Wednesday, December 19, 2007

Dr. Vahid Tarokh
Engineering and Applied Sciences, Harvard University

We consider approximations of signals by the elements of a redundant frame/dictionary of size M >= N in a complex vector space of dimension N and formulate both the noiseless and the noisy sparse representation problems.

The noiseless representation problem is to find sparse representations of a signal r given that such representations exist. First we construct a frame, referred to as the Vandermonde frame, for which the noiseless sparse representation problem can be solved uniquely using O(N^2) operations, as long as the number of non-zero coefficients in the sparse representation of r is L = \epsilon N for some 0 <= epsilon <= 0.5. It is known that epsilon <= 0.5 cannot be relaxed without violating uniqueness.

The noisy sparse representation problem is to find sparse representations of a signal r satisfying a distortion criterion. In this case, we establish a lower bound on the trade-off between the sparsity of the representation, the underlying distortion and the redundancy of any given frame.

We then study an associated problem, namely the number of measurements required to recover a sparse signal in C^M with L non-zero coefficients from it's compressed samples in the presence of noise. For a number of different recovery criteria, we prove that O(L) (an asymptotically linear multiple of L) measurements are necessary and sufficient if L grows linearly as a function of M. This improves on the existing literature that is mostly focused on variants of a specific recovery algorithm based on convex programming, for which O(L log(M − L)) measurements are required. We also show that O(L log(M − L)) measurements are required in the sublinear regime (L = o(M)).

This is a joint work with Mehmet Akcakaya.

Vahid Tarokh received the PhD in Electrical Engineering from the University of Waterloo in 1995. He then worked at AT&T Labs-Research and AT&T wireless services until August 2000, where he was the head of the Department of Wireless Communications and Signal Processing. In September 2000, he joined Department of Electrical Engineering and Computer Sciences (EECS) at MIT as an associate professor. In June 2002, he joined Harvard University as a Gordon McKay Professor of Electrical Engineering . Since July 2005, he is a Hammond Vinton Hayes Senior Fellow of Electrical Engineering at Harvard University, and also holds Perkins professorship of applied mathematics. His research is mainly focused in the areas of Signal processing, Communications (wireline and wireless) and Networking.

Dr. Tarokh has received a number of awards including the Governor General of Canada's Academic Gold Medal 1996 , the IEEE Information Theory Society Prize Paper Award 1999 , The Alan T. Waterman Award 2001 and was selected as one of the Top 100 Inventors of Years (1999-2002) by Technology Review magazine. In 2002, the IEEE Communications Society recognized him as the co-author of one of the 57 most important papers in all society's transactions during the past 50 years. He holds honorary degrees from Harvard University (2002) and the University of Windsor, Ontario, Canada (2003).

Thursday, December 13, 2007

Dr. Wei Yu
Electrical and Computer Engineering, University of Toronto

Decode-and-forward and quantize-and-forward are two fundamental strategies for the relay channel. Both can be considered as parity-forwarding strategies, in which the relay summarizes its observation by forming parity bits and forwards them to the destination. In the first part of this talk, we generalize parity-forwarding to relay networks with multiple relays. We show that a relay network can be degraded in more than one way and decode-and-forward can achieve the capacity of new classes of degraded relay networks. In the second part of this talk, we describe efficient implementation of parity-forwarding using low-density parity-check (LDPC) codes. We show that capacity-achieving codes in this case need to be "bi-layer" and need to simultaneously operate at two different SNRs: the SNR at the relay and at the destination. Using an EXIT-chart-based design methodology, it is demonstrated that a bi-layer LDPC code can approach the theoretical decode-and-forward rate to within a fraction of dB to capacity. The third part of this talk focuses on quantize-and-forward, and provides an example of a modulo-sum channel for which quantize-and-forward is capacity achieving. In this class of channels, the relay observes a corrupted version of the noise only and has a separate channel to the destination. This is a first example of a relay channel for which the well-known cut-set bound is not tight.

This work was done in collaboration with Peyman Razaghi and Marko Aleksic.

Wei Yu received the B.A.Sc. degree in Computer Engineering and Mathematics from the University of Waterloo, Waterloo, Ontario, Canada in 1997 and M.S. and Ph.D. degrees in Electrical Engineering from Stanford University, Stanford, CA, in 1998 and 2002, respectively. Since 2002, he has been an Assistant Professor with the Electrical and Computer Engineering Department at the University of Toronto, Toronto, Ontario, Canada, where he holds a Canada Research Chair. His main research interests include multiuser information theory, optimization, wireless communications and broadband access networks. Prof. Wei Yu was an Editor for IEEE Transactions on Wireless Communications from 2004 to 2007, and a Guest Editor of IEEE Journal on Selected Areas in Communications for a special issue on "Nonlinear Optimization of Communications Systems'' in 2006. He received an Early Researcher Award from Ontario in 2006, and an Early Career Teaching Award from the Faculty of Applied Science and Engineering, University of Toronto, in 2007.

Wednesday, December 12, 2007

Dr. Sennur Ulukus
Department of Electrical & Computer Engineering, University of Maryland

I will talk about two problems involving distributed coding and transmission of correlated data over noisy multiple access channels.

In the first setting, two users observe i.i.d. samples of two correlated sources and wish to transmit these samples to a receiver node through a noisy multiple access channel. The goal of the receiver is to reconstruct the two sources with arbitrarily small probability of error. Necessary and sufficient conditions for reliable transmission in this setting are unknown to this day. I will present a new necessary condition based on a new data processing inequality we developed recently.

In the second setting, a large number of nodes sample an underlying correlated Gaussian random process and wish to transmit their samples to a collector node through a Gaussian multiple access channel which allows cooperation and feedback. The goal of the collector is to reconstruct the entire random process with as little distortion as possible. This setting models a dense sensor network well. The minimum achievable distortion and optimum achievable schemes are unknown for any finite number of nodes. I will present "order-optimal" results when the number of nodes is very large.

This is joint work with Wei Kang and Nan Liu.

Sennur Ulukus received the B.S. and M.S. degrees in electrical and electronics engineering from Bilkent University, Ankara, Turkey, in 1991 and 1993, respectively, and the Ph.D. degree in electrical and computer engineering from Rutgers University, NJ, in 1998. During her Ph.D. studies, she was with the Wireless Information Network Laboratory (WINLAB), Rutgers University. From 1998 to 2001, she was a Senior Technical Staff Member at AT&T Labs-Research in NJ. In 2001, she joined the University of Maryland at College Park, where she is currently an Associate Professor in the Department of Electrical and Computer Engineering, with a joint appointment at the Institute for Systems Research (ISR). Her research interests are in wireless communication theory and networking, network information theory for wireless networks, signal processing for wireless communications, and security for multi-user wireless communications.

Sennur Ulukus is a recipient of the 2005 NSF CAREER Award, and a co-recipient of the 2003 IEEE Marconi Prize Paper Award in Wireless Communications. She serves as an Associate Editor for the IEEE Transactions on Information Theory since 2007, as an Associate Editor for the IEEE Transactions on Communications since 2003, as a Guest Editor for the IEEE Journal on Selected Areas in Communications in 2007, as the co-chair of the Communication Theory Symposium at the 2007 IEEE Global Telecommunications Conference, as the co-chair of the Medium Access Control (MAC) Track at the 2008 IEEE Wireless Communications and Networking Conference, and as the Secretary of the IEEE Communication Theory Technical Committee (CTTC).

Tuesday, December 4, 2007

Dr. Kim Roberts
Nortel, Ottawa

Due to demand for increased optical transmission capacity, lower cost, and better spectral efficiency, 40 Gb/s optical systems are emerging and 100 Gb/s transmission is being discussed. With increased baud rate, system performance becomes very sensitive to chromatic dispersion, noise, and Polarization Mode Dispersion. It is desirable to have 40 Gb/s systems operate over any line that supports 10 Gb/s today, without diminished reach or re-engineering.

A coherent 40 Gb/s modem will be described, with four 20 Gsample/s 6 bit ADCs to digitize the receive signal, and full compensation of dispersion and polarization using a 20 million gate CMOS digital engine.

Using Dual Polarization Quadrature Phase Shift Keying, the modem encodes 4 bits per symbol, allowing 40 Gb/s to be transmitted via 10 billion symbols per second. Digital signal processing, implemented in CMOS, allows 40 Gb/s coherent systems to achieve the same deployable reach as 10 Gb/s eDCO, substantially independent of the degradations from optical physics.

