Ultra-Wideband (UWB) Wireless Communications

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UltraUltra--Wideband (UWB) Wideband (UWB) Wireless CommunicationsWireless Communications

Robert QiuRobert QiuAssociate Professor Associate Professor

Tennessee Technological UniversityTennessee Technological [email protected]

Presented at Army Research LabPresented at Army Research LabAdelphi, Maryland,Adelphi, Maryland,

June 4, 2004June 4, 2004

Robert QiuWireless Networking Systems Lab TTU

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OutlineOutlineIntroductionIntroductionUWB Principles UWB Principles IEEE 802.15.3a/IEEE 802.15.4a IEEE 802.15.3a/IEEE 802.15.4a –– Receiver Design Challenges Receiver Design Challenges –– OFDM and PulseOFDM and Pulse--based UWBbased UWB

PhysicsPhysics--Based Optimum Receiver StructuresBased Optimum Receiver Structures–– Communication Theory and Physics (Communication Theory and Physics (GaborGabor 1953)1953)

Conclusion Conclusion


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Wireless Networking Systems LabWireless Networking Systems Lab

Established Aug. 1 2003Established Aug. 1 2003UWB/3G/4G physical layer and cellular network levelsUWB/3G/4G physical layer and cellular network levelsRadio Propagation and Channel ModelingRadio Propagation and Channel ModelingReceiver analysis and designReceiver analysis and designHardware prototypingHardware prototypingWorking with industrial and DOD R&D organizations. Working with industrial and DOD R&D organizations. 10+ years R&D experiences in wireless communications10+ years R&D experiences in wireless communications


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Mobile Devices Market Mobile Devices Market SegmentationSegmentation

Nokia3330

Add-OnDevices

Business /SmartPhones

BasicPhones

Data Devicesw/ IntegralWireless

Modules -Embedded AppsTelematics / Telemetry

Ericsson R380

PDQ Smart Phone

Palm

RIM Blackberry

HP Jornada 720 w/ PC Card

HandSpring Visor,Spring Board Modules

Greater Multi-Media CapabilityLarger Displays / Touch-Screensand Keyboards

Multi Wireless Modes& Generally Higher Data Rates


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WCDMA

EDGE

CDMA2000Wide Area

Network

Local Area

Network

3G & UWB Combining Air Interface3G & UWB Combining Air Interface

WLAN UWB

Not to Scale1 Wide Area cell = ~10 000 WLAN cells

Complementing Technologies

Personal Area

Network

3G


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Broadband services:Cable, xDSL,Satelite,

Terestrial

PDA

Camcorder

DVD

Desktopcomputer

Printer

DigitalCamera

LaptopcomputerTV

Hom e Ga tew ay

Monitor

Audio

The UWB Home Wireless Network

© IEEE 802.15.3a


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UWB Communications & Sensor NetworksUWB Communications & Sensor NetworksApplicationsApplications

• Remote surveillance, threat detection• Video to the foxhole/battlefield• High-resolution location services

Key TechnologiesKey Technologies• Ultra-wide band systems • Mobile, adhoc networks• Data fusion / synthesis

Open Research IssuesOpen Research IssuesOpen Research Issues• Pulse Propagation • Optimum Receiver• Test-bed development / trials

• Real-time• Distributed• Dynamic• Hostile

EnvironmentsEnvironments

IEEE 802.15.4a DARPA Networking in Extreme Environments (NETEX)


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What Is UltraWhat Is Ultra--Wideband (UWB)?Wideband (UWB)?Definition (In radar,etc)Definition (In radar,etc)

Or greater than Or greater than 500 500 MHz (FCC MHz (FCC Feb 2002Feb 2002))At FCC Part 15 powers (a few tens of At FCC Part 15 powers (a few tens of microwattsmicrowatts total total --across several GHz), cannot be reliably measured below across several GHz), cannot be reliably measured below 10 dB down points10 dB down points

fu-flfu+fl

2 ≥ 0.25=25%

Where:fu= upper 10 dB down pointfl = lower 10 dB down point


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7.5 GHz UWB Spectrum Allocated by FCC 02/20037.5 GHz UWB Spectrum Allocated by FCC 02/2003


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Time Modulated UltraTime Modulated Ultra--WidebandWideband——An An ExampleExample

Not a Not a sinewavesinewave, but , but millions of pulses per millions of pulses per secondsecond

