Overview of Ultra Wide Band (UWB) Impulse Radio · 19 UWB Effects on Receiver Performance is the ratio of the pulse rate to the IF bandwidth There are 3 primary interference cases:

UMIACS/LTS SeminarMarch 17, 2004

Overview of Ultra Wide Band (UWB)Impulse Radio

Dr. Jay PadgettSenior Research Scientist

Telcordia Technologies/ Applied ResearchWireless Systems and Networks

jpadgett@telcordia.com

2 What is Ultra Wide Band?� FCC definition of UWB signal: bandwidth is at least 20% of

center frequency, or a bandwidth of at least 500 MHz� Bandwidths can exceed 1 GHz� Example: Pulsed UWB signal (pulse width: 0.5 ns).

f (GHz)0 1 2 3 4 5

Φ(f

) / Φ

max

(dB

)

-50

-40

-30

-20

-10

0

τ = 0.5 ns

Signal is a sequence of short pulsesPulse energy spectrum

� The large UWB passband spans the operating frequencies of many existing licensed services� Interference concerns: UWB to narrowband systems (main

concern of FCC, NTIA), narrowband-to-UWB interference (UWB design issue)

3 Brief FCC / UWB History� FCC motivation: encourage development of potentially useful

new technology without causing harmful interference to existing services and devices� Sequence of FCC Notices and Orders

– Notice of Inquiry in September 1998– Notice of Proposed Rule Making, June 2000– First Report and Order, April 2002: made legal unlicensed operation

of UWB devices subject to certain restrictions– Reconsideration Order and Further NPRM, March 2003: responsive

to Petitions for Reconsideration filed in response to the first R&O

� FCC categorizes its approach to legalizing UWB “conservative” with respect to preventing harmful interference to other devicesand services. FCC has promised further evolution to UWB Rules� Allowed UWB emission levels are less than or equal to the level

allowed for unintentional radiators such as computers and other electronic devices (-41.3 dBm/MHz).

4 FCC General UWB Emission Limits

Frequency in GHz

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

UW

B e

mis

sio

n li

mit

in d

Bm

/MH

z

-80

-70

-60

-50

-40

IndoorHandheld

UWB Passband (3.1 to 10.6 GHz)1.99 GHz

1.61 GHz

−75.3 dBm

−51.3 dBm−53.3 dBm

−61.3 dBm−63.3 dBm

−41.3 dBm

960MHz

5 Applications: DARPA’s NETEX Program

� Phase I: Gain understanding of effects of UWB system operation on existing narrowband spectrum users– Testing (NAVAIR/Pax River): 16 legacy system, 39 modes, 1600

tests completed.– Modeling/Simulation (Telcordia) details below– UWB propagation and channel modeling (Virginia Tech)

� Phase II: (DARPA/ATO BAA 03-20, Industry Day April 7 ‘03)– Push UWB physical layer design to the point where it is capable of

reliably supporting advanced LPD, ranging, location and networking protocols

– Develop algorithms, protocols, and distributed control for robust, scalable ad hoc UWB networking

– Demonstrate 20-node hand held radios, 50-node video network, and 50-node radar sensor integrated into high data rate short range network.

Objective: Develop military UWB sensors and communications systems for operation in extreme environments

http://www.darpa.mil/ato/solicit/NETEX/documents.htm

6 UWB: An Undesired Result

7 UWB Interference Modeling

( )fG

( ) ( )∑∞

−∞=

−=k

kTtgtx ( )ty

victim receiver or measurement instrument (e.g., spectrum analyzer) impulse response (baseband equivalent)UWB impulse train receiver

response

( )thb

?t

( )tg

f

( )fH

f

tWhat is the effective interference power due to the UWB signal, as seen by the non-UWB receiver?

