Habilitation à Diriger des Recherches

- Rennes 1 University -

Yves LOUËT

Taking peak factor into account in telecommunication systems

SUPELEC, Rennes Campus

1

SUPELEC, Rennes Campus

IETR – Institut d’Electronique et de Télécommunications de Rennes

Thursday, 21th of January, 2010

I Research activities synthesis

II PAPR work

III Research project

Outline

2

IV Knowledge spreading

I Research activities synthesisII PAPR work

III Research project

IV Knowledge spreading

1. Professional experience

3

1. Professional experience

2. Research context

3. PhD and Post-doc supervisions

4. Scientific production in a nutshell

I-1 Professional experience (1/3)

1993-96Master Research and Engineering degrees in ENSPM/ISITV

Telecommunications

Military service in Rennes University

Project on VHF RADAR

-RADAR interface

4

1996-97

-RADAR interface

-Real outside measurements

PhD thesis in SUPELEC

PAPR mitigation with Reed-Muller codes

- PAPR equals 3 dB whatever the subcarriers number

- Reed-Muller codes associated with BCH as product codes

Benefits : error correction and PAPR mitigation

I-1 Professional experience (2/3)

5

1997-2000 Drawback : if the subcarriers number increases, the code rate decreases

codingx(t) y(t) x(t)

HPA decoding

PAPR = 3 dB

2000-2002

Research engineer in SIRADEL (Rennes)

Propagation channel modelling

I-1 Professional experience (3/3)

6

Since 2002Associate Professor

Digital communications

- french research projects (COMMINDOR, ERMITAGES, ERASME)

- bridge radio and systems

SCEE (Signal Communication Embedded Electronics )

SUPELEC

Environment Member of IETR (Research Unity of french CNRS)

Objective Cognitive radio for telecommunication systems

II-2 Research team (1/2)

7

Objective Cognitive radio for telecommunication systems

Members 10 Professors, 17 PhD, 5 post-docs (Jan. 10)

Head Jacques PALICOT

II-2 Current research activities of the author (2/2)

Digital

communications

PAPR

Multicarrier modulations

8

Software radioParametrization – theoretical approach

Parametrization – pragmatic approach

Cognitive RadioFree bands detection

Spectrum access under PAPR metric control

II-3 Supervisings (1/2)

2002 2003 2004 2005 2006 2007 2008 2009

Sidkiéta Zabré (30%)

SWR and PAPR

Completed PhD thesis

Ali Al Ghouwayel (70%)

Sylvain Tertois (30%)

amplification and NN

Thomas Ta (50%)

9

Ali Al Ghouwayel (70%)

Reconfigurable FFT

Basel Rihawi (70%)

PAPR and MIMO

Sajjad Hussain (70%)

Cognitive Radio and PAPR

Désiré Guel (30%)

PAPR and OFDM

Thomas Ta (50%)

TCB and FPGA

2007 2008 2009 2010

II-3 Supervisings (2/2)

Post-docs

Irène Mahafeno (50%)

PAPR and DVB-T2

Alexandre Skrzypczack (100%)

10

Alexandre Skrzypczack (100%)

PAPR and DVB-H / DRM

Hongzhi Wang (100%)

Parametrization

II-4 Scientific production in a nutshell (Janv. 10)

7 journal papers

3 book chapters

31 publications in international conferences

11

4 patents

6 publications in national conferences

I Research activities synthesis

II PAPR workIII Research project

IV Knowledge spreading

1. Power amplification context

12

2. PAPR analysis

3. PAPR reduction methods

4. Synthesis

II -1 Power amplification context (1/6)

- signals with modulated carriers generate high amplitude variations

- undergo non linear distortions with non linear devices

Signal : modulated carriers to be amplified

Non linear device : power amplifier

13

Base band processings

RF carrier

Power amplifier

antenna

• Power amplifier : key stage in transmitter

• About 60 % of energy in a 2.5 G terminal is due to the power amplifier

But ….

II -1 Power amplification context (2/6)

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• Power amplifiers efficiency can be very low (at best 50 % for class A HPA)

• Power amplifiers have non linear characteristics

Non linearity

0 0 .5 1 1 .5 2 2 .5 3 3 .5 40

0 .2

0 .4

0 .6

0 .8

1

1 .2

1 .4

1 .6

1 .8

2

Pe

PS

Linear area Non linear area

Pdc

A M PLIFICATEUR

Puissance d’entrée

Puissance dissipée

A lim entation

Puissance de sortie

Pe

Pdiss

Ps

Pdc

A M PLIFICATEUR

Puissance d’entrée

Puissance dissipée

A lim entation

Puissance de sortie

Pe

Pdiss

Ps

Efficiency

e(t)

y(t)

15

Linear area Non linear area

( ) ( )( ))t(eΦ)t(Ψtωcos)t(eA)t(y cc ++=

If non linear =>

- Out of band regrowth

- BER drop

PdissPdiss

dc

s

P

P=η

If low efficiency

=> Highly energy consuming

II -1 Power amplification context (4/6)

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PAPR : Peak to Average Power Ratio = peak factor

IBO : Input Back Off

To amplify a highly fluctuated signal with the less distortions as possible

II -1 Power amplification context (5/6)

Target

Solutions Back Off Linearization PAPR mitigation

17

☺☺☺☺ High linearity

High linearity

A little improvement in

efficiency

High efficiency

���� Very low efficiency Complexity Complexity, ….

