignees picked by lotteryproblem?
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© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding• lottery
– process: assignees picked by lottery– problem: companies bid with intent to resell spectrum
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-42
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding• lottery• auction
– process: competitive auction for spectrumproblem?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-43
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding• lottery• auction
– process: competitive auction for spectrum– problem: complex process
free market but antitrust issues
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-44
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding• lottery• auction
– commons : unlicensed (including ISM)• process: anyone can use subject to regulation
problem?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-45
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– exclusive use
• government, military, public safety, public interest
– command-and-control• comparative bidding• lottery• auction
– commons• process: anyone can use subject to regulation• problem: interference
– among applications (e.g. WLANs, cordless phones, µwave ovens– among providers and users of given application (e.g. WLANs)
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-46
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency rangesproblem?
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© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– problem: very inefficient use of spectrum
why?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-48
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– problem: very inefficient use of spectrum
• spectrum reserved for future use• difficult to reclaim unused spectrum
– example: UHF TV reclaimed for GSM in 850MHz
• inability to load balance among different allocations
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© James P.G. SterbenzITTC
Wireless SpectrumFCC/NTIA Spectrum Allocation
• FCC allocates and licenses spectrum in US– static allocations lead to significant inefficiency in use
[http://www.ntia.doc.gov/osmhome/allochrt.pdf]
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-50
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– problem: very inefficient use of spectrum
• spectrum reserved for future use• difficult to reclaim unused spectrum
– example: UHF TV reclaimed for GSM in 850MHz
• inability to load balance among different allocations
alternative?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-51
© James P.G. SterbenzITTC
Wireless SpectrumAllocation Process
• Spectrum allocated in fixed frequency ranges– problem: very inefficient use of spectrum
• spectrum reserved for future use• difficult to reclaim unused spectrum
– example: UHF TV reclaimed for GSM in 850MHz
• inability to load balance among different allocations
– alternative: dynamic spectrum allocation• significant technical, political, and policy challenges• fear of making things worse• currently hot topic for research
– technical and policy
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-52
© James P.G. SterbenzITTC
Wireless SpectrumDynamic Allocation
• FCC Spectrum Policy Task Force recommendationwww.fcc.gov/sptf– command-and-control should only be used when needed:
• to accomplish important public interest objectives• conform to treaty obligations
– significant expansion of commons allocation
• Dynamic spectrum management– SDR (software defined radios) a key technology– new algorithms and protocols– significant policy change
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Mobile Wireless NetworkingPL.2 Wireless Channels and Propagation
PL.1 Physical media and spectrumPL.2 Wireless channels and propagation
PL.2.1 Digital and analog signalsPL.2.2 Wireless propagationPL.2.3 Channel characteristics and challenges
PL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-54
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPL.2.1 Digital and Analog Signals
PL.1 Physical media and spectrumPL.2 Wireless channels and propagation
PL.2.1 Digital and analog signalsPL.2.2 Wireless propagationPL.2.3 Channel characteristics and challenges
PL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
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© James P.G. SterbenzITTC
CommunicationSignal Types
• Transmission of a signal through a medium
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-56
© James P.G. SterbenzITTC
CommunicationSignal Types
• Transmission of a signal through a medium
• Analog signal: time-varying levels– electrical: voltage levels– photonic: light intensity
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© James P.G. SterbenzITTC
CommunicationSignal Types
• Transmission of a signal through a medium
• Analog signal: time-varying levels– electrical: voltage levels– photonic: light intensity
• Digital signal: sequence of bits represented as levels– electrical: voltage pulses– photonic: light pulses– two levels for binary digital signal
– more levels in some coding schemes more later
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-58
© James P.G. SterbenzITTC
CommunicationDigital vs. Analog
• Digital bits are reconstructed at the receiver
0
1
time
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CommunicationDigital vs. Analog
• Digital bits are reconstructed at the receiver– all transmission is actually analog!– frequency response determines
• pulse rate that can be transmitted• shape of pulse → ability for receiver to recognise pulse
0
1
time
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-60
© James P.G. SterbenzITTC
CommunicationDigital vs. Analog
0
1
harmonic
harmonictime
• Digital bits are reconstructed at the receiver– all transmission is actually analog!– frequency response determines
• pulse rate that can be transmitted• shape of pulse → ability for receiver to recognise pulse
– high-frequency attenuation reduces quality of pulse
attenuated frequencies
adapted from [Tanenbaum 2003]
0
1
time
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 31 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-61
© James P.G. SterbenzITTC
CommunicationDigital vs. Analog in Free Space
• Digital transmission is baseband– frequency spectrum begins at 0Hz– only practical for dedicated (guided media)
• wire and fiber optic cable
• Free space transmission generally broadband– digital information modulated over a range of frequencies
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-62
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPL.2.1 Wireless Propagation
PL.1 Physical media and spectrumPL.2 Wireless channels and propagation
PL.2.1 Digital and analog signalsPL.2.2 Wireless propagationPL.2.3 Channel characteristics and challenges
PL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 32 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-63
© James P.G. SterbenzITTC
Wireless Free SpaceMedium Sharing
• Dedicated– single transmitter attached to medium– signals may be multiplexed by a single transmitter
• link multiplexing
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-64
© James P.G. SterbenzITTC
Wireless Free SpaceMedium Sharing
• Dedicated– single transmitter attached to medium– signals may be multiplexed by a single transmitter
• link multiplexing
• Shared: multiple access– multiple transmitters transmit into a the same medium
Lecture ML
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 33 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-65
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms
• Direct signal• Reflection• Diffraction• Scattering
WN
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-66
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms: Direct
• Direct signal– direct transmission from transmitter to receiver
• Reflection• Diffraction• Scattering
WN
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 34 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-67
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms: Reflection
• Direct signal• Reflection
– reflected off object large relative to wavelength
• Diffraction• Scattering
WN
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-68
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms: Diffraction
• Direct signal• Reflection• Diffraction
– bending by object comparable to wavelength
• Scattering
WN
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 35 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-69
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms: Scattering
• Direct signal• Reflection• Diffraction• Scattering
– by many objects smaller than wavelength– multiple weaker signals
WN
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-70
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms: Multipath
• Multipath– multiple signals using different propagation mechanisms
problem?