8 Victim Receiver Model and Interference Filtering

f0 f−f0

Receiver Passband

UWB PulseEnergy Spectrum

RF IF1

~ LO1

f0 fIF1IF2

~ LO2

fIF2Detector/DemodulatorCircuitry

HIF(f )

UWB Pulse Sequence IF Impulse Response (envelope shown)

9 Time Hopping PSD Example: Partial-Frame 2-ns Dithering

f0 (filter center frequency), GHz

0 1 2 3 4 5

filte

r out

put p

ower

, dB

m

-60

-50

-40

-30

-20

-10

M = 10 time hopping binsεc = 2 ns bin separationPuwb = 10 dBmR = 10 MHz pulse rateBIF = 1 MHz IF bandwidth

10 Closeup – with Simulation Results

f0 (filter center frequency), GHz

1.4 1.5 1.6

filte

r out

put p

ower

, dB

m

-60

-50

-40

-30

-20

-10

ModelSimulation

M = 10εc = 2 nsPuwb = 10 dBmR = 10 MHzBIF = 1 MHz

11 Simulation – Zero Span – 1.46 GHz

time in microseconds

0 20 40 60 80 100

filte

r out

put p

ower

in d

Bm

-60

-50

-40

-30

-20

-10

M = 10, εc = 2 ns, Puwb = 10 dBmR = 10 MHz, BIF = 1 MHzf0 = 1.46 GHz

f0 (filter center frequency), GHz

1.4 1.5 1.6

filte

r out

put p

ower

, dB

m

-60

-50

-40

-30

-20

-10

ModelSimulation

M = 10εc = 2 nsPuwb = 10 dBmR = 10 MHzBIF = 1 MHz

12 Simulation – Zero Span – 1.47 GHz

time in microseconds

0 20 40 60 80 100

filte

r out

put p

ower

in d

Bm

-60

-50

-40

-30

-20

-10

M = 10, εc = 2 ns, Puwb = 10 dBmR = 10 MHz, BIF = 1 MHzf0 = 1.47 GHzf0 (filter center frequency), GHz

1.4 1.5 1.6

filte

r out

put p

ower

, dB

m

-60

-50

-40

-30

-20

-10

ModelSimulation

M = 10εc = 2 nsPuwb = 10 dBmR = 10 MHzBIF = 1 MHz

13 Simulation – Zero Span – 1.48 GHz

time in microseconds

0 20 40 60 80 100

filte

r out

put p

ower

in d

Bm

-60

-50

-40

-30

-20

-10

M = 10, εc = 2 ns, Puwb = 10 dBmR = 10 MHz, BIF = 1 MHzf0 = 1.48 GHzf0 (filter center frequency), GHz

1.4 1.5 1.6

filte

r out

put p

ower

, dB

m

-60

-50

-40

-30

-20

-10

ModelSimulation

M = 10εc = 2 nsPuwb = 10 dBmR = 10 MHzBIF = 1 MHz

14 Simulation – Zero Span – 1.5 GHz

time in microseconds

0 20 40 60 80 100

filte

r out

put p

ower

in d

Bm

-60

-50

-40

-30

-20

-10

M = 10, εc = 2 ns, Puwb = 10 dBmR = 10 MHz, BIF = 1 MHzf0 = 1.5 GHz

f0 (filter center frequency), GHz

1.4 1.5 1.6

filte

r out

put p

ower

, dB

m

-60

-50

-40

-30

-20

-10

ModelSimulation

M = 10εc = 2 nsPuwb = 10 dBmR = 10 MHzBIF = 1 MHz

15 Example: PSD of a Swept-PRF Signal

t

r(t)

t

r(t)pulse rate

rd

2T

2T

−

r

( )22T

tT

atrtr ≤<−+=

Tra d2=

( ) ( )∑+−=

−=M

MnnTttv

1

δ

( )a

TnarrTn

42 22 +++−=

( ) ∑+−=

−=M

Mn

fTj nefV1

2π

16 Swept PRF PSD and Approximation

frequency (MHz)

0 200 400 600 800 1000

mill

iwat

ts

0

1

2

3

4

exactfirst-order analytic approximation

Swept PRF100 MHz average PRF100 kHz sweep rate4 MHz PRF span (98 to 102 MHz)1 watt total average power1.05 GHz pulse bandwidth (rectangular spectrum)

17 Closeup of Swept PRF Spectrum

frequency (MHz)

