Analysis, testing and optimisation of electrostatic comb-drive levitational actuators

This work presents an analysis of the levitation effect in electrostatic comb fingers and of its possible use for vertical or torsional actuation of micromachined structures. Two different levitational mechanical resonators were designed and fabricated in a thick-polysilicon technology. A study of the dependence of the force intensity on the geometric parameters of the actuators were performed using FEM simulations, and information about critical geometrical parameters in the design of operative levitational actuators were obtained. The devices were characterized and the obtained results were compared with FEM simulations. Antonio Molfese received the M.S. degree cum laude in Electronic Engineering from the University of Pisa, Italy on March 2003. In the summer 2003 he was at IMEC, Belgium for an internship. On November 2003 he received the diploma degree cum laude in Industrial and Information Engineering from Scuola Superiore Sant'Anna di Studi Universitari e Perfezionamento of Pisa, Italy. He is currently pursuing the Ph.D. degree in Information Engineering at University of Pisa and he is working at IEIIT-Sezione di Pisa of Italian National Research Council (CNR) as research assistant. His main research interests include design, modeling and characterization of micro-electro-mechanical systems and microfluidics. Giovanni Pennelli was born on October 23, 1967 in Lucca, Italy. He graduated in 1992, cum laude, in Electronic Engineering. He obtained his Ph.D. in 1997 for a thesis entitled "New Materials for a Silicon-Based Optoelectronics". He moved to the University of Glasgow in April 1997 to work as a Research Assistant in the MBE group concerned with optoelectronic device fabrication and process development. He developed some MBE grown structures for HEMT applications. In September 2000, Dr Pennelli has been appointed assistant professor in the Department of Information Engineering, University of Pisa, Italy, pursuing research in electron beam lithography and nanometer scale process development. Francesco Pieri received the laurea and the Ph.D. degree in Electrical Engineering, both from the University of Pisa, Italy, in 1996 and 2000 respectively. He joined the Department of Information Engineering of the same University as an assistant professor in 2001. His current research interests include applications of porous silicon to sensors and microtechnologies, and development of microelectromechanical systems. Andrea Nannini received his laurea degree in Electronic Engineering from the University of Pisa, Italy, in 1982; He received his Ph.D. degree in 1987 at the end of the first Italian Ph.D. course held by the University of Padova, Italy. From 1988 to 1992 he was a Researcher at the “Scuola Superiore di Studi Universitari e Perfezionamento S. Anna” – Pisa- Italy. Since 1992 he joined the Department of Information Engineering of the University of Pisa as an Associate Professor. Since November 2000 he is a full professor of “Sensor and Microsystem Design”. He is currently chairman of the postgraduate school of Electronic Engineering and vice-chairman of the PhD school of Information Engineering of the University of Pisa. His main research interests concern solid state sensors, microelectronic devices and technologies, MEMS.     