WN
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 36 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-71
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Mechanisms: Multipath
• Multipath interference or distortion – multiple signals using different propagation mechanisms– time-shifted versions of signal interfere with one another
WN
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-72
© James P.G. SterbenzITTC
Wireless Free SpaceAntennæ and Transmission Pattern
• Omnidirectional antennæ– RF radiated in all directions
advantages and disadvantages?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 37 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-73
© James P.G. SterbenzITTC
Wireless Free SpaceAntennæ and Transmission Pattern
• Omnidirectional antennæ– RF radiated in all directions– advantage: simple cheap design
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-74
© James P.G. SterbenzITTC
Wireless Free SpaceAntennæ and Transmission Pattern
• Omnidirectional antennæ– RF radiated in all directions– advantage:
simple cheap design– disadvantage:
no spatial reuse
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 38 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-75
© James P.G. SterbenzITTC
Wireless Free SpaceAntennæ and Transmission Pattern
• Omnidirectional antennæ• Directional antennæ
– focused beam of radiationadvantages and disadvantages?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-76
© James P.G. SterbenzITTC
Wireless Free SpaceAntennæ and Transmission Pattern
• Omnidirectional antennæ• Directional antennæ
– focused beam of radiation– advantage
• reduces contention with spatial reuse
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 39 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-77
© James P.G. SterbenzITTC
Wireless Free SpaceAntennæ and Transmission Pattern
• Omnidirectional antennæ• Directional antennæ
– focused beam of radiation– advantage
• reduces contention with spatial reuse– disadvantages
• more complex antenna design• significantly complicates
network design: beam steering MACLecture ML
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-78
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Modes
• Ground-wave propagation < 2 MHz• Sky wave propagation 2 – 30 MHz• Line-of-sight propagation > 30 MHz
ionosphere
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 40 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-79
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Modes: Ground Wave
• Ground-wave propagation < 2 MHz– signals follow curvature of earth– scattered in upper atmosphere
• Sky wave propagation 2 – 30 MHz• Line-of-sight propagation > 30 MHz
ionosphere
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-80
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Modes: Sky Wave
• Ground-wave propagation < 2 MHz• Sky wave propagation 2 – 30 MHz
– signals refracted off ionosphere– communication possible over thousands of kilometers
• Line-of-sight propagation > 30 MHz
ionosphere
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 41 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-81
© James P.G. SterbenzITTC
Wireless Free SpacePropagation Modes: Line of Sight
• Ground-wave propagation < 2 MHz• Sky wave propagation 2 – 30 MHz• Line-of-sight propagation > 30 MHz
– antennæ must be in view of one-another– terrain and earth curvature block signature
ionosphere
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-82
© James P.G. SterbenzITTC
Wireless Free SpaceSpectrum Table
Usage ExamplesPropagationRangeBand
LOS
LOS
LOS
LOS
LOS
LOS
SW
GW
GW
GW
GW
GW
Sight
770–330 nm400– 900THzvisiblevisible
IR
EHF
SHF
UHF
VHF
HF
MF
LF
VLF
VF
ELF
Name Attenuation
300GHz–400THz
30– 300GHz
3– 30GHz
300–3000MHz
30– 300MHz
3– 30MHz
300–3000kHz
30– 300kHz
3– 30kHz
300–3000 Hz
30– 300 Hz
Frequencies
optical comm.1000–770nminfrared
wireless comm.O2, H2O vapor10– 1mmext. high
wireless comm.O2, H2O100– 10mmsuper high
television, cell tel.cosmic noise1000–100mmultra high
television, FM radiotemp, cosmic10– 1 mvery high
transportationdaytime100– 10 mhigh
maritime, AM radiodaytime1000–100 mmedium
maritimedaytime10– 1kmlow
submarineatmos. noise100– 10kmvery low
voice tel., modem1000–100kmvoice
home automation10– 1Mmext. low
WavelengthDescription
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 42 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-83
© James P.G. SterbenzITTC
Wireless Free SpaceVelocity
• Velocity v = c /n [m/s]– speed of light c = 3×105 km/s– index of refraction n
Consequences?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-84
© James P.G. SterbenzITTC
Wireless Free SpaceVelocity and Delay
• Velocity v = c /n [m/s]– speed of light c = 3×105 km/s– index of refraction n
