UWB Modulation Design and Joint-Cross Layer QoS Wireless ...gajic/DLP_talk.pdf · Cell 1 Cell 2 • No interference within the cell • Interference averaged across cells leads to

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UWB Modulation Design and JointUWB Modulation Design and Joint--Cross Cross Layer Layer QoSQoS Wireless Content DeliveryWireless Content Delivery

Jie Chen Jie Chen

Division of EngineeringDivision of EngineeringBrown UniversityBrown University

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OutlineOutline• Why is the problem important?

• What is our approach?1. UWB Modulation Design2. Cross-layer QoS Wireless Content Delivery

• Conclusions

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Content

Bi-phase UWB Modulation

Cross-layer QoS Content Delivery

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History of Impulse RadioHistory of Impulse Radio• In 1893, Heinrich Hertz used a spark discharge to

generate electromagnetic waves for his experiments –that is probably the first impulse radio

Heinrich Hertz

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Ultra Wideband Ultra Wideband •• UWB uses a series of short impulseUWB uses a series of short impulses with spectrum s with spectrum

spreading from near DC to a few Gigahertzes, spreading from near DC to a few Gigahertzes,

•• High data throughput High data throughput ---- providing providing gigabit gigabit wireless connection.

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Current Standardization Current Standardization • Activities in IEEE 802.15

• IEEE 802.15 is a subset of IEEE 802.11a (<54Mb/s).• IEEE 802.15.3 targets to deliver data rate at Gbs/s

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Different UWB ApproachesDifferent UWB ApproachesUWB

FH-UWB TH-UWB OFDM-UWB

IEEE microwave magazine, June 2003

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FHFH--UWBUWB

Lie-Liang Yang, Lajos Hanzo “Residue Number System Assisted Fast Frequency-Hopped Synchronous Ultra-Wideband Spread-Spectrum Multiple-Access: A Design Alternative to Impulse Radio”, IEEE JSAC, Dec 2002

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MultibandMultiband UWBUWB

Anuj Batra, Jaiganesh Balakrishnan, et. al “Time-Frequency Interleaved Orthogonal Frequency Division Multiplexing”, IEEE 802.15.3a proposal 2002”

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Different Modulations of UWBDifferent Modulations of UWBUWB

FH-UWB TH-UWB OFDM-UWB

PPM PAM BPM CPM

Moe’s PPM (Pulse Position Modulation):

Moe Win, IEEE Trans. on Communication, 2000

BPM (Bi-Phase Modulation):

Pseudo-random sequence:

Taylor’s PAM (Amplitude modulation)M. Ho, L. Taylor, IEEE Int. Conf. Consumer Electronics, 2001

dδ

trwjC

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THTH--PPM UWBPPM UWB• PPM is based on the principle of encoding information

with two or more positions in time, referred to the nominal pulse position.

• The time between nominal position is typically at the ns scale to avoid interference between impulses.

Moe Z. Win, Robert A. Scholtz , IEEE Trans. on Comm, June 2000

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THTH--PAM UWBPAM UWB• PAM is based on the principle of encoding information

with the amplitude of impulses• More amplitude levels can be used to encode more

than one bit per symbol.

M. Ho, L. Taylor, and G.R. Aiello,“ UWB architecture for wireless video networking,” in Proc. IEEE Int. Conf. Consumer Electronics, 2001, pp. 18-19.

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THTH--BPSK UWBBPSK UWB• Information is encoded with the polarity of the

impulses

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Introduction to UWBIntroduction to UWB( )( )( )

0

( ) ( )( , ) ( ) ( )s

kC j

Nk

tr k f jj

k ku ttr

w jT u T d uS t c δ=

= − − −∑

tf: 100ns, Tc: 1.5ns, Tm: 0.7ns, : 0.156nsδWe can view different users as interferences

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Receiver DesignReceiver Design,

,, ( , ) ( )Syn j f

Syn j

T T

j Rec Sym jTd dTu T t Tν

+= − ⋅∫

1

0

SN

jjD d

−

=

= ∑ {( ) 0 0( )

1 0k when Du

when DB

>=

<

Decision

Statistics

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Ultra Wideband Ultra Wideband

100 Multi-Users 200 Multi-UsersUWB approach

Time jittering (0.1ns) can significantly lower Time jittering (0.1ns) can significantly lower BERBER

100 Multi-Users 200 Multi-Users

We can view different users as interferences

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SolutionsSolutions1.1. Increase the impulse parameterIncrease the impulse parameter

---- increase the impulse duration and sacrifice the systemincrease the impulse duration and sacrifice the systemthroughput. throughput.