Pre-equalization Techniques for Downlink and Uplink TDD MC-CDMA Systems

Time division duplex (TDD) multi carrier-code division multiple access (MC-CDMA) systems have recently been proposed as potential candidates for next generation (4G) technology. In order to mitigate multiple access interference, in this paper we investigate pre-equalization schemes for both downlink and uplink transmissions, the former also in a multiple transmit antenna scenario. In particular, new pre-equalizer techniques are introduced and complexity issues addressed. Numerical results are given to highlight the effectiveness of the proposed schemes with respect to other existing pre-equalizer solutions. Paola Bisaglia was born in Padova, Italy, on August 8, 1971. She received the Laurea (cum laude) and Ph.D. degrees in electronic engineering from the University of Padova, Padova, Italy in 1996 and 2000 respectively. In 2000 she joined Hewlett-Packard Research Laboratories, Bristol, England, working on Home Phoneline Networking and wireless LANs. From 2002 she is a research fellow at the Department of Information Engineering of the University of Padova, Italy. Her research interests include wireless local area networks; modulation, coding techniques and detection strategies for next generation (4G) broadband cellular systems, based on the combination of multi-carrier and spread-spectrum modulations. Luca Sanguinetti is a Ph.D. Student of the University of Pisa. He was born in Empoli, Italy, on February 19, 1977, and he received the Doctor Engineer degree (cum laude) in information engineering from the University of Pisa, Italy, in 2002. Since 2002 he was with the Department of Information Engineering of the University of Pisa, where he is working toward the Ph.D. degree in information engineering under the supervision of Prof. Umberto Mengali and Prof. Michele Morelli. In 2004, he was a visiting Ph.D. student at the German Aerospace Center (DLR), Oberpfaffenhofen, Germany. Currently he is involved in a research project dealing with the design and the development of base stations and user terminals for wideband wireless communications systems able to cope with those reconfigurability and interoperability characteristics required by the next generation mobile communication systems. His research interests are in wireless communication theory, with emphasis on synchronization and detection algorithms and channel estimation in multiple-access communication systems. Michele Morelli received the Laurea (cum laude) in electrical engineering and the “Premio di Laurea SIP” from the University of Pisa, Italy, in 1991 and 1992 respectively. From 1992 to 1995 he was with the Department of Information Engineering of the University of Pisa, where he received the Ph.D. degree in electrical engineering. In September 1996 he joined the Centro Studi Metodi e Dispositivi per Radiotrasmissioni (CSMDR) of the Italian National Research Council (CNR) in Pisa where he held the position of Research Assistant. Since 2001 he has been with the Department of Information Engineering of the University of Pisa where he is currently an Associate Professor of Telecommunications. His research interests are in wireless communication theory, with emphasis on synchronization algorithms and channel estimation in multiple-access communication systems. Nevio Benvenuto received the Laurea degree from the University of Padova, Padova, Italy, and the Ph.D. degree from the University of Massachusetts, Amherst, in 1976 and 1983, respectively, both in electrical engineering. From 1983 to 1985 he was with AT&T Bell Laboratories, Holmdel, NJ, working on signal analysis problems. He spent the next three years alternating between the University of Padova, where he worked on communication systems research, and Bell Laboratories, as a Visiting Professor. From 1987 to 1990, he was a member of the faculty at the University of Ancona. He was a member of the faculty at the University of L'Aquila from 1994 to 1995. Currently, he is a Professor in the Electrical Engineering Department, University of Padova. His research interests include voice and data communications, digital radio, and signal processing. Silvano Pupolin received the Laurea degree in Electronic Engineering from the University of Padova, Italy, in 1970. Since then he joined the Department of Information Engineering, University of Padova, where currently is Full Professor of Electrical Communications. He was Chairman of the Faculty of Electronic Engineering from 1990 to 1994, Chairman of the PhD Course in Electronics and Telecommunications Engineering from 1991 to 1997 and Director of the PhD School in Information Engineering from 2004. Also, he was member of the programming and development committee from 1997 to 2002 and member of Scientific Committee from 1996 to 2001 of the University of Padova; member of the budget Committee of the Faculty of Engineering from 2003. He has been actively engaged in research on: Digital communication systems over copper wires and fiber optics; Spread spectrum communication systems; Design of large reliable communications networks; Effects of phase noise and HPA nonlinearities in OFDM systems; 3G mobile radio communications systems (UTRA-FDD and TDD) and beyond 3G (OFDM modulation and MC CDMA); Packet radio, Ad-hoc networks with the use of Bluetooth and WLAN. He was Chairman of the 9-th and 10-th Tyrrhenian International Workshop on Digital Communications devoted to “Broadband Wireless Communications” and to “Multimedia Communications”, respectively, and he was General Chair of the 7th International Symposium on Wireless Personal Multimedia Communications (WPMC'04). He spent the summer 1985 at AT&T Bell Laboratories on leave from Padova, doing research on digital radio systems. He was Principal investigator for research projects entitled “Variable bit rate mobile radio communication systems for multimedia applications”, “OFDM Systems with Applications to WLAN Networks”, and “MC-CDMA: an air interface for the 4th generation of wireless systems”.     