Time coded to make Time coded to make noisenoise--likelike

–– ChannelizationChannelization–– AntiAnti--jamjam–– SmoothsSmooths spectrumspectrum

Pulse position Pulse position modulationmodulation

500 ps

Time

Randomized Time CodingA

mpl

itude

δ δ

δ = 125 ps

“0” “1”

Pow

er S

pect

ralD

ensi

ty(d

B)

-80

-40

0

Frequency (GHz)1 2 3 4 5

Frequency (GHz)

Random noise signal


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UWB UWB FCC allocated 7.5 GHz unlicensed spectrum (2002)FCC allocated 7.5 GHz unlicensed spectrum (2002)Requires shift in thinkingRequires shift in thinkingShort “Pulses” are building blocks.Short “Pulses” are building blocks.Fading is not a major issue Fading is not a major issue Too many resolvable quasiToo many resolvable quasi--static pulses static pulses Pulse distortion Pulse distortion Deterministic solutions from Maxwell’s equations Deterministic solutions from Maxwell’s equations UWB radio may be good for low data rate (<a few Mb/s) UWB radio may be good for low data rate (<a few Mb/s) applications (IEEE 802.15.4a)applications (IEEE 802.15.4a)


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Experimental SetupExperimental Setup

0.5 ns pulse


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UWB Pulse SpectrumUWB Pulse Spectrum


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IndoorIndoor


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OutdoorOutdoor

Flat grass ground

Reflection frombuildings


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Representative Measurements (USC)Representative Measurements (USC)

1000 1050 1100 1150 1200 1250-15

-10

-5

0

5

10

15

time (nanoseconds)

984 985 986 987 988 989 990 991 992 993-15

-10

-5

0

5

10

15

time (nanoseconds)

2200 2400 2600 2800 3000 3200 3400 3600 3800 4000-8

-6

-4

-2

0

2

4

6

time (nanoseconds)

2076 2077 2078 2079 2080 2081 2082 2083 2084 2085-6

-4

-2

0

2

4

6

time (nanoseconds)

2200 2400 2600 2800 3000 3200 3400 3600 3800 4000-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

time (nanoseconds)

2070 2071 2072 2073 2074 2075 2076 2077 2078 2079-1.5

-1

-0.5

0

0.5

1

1.5

2

time (nanoseconds)

Office Rcvd Blocked LoS Hold Rcvd Clear LoS Hold Rcvd Blkd LoS

50 ns 200 ns 200 ns

1 ns


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PerPer--Path Pulse distortionPath Pulse distortion

Channel distortion Channel distortion –– Pulse delay Pulse delay –– perper--path pulse distortion path pulse distortion

A new phenomenon for UWB.A new phenomenon for UWB.Caused by frequencyCaused by frequency--selectivity of the channel selectivity of the channel medium. medium.


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UWB Receiver Design ChallengesUWB Receiver Design Challenges

Energy collection versus complexity (cost)Energy collection versus complexity (cost)–– RAKE may be too costlyRAKE may be too costly

Time synchronizationTime synchronizationInterInter--symbol interference (ISI)symbol interference (ISI)–– 10 symbols overlapping for indoor (100 Mbps)10 symbols overlapping for indoor (100 Mbps)–– SymbolSymbol--level equalizer level equalizer

NonNon--coherent detectorcoherent detector–– Transmitted referenceTransmitted reference–– EnergyEnergy--detectordetector


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Why UWB and why spectrum agility?Why UWB and why spectrum agility?Why UWB for IEEE 802.15.3a?Why UWB for IEEE 802.15.3a?–– UWB technology is uniquely suited for highUWB technology is uniquely suited for high--rate, short range accessrate, short range access

»» Theoretical advantages for approaching high rates by scaling banTheoretical advantages for approaching high rates by scaling bandwidth dwidth »» Newly allocated unlicensed spectrum (7.5 GHz) that does not takeNewly allocated unlicensed spectrum (7.5 GHz) that does not take away from other away from other

narrowband systems (licensed or unlicensed)narrowband systems (licensed or unlicensed)»» CMOS implementations now possible at these higher frequenciesCMOS implementations now possible at these higher frequencies All CMOS All CMOS

architecturearchitecture

Why spectrum agility for a UWB solution?Why spectrum agility for a UWB solution?–– Just because the FCC allows UWB to transmit on top of other Just because the FCC allows UWB to transmit on top of other

services does not mean we should!services does not mean we should!»» Government regulations should be broader than industry requiremeGovernment regulations should be broader than industry requirementsnts