580 590 600 610 620

mill

iwat

ts

0.0

0.2

0.4

0.6

0.8

1.0

exactfirst-order analytic approximation

Swept PRF100 MHz average PRF100 kHz sweep rate4 MHz PRF span (98 to 102 MHz)1 watt total average power1.05 GHz pulse bandwidth (rectangular spectrum)

18 Individual Tones of the Swept PRF PSD

frequency (MHz)

585 586 587 588 589 590 591 592 593 594 595

mill

iwat

ts

0.0

0.2

0.4

0.6

0.8

1.0

exactfirst-order analytic approximation

Swept PRF100 MHz average PRF100 kHz sweep rate4 MHz PRF span (98 to 102 MHz)1 watt total average power1.05 GHz pulse bandwidth (rectangular spectrum)

19 UWB Effects on Receiver Performance� is the ratio of the pulse rate to the IF bandwidth� There are 3 primary interference cases:

– , which gives pulsed interference to the detector– with constant pulse rate, which can give a tone

within the passband– with dithering or modulation, which can give a

noise-like signal� The first two cases were explored for fixed-frequency

digital communications receivers and for an analog FM receiver. The third case, in the limit, gives results similar to those of Gaussian noise, which are well-known.�With Nu > 1, there can also be a combination of a tone and

noise (as seen previously).� Results are calculated based on the average UWB

interference power within the receiver passband.

uN

1≤uN1>uN

1>uN

20 Modeling the Test Procedure for an FM Receiver

Carrier-to-interference ratio (CIR), dB

-10 0 10 20 30

Bas

eban

d SI

NA

D (d

B)

0

10

20

30

40

Nu = 0.1

Nu = 1.0

Nu = 0.01

Gaussian noise

∆f = 2.4 kHzfm = 1 kHzBIF = 30 kHzBbb = 3 kHz

Nu = PRF ÷ IF bandwidth

21 Analysis vs. dB-Average Test Results (FM)

Test Waveform (TW) Number

1 2 3 4 5 6

CIR

for

10 d

B S

INA

D r

ecei

ver

upse

t, dB

-5

0

5

10

15

20

dB average from measurementsanalysis

Gaussian noise

22 UWB into a Noncoherent FSK Receiver

-20 -10 0 10 20 3010

-4

10-3

10-2

10-1

100

SIR (dB)

BE

RNu=0.01

Nu=0.02

Nu=0.05

Nu=0.10

Nu=1.00

−

2exp

21

BER AWGN Equivalent

SIR

-20 -10 0 10 20 3010

-4

10-3

10-2

10-1

100

SIR (dB)

BE

RNu=0.01

Nu=0.02

Nu=0.05

Nu=0.10

Nu=1.00

-20 -10 0 10 20 3010

-4

10-3

10-2

10-1

100

-20 -10 0 10 20 3010

-4

10-3

10-2

10-1

100

SIR (dB)

BE

RNu=0.01

Nu=0.02

Nu=0.05

Nu=0.10

Nu=1.00

−

2exp

21

BER AWGN Equivalent

SIR

23 Coherent PSK – Comparison of Rates

-5 0 5 10 15 10

-6

10 -5

10 -4

10 -3

10 -2

10 -1

10 0

SINR (dB)

BE

R

I/N = -30 dB I/N = 0 dB I/N = 30 dB

25.0 :Red =uN

1.0 :Green =uN05.0 :Blue =uN

u

u

NN

log10 SINR BER, lowAt 2BER SINR, lowAt

−≅≅

24 UWB/Legacy NB Coexistence Example

Rb

UWB data rate (kb/s)

1 10 100 1000

d uwb

Max

imum

UW

B p

ath

dist

ance

(met

ers)

0

200

400

600

800

1000

I/N = 0 dBI/N = 5 dBI/N = 10 dBI/N = 15 dBI/N = 20 dB

f0 = 300 MHzBuwb = 200 MHzdnb = 20 metersFnb = 10 dBFuwb = 1 dB(Eb/N0)uwb = 10 dBA(f0) = 0 dBGTX,uwb = 2 dBGRX,uwb = 2 dBGTX,uwb->nb = 2 dBGRX,nb = 2 dBLTX = LRX = 1 dBDithered pulses