Platform-based mixed signal design: Optimizing a high-performance pipelined ADC

We apply Platform-Based Design (PBD) to the power optimization of a 14 bit, 80 MS/s pipelined Analog-to-Digital Converter (ADC) in a mixed signal formulation. A platform is a library of components and interconnects, each characterized with a set of behavioral, performance and composition models, that is used to raise the level of abstraction to enable system-level design. PBD is a meet-in-the-middle methodology that consists of two phases. The bottom-up phase generates a set of platform libraries that are exploited in the system hierarchy. The top-down phase allows exploring feasible solutions within the platform libraries and selecting the optimum implementation. To evaluate the cost of each implementation, the behavioral models available through platform abstraction are used both for digital and analog components. We provide an example of the use of the methodology and its features for analog circuits by modeling two amplifiers with different topologies as analog components, showing details of the analog characterization process. Then, we create a mixed signal platform library as a combination of an analog and a digital platform (bottom-up phase). The top-down phase performs optimization across the analog/digital boundary to minimize power consumption constrained to given noise and linearity requirements. Simulation results show that interesting power saving can be achieved, as much as 64% compared with an original hand-optimized ADC. Pierluigi Nuzzo received the Laurea degree in electrical engineering from the University of Pisa, Italy, in 2003, and the Diploma from the Scuola Superiore Sant’Anna, Pisa, in 2004, both with honors. Since 2004, he has been with the Department of Information Engineering, University of Pisa, where he is currently working toward the Ph.D. degree in electrical engineering and computer science. During summer 2002 he was with the Fermi National Accelerator Laboratory, Batavia, IL as a student intern working on ASIC testing. From August 2004 to February 2005 he was with IMEC, Leuven, Belgium, as a visiting scholar, working on low power A/D converter design for ultra-wide band applications. His research interests include high speed, low power analog and mixed-signal circuits in CMOS technology, digital calibration of ADCs, system level mixed-signal design and design methodologies. Mr. Nuzzo received first place in the operational category and best overall submission in the 2006 DAC/ISSCC student design competition. Fernando De Bernardinis received the Laurea degree in Electrical Engineering from the University of Pisa, Italy, in 1996 and the M.S. degree and Ph.D. degree from the University of California at Berkeley in 2001 and 2005, respectively. Between 1992 and 1996 he was at the Scuola Superiore S. Anna in Pisa. From 1997 to 1998 he collaborated with the PARADES research center in Rome. During the summers 1999 and 2000 he was at the ST Berkeley labs, working on wireless embedded system design. From 2000 to 2006 he was assistant professor at the Department of Information Engineering at the University of Pisa, Italy. His research interests include mixed-signal design, analog CAD, system level analog design and design methodologies. In 2006 he has joined Marvell Semiconductors, Pavia, Italy, where he works on mixed-signal and RF system design. Alberto Sangiovanni Vincentelli holds the Edgar L. and Harold H. Buttner Chair of Electrical Engineering and Computer Sciences at the University of California at Berkeley. He has been on the Faculty since 1976. He obtained an electrical engineering and computer science degree (“Dottore in Ingegneria”) summa cum laude from the Politecnico di Milano, Milano, Italy in 1971. In 1980–1981, he spent a year as a Visiting Scientist at the Mathematical Sciences Department of the IBM T.J. Watson Research Center. In 1987, he was Visiting Professor at MIT. He has held a number of visiting professor positions at Italian Universities, including Politecnico di Torino, Universita’ di Roma La Sapienza, Universita’ di Roma Tor Vergata, Universita’ di Pavia, Universita’ di Pisa, Scuola Sant’Anna. He was a co-founder of Cadence and Synopsys, the two leading companies in the area of Electronic Design Automation. He is the Chief Technology Adviser of Cadence. He is a member of the Board of Directors of Cadence and the Chair of the Technology Committee, UPEK, a company he helped spinning off from ST Microelectronics, where he is the Chair of its Nominating and Governance Committee and a member of the Audit Committee, Sonics, where he serves as the Chair of the Nominating and Governance Committee, Gradient, where he is a member of the Compensation committee, Accent, an ST Microelectronics-Cadence joint venture he helped founding, and Value Partners. He is the Technology Advisor to the President of the Abruzzo Region. He is a member of the HP Strategic Technology Advisory Board, of the Science and Technology Advisory Board of General Motors and of the Scientific Council of the Tronchetti Provera foundation. He consulted for many companies including Bell Labs, IBM, Intel, United Technology, COMAU, Magneti Marelli, Pirelli, BMW, Daimler-Chrysler, Fujitsu, Kawasaki Steel, Sony, ST and Hitachi. He was an advisor to the Singapore Government for microelectronics and new ventures. He has consulted as Technology Partner for Greylock Ventures and for Vertex Investment. He served as witness in US Congressional investigations on competitiveness of the US economy. He is the founder and Scientific Director of the Project on Advanced Research on Architectures and Design of Electronic Systems (PARADES), a European Group of Economic Interest supported by Cadence, Magneti-Marelli and ST Microelectronics. He is a member of the Advisory Board of the Lester Center for Innovation of the Haas School of Business and of the Center for Western European Studies and a member of the Berkeley Roundtable of the International Economy (BRIE). He is a member of the High-Level Group and of the Steering Committee of the EU Artemis Technology Platform. In 1981, he received the Distinguished Teaching Award of the University of California. He received the worldwide 1995 Graduate Teaching Award of the IEEE (a Technical Field award for “inspirational teaching of graduate students”). In 2002, he was the recipient of the Aristotle Award of the Semiconductor Research Corporation. He has received numerous research awards including the Guillemin-Cauer Award (1982–1983), the Darlington Award (1987–1988) of the IEEE for the best paper bridging theory and applications, and two awards for the best paper published in the Transactions on CAS and CAD, three best paper awards and one best presentation awards at the Design Automation Conference. In 2001, he was given the prestigious Kaufman Award of the Electronic Design Automation Council for pioneering contributions to EDA. He is an author of over 700 papers and 15 books in the area of design tools and methodologies, large-scale systems, embedded controllers, hybrid systems and innovation. Dr. Sangiovanni-Vincentelli has been a Fellow of the IEEE since 1982 and a Member of the National Academy of Engineering, the highest honor bestowed upon a US engineer, since 1998.     

Design and implementation of an optimised wireless pressure sensor for biomedical application