Consequences

• Need to derive PAPR

- single carrier modulations case

- multi carrier modulations case (OFDM, SWR)

- different contexts (broadcasting, WLAN, mobile, …)

II -1 Power amplification context (6/6)

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• PAPR methods

- downward compatibility ?

-Trade off between complexity/performance

II-2 PAPR analysis (1/6)

- PAPR : Peak to Average Power Ratio

- calculated in base band or RF (a 3 dB gap)

- linked to many parameters

Introduction

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- depends highly on integration time and state of signal

- two ways to derive PAPR : deterministic / probabilistic

Contribution PAPR expression in signal carrier modulation

Context Sidkiéta Zabré and Basel Rihawi PhD thesis

RC filter RRC filter

II-2 PAPR analysis (2/6)

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Contribution PAPR at MIMO-OFDM receiver

Context Basel Rihawi PhD thesis

PAPR calculated at receiver

II-2 PAPR analysis (3/6)

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PAPR calculated at receiver

PAPR calculated at receiver, MIMO and multi-paths channels (in Rayleigh flat fading channels)

Contribution Frequency PAPR vision

Context Sidkiéta Zabré and Sajjad Hussain PhD thesis

II-2 PAPR analysis (4/6)

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PAPR calculated per frequency

Jacques Palicot, Yves Louet, Sajjad Hussain, Sidkieta Zabre "Frequency Domain Interpretation of Power Ratio Metric

for Cognitive Radio Systems » IET Communications Journal, vol.2, Issue 6, pp. 783-793, July 2008

Meaningful for Software radio PAPR derivation, for filtering, …

Contribution PAPR : from OFDM to SWR

Context Sidkiéta Zabré and Sajjad Hussain PhD thesis

II-2 PAPR analysis (5/6)

- SWR signal = multiplex of standards

- one standard = multiplex of carriers (orthogonal or not)

⇒ OFDM signal is a particular case of SWR signal

⇒ PAPR problem is same in SWR as OFDM

- central limit theorem => equivalence between OFDM and SWR

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- central limit theorem => equivalence between OFDM and SWR

⇒ well known methods in OFDM can also be applied in SWR

Contribution PAPR : a new sensor for cognitive radio

Context Sajjad Hussain PhD thesis

II-2 PAPR analysis (6/6)

24Yves Louet, Jacques Palicot, Sajjad Hussain "Power Amplification issues related to Dynamic Spectrum Access in

the Cognitive Radio Systems", Cognitive Radio Systems ISBN 978-953-7619-25-1, In-Tech, 2009.

II-3 PAPR reduction methods (1/13)

- a spate of methods since a dozen of years

- need to clarify the methods benefits and drawbacks

- continuous trade off between :

Introduction

25

• PAPR reduction capabilities

• other parameters corruption (BER, power, complexity)

- a classification appears to be of great use

Contribution Classification of methods at the transmitter

II-3 PAPR reduction methods (2/13)

26Yves Louet and Jacques Palicot "A classification of methods for efficient power amplification of signals"

Annals of Telecommunications, vol. 63, Issue 7-8, pp 351-368, July/August 2008

First class of proposed methods : with downward compatibility

II-3 PAPR reduction methods (3/13)

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- adding signal methods- clipping methds

Contribution Adding signal methods without BER degradation

Context Sidkiéta Zabré(1) PhD thesis, Irène Mahafeno Post-doc (2)

IFFT

X0

XN-1 +

IFFT

C0

CN-1

x(t)

c(t)

x(t)+c(t) + convex optimization (SOCP)

+ spectrum mask constraint

+ added power constraint

Out of band carriers

In band reserved carriers

II-3 PAPR reduction methods (4/13)

(1) WiFi context

(2) DVB-T2 context

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OFDM context

Irène Mahafeno, Yves Louët, Jean-François Hélard " Peak-to-average power ratio reduction using second order cone programming based tone

reservation for terrestrial digital video broadcasting systems « IET Communications Journal, vol. 3, Issue 7, pp. 1250-1261, July 2009