---- UWB bandwidth also decreasesUWB bandwidth also decreases

2.2. BiBi--phase Modulationphase Modulation

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

tj(ns)

Am

plitu

te

Stastic for bit 0 Stastic for bit 1

( )( ) ( )

0

( ) ( )( , ) (1 2 ( )( )).

s

C

Nk k

tr k f jj

k ku t

trD w jT u TS u t c

=

= − − −∑

mτ

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Timing JitterTiming Jitter--robust UWBrobust UWB

Challenges lie in waveform design

-- Orthogonal waveforms that can tolerance maximum timing jittering.

With the same bandwidth !!

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Proposed DesignProposed DesignProposed waveform:

where N is the order of the monocycle;

and

2( ) exp[ 2 ( ) ]Hm

tH t A t πτ

= ⋅ −

( ) 0H t dt∞

−∞=∫

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Proposed DesignProposed Design

-0.4 -0.2 0 0.2 0.4-3

-2

-1

0

1

2

3

t(ns)

Am

plitu

te

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

-3

-2

-1

0

1

2

3

4

t(ns)

Am

plitu

te

GaussianRayleigh

Proposed waveformGaussian:

2( ) exp[ 2 ( ) ]Hm

tH t A t πτ

= ⋅ −

2 2( ) 1 4 ( ) exp[ 2 ( ) ]Gm m

t tG t A π πτ τ

= − ⋅ −

Rayleigh:

22( ) exp[ 2 ( ) ]R

m m

t tR t A πτ τ

= ⋅ −

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Analyze the TimingAnalyze the Timing--jittering jittering PerformancePerformance

,

,,( ) ( , ) ( )Syn j f

jSyn j

T T

j Rec Sym jTd dTt u T t Tν

+= − ⋅∫

TimingTiming--jittering tolerance determined by the decision jittering tolerance determined by the decision

statisticsstatistics

here here ttjj is the timingis the timing--jitteringjittering

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Decision Statistics (Decision Statistics (RayleighRayleigh))( )

( )2

2 2 2 12

2, 4(2 )1

1/ 2

exp 2 2 / 4

/ 2 exp( / 2)/ 2(2 )

8

k kj j j

R Rj R

j kkmj jk

xt xt t xt t t kxA Ad xt

t Erfi x t tx

πτ

− −

−=−

− + ′

= − ⋅ −

∑

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

-1

-0.5

0

0.5

1

tj(ns)

Am

plitu

te

Stastic for bit 0 Stastic for bit 1

CDD

22 / mx π τ= −

CDD: correct decision duration

{( ) 0 0( )

1 0k when Du

when DB

>=

<

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Performance of Proposed Performance of Proposed SchemeScheme

Gaussian Approach Proposed Approach

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

tj(ns)

Am

plitu

te

Stastic for bit 0 Stastic for bit 1

CDD

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

tj(ns)

Am

plitu

te

Stastic for bit 0Stastic for bit 1

TP TP

CDD

Gaussian and HighGaussian and High--order waveform order waveform

----Proposed scheme provides longer CDD Proposed scheme provides longer CDD with samewith same----In addition, it provides the transition period (TP) In addition, it provides the transition period (TP)

mτ

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Why Select Order 15?Why Select Order 15?• When N<7, the value of CDD and CCD+TP are identical

5 10 15 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

CDDCDD+TP

CD

D/C

DD

+TP

Dur

atio

n (n

s)

The Order of Monocycles (Odd Order Only)

2( ) exp[ 2 ( ) ]Hm

tH t A t πτ

= ⋅ −

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Simulation ResultsSimulation ResultsMax TimeMax Time--jittering=jittering=0.20ns0.20nsConventional Gaussian-PPM approach

100 Multi-Users 200 Multi-UsersOur HOM-BPM approach

100 Multi-Users 200 Multi-Users

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Simulation Results (II)Simulation Results (II)The effects of multiple-access when there is timing jitter

Ns=100 and maximum timing jitter TMax,j=0.2ns

tf: 100ns, Tc: 1.5ns, Tm: 0.7ns, S/N: 20dB

50 100 150 200 250 300 350 400 450 500

10-4

10-3

10-2

10-1

100

The Number of Users Nu

BE

R

Gaussian BPMRayleigh BPMHOM BPM

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Simulation Results (III)Simulation Results (III)The impact of Ns when considerable timing jitter is present

TMax,j=0.2ns

The proposed design can achieve reasonable BER even Ns=50. good for bandwidth efficiency.