This paper presents design and implementation of a wireless pressure sensor system for biomedical application. The system consists of a front-end Micro-Electro- Mechanical System (MEMS) sensing capacitor along with an optimised MEMS-based oscillator for signal conditioning circuit. In this design, vertical fringed comb capacitor is employed due to the advantages of smaller area, higher linearity and larger full scale change in capacitance compared to parallel plate counterparts. The MEMS components are designed in Coventorware design suite and their Verilog-A models are extracted and then imported to Cadence for co-simulation with the CMOS section of the system using AMI 0.6-micron CMOS process. In this paper, an optimisation method to significantly reduce the system power consumption while maintaining the system performance sufficient is also proposed. A phase noise optimisation approach is based on the algorithm to limit the oscillator tail current. Results show that for the pressure range of 0–300 mmHg the device capacitance range of 1.31 pF – 1.98 pF is achieved which results in a frequency sweep of 2.54 GHz – 1.95 GHz. Results also indicate that a 42% reduction of power consumption is achieved when the optimisation algorithm is applied. This characteristic makes the sensor system a better candidate for wireless biomedical applications where power consumption is the major factor. Hai Phuong Le received his B.E. (Hons) degree in Electronic and Computer System Engineering from University of Tasmania, Hobart, Australia in 2000. He received his Ph.D. degree in Microelectronics from Victoria University, Melbourne, Australia in 2005. At present, he is a post-doctoral research fellow and lecturer in the Centre for Telecommunications and Microelectronics, Victoria University. His research and teaching interests include data acquisition system, mixed-signal integrated circuit design and wireless smart sensor systems. Kriyang Shah received his B.E. Degree in Electronics and Communication Engineering from Sardar Patel University, Vallabh Vidyanagar, Gujarat, India and his Master Degree in Microelectronics in 2004. He is currently a Ph.D. research student in the Centre for Telecommunications and Microelectronics, Victoria University, Melbourne, Australia. His research interests include MEMS Sensors, RF MEMS, process integration for MEMS and CMOS and MEMS-CMOS co-simulation. Jugdutt (Jack) Singh received his B.Sc. in Electronics Engineering from University of Brighton, UK and M.Sc. in Electronics Engineering from University of Alberta, Canada in 1978 and 1986 respectively. He completed his Ph.D. at Victoria University, Australia in 1997. Since 1989 he has been at Victoria University, Melbourne, Australia. Currently he is a Professor of Microelectronics in the Centre for Telecommunications and Microelectronics at Victoria University. His major area of research interests are in the RF, analog and mixed signal design, reconfigurable architectures, low power VLSI circuits and systems design. He has published number of articles in education and research in microelectronics and small technologies area. Aladin Zayegh received his B.E. degree in Electrical Engineering from Aleppo University in 1970 and Ph.D. degree from Claude Bernard University, France in 1979. In 1980, he joined the Faculty of Engineering, Tripoli, Libya. Since 1984 he has held lecturing position at Victoria University, Melbourne, Australia. He is currently an Associate Professor and the Head of School in the School of Electrical Engineering, Faculty of Health, Engineering and Engineering and Science at Victoria University. His research interest includes microprocessor-based system, instrumentation, data acquisition and interfacing, and microelectronics.     

Design and performance evaluation of a full-duplex operating receiver for time-hopping UWB

One of the most attractive features of time-hopping ultra-wide-band (UWB) transmission, largely ignored in the literature so far, is the possibility to operate in full-duplex mode, thanks to its very low duty-cycle. This allows a terminal to transmit and receive within the same time frame and frequency band, yielding a considerable saving of time and band resources at the radio-resource-management layer. In this paper, we propose a methodology to design channel estimation/synchronization and demodulation/decoding algorithms for a low-complexity receiver operating in full-duplex mode. The leading idea is simply to avoid, at reception, time intervals that correspond to pulse transmission. We also evaluate the performances of such a system through simulations over realistic propagation channels. Tomaso Erseghe was born in Valdagno, Italy, in 1972. He received the laurea degree and the PhD in Telecommunication Engineering from the University of Padova, Italy, respectively in 1996 and in 2002. From 1997 to 1999 he worked as an R&D Engineer at Snell & Wilcox, a British broadcast equipment manufacturer, in the areas of image restoration and motion compensation. From 2003 he is an Assistant Professor (Ricercatore) at the University of Padova. His research interests include fractional Fourier transforms, lossless encoding algorithms, and ultra-wideband transmission systems. Nicola Laurenti was born in 1970, in Adria, Italy. He graduated from the University of Padova with a laurea in Electrical Engineering in 1995, with a thesis on Image Reconstructions from Projections, and obtained a Ph.D. in Electrical and Telecommunications Engineering from the same University in February 1999, with a thesis on Implementation Issues in OFDM Systems. Since 2001 he is an Assistant Professor at the Department of Information Engineering, University of Padova. His research interests mainly focus on digital communications, especially multicarrier modulation and ultra wide band transmission, but also include signal theory, and the processing of audio and biomedical signals.     

