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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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