25 Aggregate Interference – Closed form CDF

( ) ( ) ( ) ( ) ( )∑∞

=

>−

−ΓΓ

−=<=1

0,1sin1

!1

1Prk

k

Z zkzk

kzZzF νπ

ννπ ν

( ) ( ) )interferer(nearest 0exp >−= − zzzFZν

10 log z

-10 0 10 20 30P

{ Z

< z

} [

perc

ent]

Dis

trib

utio

n of

nor

mal

ized

ag

greg

ate

inte

rfer

ence

pow

er

0.1

1

10

305070

90

99

Multiple interferers

Nearest single interferer

γ = 4.0γ = 3.5γ = 3.0

• Uniformly random distribution of interfering transmitters• Equal power• No exclusion zone

26 IS-95 PCS Blocking vs. UWB Density

ρ (active UWB transmitters/m2)

0.00 0.05 0.10 0.15 0.20

Pb (

perc

ent)

blo

ckin

g pr

obab

ility

aver

aged

ove

r cel

l are

a an

d U

WB

-to-

PCS

dist

ance

0

20

40

60

80

100

Non-uniform distance distributionγ = 3.5

ΦTXuwb = −50 dBm/MHz

−55 dBm/MHz

−60 dBm/MHz

−65 dBm/MHz

ρ (active UWB transmitters/m2)

0.00 0.05 0.10 0.15 0.20

Pb (

perc

ent)

blo

ckin

g pr

obab

ility

aver

aged

ove

r cel

l are

a an

d U

WB

-to-

PCS

dist

ance

0

20

40

60

80

100

Uniform distance distributionγ = 3.5

ΦTXuwb = −50 dBm/MHz

−55 dBm/MHz

−60 dBm/MHz

−65 dBm/MHz

r (meters)

0 1 2 3 4 5 6

f d(r)

prob

abili

ty d

ensi

ty fu

nctio

n fo

rdi

stan

ce to

nea

rest

UW

B tr

ansm

itter

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

ρ = 0.1 active UWB transmitters/m2

Non-uniform

Uniform

Truncated uniform (d0 = 1 meter)

Probability density functions for minimum UWB to PCS handset distance

These curves show the average percentage of handsets blocked on the downlink as a function of UWB deployment density and transmit power spectral density

27 C/I with Aggregate Interference� Desired signal to NB receiver Rayleigh-faded (terrestrial

multipath).� UWB transmitters uniformly randomly distributed spatially, no

fading of interfering signals (short distances).� May be an “exclusion zone” surrounding victim receiver within

which there will be no UWB transmitters.

Desired NB transmitter

Rayleigh-faded signal path

exclusion zone(no UWB transmitterswithin this area)

dmin

narrowband receiver

28 C/I CDF with Aggregate UWB Interference and no Exclusion Zone

-40 -30 -20 -10 0 10 20

Pr( C

nb/ I

UW

B <

Λ),

perc

ent

0.1

1

10

30

50

70

90

99

99.9

99.99

γ = 2.5γ = 3γ = 3.5γ = 4

Monte Carlo, γ = 3Nearest interferer, γ = 3

dB , nbX

Λ

22

1exp1Pr

2

>

−Γ

Λ−−=

Λ< γ

γ

γ

nbUWB

nb

XIC

( ) 2 :ionnormalizat γπρα atx

nbnb P

CX =

29 The Larger Picture: UWB – Challenges, Questions, and Opportunities Going Forward

� Design of UWB radios that can operate adaptively in the presence of strong in-band narrowband signals.� UWB networking: MAC layer design, ad hoc routing protocols,

QoS management, especially with narrowband interference.� Applications – what is UWB best suited for (military and

commercial)?– Radar/localization– Data networking?– Sensors?– Integrated applications (e.g., localization + communications).

� Can UWB be used to provide high data rate hotspots with connectivity to CMRS networks?� Can UWB be used to increase the accuracy of E-911 indoors?