A Prototype Bandpass Sigma-Delta Modulator Employing Crystal Resonator

This paper describes an initial work on a second-order bandpass Sigma-delta modulator employing crystal resonator. The aim of this work is to explore the possibilities of realizing bandpass sigma-delta modulator using non-electronic resonators, such as micro-mechanical resonators. The initial study is based on crystal resonators as they have similar characteristics as the other types of resonator and are readily available. In order to obtain the desired loop transfer function, a compensation circuit is proposed to cancel the anti-resonance in the crystal resonator. The modulator chip is fabricated in a 0.6-μ m CMOS process. The bandpass noise shaping is demonstrated in the experiment with a 1- and 8-MHz crystal resonator, respectively. Yong Ping Xu graduated from Nanjing University, P.R. China in 1977. He received his Ph.D. from University of New South Wales (UNSW) Australia, in 1994. From 1978 to 1987, he was with Qingdao Semiconductor Research Institute, P.R.China, initially as an IC design engineer, and later the deputy R&D manager and the Director. From 1993 to 1995, he worked on an industry collaboration project with GEC Marconi, Sydney, Australia, at the same university, involved in design of sigma-delta ADCs. He was a lecturer at University of South Australia, Adelaide, Australia from 1996 to 1998. He has been with the Department of Electrical and Computer Engineering, National University of Singapore since June 1998 and is now an Associate Professor. His general research interests are in the areas of mixed-signal and RF integrated circuits, and integrated MEMS and sensing systems. He is a Senior Member of IEEE. Xiaofeng Wang was born in Shangqiu, China, in 1980. He received B.Eng. degree from Northwestern Polytechnical University, Xi'an, China, in 2000 and M. Eng. degree from National University of Singapore, Singapore, in 2003, both in electrical engineering. He is currently working toward the Ph.D. degree at Tufts University, Medford, USA. His research is on high speed ADC design. Wai Hoong Sun was born in Taiping, Malaysia in 1976. He received the B. App. Sc. (Honours) degree in electrical engineering from the University of Toronto, Canada in 1999. After graduating, he joined Sharp Electronics Singapore as an R&D Engineer where he was involved in FPGA and digital IC design of display related circuits. In 2001 and 2002, he did full time research in the National University of Singapore on bandpass sigma-delta modulators. During that period, he was also a Graduate Tutor in electronics for second year electrical and computer engineering students. He then joined Philips Electronics Singapore in 2002 as a Lead Engineer. He did board-level designs for LCD and plasma televisions. He was also development project leader for a project that was successful in bringing to the market a range of LCD and plasma televisions. Currently, he is a Hardware Architect where he is responsible for the system-level electrical design of the television board.     

On-Chip Pseudorandom MEMS Testing

This paper presents a Built-In-Self-Test (BIST) implementation of pseudo-random testing for MEMS. The technique is based on Impulse Response (IR) evaluation using pseudo-random Maximum–Length Sequences (MLS). The MLS approach is capable of providing vastly superior dynamic range in comparison to the straightforward technique using an impulse excitation and is thus an optimal solution for measurements in noisy environments and for low-power test signals. The use of a pseudo-random sequence makes the practical on-chip implementation very efficient in terms of the extra hardware required for on-chip testing. We will demonstrate the use of this technique for an on-chip fast and accurate broadband determination of MEMS behaviour, in particular for the characterisation of cantilever MEMS structures, determining their mechanical and thermal behaviour using just electrical tests.Libor Rufer has received Engineering and PhD degrees from the Czech Technical University, Prague, Czech Republic. Until 1993 he was with the Faculty of Electrical Engineering of the Czech Technical University, Prague and since 1994, he is Associate Professor at the Joseph Fourier University, Grenoble, France. In 1998, he joined the Microsystems research team of the TIMA Laboratory. Currently he is a member of the Reliable Mixed-signal Systems Group of the same Laboratory. His expertise and research interests pertain MEMS-based sensors and actuators, electro-acoustic and electro-mechanical transducers, their modelling, applications, associated measurement techniques, and analogue and mixed-signal system test.Salvador Mir has an Industrial Engineering (Electrical, 1987) degree from the Polytechnic University of Catalonia, Barcelona, Spain, and M.Sc. (1989) and Ph.D. (1993) degrees in Computer Science from the University of Manchester, UK. He is a researcher of Centre National de la Recherche Scientifique, France, and he is leading the RMS (Reliable Mixed-signal Systems) Group at TIMA Laboratory in Grenoble, France. He is the author of many research papers and editor of two books on silicon microsystems. His research interests include analogue, mixed-signal, RF and microsystem design and test, and applications of Artificial Intelligence to Computer-Aided Design.Emmanuel Simeu received Electrical Engineering degree, DEA and Ph.D. in Automatic Control from National Polytechnic Institute of Grenoble in 1987, 1988 and 1992, respectively. He is Associate Professor of Automatic Control and Electrical engineering in Joseph Fourier University of Grenoble. He is also a researcher in the RMS Group at TIMA Laboratory. His research interests include system modelling, reliability of integrated systems, online testing of analogue, digital and mixed signal systems.Christian Domingues was born in Lyon, France, in 1978. He received a Master degree in Microelectronics from the Institut National Polytechnique de Grenoble, France, in 2001. He is currently pursuing a Ph.D. degree at TIMA Laboratory in Grenoble, France. His research interests include mixed-signal integrated circuit design, and micromachined sensors and actuators.     

