Uwb Applications Interference

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Thales Research and Technology

UWB Applications and Interference(UWB Colloquium 23rd July 2002)

Ewan Frazer, Dave Harmer (Thales Research & Technology, Reading, UK)

Presenter: Ewan Frazer


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Introductionl Main points that will be covered:

UltraWideBand (UWB) and where it is useful

Pulse UWB (P-UWB) and Frequency Hopped UWB (FH-UWB)A Typical Positioning System

The Challenges and Possible Solutions:

n Interference to other systems (Regulation)

n Interference from other systems

n Multipath

Summary of Pros and Cons of FH-UWB versus P-UWB

Potential Applications


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Applicationsl Positioning

High Multipath Environments

Obscured Environmentsl Communications

High Multipath Environments

Short Range High Data Rate

Low Probability of Intercept/ Interference

l Radar/Sensor

Military and Commercial: Asset Protection

Anti-Terrorist/Law Enforcement

Rescue Applications


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Potential Positioning Applicationsl Current positioning applications using GNSS stop

at building entrances (or even before)

l Accuracy required depends on the application(generally higher accuracy required than outdoors)

l Examples

Navigation or tracking within a shopping Mall

n Lost Children, Advertising

Lone Workers (safety)

Navigation in Airports, Railway stations, car parks etc

l More applications once initial systems deployed

l Data transmission can be included

Data Rate depends on range (a few tens of kbps to Mbps)


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Position Accuracy Requirements by Application

0.001

0.01

0.1

1

10

100

Automated

handlin

g

Route

Guida

nce

for

Blin

d

In-buildi

ngsurvey

Toolp

ositi

oning

In-buildin

grobot

guidance

Forma

tionflyin

g

Recreation

and

toys

Urb

ancanyon

-off-ro

ad

Urb

ancanyon

-marin

e

Incidenttra

cking

/guid

ance

Urb

ancany

on-other

Exhibit

commentary

Good

s&

item

trackin

g

Hazard

warnin

gs

Ped

estrianroute

guidanc

e

In-buildin

gtracki

ng-othe

r

In-buildin

gworke

rtracking

Urb

ancany

on

-rail

Pre

cisio

nlandin

g

Acce

sscontrol

Location-based

servic

es

Public

service

stracking

Docking

Parole

etracking

Localin

form

ation

Train/air/bu

sin

form

ation

Advertisin

g

Po

sitionAccuracy(m9

5%)


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UWB & Positioningl A signal with greater than 25% fractional bandwidth

Eg. 4GHz centre frequency and > 1GHz bandwidth

First used by DARPA, generally acceptedl Wide bandwidth

High accuracy timing

High accuracy positioningSeparation of closely spaced multipath components

l GPS or other systems indoors

Long averaging time and hence low update rate

High errors due to multipath

Relatively Low Accuracy


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Pulse and Frequency Hopped UWBl Two of a number of methods of generating UWB

l Studies by Thales Research and Technology

Pulse and Frequency Hopped options were the most promisingcandidates

l Pulse UWB

Very short (sub nanosecond) pulses tens of nanoseconds apart

Inherently wide band

l Frequency Hopped UWB

Typically a Direct Sequence Spread Spectrum Signal of about

10 to 20MHz bandwidth, hopped over around 1GHz at 10k to100k hops per second


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Pulse UWB

No

distortion

Filtered-

Ringing


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Seamless Indoor and Outdoor Positioning


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Challenges & Possible Solutionsl Sharing Frequencies with Other Services

Interference to and from Other Systems

l Interference to Other ServicesPower into victim receiver reduced by bandwidth ratio

Pulses can cause ringing in receiver front ends

Some services are particularly sensitive (e.g. GPS)

l Interference from Other Services

System is restricted to very low power (regulation) and thereforemore susceptible to interference even with high processing gain

Interfering devices can be at very close range (e.g. MobilePhones)

l Solutions - depend on the type of UWB


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RegulationFCC Provisional Band Mask - UWB

-40

-35

-30

-25

-20

-15

-10

-5

0

0 1 2 3 4 5 6 7 8 9 10 11 12

Frequency (GHz)

dBPowerspectraldensity

(relativet

oPart15limit)

Example Indoor Imaging Thru wall Outdoor ARNS 1.6G ARNS 1.2G

ARNS

Outdoor

Indoor

Thru

Wall

Imaging


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P-UWB - Interference to Other Servicesl Shaping the Transmit Spectrum

Passive Filtering

n Ringing - Reduced accuracy - Reduced multipath resistance

Choice of Pulse sequences (Spacing and Rate)

n Can insert nulls into the transmit spectrum

nAttenuation achievable limited by hardware constraints (for example

maximum pulse rate)n Compromise

- Reduces interference to other systems

- Restricts the choice of Pulse Sequences

Use a combination of both of the above


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Technique for avoiding ARNS Bands - Pulse UWB


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Avoidance of 1.2GHz ARNS Band

-40

-30

-20

-10

0

10

1140 1160 1180 1200 1220 1240

Frequency, MHz

Response

Response

Mask


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Avoidance of 1.6GHz ARNS Band

-40

-30

-20

-10

0

10

1535 1555 1575 1595 1615 1635

Frequency, MHz

Response

Response

Mask


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FH-UWB - Interference to Other Services

l Spectrum easily shaped

l Easily modified if the regulations change

l Power levels can be matched to the frequenciesl Limited by the hop spacing

l Removing parts of the spectrum reduces multipath

performancel High performance achievable even with large

missing portions of spectrum


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Avoiding ARNS Bands - FH-UWB

Frequency Hopped UWB Spectrum

-50

-40

-30

-20

-10

0

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500

Frequency, MHz

RelativeP

owerdB

ARNS BANDS


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Interference from Other Systems

Interference Excision - Pulse UWB

4 tap rake spectrum

-40

-30

-20

-10

0

0 1 2 3 4 5

Frequency, GHz

Powe

r,dB


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Summary & Conclusions

l Most indoor applications require high accuracy

l UWB is a promising technology which is likely to

provide the required performancel Potentially a large market for UWB

l Small size, low cost and low power consumption are

believed to be achievablel Interference issues have potential solutions

l Thales Research and Technology acknowledge thesupport of the British National Space Centre formuch of the work reported here


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