As a student, Kim applied digital signal analysis to the human brain for accurate diagnosis of Multiple Sclerosis. Since 1984, he has been developing innovative solutions for optical networks. Optical products that Kim initiated have generated billions of dollars in revenue. He has been granted 75 US patents while at the Nortel labs in Ottawa Canada, and Harlow UK. He recently demonstrated the first 10 Gb/s packet encryption, integrated into an optical multiservice switch. Kim's digital signal processing in the eDCO product has made optical compensation devices obsolete. Along with the other members of the modem development team, he is continuing that quest at 40 and 100 Gb/s.

Roberts holds a Bachelor degree in Electrical Engineering with honors mathematics and a Masters degree in Electrical Engineering with a focus on signal processing for biomedical engineering, both from the University of British Columbia (Canada).

Monday, December 3, 2007

Dr. Babak Hassibi
Electrical Engineering Department, California Institute of Technology

There has been a great deal of recent interest in the problem of information transmission over wired and wireless networks. While information theory is well poised to have an impact on the manner in which future networks are designed and maintained, the challenge is that almost all network information theory problems (even for the simplest networks) are open. In particular, there are only a limited number of tools available and so fresh approaches are required.

We will study the problem by introducing the notion of normalized entropy vectors. In particular, we show that, for a large class of acyclic memoryless networks, the capacity region for an arbitrary set of sources and destinations can be found by maximization of a linear function over the convex set of channel-constrained normalized entropic vectors and some linear constraints. While this may not necessarily make the problem simpler, it certainly circumvents the “infinite-letter characterization” issue, as well as the “nonconvexity” of earlier formulations. More importantly, it exposes the core of network information theory problems as that of determining the convex space of entropy vectors. We also show that the framework allows one to recover the classical cutset bounds via a duality argument, as well as results in network coding.

For n=2,3 random variables the space of normalized entropic is well understood, whereas characterizing it for n>3 is an open problem. We will develop some inner and outer bounds to this space, as well as describe the connections to finite group theory, quasi-uniform distributions, non-Shannon inequalities, matroids, and determinantal inequalities.

Babak Hassibi is an associate professor and vice-chairman of the electrical engineering department at the California Institute of Technology, where he has been since 2001. From 1998 to 2001 he was a member of the technical staff at the Mathematical Sciences Research Center at Bell Laboratories, Murray Hill, NJ, and prior to that he obtained his PhD in electrical engineering from Stanford University. His research interests span different aspects of communications, signal processing and control, and he has co-authored three books and numerous papers in these areas. Among other awards, he is a recipient of an Alborz Foundation Fellowship, the O. Hugo Schuck best paper award of the American Automatic Control Council, the National Science Foundation Career Award, the David and Lucille Packard Foundation Fellowship, and the Presidential Early Career Award for Scientists and Engineers (PECASE), and he was a participant in the National Academy of Engineering “Frontiers in Engineering” program. He was an associate editor of the IEEE Transactions on Information Theory from 2004-2006, and is currently on the editorial board of Foundations and Trends in Information and Communication.

Tuesday, November 6, 2007

Dr. Catherine Rosenberg
University of Waterloo

In this talk, we address the following two questions concerning the capacity and configuration of fixed multi-hop wireless networks: (i) given a set of wireless nodes with arbitrary but fixed locations, and a set of data flows, what is the max-min achievable throughput? and (ii) how should the network be configured to achieve the optimum? We consider these questions from a networking standpoint assuming that the network is operated using an appropriate schedule of conflict-free link activations, and employ a rigorous physical layer model to model conflict relationships between them. We develop and investigate a novel optimization framework to determine the optimal throughput and configuration, i.e., flow routes, link activation schedules and physical layer parameters. Determining the optimal throughput is a computationally hard problem, in general. However, using a smart enumerative technique we obtain numerical results for different scenarios of interest including one based on multiple modulations and powers, one on smart antennas and one focusing on gateway placement. We obtain several important insights into the structure of the optimal routes, schedules and physical layer parameters. Besides determining the achievable throughput, we believe that our optimization-based framework can also be used as a tool, for configuring scheduled wireless networks, such as those based on IEEE 802.16.

This work was done in collaboration with A. Karnik, A. Iyer, and S. Muthaiah.

Catherine Rosenberg is a Professor and a University Research Chair in Electrical and Computer Engineering, University of Waterloo. From 1984-86, Dr. Rosenberg was an engineer with ALCATEL, Lannion, France. From 1987-1988 she was a Member of Technical Staff at AT&T Bell Labs., Holmdel, N.J. From 1988-1996, she was a faculty member at the Department of Electrical and Computer Engineering, Ecole Polytechnique, Montréal, Canada. She was with Nortel Networks, Harlow, UK from September 1996 to July 1999 where she created and headed the R&D Department in Broadband Satellite Networking. She was also a Visiting Professor in the Department of Electrical and Electronics Engineering at Imperial College, London till January 2000. Dr. Rosenberg joined the faculty of the School of Electrical and Computer Engineering at Purdue University in August 1999 where she co-founded in May 2002 to the Center for Wireless Systems and Applications (CWSA). She joined University of Waterloo on Sept 1st, 2004 as the Chair of the Department of Electrical and Computer Engineering.

Catherine Rosenberg is on the Scientific Advisory Board of France-Telecom and on the board of governors of the IEEE Communications Society since January 2007. She was an Associate Editor for IEEE Communications Magazine, Telecommunications Systems, and IEEE Transactions on Mobile Computing, and served as IEEE Communications Surveys and Series co-Editor for the Series on Adhoc and Sensor Networks for IEEE Communications Magazine. She has been and is involved in many conferences including IEEE Infocom, IEEE Globecom, International Teletraffic Congress (ITC) and IFIP Broadband Communication. She has authored over 100 papers on broadband and wireless networking and traffic engineering and has been awarded eight US patents.

Monday, October 15, 2007

Dr. Manoj Sachdev
University of Waterloo

Embedded random access memories can occupy up to 80% of the total area of modern System on Chips (SoCs). Embedded SRAMs are the most popularly used due to its robustness compared to DRAMs. Owing to a number of constraints, embedded SRAMs have a significant impact on power, performance, testability and yield of complex SoCs. In this presentation, some of these issues will be discussed.

Manoj Sachdev is a professor in Electrical and Computer Engineering department at the University of Waterloo, Canada. His research interests include low power and high performance digital circuit design, mixed-signal circuit design, test and manufacturing issues of integrated circuits. He has written three books, three book chapters on integrated circuits and has contributed to more than one hundred twenty five articles in conferences and journals. He and his co-authors won several awards. He received the best paper award for his paper in European Design and Test Conference, 1997 and an honorable mention award for his paper in International Test Conference, 1998. He holds more than 15 granted and several pending US patents in the area of VLSI design and test. He is a senior member of IEEE.

He was with Semiconductor Complex Limited, Chandigarh (India) from 1984 till 1989 where he designed CMOS Integrated Circuits. From 1989 till 1992, he worked in the ASIC division of SGS-Thomson at Agrate (Milan). From 1992 till 1998, he worked in Philips Research Laboratories, Eindhoven, where he researched on various aspects of VLSI circuit design, testing and manufacturing.

Wednesday, September 26, 2007

Dr. George V. Eleftheriades
University of Toronto

Recently there has been renewed interest in artificial materials with electromagnetic properties that cannot be found in nature. Therefore these materials are referred to as “metamaterials” (“meta” means “beyond” in Greek). This lecture addresses metamaterials that can support negative refraction of electromagnetic waves. For example, the feasibility of media that simultaneously exhibit negative permittivity and negative permeability, hence a negative refractive index, has been known since the sixties. However it is only recently that people invented ways to realize them. In such negative-refractive-index (NRI) or “left-handed” metamaterials, waves can be thought of as propagating backwards instead of forwards. When interfaced with conventional dielectric materials, incident waves become focused on a point instead of diverging outwards, thus suggesting the implementation of lenses with flat surfaces.