A Joint MAC-PHY Approach for Medium Access Control in VBR MC-CDMA Broadband Indoor Connections

Multicarrier Code Division Multiple Access (MC-CDMA) techniques were originally proposed at mid of 90's for wideband multi-user communications in wireless environments characterized by hostile propagation characteristics. In this work, the design of a MC-CDMA-based infrastructure is considered for VBR broadband indoor connections with real-time asynchronous multiple access. At the present time, Broadband Fixed Wireless Access (BFWA) standards like IEEE 802.16 and HIPERMAN can bring broadband services inside buildings, but indoor access should be conveniently provided by a local area connection. The capability of MC-CDMA of supporting asynchronous multi-user variable-bit-rate (VBR) transmission is exploited jointly with an efficient and real-time Medium Access Control (MAC) strategy in order to allow a significant number of indoor VBR users to transmit information in CDMA modality with different quality of service (QoS) profiles. Different classes of users are defined at the MAC level. The available radio resources (i.e. the orthogonal subchannels) are selectively attributed to transmitting users depending on their performance achieved at MAC level and measured by an “intelligent” gateway. When the quality level is not satisfactory for one or more users, the AP issues a decrease of the data rate for such users while providing them with an increased number of subcarriers, guaranteeing a slower transmission fostered against frequency-selective channel distortions. The paper presents an overview of the system and tests its performance through extensive simulations. The proposed joint MAC-PHY approach demonstrates good performance in terms of achieved throughput and high flexibility in radio resource management.This work has been partially supported in Italy by the “NETMOBS -Network-supported Mobility for the Student” – Create-NET project funding, 2005. Claudio Sacchi was born in Genoa (Italy) in 1965. He obtained the Laurea degree in Electronic Engineering, and the Ph.D. in Space Science and Engineering at the University of Genoa (Italy). Since August 2002, Dr. Sacchi has been holding a position as assistant professor at the Faculty of Engineering of the University of Trento (Italy). In 2004, he was appointed by the Department of Information and Communication Technology of the University of Trento as leader of the Research Program titled: “Wireless and Satellite Communications”. The research interests of Dr. Sacchi are focused on wideband mobile and satellite transmission systems based on space, time and frequency diversity, multi-user receivers based on non conventional techniques, and high-frequency ultra-wideband satellite communications. Dr. Sacchi is author and co-author of more than 40 papers published in international journals and conferences. He is member of IEEE. Giovanni Berlanda Scorza was born in Trento (Italy) in 1978. He received the Laurea in Telecommunications Engineering in 2002 at the “Politecnico di Milano” Technical University. Since October 2002, he is a Ph.D student at the Information and Communications Technologies (ICT) International Doctorate School of the University of Trento. His research interests mainly concern with specific aspects related to OFDM and MC-CDMA transmission techniques like e.g.: computationally-affordable multi-user receivers, Medium Access Control strategies, multicarrier-based multiplexing of multi-layered MPEG-4 coded video streams, etc. Fabrizio Granelli was born in Genoa in 1972. He received the “Laurea” (M.Sc.) degree in Electronic Engineering from the University of Genoa, Italy, in 1997, and the Ph.D. in Telecommunications from the same university, in 2001. Since 2000 he is carrying on his teaching activity as Assistant Professor in Telecommunications at the Dept. of Information and Communication Technology – University of Trento (Italy). In August 2004, he was visiting professor at the State University of Campinas (Brasil). He is author or co-author of more than 50 papers published in international journals, books and conferences, and he is member of the Technical Committee of the International Conference on Communications (ICC2003, ICC2004 and ICC2005) and Global Telecommunications Conference (GLOBECOM2003 and GLOBECOM2004). Dr. Granelli is guest-editor of ACM Journal on Mobile Networks and Applications, special issue on “WLAN Optimization at the MAC and Network Levels” and Co-Chair of 10th IEEE Workshop on Computer-Aided Modeling, Analysis, and Design of Communication Links and Networks (CAMAD'04). Dr. Granelli is General Vice-Chair of the First International Conference on Wireless Internet (WICON'05). His main research activities are in the field of networking and signal processing, with particular reference to network performance modeling, medium access control, wireless networks, next-generation IP, and video transmission over packet networks. Francesco G.B. De Natale received the Laurea in Electronic Engineering in 1990, and the Ph.D. in Telecommunications in 1994, both from the University of Genoa, Italy. In 1995–96 he was Visiting Professor at the University of Trento, Italy and from 1996 to 1999 Assistant Professor at the University of Cagliari, Italy. At present he is Full Professor of Telecommunications at the University of Trento, where he coordinates the didactic activities of the Bachelor and Master Courses in Telecommunications Engineering. Prof. De Natale is Deputy Head of the Dept. of Information and Communication Technologies, where he leads the research activities of the Multimedia Communications Lab. The research interests of Prof. De Natale are focused on image and signal processing, with particular attention to multimedia data compression, processing and transmission. He was General Co-Chair of the Packet Video Workshop in 2000 and is Technical Program Co-Chair of the IEEE Intl. Conf. on Image Processing to be held in 2005. In 1998 he was co-recipient of the IEEE Chester-Sall Best Paper Award. Prof. De Natale is a Senior Member of IEEE.     