• this is why velocity slower than c in fiber and wire
• Delay d = 1/v [s/m]– generally we will express delay in [s] given a path length
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 43 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-85
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPL.2.3 Channel Characteristics and Challenges
PL.1 Physical media and spectrumPL.2 Wireless channels and propagation
PL.2.1 Digital and analog signalsPL.2.2 Wireless propagationPL.2.3 Channel characteristics and challenges
PL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-86
© James P.G. SterbenzITTC
Wireless ChannelCharacteristics and Challenges
• Goal for communications link– receiver reconstructs signal transmitter sent– propagation (PL.2.2)
• Challenges to meeting this goal– path loss and attenuation– fading– noise and interference– Doppler Shift– transmission rate constraints
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 44 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-87
© James P.G. SterbenzITTC
Wireless Channel ChallengesPath Loss and Attenuation
• Path loss and attenuation• Fading• Noise and interference• Doppler Shift• Transmission rate constraints
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-88
© James P.G. SterbenzITTC
Path Loss and AttenuationTransmission Length
• Link Length– distance over which signals propagate– constrained by physical properties of medium
Consequences?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 45 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-89
© James P.G. SterbenzITTC
Path Loss and AttenuationTransmission Length
• Attenuation: decrease in signal intensity– over distance expressed as [dB/m]– at a particular signal frequency
how to compute?
dB
m
mdB
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-90
© James P.G. SterbenzITTC
Path Loss and AttenuationTransmission Length
• Attenuation– signal strength decreases as 1/r 2 in perfect medium
why?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 46 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-91
© James P.G. SterbenzITTC
Path Loss and AttenuationTransmission Length
• Attenuation– signal strength decreases as 1/r 2 in perfect medium– signal may decrease as 1/r x with multipath interference
• rural environments: x > 2• urban environments: x → 4
more later
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-92
© James P.G. SterbenzITTC
Path Loss and AttenuationFrequency Response
• Attenuation: decrease in signal intensity– over distance expressed as [dB/m]– at a particular signal frequency
• Frequency response of media– wire: generally falls off above a certain fmax
– fiber optic cable & free space transparent to certain rangesanalogy:UV blocking sunglasses (high attenuation )
vs.standard glass (moderate attenuation )
vs.UV transparent black light glass (low attenuation )
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 47 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-93
© James P.G. SterbenzITTC
Path Loss and AttenuationSpectrum Table: Frequency Response
Usage ExamplesPropagationRangeBand
LOS
LOS
LOS
LOS
LOS
LOS
SW
GW
GW
GW
GW
GW
Sight
770–330 nm400– 900THzvisiblevisible
IR
EHF
SHF
UHF
VHF
HF
MF
LF
VLF
VF
ELF
Name Attenuation
300GHz–400THz
30– 300GHz
3– 30GHz
300–3000MHz
30– 300MHz
3– 30MHz
300–3000kHz
30– 300kHz
3– 30kHz
300–3000 Hz
30– 300 Hz
Frequencies
optical comm.1000–770nminfrared
wireless comm.O2, H2O vapor10– 1mmext. high
wireless comm.O2, H2O100– 10mmsuper high
television, cell tel.cosmic noise1000–100mmultra high
television, FM radiotemp, cosmic10– 1 mvery high
transportationdaytime100– 10 mhigh
maritime, AM radiodaytime1000–100 mmedium
maritimedaytime10– 1kmlow
submarineatmos. noise100– 10kmvery low
voice tel., modem1000–100kmvoice
home automation10– 1Mmext. low
WavelengthDescription
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-94
© James P.G. SterbenzITTC
Path Loss and AttenuationFrequency Response
• Atmospheric transparency bands– RF: 10MHz – 10GHz
• VHF meter band, UHF millimeter band– Infrared: N-band
RF
0.5
1.0
0.0
Atm
osph
eric
Opa
city
Wavelength [m] | Frequency [Hz]
10µm0.1nm 10nm 10m 100m 1km1m10cm1cm1mm100µm1µm1nm 100nm
adapted from[coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html]
10THz1EHz 10Pz 10MHz 1MHz 100KHz100MHz1GHz10GHz100GHz1THz100THz100PHz 1PHz
IR
UHF VHF
microwave shortwave
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 48 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-95
© James P.G. SterbenzITTC
Wireless Channel ChallengesFading
• Path loss and attenuation• Fading• Noise and interference• Doppler Shift• Transmission rate constraints
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-96
© James P.G. SterbenzITTC
Wireless Channel FadingDefinition