50 100 150 200 250 300 350 400

10-4

10-3

10-2

10-1

100

The Number of Impulse Used(With Tmax =0.2ns)

BE

R

Gaussian BPMRayleigh BPMHOM BPM

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ConclusionConclusion• We propose a waveform modulation scheme for timing

jitter-robust UWB communication

• The wave form can be generated by the linear combinations of a set of derivatives.

• It can achieve better bandwidth efficiency

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Content

Bi-phase UWB Modulation

Cross-layer QoS Content Deliver

Motivation

Significant difficulties in developing IPSignificant difficulties in developing IP--based based wireless data networks to meet wireless data networks to meet QoSQoSrequirements requirements ---- Dynamic Link CharacteristicsDynamic Link Characteristics---- Resource ContentionResource Contention

The conventional protocol structure is The conventional protocol structure is inflexible as various protocol layers can only inflexible as various protocol layers can only communicate in a strict manner. communicate in a strict manner.

MotivationIn such a case, the layers are designed to In such a case, the layers are designed to

operate under the worst conditions, rather than operate under the worst conditions, rather than adapting to changing channel conditions. adapting to changing channel conditions.

This leads to the inefficient use of spectrum This leads to the inefficient use of spectrum and energy.and energy.

Adaptation represents the ability of network Adaptation represents the ability of network protocols and applications to observe and protocols and applications to observe and respond to the channel variation. respond to the channel variation.

Central to adaptation is the concept of Central to adaptation is the concept of cross cross layer designlayer design. .

Proposed dynamic resource allocation schemes:Proposed dynamic resource allocation schemes:---- Power control, rate adaptationPower control, rate adaptation---- dynamic channel allocationdynamic channel allocation---- beamformingbeamforming---- multiusermultiuser detectiondetection---- joint design between power and joint design between power and beamformingbeamforming, , between rate adaptation and power controlbetween rate adaptation and power control

In general, the cross layer design In general, the cross layer design involves the involves the different layersdifferent layers in an overall protocol stack.in an overall protocol stack.

The adaptation can also take place in the underlying The adaptation can also take place in the underlying layers such as the TCP and UDP, so that the layers such as the TCP and UDP, so that the application originally developed for different networks application originally developed for different networks remain unchanged.

Most Current Designs

remain unchanged.

Technical Challenges & SolutionsTechnical Challenges & Solutions1. 1. ApplicationApplication--layerlayer: Adjust media source rate : Adjust media source rate

2. 2. TransportTransport--layerlayer: The protocol should differentiate : The protocol should differentiate various packet loss patterns, i.e. packet losses due to a various packet loss patterns, i.e. packet losses due to a network congestion or from channel errorsnetwork congestion or from channel errors

3. 3. LinkLink-- and Networkand Network--layerlayer: The link layer scheduler : The link layer scheduler should allocate radio resources to various packet flows should allocate radio resources to various packet flows based on their based on their QoSQoS priorities.priorities.

4. 4. Predict Future NetworkPredict Future Network and Channel Conditionsand Channel Conditions..

All IP NetworkFH-OFDM

Mobile Mobile Broadband

WirelineWirelineVoice AMPS AMPS –– PCS PCS –– 3G3G

IP over VoiceIP over Voiceis inefficient approachis inefficient approach

to Data Mobilityto Data Mobility

AMPS – PCS – 3G

WirelineWirelineData (IP) BroadbandData (IP)