Input-Matching and Offset-Cancelling Networks for Limiting Amplifiers in Optical Communication Systems

The diffusion of optical communication systems in the access network and for short-haul datacom applications requires the use of low-cost plastic packages: the functional block most affected is the limiting amplifier, that is often the first stage of the Clock and Data Recovery (CDR) IC. In this paper we illustrate the design issues of the input-matching and offset-cancelling network for a differential limiting amplifier for optical communication systems, with particular emphasis on the effect of bond wires. We discuss the limitations of passive feedback networks when used both for offset suppression and for input matching, and propose a topology that overcomes such limitations by using an active feedback loop. A 50 Ω-loaded differential pair is used to achieve input matching and high offset suppression, and its buffering action desensitizes the input matching from the effect of the bond wires connecting off-chip filtering capacitors. Very good performance even with low cost plastic packages can be achieved by solving the trade-off between power consumption, offset suppression and the value of the low-pass filtering capacitors. Design examples of CDR IC's for 2.5 Gb/s optical systems are presented to compare the proposed topology with solutions based on passive feedback networks. Marco Balsi received the laurea (M.Sc.) degree in 1991 and the dottorato di ricerca (Ph.D.) in 1995 in Electronic Engineering from University of Roma “La Sapienza”, Roma, Italy. Since 1996 he is with “La Sapienza” University as ricercatore (assistant professor). He is engaged in research in nonlinear and soft-computing-based signal processing (especially for biomedical imaging), artificial vision, mechatronics, and anti-personnel mine detection. He has published about 60 paper in international journals and refereed conferences. Francesco Centurelli received the laurea degree (cum laude) and the Ph.D. degree in electronic engineering from the University of Roma “La Sapienza”, Roma, Italy, in 1995 and 2000, respectively. He is currently doing postdoctoral work with the Electronic Engineering Department of the University of Roma “La Sapienza.” His research interests include system-level analysis and design of clock recovery circuits and high-speed analog integrated circuits, with particular emphasis on gigabit-rate optical communication systems. Andrea Pallotta received the M.S. degree in electronic engineering from the University of Ancona, Ancona, Italy. From 1991 to 1999, he was with Italtel, Italy, where he joined several European Community research projects in the field of SDH and WDM fiber-optic transmission systems for both transport and access networks. From 1999 to 2000, he was with Siemens Information and Communication Networks, where he was responsible for the SDH Cross-Connect advanced development group. In September 2000, he joined the STMicroelectronics Company, where he is currently responsible for the electrooptical interface design group. His research interests include GaAs and silicon high-speed ICs, active optical devices, high-speed TX and RX optical modules, and fiber-optic transmission system engineering. Alessandro Trifiletti was born in Roma, Italy, in 1959. In 1991, he joined the Electronic Engineering Department of the University of Roma “La Sapienza” as a Research Assistant and is currently an Assistant Professor. His research interests include high-speed circuit design techniques and III-V device modeling.     

Methodology for Refinement and Optimisation of Dynamic Memory Management for Embedded Systems in Multimedia Applications