• Channel fading– changes of signal intensity over time
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 49 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-97
© James P.G. SterbenzITTC
Wireless Channel FadingTypes and Cause
• Channel fading– changes of signal intensity over time
• Fast fading– rapid fluctuations in intensity– mobility on the order of 1/2 wavelength
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-98
© James P.G. SterbenzITTC
Wireless Channel FadingTypes and Cause
• Channel fading– changes of signal intensity over time
• Fast fading– rapid fluctuations in intensity– mobility on the order of 1/2 wavelength
• Slow fading– long-term fluctuations in intensity (seconds to minutes)
causes?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 50 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-99
© James P.G. SterbenzITTC
Wireless Channel FadingTypes and Cause
• Channel fading– changes of signal intensity over time
• Fast fading– rapid fluctuations in intensity– mobility on the order of 1/2 wavelength
• Slow fading– long-term fluctuations in intensity (seconds to minutes)– causes
• obstructions such as rain (rain fade )• micro-mobility among buildings in urban areas• macro-mobility between base stations
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-100
© James P.G. SterbenzITTC
Wireless Channel FadingTypes and Cause
• Channel fading– changes of signal intensity over time
• Flat fading (nonselective)– uniform fade across frequency range
• Selective fading– different frequency components suffer different attenuation
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 51 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-101
© James P.G. SterbenzITTC
Wireless Channel ChallengesInterference
• Path loss and attenuation• Fading• Noise and interference• Doppler Shift• Transmission rate constraints
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-102
© James P.G. SterbenzITTC
Noise and InterferenceDefinition
• Superposition interaction of waves is interferenceCauses?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 52 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-103
© James P.G. SterbenzITTC
Noise and InterferenceCauses
• Superposition interaction of waves is interference• Causes
– noise– co-channel interference– adjacent channel interference
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-104
© James P.G. SterbenzITTC
NoiseCauses
• Noise interferes with signals• Thermal noise [W/Hz]
– caused by agitation of electrons: function of temperature t– independent of frequency: white noise
N = kTB ; k = 1.38×10-23 [J/K] (Boltzmann constant)B = bandwidth [Hz]
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 53 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-105
© James P.G. SterbenzITTC
NoiseCause and Effect: SNR
• Noise interferes with signals• Thermal noise [W/Hz] = [(J/s)/s–1] = [J]
– caused by agitation of electrons: function of temperature t– independent of frequency: white noise
N = kTB ; k = 1.38×10-23 [J/K] (Boltzmann constant)B = bandwidth [Hz]
• Background noise No– thermal noise + other sources (e.g. cosmic radiation)– No interferes with the signal bit energy Eb
– SNR: signal to noise ratio = 10 log10 (Eb /No ) [db] (decibels)
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-106
© James P.G. SterbenzITTC
InterferenceCo-Channel Interference
• Co-channel interference within given frequency bandCauses and solutions?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 54 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-107
© James P.G. SterbenzITTC
InterferenceCo-Channel Interference
• Co-channel interference within given frequency band• Multiple users sharing channel
– motivates medium access control (MAC) Lecture ML
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-108
© James P.G. SterbenzITTC
InterferenceCo-Channel Interference
• Co-channel interference within given frequency band• Multiple users sharing channel
– motivates medium access control (MAC) Lecture ML
• Malicious attack: jamming of channel– faraday cage to repel – spread spectrum techniques Lecture ML– resilience techniques EECS 983
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 55 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-109
© James P.G. SterbenzITTC
InterferenceCo-Channel Interference
• Co-channel interference within given frequency band• Multiple users sharing channel
– motivates medium access control (MAC) Lecture ML
• Malicious attack: jamming of channel– Faraday cage to isolate when possible – spread spectrum techniques Lecture ML– resilience techniques EECS 983
• Natural phenomena– e.g. sunspots
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-110
© James P.G. SterbenzITTC
InterferenceAdjacent Channel Interference
Solutions?
