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Research highlights

• Framework for Traffic Analysis in Wireless Networks,

first exact solution for outage in cellular networks

• 1st paper on MC-CDMA

• ICI mitigation in mobile OFDM

• New Attacks on Watermarking

• Detection theory applied to watermarking

• Privacy in Biometrics

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Research Highlight 1991: Framework for Traffic Analysis in Wireless Networks

• Mathematical framework based on Laplace Transforms for the analysis of random access schemes (MAC ) for wireless networks (considering PHY)

• Basic idea: – Rayleigh fading gives exponential pdf of power– Average performance = Laplace {performance | channel}– Interference power = sum of power of individual components – Average performance

• Visibility, Impact, Results: – Vederprijs 1992, MSc Cum laude, PhD cum laude– Monograph published by Artech House (their 2nd book on Wireless) – More than 119 citations (+ 34 + 33 + 17 + 15 + 14 + 10 + ..)– Virtual Cellular Network: in Chinese cellular proposal

area

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i

i P

zPfcapture

0),()Pr( L

3

Research Highlight 1993:

1st paper on MC-CDMA

• Basic idea:– cascade CDMA and OFDM,

or equivalently,– define spreading codes in the frequency

domain– Advantages in simultaneous user

separation in multipath channels

Frequency

Tim

e +-+--+-+

DS-CDMA

Frequency

Tim

e

+ - + -

+ - +-

+ - +-

MC-CDMA

Frequency

Tim

e

OFDM

P/SI-FFT

NS/P N

B

Code

Matrix

C

N

A

• Impact: – Name and concept MC-CDMA proposed first in 1993 paper– Citations 405 + 37 + 38 + 26 + 20– MC-CDMA has become a major research topic (85,300 Google hits)– MC-CDMA proposed in several standards (ETSI, IEEE 802)

S/P P/SI-CodeMatrixC-1

FFTN N N

Y

WeighMatrixW

N

A

Credit also to Gerhard Fettweis

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Research Highlight 2002 - 2004: ICI mitigation in mobile OFDM• Basic idea

– series expansion of temporal behavior of subcarriers allows simple modeling of Inter Carrier Interference

– Extension of statistical propagation model: behavior for derivatives

• Impact, Visibility– 2 IEEE Transactions papers (2004)– patent applications– Basis for solution implemented in two ICs: – 15 + 10 + 8 citations

0 10 20 30 40 50 60 700

5

10

15

20

25

30

Subcarrier number

Ou

tpu

t S

INR

Conventional OFDM MMSE equalization

MMSE ICI canceller

Conventional OFDM

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50120

srms

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mpn Tmnj

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qp

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Credit also to Stan Baggen et al.

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Research Highlight 1997: Detection theory applied to watermarking

The basic idea• Watermarking is equivalent to the detection of weak

signals in the presence of structure interference• Hollywood content is not AWGN • Exploit structure (predictability) in the content

Impact• Papers, 60 + 19 + 15 + .. citations• Basic patent granted on predictive filtering for WM

detection• Applied in Watercast product

“you have seen content with our invisible watermarks, which are detected 24/24 on 1000 tv stations, using algorithms based on this idea”

H-1AWGN Image

Watermark + H X

H

Watermark

MF

Credit also to Ton Kalker

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Research Highlight 1998: New Attacks on Watermarking

• Basic Idea: – robustness of watermark requires contiguous

decision regions, whereas confidentiality of the key would require scattered chaotic regions

– Search for point on “the” decision threshold of WM detector

– Then evaluate sensitivity to small perturbations, say, dimension by dimension

• This strongly suggests the Conjecture:– Public-key watermarking can not exist

• Impact– Patented countermeasures– IEEE Proceedings paper and IHW– Citations: 150 + 71 + 62 + 38

Space of images

Set of random images

Set of watermarked images

Yes

No

No

No

NoNo

Yes

Yes

Yes

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fingerprintfingerprint

Research Highlight 2002: Privacy in BiometricsThe issue with conventional biometry:• Biometric template data can be misused by dishonest verifiers

• Someone who finds your passport can misuse your fingerprint • How to set up a public data base for biometric verification?

Basic idea:• One-way functions (cf. password protection) can be used if(f!)

biometric measurements are preconditioned by ‘helper data’

• Information theoretic proof that helper data reveal less than , that is, I(W;X)

• Helper date does not need to affect reliability (FAR & FRR)

F(x)XY

Y

X

F

F(x)Y

noise

N

G(x,w)X

Challenge

Helper data W

Impact• leading theme for 10 fte project now at Philips

Research, and project at universities.• Potential impact: passports that contain

verification data for biometrics, without allowing misuse

• Privacy protection even in public database with dishonest verifiers of fingerprint

• Basis for PUF Research • Citations: 15 + 9 (since 2003)• Tuyls, Willems: “effective cryptographic key

length = Shannon capacity of biometric measurement channel”

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Curriculum vitae: Education

• Masters: • Eindhoven University of Technology, The Netherlands• Ir., Cum Laude, December 1986

• PHD• Delft University of Technology, The Netherlands• Dr., Cum Laude, December 18, 1991• Promoter Prof. Jens Arnbak

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Curriculum vitae: Professional experience• Physics and Electronics Lab (FEL-TNO): radio propagation models for

frequency and operations planning – 1987-1988: Research Scientist, on military service (ROAG)

• Delft University of Technology: Teletraffic in wireless networks– 1988-1991: Universitair Docent (Asst. Prof.) – 1994: Universitair Hoofddocent (Assoc. Prof.)

• The University of California at Berkeley: Wireless Multimedia Communication

– 1992-1993: Assistant Professor– 1995-1998: Adjunct Asst. Professor

• Nat.Lab. Philips Research, Eindhoven: Conditional access, Copy management, Watermarks, Biometrics till 2003, Communication Systems after 2002

– 1995-1998: (Senior) Research Scientist– 1998-2000: Principal Scientist– 2001-now: Department Head, Senior Director

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Teaching experience• T.U. Delft

– Transmission systems

• U.C. Berkeley – Signal and Systems EECS 120, – Probability Theory EECS 226, started EECS 126, – Selected Topics in Communications EE 290i: Wireless Communication

• Short Courses & Tutorials– U.C. Extension: Wireless Communication Networks– Philips CTT: Wireless Basics; Advanced wireless; RF Transceivers; CoCoSec

(Security and DRM)– EESI; PATO; IPA; EIDMA; WIC; EPFL

• Coaching of students in during internships, and MSc, PhD, postdocs– UC Berkeley; TU Delft; Philips Research

• Freelance radio presenter– NOS, ROZ; various local radio stations; Internet webstation

• Educational CD-ROM and Internet– Kluwer; Springer