UWB Presentation

8/8/2019 UWB Presentation

1/17

An IntroductionAn Introduction toto

Impulse Radio UltraImpulse Radio Ultra--Wide BandWide Band(IR(IR--UWB)UWB)

Presenter Tamim Arabi

Supervisor Dr. Zhizhang (David) Chen

Part of M.A.Sc Thesis Program Requirements at Dalhousie University


2/17

OutlineOutline

y Definitions

y IR UWB pulses

y

Advantagesy Challenges

y Synchronization

y

Future work


3/17

IntroductionIntroduction

yy UWBUWB is a wireless communication technologyfor transmitting digital data at high rates over awide spectrum of frequencies using very low

power levels.

y This makes it a good candidate technique forshort range indoor communication.


4/17

DefinitionDefinition

y FCC:

UWB signals fractional bandwidth (Bf) > 20%

Or: more than 500 MHz of absolute bandwidth

FCCs ( First Note And Order 2002 )


5/17

IRIR--UWB PulsesUWB Pulses

Carrier-less, short-duration pulses (ns~ps)with a very low duty cycle (< 0.5%)

E.g. A Gaussian monocycle.


6/17

NarrowbandNarrowband vsvs UWBUWB

Narrowband Bf< 1%Wideband 1% < Bf< 20%

Ultra-Wideband Bf> 20%


7/17

AdvantagesAdvantages

y Sharing the RF spectrum

Max of 41.3 dBm/MHz 75 nanowatts/MHz

y Large Channel Capacity {C=B log2 (1 + SNR)}

Low SNR

y Low transmit power

y Resistance to Jamming

y High Performance in Multipath Channels

y Simple transceiver architecture


8/17

ChallengesChallenges

y Pulse-Shape Distortion

y Channel Estimation

y

Multiple-User Interferencey High-Frequency Synchronization

Sync must be achieved accurately.

Timing errors in the order ofnano seconds

can severely degrade system performance.

Different sync methods leads to differentreceivers: Coherent and Non-coherent.


9/17

SynchronizationSynchronization

y Rake Receiver

The first proposal for coherent receivers.

Assigns number offingers to each multipath

component.

Very high number of fingers = very high powerconsumption, not acceptable.


10/17

Synchronization..Synchronization..

y Transmitted Reference (TR) UWB

Bypasses the channel estimation.

In TR, a ref pulse is sent prior to each data

pulse.

Drawback: wastes transmission power andreduces transmission rate.


11/17


y Frequency-Shifted Reference (FSR) UWB

Avoided the delay element in the TR Receiver.

Drawbacks: Performance is affected by

frequency, phase, and amplitude offsets.


12/17


y Coded-Shifted Reference (CSR) UWB

Does not require any delay element (TR),separation is being done using digital codes

instead of analog carriers (FSR).


13/17


y Differential-CSR (DCSR) UWB

Data pulses are differentially encoded

Each data pulse sequence can be used as a ref

sequence of the next.


14/17

Synchronization..Synchronization..yy FrameTimingFrameTiming: start of individual frames with

respect to receivers clock.

yy SymbolTimingSymbolTiming: Location of first frame in eachsymbol.

Future WorkFuture Worky Enhancing the performance of the

implemented CSR UWB system, focusing onthe Synchronization at the frame level of theCSR IR-UWB System.


15/17

ReferencesReferences1. H. Nie and Z. Chen, Code-Shifted Reference Ultra-Wideband (UWB)

Radio, Proc. Comm.NetworksandServicesResearch Conf., pp. 385-389, 2008

2. C. Wei, H. Nie,and Z. Chen, Non-Aided-Data Code Synchronization forthe Code-Shifted Reference Ultr-Wideband (UWB) System, Proc. AnnualComm. NetworksandServicesResearch Conf. 2010, pp. 56-60,

3. C. Carbonelli and U. Mengali, Synchronization Algorithms for UWB

Signals, IEEETrans.On Communications,Vol. 54 No. 2, pp. 329-338, Feb. 2006

4. Biao Liu,etal, A Novel Synchronization Algorithm in Ultra-WidbandSystem, IEEEInt. Conf.on Ultra-Wideband,Sep. 2009, pp. 556-559

5. Mario R. Casu1 and Giuseppe Durisi, Implementation aspects of atransmitted-reference UWB receiver, Wireless CommunicationsandMobileComputing,Vol. 5,pp. 537549, 2005.

6. Nekoogar, Faranak. Ultra-WidebandCommunications:FundamentalsandApplications,Upper Saddle River, NJ : Prentice Hall Professional TechnicalReference, 2005


16/17

ThankYou


17/17

Documents

UWB Presentation