• Adjacent channel interference between freq. bands
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 56 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-111
© James P.G. SterbenzITTC
InterferenceCo-Channel Interference
Guard bands– reserved bandwidth between frequency bands
• Adjacent channel interference between freq. bands
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-112
© James P.G. SterbenzITTC
InterferenceAdjacent Channel Interference
• Spatial partitioning– adjacent channels not used in same geographic area
• e.g. TV broadcast channels (2,4,5,7,9,11,13 vs. 3,6,8,10,12)• e.g. FM broadcast stations • e.g. cellular frequency plan for mobile telephony
• Adjacent channel interference between freq. bands
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 57 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-113
© James P.G. SterbenzITTC
InterferenceAdjacent Channel Partitioning: Broadcast TV
• Spatial partitioning example: broadcast television– large cities get channels 2,4,5,7,9,11,13
recall guard band between 4/5 and 6/7– small towns in-between get channels 3,6,8,10,12
• Spatial partitioning example: broadcast FM radio– adjacent frequencies not used in same city
METROPOLISCh. 2,4,5,11GOTHAM
Ch. 2,4,5,7,9,11,13
SmallvilleCh. 10, 12
Elk’s BreathCh. 6
MayberryCh. 3,8
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-114
© James P.G. SterbenzITTC
InterferenceAdjacent Channel Partitioning: Cellular
• Spatial partitioning example: cellular telephony– most efficient circular packing is hexagonal– frequency channels mapped to hexagonal tiling– adjacent cells assigned different frequencies Lecture MT
cell
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-115
© James P.G. SterbenzITTC
Wireless Channel ChallengesDoppler Shift
• Path loss and attenuation• Fading• Noise and interference• Doppler Shift• Transmission rate constraints
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-116
© James P.G. SterbenzITTC
Doppler ShiftDefinition
• Doppler shift– explained by Austrian scientist Christian Doppler in 1800s
what is it?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 59 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-117
© James P.G. SterbenzITTC
Doppler ShiftDefinition
• Doppler shift– explained by Austrian scientist Christian Doppler in 1800s– wavelength changes with relative velocity– recall decreasing pitch of horn as train passes
• Doppler effectfd = v/λ
Consequences?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-118
© James P.G. SterbenzITTC
Doppler ShiftConsequences
• Doppler shift– explained by Austrian scientist Christian Doppler in 1800s– wavelength changes with relative velocity– recall decreasing pitch of horn as train passes
• Doppler effectfd = v/λ
• Consequences– frequency perceived by receiver different from expected– concern networks with high node mobility
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 60 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-119
© James P.G. SterbenzITTC
Wireless Channel ChallengesTransmission Rate Constraints
• Path loss and attenuation• Fading• Propagation modes and interference• Doppler Shift• Transmission rate constraints
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-120
© James P.G. SterbenzITTC
Transmission Rate ConstraintsOverview
• Transmission rate constraints– transceiver switching frequency– Nyquist rate– Shannon rate
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 61 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-121
© James P.G. SterbenzITTC
Transmission Rate ConstraintsSwitching Frequency
• Rate constrained by switching frequency– transmitter and receiver [b/s]– dictated by electronic circuits
• switching time of transistors• propagation delay through circuits
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-122
© James P.G. SterbenzITTC
Transmission Rate ConstraintsNyquist Rate
• Channel capacity C [b/s]– determined by bandwidth
(max CS bandwidth determined by EE bandwidth)– constrained by number of quantization levels per bit
C = 2B log2 LB = channel bandwidth [Hz] = [1/s]L = number of quantization levels
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 62 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-123
© James P.G. SterbenzITTC
Transmission Rate ConstraintsShannon Theorem
• Maximum data rate for noisy channel– noise reduces data rate
C = B log2 (1+ S/N ))C = channel capacity [b/s]B = channel bandwidth [Hz] = [1/s]S = signal power [dB]N = noise power [dB]
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-124
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPL.3 Modulation, Coding, and Error Control
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error control
PL.3.1 Modulation and codingPL.3.2 Error control
PL.4 Mobile wireless environment
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
– 63 –
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-125
© James P.G. SterbenzITTC
Mobile Wireless NetworkingPL.3.1 Modulation and Coding
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error control
PL.3.1 Modulation and codingPL.3.2 Error control
PL.4 Mobile wireless environment
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-126
© James P.G. SterbenzITTC
Modulation and CodingDigital Communication
• Digital Communication– we consider only digital communication for networking
• transmission of binary data (bits) through a channel
– recall: in free space digital signal is analog modulated• broadband, not baseband
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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© James P.G. SterbenzITTC
Modulation and CodingLine Coding
• Line coding– way in which bits are encoded for transmission– digital codes (binary, trinary, …)– analog modulation
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-128
© James P.G. SterbenzITTC
Modulation and CodingLine Coding and Symbol Rate
• Line coding– way in which bits are encoded for transmission– digital codes (binary, trinary, …) EECS 780– analog modulation
• Symbol rate– baud rate [symbols/s]
• baud = b/s only if one symbol/bit
– clever encodings (e.g. QAM) allow high baud rates
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-129
© James P.G. SterbenzITTC
Line CodingAnalog Coding
• Analog line coding– modulate an analog carrier
with a digital signal
0 0 1 0 0 1 0 1 1 1
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-130
© James P.G. SterbenzITTC
Analog Line CodingAmplitude Modulation
• Analog line coding– modulate an analog carrier
• Amplitude modulation– each symbol a different level of carrier
• one may be zero voltage
– compare to AM radio• modulate an analog carrier with
an analog signal
0 0 1 0 0 1 0 1 1 1
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-131
© James P.G. SterbenzITTC
Analog Line CodingFrequency Modulation
• Analog line coding– modulate a carrier
• Amplitude modulation– each symbol a different level
• Frequency modulation– each symbol a different frequency– FSK (frequency shift keying)– compare to FM radio
• modulate an analog carrier withan analog signal
0 0 1 0 0 1 0 1 1 1
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-132
© James P.G. SterbenzITTC
Analog Line CodingPhase Modulation
• Analog line coding– modulate a carrier
• Amplitude modulation– each symbol a different level
• Frequency modulation– each symbol a different frequency
• Phase modulation– each symbol a different phase– e.g. 0°, 180°
0 0 1 0 0 1 0 1 1 1
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-133
© James P.G. SterbenzITTC
Analog Line CodingCombination Codes
• Analog line coding: – modulate a carrier
• Amplitude modulation– each symbol a different level
• Frequency modulation– each symbol a different frequency
• Phase modulation– each symbol a different phase
• Combinations possiblewhy?