Yves Louet, Sidkiéta Zabré, Jacques Palicot, Christian Lereau "Traitement d’un signal de communication avant amplification en

modulation mutliporteuse" FR 0701922

no BER degradation

Contribution Adding signal methods without BER degradation

Context Basel Rihawi(1) and Sajjad Hussain(2) PhD thesis

(1) MIMO-OFDM context (2) Cognitive Radio context

II-3 PAPR reduction methods (5/13)

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Multiplex of GSM carriers(WiMax)

Basel Rihawi and Yves Louet "PAPR Reduction Scheme with SOCP for MIMO-OFDM systems

International Journal of Communications, Network and System Sciences, vol.1, no 1, pp 29-35, Feb. 2008

Contribution Distortion methods viewed as adding signal methods

Context Désiré Guel PhD thesis

- Bussgang theorem:

PAPR reduction signal

In band term (responsible from BER drop)

Out of band term (shoulders regrowth)

+

C

II-3 PAPR reduction methods (6/13)

30

- Bridge Tone Reservation (TR) and distortion methods

C

Any distortion methods does not modify BER if formulated as TR

Contribution New method : geometric method

Context Désiré Guel PhD thesis

Proposed method Signal overview

II-3 PAPR reduction methods (7/13)

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• Si ∆f increases, PAPR gain drops

Si ∆f decreases, BER increases

• 2 dB better than literature but RF complexity (filter + HPA)

Main results

Yves Louet, Desiré Guel, Jacques Palicot, Sidkiéta Zabré, Christian Lereau "Génération d’un signal additionel et réduction de la

dynamique d’un signal de modulation numérique" FR 0701174

with BER degradation

Contribution New method : hyperbolic clipping

Context Désiré Guel PhD thesis

PAPR and mean added power derivationsPrinciple

II-3 PAPR reduction methods (8/13)

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Results • PAPR reduction gain without additional power

• no BER increase if formulated as TR

Desiré Guel, Jacques Palicot, Yves Louet, "Clipping HSC tenant compte des porteuses non utilisées" FR 0950895

Contribution Deep-clipping method applied to DVB-H

Context Alexandre Skrzypczack Post-doc

Principle

• clipping is always followed by a filter

• deep-clipping : mitigate peak regrowth after filtering

II-3 PAPR reduction methods (9/13)

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Proposed schemes for DVB-H

DC : Deep-Clipping, RC : regular clipping

DC vs RC

Second class of proposed methods : without downward compatibility

34

Contribution Using pilot carriers for PAPR reduction

Context Irène Mahafeno and Anh Tai Ho Post-docs

Principles

• using pilots carriers rather than reserved carriers

• PAPR reduction and channel estimation are done jointly

• need a deterministic law between pilot symbols

=> the receiver has to be modified so as to recover pilot symbols and estimate channel coefficients

II-3 PAPR reduction methods (11/13)

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16 pilots (over 2048)

Additive law between symbols

BER is increased if bad channel estimation

Irène Mahafeno, Jean-François Hélard, Yves Louet "Procédé et dispositif de transmission d’un signal multiporteuse

utilisant les mêmes porteuses pilotes pour réduire le rapport puissance crête à puissance moyenne" FR 0952964

Third class of proposed methods : at the receiver

at the transmitter at the receiver

equalization

36

estimation

Contribution To offset non linearities with a neural network

Context Sylvain Tertois PhD thesis

II-3 PAPR reduction methods (13 /13)

37

neural network

Offset non linearities

In time or frequency domain

What is under investigation at SCEE :

Turbo non linear interferences canceller

Projects

Two-sided

FTR&D (2004-05) SWR and PAPR

ALCATEL (2006-07) Bibliography on PAPR reduction methods

AMONT (2008-10)

(Pôle I&R)PAPR applied to DRM and DVB-H

II-4 Synthesis regarding PAPR (1/3)

38

Co-operated

(Pôle I&R)PAPR applied to DRM and DVB-H

DTTV2 (2008-10)

(Pôle I&R)PAPR applied to DVB-T2

IGYC (2010-11)

UEBGreen communication and PAPR

B21C (2007-09)

(European CELTIC project)PAPR and DVB-T2

Research activities organisations

Tutorials

ISSPIT 2007 (Cairo)PAPR mitigation and linearity enhancement methods :

an overview and a classification

ISWCS 2008 (Reykjavik)Recent advances in PAPR reduction methods for

multicarrier signals

II-4 Synthesis regarding PAPR (2/3)

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Special

sessions

convener

ISSPIT 2006 (Vancouver)Peak to Average Power Ratio of a Multiplex of

Modulated Carriers

EW 2007 (Paris) PAPR mitigation in OFDM

URSI 2008 (Chicago) Signal Processing for Software radio systems

II-4 Synthesis regarding PAPR (3/3)