In this lecture, first the fundamental properties of NRI metamaterials will be reviewed. Subsequently, it will be demonstrated that NRI metamaterials can be synthesized using planar networks of loaded transmission lines (TL). The resulting NRI-TL metamaterials can be easily constructed using embedded capacitors and inductors, and they offer wide operating bandwidths. The extension of these media to 3D isotropic and related volumetric NRI-TL metamaterials will also be discussed. Based on this approach, microwave NRI metamaterial lenses that can resolve details beyond the classical diffraction limit will be presented. Moreover, a number of useful antenna and microwave devices, enabled by such NRI-TL metamaterials will be demonstrated. Finally, potential realizations of NRI-TL metamaterials and related devices at optical frequencies will be briefly discussed. These enabling materials and devices can find applications in diverse areas such as wireless communications, defence, medical imaging, photolithography and microscopy.

George V. Eleftheriades earned his Ph.D. and M.S.E.E. degrees in Electrical Engineering from the University of Michigan, Ann Arbor, in 1993 and 1989 respectively, and a diploma in Electrical Engineering from the National Technical University of Athens, Greece in 1988. In the period 1994-1997 he was with the Swiss Federal Institute of Technology in Lausanne. Presently he is a full Professor and the Canada Research Chair/Velma M. Rogers Chair at the Department of Electrical and Computer Engineering at the University of Toronto. In June 2005 he co-edited/co-authored a book titled “Negative-Refraction Metamaterials: Fundamental Principles and Applications” published by Wiley & IEEE Press.

Dr. Eleftheriades received the Ontario Premier's Research Excellence Award in 2001. In 2004 he received an E.W.R. Steacie Fellowship from the Natural Sciences and Engineering Research Council of Canada. Dr. Eleftheriades is a Fellow of the IEEE and serves as a Distinguished Lecturer for the IEEE Antennas and Propagation Society.

His present research interests include negative-refraction metamaterials for microwave and optical applications, antennas and components for wireless communications, novel antenna beam-steering techniques, low-loss Silicon micromachined components, plasmonic nano-structures, and electromagnetic design for high-speed digital circuits.

Wednesday, September 12, 2007

Dr. Omar M. Ramahi
University of Waterloo

As digital circuits become faster and more powerful, direct radiation from printed circuit boards (PCB) increases due to simultaneous switching noise. In fact, as the clock frequency increases and the wavelength shrinks, structures that were electromagnetically quite, are now radiating like never before. How can we roll back this nauseating trend of more and more radiation and more and more restrictive radiation standards? We can try the same old tricks we did for many years, but many will probably agree that the effectiveness of voodoo, black magic and decoupling capacitors is reaching its theoretical limit. Recent years have witnessed the introduction and development of new type of structures referred to as Electromagnetic Band Gap (EBG) material (other names are also given to these materials such as photonic band gap, High-Impedance Surfaces (HIS), or Metallo-Dielectric material). These novel structures are essentially tiny resonators whose behavior is frequency dependent. EBGs have been used in different electromagnetic applications but primarily in improving the radiation characteristics of antennas. The fact that EBGs are composed of resonators, in essence they mimic the behavior of filters. For this particular reason, EBG structures have a strong role to play in the wide area of noise mitigation and control within boards and packages.

 In this seminar, we introduce EBG concepts and structures. We briefly discuss the theoretical background with the intention to enable their design for custom applications. We discuss EBG structures’ use for wireless boards applications and focus on their potential for suppressing common-mode noise and the important tradeoffs that affect the signal integrity. Finally, we show the potential of EBG structures for suppression noise on packages and for isolation in mixed-signal system design.

Omar M. Ramahi received the BS degrees in Mathematics and Electrical and Computer Engineering (summa cum laude) from Oregon State University, Corvallis, OR. He received his M.S. and Ph.D. in Electrical and Computer Engineering from the University of Illinois at Urbana-Champaign. From 1990-1993, Dr. Ramahi held a visiting fellowship position at the University of Illinois at Urbana-Champaign. From 1993 to 2000, he worked at Digital Equipment Corporation (presently, HP), where he was member of the alpha server product development group. In August of 2000, he joined the faculty of the James Clark School of Engineering at the University of Maryland at College Park. At Maryland he was also a faculty member of the CALCE Electronic Products and Systems Center. Presently, he is the Associate NSERC/RIM Industrial Research Chair in the Electrical and Computer Engineering Department, University of Waterloo, Waterloo, Ontario, Canada.

Dr. Ramahi was instrumental in developing computational techniques to solve a wide range of electromagnetic radiation problems in the fields of antennas, high-speed devices and circuits and EMI/EMC. His interests include experimental and computational EMI/EMC studies, high-speed devices and interconnects, biomedical applications of electromagnetics, novel optimization techniques, and interdisciplinary studies linking electromagnetic application to novel materials. He has authored and co-authored over 150 journal and conference paper. He is a co-author of the book EMI/EMC Computational Modeling Handbook, 2nd Ed. (Springer-Verlag, 2001). Dr. Ramahi served as a consultant to several companies and was a co-founder of EMS-PLUS, LLC and Applied Electromagnetic Technology, LLC.

Thursday, July 26, 2007

Dr. Giuseppe Caire

EE Department, Viterbi School of Engineering
University of Southern California

We consider a linear time-invariant channel with given transfer function, whose output is corrupted by additive white Gaussian noise and random erasures. Determining the capacity of this channel requires obtaining the asymptotic spectral distribution of a submatrix of a nonnegative definite Toeplitz matrix obtained by retaining each column/row independently and with identical probability.

This is a new problem in random matrix theory that does not follow from previously known results. We find explicitly the required asymptotic eigenvalue distribution in terms of a fixed-point equation, that yields the eta-transform of the distribution. This results represents the first known connection between the well-known theory of large Toeplitz matrices (Grenander-Szego) and random matrices.

Also, we shall stress an appealing formal analogy with free-probability and the S-transform, even though freeness does not generally apply to this problem. This may suggest that freeness is a too restrictive condition for the S-transform to apply.

Furthermore, we find the optimal input spectrum that achieves capacity and show that this is given by the waterfilling solution as in the case of no erasures, but computed for a scaled SNR that takes into account the preence of erasures.

We find simple and easily computable upper and lower bounds to capacity, and we characterize the effect of erasures on the key quantities that determine the high-SNR and low-SNR regimes of spectral efficiency versus Eb/N0.

Applications of these results are, for example, the capacity of Gaussian channels with impulsive noise, in the limit of very large impulse power, the capacity of a Wyner-model cellular system with centralized processing, where the base stations are connected to the central processor through unreliable links that can be either ``on'' or ``off'' with a certain probability, and the characterization of the mean-square error of a linear predictor (e.g., a Kalman filter) with randomly missing observations.

Giuseppe Caire was born in Torino, Italy, in 1965. He received the B.Sc. in Electrical Engineering from Politecnico di Torino (Italy), in 1990, the M.Sc. in Electrical Engineering from Princeton University in 1992 and the Ph.D. from Politecnico di Torino in 1994. He was a recipient of the AEI G.Someda Scholarship in 1991, has been with the European Space Agency (ESTEC, Noordwijk, The Netherlands) from May 1994 to February 1995, was a recipient of the COTRAO Scholarship in 1996 and of a CNR Scholarship in 1997.

He has been visiting Princeton University in summer 1997 and Sydney University in summer 2000. He has been Assistant Professor in Telecommunications at the Politecnico di Torino, Associate Professor at the University of Parma, Italy, Professor with the Department of Mobile Communications at the Eurecom Institute, Sophia-Antipolis, France, and he is now professor with the EE Department of the Viterbi School of Engineering, University of Southern California, Los Angeles, CA.

He served as Associate Editor for the IEEE Transactions on Communications in 1998-2001 and as Associate Editor for the IEEE Transactions on Information Theory in 2001-2003. He received the Jack Neubauer Best System Paper Award from the IEEE Vehicular Technology Society in 2003, and the Joint IT/Comsoc Best Paper Award in 2004. Since November 2004 he is member of the Board of Governors of the IEEE Information Theory Society and is Fellow of IEEE.

His current interests are in the field of communications theory, information theory and coding theory with particular focus on wireless applications.

Thursday, July 12,2007

Dr. Frank R. Kschischang
University of Toronto

Random network coding is a powerful tool for efficient information dissemination in networks, wherein information is transmitted as fixed-length vectors over a finite field F, and intermediate nodes are permitted to forward random F-linear combinations of packets that they receive. Unfortunately, random network coding is highly susceptible to errors caused by noise, intentional jamming or packet losses.