0 0 1 0 0 1 0 1 1 1
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-134
© James P.G. SterbenzITTC
Analog Line CodingCombination Codes
• Analog line coding: – modulate a carrier
• Amplitude modulation– each symbol a different level
• Frequency modulation– each symbol a different frequency
• Phase modulation– each symbol a different phase
• Combinations possible– e.g. amplitude and phase
0 0 1 0 0 1 0 1 1 1
00 10 01 01 11 00 10 01 01 11
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-135
© James P.G. SterbenzITTC
Analog Line CodingQPSK and QAM
• Combination of amplitude- and phase-modulation– allows more bits per symbol
• QAM: quadrature amplitude modulation– quadrature = 4 phases carried on two sine waves– PAM is case for only one phase– QPSK is case for only one amplitude
844QAM-256
643QAM-64
442QAM-16
241QPSK
Bits/SymbolPhasesAmplitudesName
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-136
© James P.G. SterbenzITTC
Analog Line CodingQPSK and QAM
• QAM: amplitude- and phase modulation• Represented by constellation diagram
– amplitude is distance from origin– phase is angle
0°180°
90°
270°
0°180°
90°
270°
0°180°
90°
270°
QAM-64QAM-16QPSK
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Mobile Wireless NetworkingPL.3.2 Error Control
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error control
PL.3.1 Modulation and codingPL.3.2 Error control
PL.4 Mobile wireless environment
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-138
© James P.G. SterbenzITTC
Error ControlIntroduction and Motivation
Motivation for error control?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-139
© James P.G. SterbenzITTC
Error ControlIntroduction and Motivation
• Motivation for error control– channels are imperfect
• cause: noise and interference• result: bit errors
– components can fail– packets my be dropped due to congestion EECS 780
• Therefore need error controlwhere to perform?
physical layer?link layer?transport layer?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-140
© James P.G. SterbenzITTC
Error ControlHop-by-Hop vs. End-to-End
• Per-hop error control for frame transfersWhy?
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-141
© James P.G. SterbenzITTC
Error ControlHop-by-Hop vs. End-to-End
• Per-hop error control for frame transfers• Recall end-to-end arguments:
– if error checking and correction needed E2E …… it must be done end-to-end by transport (or application)
• Hop-by-hop control to improve overall performance– physical layer for bit errors in noisy channel– link layer at frame granularity Lecture ML
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-142
© James P.G. SterbenzITTC
Error ControlDetection Techniques
• Byte, word, or (small) block: done at physical layer– parity– 2-dimensional parity– Hamming codes
• Frame: done at link layer Lecture ML– checksum– CRC
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-143
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Block Error DetectionParity
• Parity: detect single errors– no ability to correct errors– only an odd number of bit errors detected
• only useful if bit error probability very low
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-144
© James P.G. SterbenzITTC
Block Error DetectionParity
• Parity: detect single errors– no ability to correct errors– only an odd number of bit errors detected
• only useful if bit error probability very low
• Parity bit covers n bit block• Even parity: even number of 1s (including parity)
– example: 0111 0001 1010 1011 ?
• Odd parity odd number of 1s (including parity)– example: 0111 0001 1010 1011 ?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-145
© James P.G. SterbenzITTC
Block Error DetectionParity
• Parity: detect single errors– no ability to correct errors– only an odd number of bit errors detected
• only useful if bit error probability very low
• Parity bit covers n bit block• Even parity: even number of 1s (including parity)
– example: 0111 0001 1010 1011 1
• Odd parity odd number of 1s (including parity)– example: 0111 0001 1010 1011 0
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-146
© James P.G. SterbenzITTC
Block Error Detection & Correction2-Dimensional Parity
• 2-dimensional parity: correct single bit errors– detects which bit flipped and can therefore correct
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-147
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Block Error Detection & Correction2-Dimensional Parity
• 2-dimensional parity: correct single bit errors– detects which bit flipped and can therefore correct
• n + m parity bits covers n × m bit block– n row parity bits cover m data bits each– m column parity bits cover n data bits each
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-148
© James P.G. SterbenzITTC
Block Error Detection & Correction2-Dimensional Parity
• 2-dimensional parity: correct single bit errors– detects which bit flipped and can therefore correct
• n + m parity bits covers n × m bit block– n row parity bits cover m data bits each– m column parity bits cover n data bits each