MobileMobileVoiceVoiceVoice

FH-OFDM is to Broadband Mobile IPWhat CDMA is to Cellular Voice

FHFH--OFDM IllustratedOFDM Illustrated

11

11

11

11

11

11

11

22

2 2

22

22

22

22

22

timetime timetime

tonetonetonetone

AA

AA

AA

AA

AA

AA

AA

BB

BB

BB

BB

BB

BB

BB

Cell 1Cell 1 Cell 2Cell 2

• No interference within the cell• Interference averaged across cells leads to

– Improved physical layer spectral efficiency (> W-CDMA)– More efficient support of bursty traffic

RNS FH-OFDM Illustrated

f2,0 f2,m

f1,0 f1,n

2

1

i i is q

sf f f

=

= +∑

FH pattern's design must:

i) avoid ambiguity when identifying users; ii) reduce the chances of a collision between two FH patterns; iii) distribute sub-carriers evenly; and iv) keep adjacent FH patterns far from each other.

RNS OFDM Scheme RNS OFDM Scheme (Cell Site 1)(Cell Site 1)

2, 12, 1

1, 01, 0

0, 120, 12

11, 1111, 11

10, 1010, 10

AccumulatorAccumulator

m=12, m=12, n=13n=13

User 2User 2(21(21 9,8)9,8)

m=12, n=13m=12, n=13

User 1User 1(15(15 3,2)3,2)

m=12, n=13m=12, n=13

2,1 1 1,12f F f× +

2,2 1 1,0f F f× +

2,3 1 1,1f F f× +

2,4 1 1,2f F f× +

2,5 1 1,3f F f× +

2,9 1 1,7f F f× +

2,10 1 1,8f F f× +

2,11 1 1,9f F f× +

RNS OFDM Scheme (Cell Site 2)

5, 55, 5

4, 44, 4

3, 33, 3

2, 22, 2

1, 11, 1

AccumulatorAccumulator

m=9, m=9, n=10n=10

User 2User 2(34(34 7,4)7,4)

m=9, n=10m=9, n=10

User 1User 1(17(17 8,7)8,7)

m=9, n=10m=9, n=10

2,0 1 1,8f F f× +

2,1 1 1,9f F f× +

2,2 1 1,0f F f× +

2,3 1 1,1f F f× +

2,4 1 1,2f F f× +

2,2 1 1,8f F f× +

2,3 1 1,9f F f× +

Transition among Different QoSStates

Service Priority/Pricing ( ): Gold, Silver, Service Priority/Pricing ( ): Gold, Silver, ……

Traffic Class ( )

classQoS

streamQoS

Assignment of MAC StatesAssignment of MAC States

Traffic Class ( )

*class streamQoS QoS QoS=

MAC SchedulerMAC scheduler determines physical resource based on cost measurement (applicable for both uplink and downlink traffic).

1 2 3 4

1 2 3 4

* * * *Cost w BER w SL w SO w DELw w w w

= + + +∀ + + +

Conclusion•Proposed a cross-layer design scheme, especially among application, MAC and physical layer, for the wireless QoS content delivery.

•Our open end-to-end IP-based network structure allows inter-networking with heterogeneous networks and IP applications

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Acknowledge:Acknowledge:TiejunTiejun LvLvHaitao ZhengHaitao ZhengYingda ChenYingda Chen

For the details, please visit For the details, please visit http://http://binary.engin.brown.edubinary.engin.brown.edu

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Recent Journal PapersRecent Journal Papers• Jie Chen, Y. Chen, Tiejun Lv and W Zhu “A Timing-jitter Robust and FCC/WLAN Compliant UWB Modulation Scheme”, submitted to IEEE Wireless Communication

• Tiejun Lv, Hua Li and Jie Chen “Joint Blind Estimation of Symbol-timing and Carrier-frequency Offset of OFDM Systems over Fast Time-varying MultipathChannels”, to appear IEEE Trans. on Signal Processing

• Tiejun Lv, Jie Chen, and Hua Li “Low-complexity Blind Symbol Timing Offset Estimation in OFDM Systems”, to appear in EURASIP Applied Signal Processing, 2004

• Jie Chen, Tiejun Lv and Haitao Zeng “Joint Cross-layer Design for Wireless QoS Content Delivery”, to appear in EURASIP Applied Signal Processing, 2004

• Guolin Sun, Jie Chen, Wei Guo, and K. J. Ray Liu, “Signal ProcessingTechniques in Network-aided Positioning: A Survey”, to appear in IEEESignal Processing Magazine, 2005