In this talk I will describe a new approach to the problem of error-control in random network coding.
Motivated by the property that, in the absence of errors, random network coding is vector-space
preserving, information transmission is modeled as the injection into the network of a basis for a vector
space V over F and the collection by the receiver of a basis for a vector space U. After introducing a
suitable metric on the collection of subspaces, I will show that a minimum distance decoder for this
metric achieves correct decoding if the dimension of the intersection of V and U is large enough. If the
dimension of each codeword is restricted to a fixed integer, the code corresponds to a well-separated subset of the vertices of a Grassmann graph. Sphere-packing and sphere-covering bounds as well as generalization of the Singleton bound are provided for such codes. Finally, I will describe a Reed-Solomon-like code construction and a decoding algorithm for error-and-erasure correction.

This is joint work with Ralf Koetter, Technical University of Munich.

Frank R. Kschischang is a Professor in the Department of Electrical and Computer Engineering at the University of Toronto, where he holds the Tier-I Canada Research Chair in Communications Algorithms. He received the B.A.Sc. degree from the University of British Columbia in 1985 and M.A. Sc. and Ph.D. degrees from the University of Toronto in 1988 and 1991, respectively, all in electrical engineering.

A former associate editor for Coding Theory of the IEEE Transactions on Information Theory, he is now a member of the Board of Governors of the IEEE Information Theory society. He served as technical program co-chair for the 2004 IEEE International Symposium on Information Theory (ISIT) held in Chicago, and serves as general co-chair for the 2008 ISIT, which will be held in Toronto.

A popular teacher, Professor Kshischang has three times been voted “Professor of the Year” by undergraduate students, and he received the University of Toronto Faculty of Applied Science and Engineering Faculty Teaching Award in 2006. He is a recipient of the Ontario Premier’s Research Excellence Award. He is a Fellow of the Engineering Institute of Canada and also a Fellow of IEEE.

Wednesday, July 11, 2007

Dr. Raafat R. Mansour
University of Waterloo

The Micro-Electro-Mechanical System (MEMS) technology is the next logical step in the silicon revolution. It is destined to become the hallmark technology over the next two decades with numerous applications having a dramatic impact on everything from biotechnology to aerospace. The technology has the potential of replacing many Radio Frequency (RF) components used in today’s mobile, communication and satellite systems. In many cases, such RF MEMS components would not only reduce substantially the size, weight and power consumption but also promise superior performance in comparison with current technologies. The talk outlines the research activities at the University of Waterloo in RF MEMS with a focus on:

1. RF MEMS switches and integrated switch matrices.

2. RF MEMS tunable filters and phase shifters

3. MEMS integration with CMOS circuits

4. MEMS on flexible substrates for antenna applications

5. Intelligent reconfigurable MEMS-based receivers

6. MEMS-based wireless sensors for biomedical applications

Dr. Mansour received his Ph.D degree in Electrical Engineering from the University of Waterloo, Ontario, Canada in 1986. He Joined COM DEV, Cambridge, Ontario, Canada, in November 1986 where he held several key positions at COM DEV’s Corporate R&D Department from 1986-1999. In December 1999, he joined the University of Waterloo as a Professor. He has 29 US and Canadian patents to his credit (25 awarded, 4 pending). Dr. Mansour is a Fellow of the IEEE. He is an author of four book chapters published in 2001 and 2005. He is a co-author of a book (in-print) to be published by Wiley in 2007. Over the past years, Dr. Mansour has directed several research projects funded by both Government and industry in Canada and US, including research projects funded by US DARPA and Office of Naval Research. Prof. Mansour holds an NSERC / COM DEV Industrial Research Chair on RF Engineering at the University of Waterloo. He leads a research group consisting of 20 Ph.D graduate students and research engineers. He is the founding Director of the Center for Integrated RF Engineering (CIRFE) at the University of Waterloo. (www.cirfe.uwaterloo.ca).

Thursday, June 14, 2007

Dr. Steve Hranilovic
McMaster University

Free-space and indoor optical wireless links provide an exciting compliment to RF systems for broadband content distribution. Such optical wireless systems enjoy many advantages over conventional RF communications; namely, high data rates, unregulated bandwidth, immunity from interference and higher security. In indoor environments, wireless optics provides low cost high rate links using infrared or visible wavelengths. Free-space optical (FSO) links provide data rates in excess of 1 Gbps over line-of-sight links of 2km, at a much lower cost than fibre. Inherent with optical wireless, however, is the need to design modems which are able to combat the effects of atmospheric turbulence, weather conditions and misalignment.

This talk presents an overview of the current state-of-the-art in FSO and indoor wireless optical links. It highlights the work done in the Free-Space Optical Communication Algorithms Laboratory (FOCAL) at McMaster University in the development of novel channel topologies, modulation, coding and MIMO techniques. A number of key applications for such links will be presented and the role of FSO and indoor wireless in providing cost effective broadband access will be emphasized.

Steve Hranilovic received the B.A.Sc. degree with honours in electrical engineering from the University of Waterloo, Canada in 1997 and M.A.Sc. and Ph.D. degrees in electrical engineering from the University of Toronto, Canada in 1999 and 2003 respectively.

Tuesday, May 15, 2007

Dr. Andrei Sazonov
University of Waterloo

Flexible electronics is a rapidly developing area of electronics which deals with electronic systems fabricated on thin flexible substrates (metal foil, plastic foil, etc.). Due to several advantages such as light weight, unbreakability, low thermal budget, and potential for reduced manufacturing cost due to large-area, roll-to-roll fabrication capability, flexible electronics is highly attractive for commercial applications, including rollable displays, imaging sensors, solar cells, thin film printed CMOS circuits, RF ID tags, and more. This presentation will concern with the state of the art in flexible electronics, including an overview of existing and emerging applications, a review of materials and technologies currently used or researched for flexible electronics manufacturing, the issues related to the use of flexible substrates, and most recent results on flexible devices and circuits fabricated using nanocrystalline thin film semiconductors.

Andrei Sazonov (M’03) received the B.Sc. and Ph.D. in electrical engineering from Moscow Institute of Electronic Technology (Technical University), Moscow, Russia, in 1991 and 1997, respectively. From 1991 to 1993, he was a Research Engineer at Materials Science Department, Moscow Institute of Electronic Technology, and Research Engineer at Elma Corp., and Mikron Corp. (Moscow, Russia). From 1995 to 1996, he was a Visiting Research Fellow at the Institute of Physical Electronics, University of Stuttgart, Germany, under a German Academic Exchange Service (DAAD) scholarship. In 1998, he joined Electrical and Computer Engineering Department, University of Waterloo, as a Post-doctoral Research Associate, in 2000 he became an Assistant Professor, and in 2006, an Associate Professor. He is currently Director of Waterloo Giga-to-Nanoelectronics (G2N) Centre.

His research interests include thin film technology, amorphous, nanocrystalline, and polycrystalline semiconductors and dielectrics, semiconductor devices and their applications (solar cells, radiation sensors, memory devices, RF ID), large area electronics and flexible electronics. Dr.Sazonov published over 130 journal and conference papers in his research field. He is a recipient of a 2001 Canadian Foundation for Innovation New Opportunities Award, 2002 Ontario Premier’s Research Excellence Award, and 2004 IEE Institution Premium.

Monday, May 14, 2007

Dr. Reza Navid
Rambus Inc.

Since the commercialization of MOSFETs in the 70s, the continual scaling of these devices has been a tremendous drive for the electronic industry. These scaling efforts have recently lead to the emergence of several types of nanoelectronic devices on silicon and non-silicon substrates. Understanding noise in these devices and its impact on the performance of RF circuits is an ongoing challenge in the area of nanoelectronic circuit design. Experimental observations show that the classical long-channel MOSFET noise formulation underestimates the drain current noise of nano-scale MOSFETs by a factor often referred to as the excess noise factor. Several other nano-scale devices such as nanotubes and nanowires are expected to show a similar noise behavior because the fundamental phenomenon responsible for noise in these devices is essentially the same. In order to predict the effects of this excess noise on amplitude and phase noise in future RF circuits, it is crucial to have a reliable noise model and an accurate phase noise formulation. This presentation outlines the latest findings in this area. By presenting an accurate phase noise formulation, we discuss the impact of the excess noise on the performance of future communication circuits implemented using nano-scale devices. These studies are part of a global effort aimed at the realization of a complex system using nanoelectronic technologies.