• Example (odd parity)0111 00001 01010 11011 01000
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-149
© James P.G. SterbenzITTC
Block Error Detection & Correction2-Dimensional Parity
• 2-dimensional parity: correct single bit errors– detects which bit flipped and can therefore correct
• n + m parity bits covers n × m bit block– n row parity bits cover m data bits each– m column parity bits cover n data bits each
• Example (odd parity)0111 0 0111 00001 0 0001 01010 1 1110 1 ← detects and can correct flip1011 0 1011 01000 1000
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-150
© James P.G. SterbenzITTC
Block Error Detection & CorrectionHamming Codes
• Hamming codes: correct single bit errors– detects which bit flipped and can therefore correct– k parity bits per block cover different sets of n data bits
KU EECS 882 – Mobile Wireless Networking – Physical Layer and Mobile Wireless Environment
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-151
© James P.G. SterbenzITTC
Block Error Detection & CorrectionHamming Codes
• Hamming codes: correct single bit errors– detects which bit flipped and can therefore correct– k parity bits per block cover different sets of n data bits
• SECDED: single error correct double error detect
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-152
© James P.G. SterbenzITTC
Block Error Detection & CorrectionHamming Codes
• Hamming codes: correct single bit errors– detects which bit flipped and can therefore correct– k parity bits per block cover different sets of n data bits
• SECDED: single error correct double error detect• Example 4 data bits covered by 3 parity bits
– parity bits p2 p1 p0 interleaved with data bits d3 d2 d1 d0
1011010 d3 d2 d1 p2 d0 p1 p0
1‐1‐0‐1 d3 d1 d0 covered by p0
10‐‐00‐ d3 d2 d0 covered by p1
1011‐‐‐ d3 d2 d1 covered by p2
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-153
© James P.G. SterbenzITTC
Block Error Detection & CorrectionHamming Codes
• Hamming codes: correct single bit errors– detects which bit flipped and can therefore correct– k parity bits per block cover different sets of n data bits
• SECDED: single error correct double error detect• Example 4 data bits covered by 3 parity bits
– parity bits p2 p1 p0 interleaved with data bits d3 d2 d1 d0
1011010 d3 d2 d1 p2 d0 p1 p0 11110101‐1‐0‐1 d3 d1 d0 covered by p0 1‐1‐0‐110‐‐00‐ d3 d2 d0 covered by p1 11‐‐00‐ p1 detects error1011‐‐‐ d3 d2 d1 covered by p2 1111‐‐‐ p2 detects error
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-154
© James P.G. SterbenzITTC
Error Detection & CorrectionForward Error Correction
• Forward error correction (FEC)– redundant information added to data– allows detection of errors– also allows correction of errors
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-155
© James P.G. SterbenzITTC
Error Detection & CorrectionForward Error Correction
• Forward error correction (FEC)– redundant information added to data– allows detection of errors– also allows correction of errors
• Types of FEC codes– block codes: FEC header over link layer frame Lecture ML– convolutional code: redundant bits interspersed in stream– turbo codes: iterative convolutional coder
• performs closer to theoretical Shannon limit
EECS 869
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-156
© James P.G. SterbenzITTC
Forward Error CorrectionConvolutional Coder
• Convolutional code– redundant bits interspersed in stream
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-157
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Mobile Wireless NetworkingPL.4 Mobile Wireless Environment
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
PL.4.1 Network impact of wireless channelPL.4.2 Network impact of mobility
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-158
© James P.G. SterbenzITTC
Mobile Wireless EnvironmentImpact on the Network
• Recap: brief introduction to physical layerWhy does this matter to the network?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-159
© James P.G. SterbenzITTC
Mobile Wireless EnvironmentImpact on the Network
• Recap: brief introduction to physical layer• Network consists of nodes interconnected by links
– characteristics of links and nodes impact network
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-160
© James P.G. SterbenzITTC
Mobile Wireless EnvironmentImpact on the Network
• Recap: brief introduction to physical layer• Network consists of nodes interconnected by links
– characteristics of links and nodes impact network
• Traditional PSTN and Internet– static (non-mobile) nodes– reliable wired links– many design decisions based on these assumptions
What is different and why does it matter?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-161
© James P.G. SterbenzITTC
Mobile Wireless EnvironmentPL.4.1 Network Impact of Wireless Channel
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
PL.4.1 Network impact of wireless channelPL.4.2 Network impact of mobility
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-162
© James P.G. SterbenzITTC
Impact of Wireless ChannelChannel Connectivity
Impact of wireless channel on connectivity?