• PAPR has become a hot topic in digital communications since a dozen of years

• companies are now well aware of PAPR reduction necessity in telecommunication systems

• current need of energy saving justifies as much again PAPR studies

• up to date methods : reserved tones (DVB-T2) (need further studies → pilots, clipping)

• today’s needs:

1. Take PAPR into account ASAP in standards proposals

4040

1. Take PAPR into account ASAP in standards proposals

2. Need to balance :

- PAPR algorithms complexities

- performance drop (BER, ACPR, spectral efficiency, …)

3. An overview of effective PAPR gain when PAPR method is applied

(by taking into account all key parameters)

I Research activities synthesis

II PAPR work

III Research projectIV Knowledge spreading

1. PAPR issue

41

1. PAPR issue

2. Parametrization issue

III-1 Research Project (1/5)

PAPR issue

Projects Why ? Ideas

Frequential PAPR

To simplity PAPR reduction methods (as TR)

Understand filtering influence on PAPR

Expect to find new methods

Probabililty

42

System overview Need to dwell on effective PAPR gain by taking all into accountAnalytical

solutions

PAPR and random

matrix theoryNew PAPR view, new PAPR methods expected

Singular value of

Hankel matrix

PAPR and

linearization

Joint scheme

(Master Research internship 2010, national research projects ...) Feed-back

III-2 Research Project (2/5)

Axe Parametrization issue

- Three PhD thesis completed:

Sufi Tabassum Gul (2006-09), Ali Al Ghouwayel (2004-08), Hongzhi Wang (2005-08)

- post-doc de Virgilio Rodrigez (2006-07)

- co-operation with CEA LETI : Laurent Alaus PhD thesis (2006-10)

Work already done

43

- co-operation with CEA LETI : Laurent Alaus PhD thesis (2006-10)

- with CEA LETI : Malek Naoues (2009-12)

(triple PhD scheme with SUPELEC, CEA, SUPCOM Tunis)

- with Lebanese University of Beirut : Patricia Kaiser (joint PhD with SUPELEC (2009-12))

Coming PhD thesis

Contribution New common operators for pragmatic approach

Context Ali Al Ghouwayel and Laurent Alaus* PhD thesis

III-2 Research Project (3/5)

Parametrization issue

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reconfigurable FFT (over C and GF) LFSR

* not supervised by author

Need more investigations (scheduling)

- Malek Naoues PhD thesis (2009-12) -

Ali Al Ghouwayel and Yves Louet "FPGA implementation of a re-configurable FFT for multi-standard systems

in software radio context", IEEE Trans. On Consumer Electronics Journal, vol. 55, n°2, pp. 950-958, May 2009.

L.Alaus, J. Palicot, C. Roland, Y. Louët, D.Noguet "Promising technique of parametrisation for reconfigurable radiothe Common Operators Technique : fondamentals and examples", to be published in The Journal of Signal Processing Systems (2009)

Contribution Theoretical approach

Context Sufi Tabassum Gul* PhD thesis

III-2 Research Project (4/5)

Parametrization issue

- SWR and graph modelling

- cost function optimization

45* not supervised by author

- common operator search as the optimal of the cost function

S. T. Gul, Ali Al-Ghouwayel, C. Moy and Y. Louët, “A Novel Design of Reconfigurable Fourier Transform Operator Over CC and

GF(GF(FFtt)) for Future Multi-standards SDR Equipments,” International Journal of Communication Networks and Distributed Systems-

IJCNDS Accepted in June 2009 for publication by the end of 2009.

Need more mathematical developments as graph theory

- Patricia Keiser PhD thesis (2009-12) -

Parametrization

ANR INFOP (2007-10)Spectrum access on free analog television bands

Bi-standards terminal design

III-2 Research project (5/5)

46

NoE NEWCOM, NEWCOM ++

(2005-10)

Parametrization techniques (Dept. D, WP4, WPRC)

I Research activities synthesis

II PAPR work

III Research projects

IV Knowledge spreading

Teaching activities and continuing education

47

IV Knowledge spreading (1/1)

Teaching (SUPELEC Engineering degree)

Courses on Digital Communications (second year)

Courses on Channel modelling (third year)

Courses on channel coding (third year)

Teaching (Lebanese University, Beirut)

4848

Continuing eduction

Digital television

SWR

OFDM / MC-CDMA

Telecommunication systems (Math. Master)

General conclusion

PAPR and parametrization : towards more economic telecommunication systems

• telecom is responsible for 2 to 3 % of the world’s greenhouse gaz emission (CO2)

• need to bridge « sustainable energy » and telecom

• signal processing can do a lot to target ernergy saving and telecom

…. but our behaviors towards telecoms need to change

49

HDR : the outcome of joint works

• SCEE and SUPELEC members involvement

• huge work provided by PhD students and Post-docs