Reza Navid received his B.S. and MS degrees in electrical engineering in 1996 and 1998 from the University of Tehran and Sharif University of Technology, respectively. From 1998 till 2000 he was with ParsElectric MFG Corp., Tehran, Iran, working on TV tuner characterization and improvement. During 2000 and 2001 he was with the University of Michigan, Ann Arbor, Michigan. During the summer 2001 he was with Maxim Integrated Products, Hillsboro, Oregon where he designed a 3.125Gbit/s optical receiver front-end. From Sep. 2001 to June 2005 he was with Stanford University to pursuing his Ph.D. on amplitude and phase noise in nano-scale circuits. He is now with Rambus Inc., Los Altos, California. His current research interests focus on the implementation of analog, mixed signal and digital systems using the emerging nanoelectronic devices.

Tuesday, May 8, 2007

Dr. Hamed Majedi
Institute for Quantum Computing

Quantum communication is the natural extension of classical communication into the era of quantum technologies. The fundamental ingredient underlying most quantum communication protocols is the qubit. In optical quantum communication the natural candidate for realization of qubit is photons. They are relatively immune to decoherence and hardly interact with each other. Quantum properties of photonic qubit provide unique features for communication; the most important one is absolutely secure quantum key distribution (QKD). Although the performance of photon source, optical fiber and photon detector highly affects the maximum transmission distance and quantum bit error rate (QBER) but their non-ideal behaviors do not necessarily render QKD unsecure.

My talk will be divided to three parts; Review of quantum communication, Systems and devices for optical fiber quantum communication, and introducing Nanowire superconducting single photon detector (SSPD) and its figures of merit.

Hamed Majedi was born in Tehran, Iran, on April 24, 1971. He received B.Sc. degree in Electrical Engineering with a major in microwave engineering from K. N. Toosi University of Technology, Tehran, Iran in 1994 and M.Sc. in Electrical Engineering with a major in photonics from Amir Kabir University of Technology, Tehran, Iran in 1996. In 1998, he joined the Electrical & Computer Engineering (E&CE) Department, at the University of Waterloo, ON, Canada, and obtained his PhD with distinction on December 2001. His PhD thesis investigated the optical-microwave interaction in superconducting transmission lines for optoelectronic applications. After 10 months being as a Postdoctoral Fellow, he joined the Institute for Quantum Computing (IQC), cross-appointed with the E&CE dept., as a Research Assistant Professor and in 2005 became an assistant professor in E&CE cross-appointed to IQC and dept. of Physics. He is conducting Integrated Quantum Optoelectronics Lab (IQOL) as the first laboratory in faculty of engineering supported by IQC. His group consists of one guest PDF, three PhD candidates and three MSc students.

His main research interests and activities include superconducting microwave/photonic devices, THz optoelectronics, superconducting and photonic quantum devices for quantum communication and metrology, quantum nano-electrodynamics, plasmonics and metamaterials.

Monday, May 7, 2007

Dr. Simon Doclo
Katholieke Universiteit Leuven, Belgium

Simon Doclo received the M.Sc. degree in electrical engineering and the Ph.D. degree in applied sciences from the Katholieke Universiteit Leuven, Belgium, in 1997 and 2003, respectively. Currently, he is a postdoctoral fellow of the Fund for Scientific Research - Flanders, affiliated with the Electrical Engineering Department of the Katholieke Universiteit Leuven. In 2005, he was a Visiting Postdoctoral Fellow at the Adaptive Systems Laboratory, McMaster University, Canada. His research interests are in microphone array processing for speech enhancement and source localization, adaptive filtering, computational auditory scene analysis and hearing aid processing. Dr. Doclo received the Master Thesis Award of the Royal Flemish Society of Engineers in 1997, a Best Student Paper Award at the International Workshop on Acoustic Echo and Noise Control in 2001, and the EURASIP Signal Processing Best Paper Award in 2003 (with Marc Moonen). He was secretary of the IEEE Benelux Signal Processing Chapter (1998-2002), and serves as a Guest Editor for the EURASIP Journal on Applied Signal Processing.

Monday, April 30, 2007

Dr. Raymond Laflamme
Canada Research Chair in Quantum Information
Director, Institute for Quantum Computing
Director, CIAR QIP program

Advances in computing are revolutionizing our world. Present day computers advance at a rapid pace toward the barrier defined by the laws of quantum physics. The quantum computation program short-circuits that constraint by exploiting the quantum laws to advantage rather than regarding them as obstacles. Quantum computer accepts any superposition of its inputs as an input, and processes the components simultaneously, performing a sophisticated interference experiment of classical inputs. This “quantum parallelism” allows one to explore exponentially many trial solutions with relatively modest means, and to select the correct one. This has a particularly dramatic effect on factoring of large integers, which is at the core of the present day encryption strategies (public key) used in diplomatic communication, and (increasingly) in business. As demonstrated some years ago, quantum computers could yield the most commonly used encryption protocol obsolete. Since then, it was also realized that quantum computation can lead to breakthroughs elsewhere, including simulations of quantum systems, implementation of novel encryption strategies (quantum cryptography), as well as more mundane applications such as sorting. I will describe how a quantum computer work and will give a demonstration using NMR technology.

Raymond was born in Quebec City and did his undergraduate studies in Physics at Université Laval. He then moved to Cambridge, England, where he withstood Part III of Mathematical Tripos before doing a PhD in the Department of Applied Mathematics and Theoretical Physics (DAMTP) under the direction of Stephen Hawking. He and Don Page are responsible for having changed Hawking’s mind on the reversal of the direction of time in a contracting Universe (see Hawking's book “A brief history of time”). After his PhD, Raymond became a Killam post-doctoral fellow at UBC where he met his wife Janice Gregson. Raymond moved back to Cambridge in 1990 as a Research Fellow at Peterhouse. He finally settled down for 9 years at Los Alamos National Laboratory. He arrived as a Director funded post-doctoral fellow, became an Oppenheimer Fellow in 1994 and a proud father of Patrick and Jocelyne. In 1998, the work on quantum error correction that he accomplished with MIT and Los Alamos colleagues was named in the “Top 10 Breakthrough of the Year” in the journal Science. He was Technical Staff at Los Alamos until 2001 when he moved back to Canada joining the University of Waterloo as a Canada Research Chair in Quantum Information and joined Perimeter Institute for Theoretical Physics as a founding member. Raymond is Director of the Institute for Quantum Computing that he established in 2002 with Michele Mosca. Raymond is a recipient of Ontario's Premier Research Award. In 2005, he received the Médaille Grande Escolle from the Association des Diplômés of Université Laval. He is Director of the Quantum Information program and Ivey Foundation Fellow of the Canadian Institute for Advanced Research. He is also Scientific Director of QuantumWorks, a Canadian network that brings together academia, industry and government in the area of quantum information.

Wednesday, April 25, 2007

Dr. Patrick Lam
McGill University

Developers often build software systems with a collection of design properties in mind. Explicitly-stated design properties can serve as valuable system documentation; furthermore, software systems may malfunction if design properties are violated. However, while software implementations inevitably evolve over time, software specifications rarely evolve in concert with the implementations. One of the most important reasons that specifications lag implementations is that the manual verification of specifications is time-consuming and provides few guarantees. The goal of my research is therefore to enable the automatic static verification of software design properties. Static verification would reward developers for keeping their specifications up-to-date by guaranteeing that specifications continue to properly describe the implementations, which in turn enables developers to use specifications to soundly reason about their programs.

My research focuses on the development of static analysis tools for verifying software design properties and on specification languages for use with my static analysis tools. Because a program's heap summarizes its past actions and constrains its future actions, I believe that understanding the possible state of the heap is key to understanding the behaviour of the program. An important class of software design properties can therefore be stated in terms of constraints on the heap, and in particular in terms of relationships between various heap data structures.

Researchers have developed a number of static analysis techniques for verifying data structures; some of these techniques are specialized for verifying particular classes of data structures, and many of these techniques scale poorly with respect to program size. Because each analysis will generally use a custom-built abstraction for describing the program state, it is both conceptually and practically difficult to combine analyses to verify programs with heterogeneous data structures.

One of my key contributions is therefore in the design and implementation of a set-based specification language. This language enables different analysis techniques to cooperate in verifying design properties. The set-based specification approach furthermore enables modular analysis, which permits the use of expensive analysis techniques by applying them only to the relevant sections of programs. My preliminary results show that it is possible to successfully verify detailed design properties of benchmark applications.
 