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-163
© James P.G. SterbenzITTC
Wireless ChannelChannel Connectivity
• Weak time-varying connectivity– limited bandwidth of shared medium– time-varying channel capacity
• noise• interference• fading
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-164
© James P.G. SterbenzITTC
Wireless ChannelChannel Connectivity
• Weak time-varying connectivity• Intermittent and episodic connectivity
– long fades (e.g. rain fades)– interference and jamming
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Wireless ChannelChannel Connectivity
• Weak time-varying connectivity• Intermittent and episodic connectivity• Asymmetric connectivity due to heterogeneous nodes
– unequal transmitter power• design• available power over battery life
– different up/downlink characteristics• mobile phones• satellite links
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-166
© James P.G. SterbenzITTC
Wireless ChannelImpact of Weak Connectivity
• Traditional networks– strong symmetric connectivity assumed– weak connectivity treated as failure
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© James P.G. SterbenzITTC
Wireless ChannelImpact of Weak Connectivity
• Traditional networks– strong symmetric connectivity assumed– weak connectivity treated as failure
Impact of weak connectivity?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-168
© James P.G. SterbenzITTC
Wireless ChannelImpact of Weak Connectivity
• Traditional networks– strong symmetric connectivity assumed– weak connectivity treated as failure
• Impact of weak connectivity– bit errors → packet loss → performance impact– link failures → routing reconvergence– loss discrimination important Lecture WI
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Wireless ChannelImpact of Weak Connectivity
• Traditional networks– strong symmetric connectivity assumed– weak connectivity treated as failure
• Impact of weak connectivity– bit errors → packet loss → performance impact– link failures → routing reconvergence– loss discrimination important Lecture WI
• Mobile wireless networks– weak, asymmetric, intermittent, episodic connectivity routine– network architecture and protocol design for this
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-170
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• Millimeter-wave links– 60–90 GHz, 1–10 Gb/s– severe rain attenuation
• Mesh architecture– high degree of connectivity– alternate diverse paths
• WDTN solution– reroute before failures occur– avoid high error links– P-WARP, XL-OSPF
[Jabbar Rohrer Oberthaler Çetinkaya Frost Sterbenz 2009]
Example Weak Connectivity ScenarioWDTN Millimeter-Wave Mesh Network
802.163–4G
CO/POP
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Wireless ChannelOpen Channel
• Open channelproblems?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-172
© James P.G. SterbenzITTC
Wireless ChannelOpen Channel
• Open channel subject to attack– eavesdropping
• network and traffic analysis
– interference• jamming and denial of service
– injection of bogus signalling and control messages
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© James P.G. SterbenzITTC
Wireless ChannelImpact of Open Channel
• Open channel subject to attack– eavesdropping
• network and traffic analysis
– interference• jamming and denial of service
– injection of bogus signalling and control messages
• Security and resilience more importantLecture RSECS 983
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-174
© James P.G. SterbenzITTC
Mobile Wireless EnvironmentPL.4.2 Network Impact of Mobility
PL.1 Physical media and spectrumPL.2 Wireless channels and propagationPL.3 Modulation, coding, and error controlPL.4 Mobile wireless environment
PL.4.1 Network impact of wireless channelPL.4.2 Network impact of mobility
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Impact of MobilityOverview
Impact of mobility?
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-176
© James P.G. SterbenzITTC
Impact of MobilityOverview
• Impact of mobility– connectivity– dynamic topologies– QoS
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Impact of MobilityConnectivity
• Mobility impacts connectivity– nodes move in and out of range of one another– long fades– episodic and intermittent connectivity
• Design for weak connectivity– as for wireless channel impacts
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-178
© James P.G. SterbenzITTC
Impact of MobilityDynamic Topologies
• Mobility means nodes and subnets move– result: dynamic topology– changing links, clustering, and federation topology– difficult to achieve routing convergence– mobility may exceed ability of control loops to react
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22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-179
© James P.G. SterbenzITTC
Impact of MobilityDynamic Topologies
• Mobility means nodes and subnets move– result: dynamic topology– changing links, clustering, and federation topology– difficult to achieve routing convergence– mobility may exceed ability of control loops to react
• Design for mobility– addressing mechanisms must not assume static location– routing algorithms must assume dynamic topologies
• predictive• reactive
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-180
© James P.G. SterbenzITTC
Impact of MobilityQuality of Service
• Mobility impacts QoS (quality of service)
1
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Impact of MobilityQuality of Service
• Mobility impacts QoS (quality of service)– changes in inter-node distance
• requires power adaptation• changes node density and impacts degree of connectivity
– latency issues (routing optimisations temporary)
2
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-182
© James P.G. SterbenzITTC
Impact of MobilityQuality of Service
• Mobility impacts QoS (quality of service)– changes in inter-node distance
• requires power adaptation• changes node density and impacts degree of connectivity
– latency issues (routing optimisations temporary)
3
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Airborne Telemetry NetworkingScenario and Environment
• Very high relative velocity– Mach 7 ≈ 10 s contact– dynamic topology
• Communication channel– limited spectrum– asymmetric links
• data down omni• C&C up directional
• Multihop– among TAs– through relay nodes
GSGS
RN
TATA
TAs
Internet
GWGW
TA – test articleRN – relay node
GS – ground stationGW – gateway
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-184
© James P.G. SterbenzITTC
Mobile Wireless EnvironmentImpact on Network
• Now we are ready for the rest of the course…
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Physical LayerFurther Reading
• William Stallings,Data and Computer Communications, 8th ed.Pearson Prentice Hall, Upper Saddle River NJ, 2007.
22 August 2011 KU EECS 882 – Mobile Wireless Nets – Phy. Layer & Env. MWN-MW-186
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Physical LayerAcknowledgements
Some material in these foils is based on the textbook• Murthy and Manoj,
Ad Hoc Wireless Networks:Architectures and Protocols
Significant material in these foils enhanced from EECS 780 foils