–– Spectrum usage and interference environment changes by country Spectrum usage and interference environment changes by country location, within a local usage area, and over timelocation, within a local usage area, and over time

»» Enable adaptive detection and avoidance strategies for better coEnable adaptive detection and avoidance strategies for better coexistence and possible existence and possible nonnon--contiguous spectrum allocations for flexible regulations in futucontiguous spectrum allocations for flexible regulations in futurere

–– Allow for simple backward compatibility and future scalabilityAllow for simple backward compatibility and future scalability


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0 1 2 3 4 5 6 7

Reserved 9 10 11 12 13 14 15

Low Frequency Group High Frequency Group

Drop band in Japan Drop band in Europe

0 1 2 3 4 5 6 7

Reserved 9 10 11 12 13 14 15


~ ~

0 1 2 3 4 5 6 7

Reserved 9 10 11 12 13 14 15


Drop band in Japan Drop band in Europe

0 1 2 3 4 5 6 7 9 10 11 12 13 14 15

Low Frequency Set High Frequency Set

~ ~~ ~

Unexpected Interferer

Sacrifice sub-band for coexistence and interference mitigation (based on regulation and geographical location)

3.1 10.6

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Flexible Spectrum UseFlexible Spectrum Use

Center frequencies chosen for Center frequencies chosen for ease of ease of implementationimplementation440 MHz band separation for 440 MHz band separation for improved flexibilityimproved flexibility~538 MHz wide bands to best utilize spectrum~538 MHz wide bands to best utilize spectrum


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Communications and Physics Communications and Physics ((GaborGabor 1953)1953)

The electromagnetic signals used in wireless The electromagnetic signals used in wireless communication are subject to the general laws of communication are subject to the general laws of radiation and propagation.radiation and propagation.Communication theory developed mainly Communication theory developed mainly mathematical lines, taking for granted the physical mathematical lines, taking for granted the physical significance of the quantities which figure in its significance of the quantities which figure in its formalism.formalism.Communication is the transmission of physical effects.Communication is the transmission of physical effects.Hence communication theory should be Hence communication theory should be considered as a branch of physicsconsidered as a branch of physics. .


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PhysicsPhysics--Based Channel Model and Based Channel Model and Optimum Receiver StructuresOptimum Receiver Structures

Goal: Connect the timeGoal: Connect the time--domain electromagnetics and domain electromagnetics and communication (information) theory.communication (information) theory.Mission: Develop the optimum detection theory of physical Mission: Develop the optimum detection theory of physical signals governed by Maxwell’s Equations.signals governed by Maxwell’s Equations.Tasks: Tasks: –– Channel model models based on experiments and theory Channel model models based on experiments and theory

(analytical and computer simulations) (analytical and computer simulations) –– Optimum detection theory and information theoryOptimum detection theory and information theory–– SubSub--optimum receiversoptimum receivers–– Hardware system (transceiver) prototyping Hardware system (transceiver) prototyping


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Rx

TX

A

BA

Per-Path Pulse Distortion Based UWB Channel

1

1

1

( ) ( )

1( ) ( )( )

n n

n

Nj

nn

N

n nn n

H A j e

h A

α ωτ

α

ω ω

τ τ δ τ τα

=

− −

=

=

= ⊗ −Γ −

∑

∑

12 for a single edge diffractionnα = −

2 2( ) ( , , ) ( )k k δ∇ + =E r r' r - r'2

22 2

1( ) ( , '; , ( )t t t - t')c t

δ δ∂∇ −

∂E r r') = - ( r - r'

Multiple diffraction must be included !


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Concept of UWB Pulse Distortion due to DiffractionConcept of UWB Pulse Distortion due to Diffraction

Distorted Pulse

Wedge Wedge

Ground

1 2 /

1 1 1 1

( ) ( ) ( ) ( ) ( ) ( ) [ ( ) ( )] ( )GO GO GTD GO GTDN N N N

n n n n n n n n n n n nn n n n

h A B R C g D R gτ δ τ τ τ δ τ τ τ δ τ τ τ τ δ τ τ= = = =

= − + ⊗ − + ⊗ − + ⊗ −∑ ∑ ∑ ∑

1

1

1

( ) ( )

1( ) ( )( )

n n

n

Nj

nn

N

n nn n

H A j e

h A

α ωτ

α

ω ω

τ τ δ τ τα

=

− −

=

=

= ⊗ −Γ −

∑

∑UWB pulse distortion is a physical phenomenon !!!