Patrick Lam is a Postdoctoral Fellow in the School of Computer Science at McGill University. Most recently, he completed his PhD at the Massachusetts Institute of Technology in December 2006. His research interests include program verification and static analysis.

Friday, April 20, 2007

Dr. Eytan Modiano
Massachusetts Institute of Technology

In this talk we will describe algorithms for resource allocation in heterogeneous networks that include wireless, satellite and wired (e.g., optical) sub-networks. We consider a network with stochastic traffic and randomly varying channel conditions. In the first part of the talk we address the joint problem of flow control, routing, and scheduling in a heterogeneous network subject to quality of service requirements. In particular, we will describe a dynamic control strategy that maximizes the sum utility in the network, and can be used to achieve a wide range of service objectives. This scheduling algorithm is centralized in its nature and requires the solution of a complex optimization problem. Hence, in the second part of the talk we will discuss distributed algorithms for solving the optimal scheduling problem with low computation and communication complexity. In particular, we will describe randomized algorithms for scheduling and routing in a wireless network that maximize network throughput with communication and computation requirements that are comparable to those of existing algorithms that can only guarantee 50% throughput.

Eytan Modiano received his B.S. degree in Electrical Engineering and Computer Science from the University of Connecticut at Storrs in 1986 and his M.S. and PhD degrees, both in Electrical Engineering, from the University of Maryland, College Park, MD, in 1989 and 1992 respectively. He was a Naval Research Laboratory Fellow between 1987 and 1992 and a National Research Council Post Doctoral Fellow during 1992-1993. Between 1993 and 1999 he was with MIT Lincoln Laboratory where he was the project leader for MIT Lincoln Laboratory's Next Generation Internet (NGI) project. Since 1999 he has been on the faculty at MIT; where he is presently an Associate Professor. His research is on communication networks and protocols with emphasis on satellite, wireless, and optical networks.

He is currently an Associate Editor for Communication Networks for IEEE Transactions on Information Theory and for The International Journal of Satellite Communications. He had served as a guest editor for IEEE JSAC special issue on WDM network architectures; the Computer Networks Journal special issue on Broadband Internet Access; the Journal of Communications and Networks special issue on Wireless Ad-Hoc Networks; and for IEEE Journal of Lightwave Technology special issue on Optical Networks. He served as the Technical Program co-chair for Wiopt 2006, IEEE Infocom 2007, and ACM MobiHoc 2007.

Wednesday, April 18, 2007

Mr. Nachiketh Potlapally
Princeton University

Pervasive networks have led to widespread use of embedded systems, like, cell phones, PDAs, RFIDs etc, in increasingly diverse applications. Many of these embedded system applications handle sensitive data (e.g., credit Card information on a mobile phone/PDA) or perform critical functions (e.g., medical Devices or automotive electronics), and the use of security protocols is imperative to maintain confidentiality, integrity and authentication of these applications. Typically embedded systems have low computing power and finite energy supply based on a battery, and these factors are at odds with the computationally intensive nature of security protocols. In addition, embedded systems are vulnerable to many types of side-channel attacks which exploit their implementation characteristics. Thus, design of secure embedded systems is driven by three factors: good performance, low energy consumption (and, thus, longer battery life), and robustness against side-channel attacks.

I will enumerate my work on tackling these three issues in design of secure embedded systems. The focus of this talk will be on robustness and energy consumption. I will talk about a Satisfiability-based framework for enabling side-channel attacks on cryptographic software running on an embedded processor. This side-channel framework helps us identify the variables whose leakage leads to the disclosure of secret keys used by the cryptographic algorithm. Next, I will explain some novel ways of optimizing energy consumption of security protocols executing on an embedded device. I will discuss the energy consumption characteristics of different cryptographic algorithms, and the manner in which this information can be used to adapt the operation of security protocols to save energy. This will be demonstrated using the widely employed secure sockets layer (SSL) protocol.

Nachiketh Potlapally is a PhD candidate in the department of Electrical Engineering at Princeton University. He is interested in applied cryptography, and his research includes developing security protocols, investigating hardware-software architectures for efficient security processing, and side-channel attacks. Before coming to Princeton, he worked as a research assistant at NEC labs America where he was involved in the development of NEC's register transfer level power estimation tool.

Monday, April 16, 2007

Dr. Arijit Raychowdhury
Purdue University

With technology scaling the electrical characteristics of MOSFETs have degraded from near-ideal switches to mere dimmers. Short channel effects and exponentially increasing leakage currents have necessitated the use of low power techniques in circuits and systems. In this talk, I will present a lateral paradigm of ultralow power design using leakage currents. Subthreshold current, flowing through transistors operating under their threshold voltage, can be used to perform useful computation with low to medium (several kHz to MHz) performance. I will present how devices, circuits and systems can be optimized to obtain the lowest power at iso-performance, using subthreshold logic and provide measurement results on ultralow power test-chips that we have fabricated.

In the later half of my talk, I will mention the feasibility of using futuristic super cut-off devices (where the subthreshold slope is below the thermal limit of 60mV/decade) in ultralow power design. More specifically, I will talk about the promise of carbon nanotube based FETs and how the use of these novel devices can potentially help us sustain Moore’s Law in a post 2015 timeframe.

Arijit Raychowdhury received his B.E. degree in 2001 in Electronics and Telecommunication engineering from Jadavpur University, Calcutta, India. Since 2002, he has been pursuing Ph.D. in Electrical and Computer engineering at Purdue University, IN. He has worked as an Analog Circuit Designer with Texas Instruments Inc. (2002 to 2003) and with the Circuit Research Labs, Intel Corporation (summer of 2005 and 2006) pursuing design ideas with novel nano-devices. His research interests include device/circuit design for scaled silicon and non-silicon technologies. Mr. Raychowdhury has received academic excellence awards in 1997, 2000, and 2001, the Meissner Fellowship from Purdue University in 2002, the NASA INAC Fellowship in 2003 and the Intel PhD Fellowship Award in 2005. He has received Best Paper Awards at IEEE NANO 2003 and ISLPED, 2006. He holds six patents and has published over thirty articles in journals and refereed conferences.

Thursday, April 12, 2007

Dr. Aaron Gulliver
University of Victoria

Due to the availability of low-cost optical devices and virtually unlimited bandwidth, optical wireless communications (OWC) (communications using light pulses) has recently become an attractive alternative to congested radio frequency systems. OWC provides very high security and no interference between rooms since optical signals cannot penetrate through walls. However, OWC performance is severely degraded by interference between light pulses. Practical modulation and error-control coding techniques are considered that significantly reduce this interference.

Modulation techniques with good power and bandwidth efficiency are a major concern. Pulse-position modulation (PPM), where the information is contained in the pulse timing within a fixed interval, offers very high power efficiency and has been proposed in several communications standards. However, PPM has high bandwidth requirements, and its performance is severely degraded by interference. A hybrid between pulse-amplitude modulation (PAM), where the information is contained in the pulse amplitude, and differential pulse-position modulation (DPPM), where the information is contained in the time between pulses, is proposed, termed differential amplitude pulse-position modulation (DAPPM). The analysis presented shows that DAPPM yields better bandwidth and/or power efficiency than conventional modulation schemes. Since DAPPM has variable symbol lengths, its channel capacity is determined using a novel method for calculating the capacity of a Markov process channel. The results show that DAPPM achieves the highest capacity and is the least sensitive to ISI.

Since the complexity of optimal soft-decision decoding (SDD) is extremely high, low complexity sub-optimal algorithms are presented which have performance which is close to optimal. In particular, a novel very low complexity SDD algorithm is introduced which has performance independent of knowledge of the channel model, while other algorithms (including optimal decoding), have impaired performance without this knowledge. Error control coding in OWC is investigated to correct the insertion/deletion errors which exist in variable symbol length systems (for which conventional coding techniques cannot be used). A novel concatenation of marker and Reed-Solomon codes is presented which can efficiently correct these errors.

Wednesday, April 11, 2007

Dr. Wei Jiang
Omega Optics

Photonic crystals are considered a promising structural platform for next generation photonic devices. Photonic crystal based resonators, waveguides, wavelength demultiplexers, lasers, and modulators have aroused widespread interest owing to their compact sizes and potential for significant performance improvement.

