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)
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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%)
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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%)
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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
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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
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☺☺☺☺ 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)
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- 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
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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
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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)
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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
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- 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
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HDR : the outcome of joint works
• SCEE and SUPELEC members involvement
• huge work provided by PhD students and Post-docs