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PhysicsPhysics--Based Multipath Channel ModelBased Multipath Channel Model1τ τ−

2τ τ− Nτ τ−

⊗⊗⊗

∑

11

jA e φ 22

jA e φ NjNA e φ

( )δ τ

1τ τ−2τ τ− Nτ τ−

⊗⊗⊗

∑

11

jA e φ 22

jA e φ NjNA e φ

( )δ τ

1( )h τ 2 ( )h τ ( )Nh τ

( )1

( ) n

Nj

n nn

h A e φτ δ τ τ=

= −∑

( )1

( ) ( )n

Nj

n n nn

h A e hφτ τ δ τ τ=

= ⊗ −∑

Turin’s Model

Since 1956

Qiu 1995

( ) per path impulse responsenh τ =


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DiffractionDiffraction--Based Pulse Shape DistortionBased Pulse Shape Distortion

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-1.5

-1

-0.5

0

0.5

1

1.5

time t (ns)

d(t)

and

v(t)

alpha= -1: 0.25: 0 (bottom to top)

-- alpha=0 <==> Incident Waveform

__Red dashed Template Pulse v(t)

Diffracted Signal d(t)and Template Signal v(t)














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PerPer--Path Impulse Response Path Impulse Response (Characterizing the Pulse Waveform)(Characterizing the Pulse Waveform)

0 00

1 1( ) ( ) ( )! ( ) ! ( )

n t n tn nn n n

n

D t C tH t e dt t e dtn j j n j j

ω η ξω ω ω ω

∞ ∞ ∞− −

=

= − − −

∑ ∫ ∫

0

0

( ) ( ) ,!

( )( ) ( ) ,

!

nn

nn

nn

n

Cn

hDn

α α α

α α α

ξ τ τ τ τ τ ττ

η τ τ τ τ τ τ

∞

=

∞

=

− − <= − − >

∑

∑

( ) 1 /ξ τ τ= ( ) 1/η τ τ=Example:Pulse diffracted by a PEC Edge


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Comparison of Exact Solution with Asymptotic Comparison of Exact Solution with Asymptotic GTD/UTD SolutionsGTD/UTD Solutions

0 0.5 1 1.5 2 2.5 3 3.5 4-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

time t (ns)

Cro

ss-C

orre

latio

n Direct=0.35 Reflected = 0.65 Diffracted= 0.92735

UTDKellerFelsen Exact


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UWB Pulse Shape Transform Caused by UWB Pulse Shape Transform Caused by DiffractionDiffraction

-6 -4 -2 0 2 4 6-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

time t

Cro

ss-C

orre

latio

n R

xy(t)

Alpha=-1:0.25:0

Alpha=0

Alpha=-1

( ) ( ) nnH j j αω ω=


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PhysicsPhysics--Based Optimum Receiver Based Optimum Receiver StructuresStructures

*

Matched Filtery (-t) s

samplert nT= ( )

MLSEViterbi

recivedsignals

dataoutput

( ) ( ) ( )n sn

r t a y t nT n t∞

=−∞

= − +∑

( )r t

( ) ( ) ( )y t x t h t= ⊗

1

( ) ( ) ( )N

n n nn

h t A h t tδ τ=

= ⊗ −∑Inter-symbol Interferenceor Multiuser Detection

( ) transmitted pulse shapex t =


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Summary Summary

UWB is one of the most promising technologies UWB is one of the most promising technologies –– 7.5 GHz unlicensed spectrum from 3.17.5 GHz unlicensed spectrum from 3.1--10.6 GHz10.6 GHz–– Volume products will be shipped in 3Volume products will be shipped in 3--4 years4 years

UWB is good for both shortUWB is good for both short--range (10range (10--30m) and long30m) and long--range range (100(100--1000m)1000m)Per path pulse distortion in a UWB channel is one of the major Per path pulse distortion in a UWB channel is one of the major potential problems in system designpotential problems in system design–– Experimental measurements verifiedExperimental measurements verified

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Thank You !Thank You !

Robert Qiu [email protected]

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Ultra-Wideband (UWB) Wireless Communications