We will present our theory for light refraction, transmission, and coupling at a photonic crystal surface. The theory shows the way to rigorously calculate the transmission through both an ordinary Miller-indexed surface and a naturally cut quasi-periodic surface, and is believed to be the first unified and systematical solution to a generic surface coupling problem in any type of periodic lattice. Application of this theory to wavelength demultiplexers, laser beam steering, grating diffraction, and photonic crystal waveguide mode calculation will be discussed to illustrate its broad impact. Slow speed of light has been observed in photonic crystal waveguides, which has been proposed for enhancing light-matter interaction. We will present our recent work on compact silicon photonic crystal waveguide modulators, which exploit the slow light effect to produce gigahertz modulation at a low driving voltage. Gigahertz optical modulation in silicon was a puzzle for nearly two decades. We will discuss some fundamental scaling issues for high speed silicon modulators.

“Siliconizing” photonics, as Intel put it, could revolutionize the computing and communications industries by furnishing a “native” high-speed optical interconnect technology for ever-faster microprocessors as well as spawning numerous novel devices. The opportunities and challenges in the general area of silicon photonics will be summarized.

Tuesday, April 3, 2007

Dr. Gerhard Kramer
Bell Laboratories, Murray Hill, NJ, USA

Network coding has recently become a rapidly evolving area in Information Theory. We begin by examining the basic concept behind network coding and contrast it to the conventional routing approach in existing networks. We highlight the capacity gain by allowing each node in a network to re-encode its input information instead of simply storing and forwarding data. We then discuss some recent progress in network coding. A bound on network coding rates is presented that generalizes an edge-cut bound on routing rates. The bound, called a progressive d-separating edge set (or PdE) bound, involves progressively removing edges from a network graph and checking whether certain strengthened d-separation conditions are satisfied. We show that the PdE bound and one of its extensions proves that routing is rate-optimal for multiple unicast sessions on bidirectional ring networks. We further show that the PdE bound improves on a standard cut-set bound for networks with broadcasting, interference, and noise.

This work was done jointly with Serap A. Savari from the University of Michigan, Ann Arbor.

Gerhard Kramer received the B.Sc. and M.Sc. degrees in electrical engineering from the University of Manitoba, Winnipeg, MB, Canada, in 1991 and 1992, respectively, and the Dr. sc. techn. (Doktor der Technischen Wissenschaften) degree from the Swiss Federal Institute of Technology (ETH), Zurich, Switzerland, in 1998. From July 1998 to March 2000, he was with Endora Tech AG, Basel, Switzerland, as a communications engineering consultant. Since May 2000 he has been with the Communications and Statistical Sciences Department, Bell Laboratories, Murray Hill, NJ, USA.

Dr. Kramer is currently serving as an Associate Editor for Shannon Theory for the IEEE Transactions on Information Theory and as a Guest Editor for an IEEE Transactions on Information Theory Special Issue on Relaying and Cooperation in Communication Networks. He served as a Publications Editor for the same transactions during 2004-2005. He is a co-recipient of the 2005 IEEE Communications Society Stephen O. Rice Prize paper award.

Tuesday, April 3, 2007

Dr. Michael Backes
Computer Science Department
Saarland University, Saarbruecken, Germany

Automated tools such as model checkers and theorem provers for the analysis of security protocols typically abstract from cryptography by Dolev-Yao models, i.e., they replace real cryptographic operations by term algebras. However, there was traditionally no cryptographic justification for this abstraction, i.e., no theorem that said what a proof with a Dolev-Yao abstraction implied for a real implementation, even if provably secure cryptographic primitives are used.

We show how to justify a Dolev-Yao model in the strong sense of blackbox reactive simulatability (BRSIM)/UC, a security notion that entails the preservation of essentially arbitrary security properties under active attacks in arbitrary protocol environments. This result enables cryptographically sound, abstract protocol analyses of common Dolev-Yao style protocols, and by the compositionality of BRSIM/UC automatically also for all protocols using them. Security holds in the standard model of cryptography and under standard assumptions of adaptively secure primitives. The proof is a novel combination of a probabilistic, imperfect bisimulation with cryptographic reductions, a hybrid argument, and a static information-flow analysis.

While these positive results hold for many of the common Dolev-Yao operations such as (a-)symmetric encryption, signatures, and MACs, modern tools and complexity results around Dolev-Yao models also allow more algebraic operations. The first such operation considered is typically XOR because of its clear structure and cryptographic usefulness. We show that it is impossible to extend the strong soundness results in the sense of BRSIM/UC to XOR, at least not with remotely the same generality and naturalness as for the core cryptographic systems. A similar negative result holds for hash functions: We show that it is impossible to extend the strong BRSIM/UC results to usual Dolev-Yao models of hash functions in the general case, i.e., by treating hash functions as free operators of the term algebra. On the positive side we can show that these models are sound in the same strict sense of BRSIM/UC in the random oracle model of cryptography.

Michael Backes holds the chair of information security and cryptography at Saarland University. Before joining Saarland University, he was a permanent research staff member at the IBM Zurich Research Lab, where he was responsible for projects on verification of security protocols, cryptographic foundations, Web Services security, and enterprise privacy management. Michael Backes (co-)authored more than 60 research papers in security, privacy and cryptography. His scientific accomplishments include the establishment of a strong link between cryptography and formal verification, the development of suitable techniques for enterprise privacy management, as well as the security analysis and verification of well-known cryptographic protocols.

Monday, April 2, 2007

Dr. Bao Liu
University of California, San Diego

Recent development in nanotechnology has provided promising pictures for future VLSI designs. However, significant challenges lay ahead before we achieve nanotechnology VLSI systems. Among the most significant challenges for nanotechnology VLSI designs are variability and reliability issues, which have become inevitably increasingly significant even for current technology. Increased process variations have introduced significant VLSI performance, power, temperature, and supply voltage variations. Increased defect density and soft error rate have lead to increased occurrence of circuit logic malfunction and system lifetime reduction. Statistical analysis and robust design techniques are necessary for future nanotechnology VLSI design.

In this talk, I present latest research developments on VLSI statistical performance analysis and robust design. In particular, I present two techniques. 1. Statistical timing analysis in the Presence of Signal Integrity Effects. 2. Layout level redundancy for yield and robustness improvements

Dr. Bao Liu (born oct. 1973) received his B.S. and M.S. degrees in Electrical Engineering in Fudan University, China, and his Ph.D. degree in Computer Science in University of California, San Diego, in 1993, 1996, and 2003, respectively. He is currently a post-doctoral researcher at University of California, San Diego. He has published over 30 journal and conference papers, received a best paper award from International Conference on Computer Design in 2005, and serves as co-chair for Emerging/Innovative Process & Device Technologies and Design Issues in International Symposium on Quality Electronic Design in 2007. His research areas include VLSI variability and reliability analysis, signal integrity analysis, robust design, and on-chip interconnect techniques.

Wednesday, March 21 2007

Mr. Sayan Mitra
Massachusetts Institute of Technology

The growing complexity of embedded software systems calls for new design and verification technologies. To meet this challenge, we have developed a linguistic framework for analyzing blueprints of embedded systems, based on a mathematical model that combines state machines with dynamical systems. In this talk, I begin by describing the new design language called HIOA. On the one hand, HIOA can abstractly specify the requirements of a system component in terms of behaviour of its interface. On the other hand, HIOA can also specify implementation of system components in terms of control laws, algorithms, and data structures. The specifications thus obtained can be simulated and are amenable to an array of formal analysis techniques, such as model checking and theorem proving. Next, I describe a particular technique for verifying stability properties of systems specified in HIOA. This technique relies on proving a new kind of abstraction relation that preserves the switching behaviour of the system. and verifying the resulting abstract model through mixed integer linear programming. Finally, I will provide a brief overview of my research in applying this framework to a number of domains, including real-time distributed algorithms, mobile robotic systems, and security protocols.

Sayan Mitra is a Ph.D. candidate in the MIT Computer Science and Artificial Intelligence Lab. He is a member of the Theory of Distributed Systems group supervised by Professor Nancy Lynch. He received his M.Sc. in computer science from Indian Institute of Science in 2001, and his bachelors degree in electrical engineering from Jadavpur University in 1999. His research interests include modeling and verification of real-time, distributed, and hybrid systems, mechanical theorem proving, software engineering, and formal methods.

Wednesday, March 14, 2007

Dr. Sebastian Fischmeister
University of Pennsylvania

Distributed real-time systems realize distributed applications with timeliness requirements. They typically manifest at the border between the physical and the logical world, and as such they allow us to manipulate our physical world based on programmed algorithms. Consequently, such systems must be reliable, because logic and timing errors no longer stop at our workstation, but can cause physical damage to equipment, the environment, and humans.

A critical resource in a distributed real-time system is its shared communication medium. Due to the system's decentralized nature, any connected node can access it anytime and can cause collisions of network communication, which scrambles data and typically results in retransmissions. Since such collisions reduce the system's reliability, one primary research goal in this area is to provide effective coordination models for controlling access to the shared medium and its channels.

In this talk, I will present Network Code, a verifiable, executable model for programming stateful communication schedules to coordinate distributed access to a shared medium. The work is targeted for real-time systems and aims to provide a powerful, expressive programming environment for communication among distributed software components. One salient aspect of Network Code is that its programs can be translated to formal specifications, which can be model-checked to verify aspects of reliability such as absence of collisions, overhead, schedulability, and integrity (e.g., sender/receiver pairing, content typing, over/underflows). I will describe my experience with building two implementations for Network Code (one for RTLinux using Ethernet and one for the MicroChip PIC18F using CAN) and address the current state of my work and open problems. Finally, I will also provide a brief overview of my research on reconfigurability of real-time systems, resource balancing in the LET model, and my prior work on pervasive computing and mobile code.

Sebastian Fischmeister is a research associate at the University of Pennsylvania. He received his MS from the Vienna University of Technology in 2000, and his PhD from the University of Salzburg in 2002. He subsequently worked as a lecturer and researcher at the University of Salzburg, before joining the Real-Time Systems Group at UPenn as a PostDoc in 2005. Simultaneously, he received the Austrian APART fellowship in 2005 and now works at UPenn as a research associate.

Monday, March 12, 2007

Dr. Vincent Gaudet
University of Alberta

Low-density parity-check (LDPC) codes have become one of the preferred methods for forward error control in digital communications systems. These codes approach the Shannon capacity limit, and as such address the issue of transmit power. However, the use of such coding techniques also incurs a computational energy cost at the receiver that is not traditionally accounted for in the code design process. LDPC decoding is typically conducted using a message-passing algorithm that runs over a graphical representation of the code. Typical graphs may have tens of thousands of connections, each requiring several multi-bit messages to be passed during a decoding cycle, and perhaps requiring aggregate signaling rates on the order of Terabits per second! Since dynamic power consumption in a VLSI chip is related to the signaling rate, this represents a considerable challenge. In this talk I will present message-passing VLSI architectures that are guided by these computational energy constraints.

Analog decoders are message passing decoders that process log-likelihood messages in continuous-time and using continuous-valued voltages and currents to represent likelihood messages. Only the outputs of decoders are binary, and as such analog decoders do not require high-speed analog-to-digital converters as a front end. Such decoders, often based on the well-known Gilbert multiplier using sub-threshold mode CMOS transistors, have been shown in physical measurements to be computationally efficient. For example a recent chip designed in a 180-nm CMOS technology operates on a 0.5V supply, and consumes significantly less than 1-nJ per transmitted information bit. This talk will provide an introduction to the circuits used in such analog decoders, as well as the design challenges and limitations of the technology.

Dr. Vincent Gaudet received the Bachelor of Science in Computer Engineering degree from the University of Manitoba in 1995, the Master of Applied Science degree from the University of Toronto in 1997, and the Ph.D. from the University of Toronto in 2003. From February to July 2002, Dr. Gaudet was a Research Associate at the Ecole Nationale Supirieure des Tilicommunications de Bretagne in Brest, France. Currently, he is an Assistant Professor in the Department of Electrical and Computer Engineering at the University of Alberta. His research interests centre on information processing microsystems, and more specifically on energy-efficient graph-based decoding of error control codes. He has received funding from NSERC, Micronet R&D, Canada Foundation for Innovation, Alberta Innovation and Science, and the Faculty of Engineering. During his studies, he held the NSERC Postgraduate Scholarship, the Ontario Graduate Scholarship in Science and Technology, and the Walter Sumner Memorial Fund Scholarship. Dr. Gaudet is a Member of IEEE, is licensed as a Professional Engineer (Ontario), and has served on the Technical Program Committees for the 2005 IEEE International Symposium on Information Theory, IEEE Globecom 2005, and the 2006 and 2007 Analog Decoding Workshops.

Wednesday, Mar. 7, 2007

Dr. Sergiy Vorobyov
University of Alberta

Recently, robust adaptive beamforming bas attracted considerable interest due to its practical importance for radar, sonar, wireless communications, microphone array speech processing, medical imaging, radio astronomy, and other fields. The importance of robust designs is dictated by the fact that the adaptive array performance may be quite sensitive even to slight mismatches between the presumed and actual signal steering vectors (spatial signatures). Such mismatches can occur as a result of environmental nonstationarities, look direction errors, imperfect array calibration, distorted antenna shape, as well as distortions caused by medium inhomogeneities, near-far mismatch, source spreading, and local scattering.

In this talk, we present two basic approaches to robust adaptive beamorming design. One of them is based on the optimization of the worst-case performance, According to this approach the natural formulation of adaptive beamforming problem involves minimization of a quadratic function subject to infinitely many noneonvex quadratic constraints. We show that this (originally intractable) problem can be reformulated in a convex form as the so-called second-order cone (SOC) programming problem and solved efficiently with the same computational complexity as the conventional beamforming methods, We also show how such robust approach can be extended to designing adaptive beamforming with joint robustness against steering vector mismatches and interference nonstationarities. Another approach to robust adaptive beamforming design is based on probability-constrained optimization, and is more flexible as compared to the worst-case based approach. Unlike the general probability-constrained optimization problem which might be nonconvex, our problem can be reformulated as a convex SOCP problem and solved efficiently. Simulation results show the improved performance of the robust adaptive beamformers as compared to the existing state-of-the-art robust techniques in scenarios with steering vector errors, As an application example, the problem of robust multiuser multiple-input multiple-output (MIMO) receivers design is also considered.

Sergiy A. Vorobyov received the M.Sc. and Ph,D. degrees in Systems and Control from Kharkov National University of Radioelectronics (KNURE), Ukraine in 1994 and 1997, respectively. From 1997 to 2006 he has held long- and short-time research positions in KNURE; Brain Science Institute of the Institute of Physical and Chemical Research (RIKENJ, Japan; McMaster University, Canada; Duisburg-Essen University, Germany; Technion - Israel Institute of Technology, Israel; and Darmstadt University of Technology, Germany. He is currently with the University of Alberta as an Assistant Professor.

His research interests span several areas of signal processing with particular emphasis on array processing, adaptive beamforming, signal processing for wireless communications, and applications of linear algebra and convex optimization techniques in communications and signal processing. He has published 27 journal papers, 49 conference papers, and 1 textbook. Dr. Vorobyov is a Senior Member of the IEEE. He was a recipient of the 2004 IEEE Signal Processing Society Best Paper Award for his paper on robust adaptive beamforming. He serves as an Associate Editor of the IEEE Transactions on Signal Processing.

Monday, Feb. 26, 2007

Mr. Ibrahim Gedeon
Chief Technology Officer, TELUS

. The competitive landscape - will telcos become known as broadband application providers? How will MSOs adopt IP technology?

Ibrahim Gedeon, as the Chief Technology Officer, is responsible for technology strategy, network and services architecture and network support systems for TELUS Communications Inc. In his role as CTO he is responsible for the Wireless-Wireline service and network convergence, enterprise applications and network infrastructure strategies and evolution.

Mr. Gedeon began his career in telecommunications engineering and research in 1990 when he joined Bell Northern Research designing signal-processing software in the cryptographic systems division. He moved to Nortel Networks in 1994 as a network design engineer, where he provided technical network design expertise to Nortel Networks' customer base globally. He was named vice president and director of Data Network Engineering at Nortel in 1996, and vice president of Internet Brand Management in 1999, where he was responsible for IP/MPLS/ATM standards, engineering, and market development. He was appointed senior vice president of Wireless Engineering in 2000 and led the global engineering team responsible for operations, sales support, and systems engineering.

Mr. Gedeon has held numerous leadership roles in the Institute of Electrical and Electronics Engineers (IEEE) and has received several professional awards, including IEEE Canada's Outstanding Canadian Engineer Award. Ibrahim has a bachelor's in electrical engineering from the American University of Beirut and a Masters' in Electronics Engineering from Carleton University.