In multimedia applications, run-time memory management support has to allow real-time memory de/allocation, retrieving and processing of data. Thus, its implementation must be designed to combine high speed, low power, large data storage capacity and a high memory bandwidth. In this paper, we assess the performance of our new system-level exploration methodology to optimise the memory management of typical multimedia applications in an extensively used 3D reconstruction image system [1, 2]. This methodology is based on an analysis of the number of memory accesses, normalised memory footprint¹ and energy estimations for the system studied. This results in an improvement of normalised memory footprint up to 44.2% and the estimated energy dissipation up to 22.6% over conventional static memory implementations in an optimised version of the driver application. Finally, our final version is able to scale perfectly the memory consumed in the system for a wide range of input parameters whereas the statically optimised version is unable to do this.The original version of this paper first appeared in the Proceedings of Signal Processing Systems 2003.Marc Leeman has as professional research interests hardware/software co-design, code optimisation in general and optimisation of dynamic data types and dynamic memory management for low power embedded systems in particular. Personal interests include Open and Free software development, software configuration and GNU/Debian package maintenance. He received an engineering degree, a master in artificial intelligence and a Ph.D. in electrical engineering in 1997, 1998 and 2004 respectively, all at the K.U. Leuven. He is a member of the IEEE Computer Society. Currently, he works as an R&D Engineer for Barco Control-rooms Division (BCD) on hardware/software co-design for streaming video products.David Atienza received the M.Sc. degree in Computer Sciences from the Complutense University of Madrid (UCM), Spain in 2001. Since then he has joined the Department of Computer Architecture and Automation of Complutense University of Madrid as a sandwich Ph.D. student half-time at the Inter-university Micro-Electronics Centre (IMEC), Heverlee, Belgium. His research interests include optimisation of dynamic memory management on multimedia and wireless network applications for low power and high performance embedded systems, computer architecture and high-level design automation.Geert Deconinck is Associate Professor (hoofddocent) at the K.U. Leuven (Belgium) since 2003 and staff member of the research group ELECTA (Electrical Energy and Computing Architectures). His research interests include the design and assessment of software-based solutions to meet dependability, real-time, and cost constraints for embedded systems. In this field, he has authored and co-authored more than 120 publications in international journals and conference proceedings. He received his M.Sc. in Electrical Engineering and his Ph.D. in Applied Sciences from the K.U. Leuven, Belgium in 1991 and 1996 respectively. He was a visiting professor (bijzonder gastdocent) at the K.U. Leuven in 1999–2003. - Flanders (Belgium) in the period 1997–2003.Vincenzo De Florio received his MSc degree in computer science in 1987 and his PhD degree in engineering in 2000, respectively from the University of Bari, Italy, and the University of Leuven, Belgium. He is currently post-doctoral researcher at the University of Antwerp, where he is doing research on adaptive and dependable mobile applications. Previously he had been researcher and lecturer with Tecnopolis/SASIAM (ECMI School for Advanced Studies in Industrial and Applied Mathematics) and member of Tecnopolis/Robotic lab, where he was responsible for design of parallel robotic vision applications. Currently he is also a reviewer for several conferences and for the Journal of System Architectures.José M. Mendías received the M.Sc. and Ph.D. degrees in physics from the Complutense University of Madrid in 1992 and 1998, respectively. He joined the Department of Computer Architecture and Systems Engineering, Complutense University in 1992 as a lecturer, and became an associate professor in 2001. Since 2002, he is Vice-dean of the Computer Science Faculty at the same University. His current research interests include design automation, computer architecture and formal methods.Chantal Ykman-Couvreur is born in 1956. She received the mathematics degree from the Facultes Universitaires Notre-Dame de la Paix of Namur in 1979. She first worked at PHILIPS Research Laboratory of Belgium, from 1979 until 1991. Her main activities were concentrated on information theory and coding, cryptography and multi-level logic synthesis for VLSI circuits. Then, she joined IMEC, where she was responsible at IMEC for the dynamic memory management and the system-level design flow in the Matisse compiler for network protocol components (ATM, Internet Protocol, etc). Currently, she works on the task concurrency management design flow in the Matador project.Francky Catthoor received the engineering degree and a Ph.D. in electrical engineering from the Katholieke Universiteit Leuven, Belgium in 1982 and 1987 respectively. Since 1987, he has headed several research domains in the area of high-level and system synthesis techniques and architectural methodologies, all within the Design Technology for Integrated Information and Telecom Systems (DESICS—formerly VSDM) division at the Inter-university Micro-Electronics Centre (IMEC), Heverlee, Belgium. Currently he is an IMEC fellow. He is part-time full professor at the EE department of the K.U. Leuven.In 1986 he received the Young Scientist Award from the Marconi International Fellowship Council. He has been associate editor for several IEEE and ACM journals, like Transactions on VLSI Signal Processing, Transactions on Multi-media, and ACM TODAES. He was the program chair of several conferences including ISSS97 and SIPS01.Rudy Lauwereins is vice-president of IMEC, Belgiums Interuniversity Micro-Electronic Centre, which performs research and development, ahead of industrial needs by 3 to 10 years, in microelectronics, nano-technology, enabling design methods and technologies for ICT systems. He leads the DESICS division of 185 researchers, currently focused on the development of re-configurable architectures, design methods and tools for wireless and multimedia applications. He is also a part-time Professor at the Katholieke Universiteit Leuven, Belgium. He had obtained a Ph.D. in Electrical Engineering in 1989. Rudy Lauwereins served in numerous international program committees and organisational committees, and gave many invited and keynote speeches. He is vice-chair of the board of DSP Valley and member of the board of several spin-off companies. He is a senior member of the IEEE.     

The ultra-wide bandwidth outdoor channel: From measurement campaign to statistical modelling

This paper proposes an investigation of the propagation behaviour for Ultra-Wide Bandwidth (UWB) signals in outdoor environments. Specifically, we first report on the results of an extensive measurement campaign carried out in three selected scenarios, namely “forest”, “hilly” and “sub-urban” environments. Then, we present the statistical model derived through the post-processing of collected samples by the CLEAN algorithm. While an extensive collection of results is provided in the paper, the main achievements can be summarized as follows: (i) the path-loss exponent varies from 2 to 3.5 and depends on the reference scenario and on the height of transmission and reception equipments with respect to the ground floor, (ii) the local mean of the received power experiences a Log-Normal shadowing with a standard deviation that may depend on the azimuth position, (iii) the statistics of the first received echo in the small-scale analysis also well fit a Log-Normal distribution; (iv) the delay spread in the small-scale multipath scenario turns out to be quite small (i.e. roughly 10 ns in the forest scenario and less than 32 ns in the sub-urban scenario). Marco Di Renzo (S’05) received the laurea degree (cum laude) in Electronic Engineering from the University of L’Aquila, Italy, in 2003. In 2002 he was with the Center of Excellence in Research DEWS (Design Methodologies for Embedded Controllers, Wireless Interconnections and System–on-Chip) at the Department of Electrical Engineering, University of L’Aquila, doing research on the analysis and design of Ultra Wide Band digital receiver architectures. Since 2003 he has been with the Department of Electrical Engineering, University of L’Aquila, where he worked on channel sounding and modelling for Ultra Wide Band systems and where he is currently pursuing his Ph.D. degree in Electric and Information Engineering. His current research activity is focused on channel modelling, synchronization and detection theory with specific interest to the Ultra Wide Band technology. In 2004 he played a key role in the successful creation of WEST Aquila S.r.l. (Wireless Embedded Systems Technologies Aquila), a R&D Spin-Off of the University of L’Aquila and the Center of Excellence in Research DEWS, where he currently holds the position of research engineer. Fabio Graziosi (S’96–M’97) was born in L’Aquila, Italy, in 1968. He received the Laurea degree (cum laude) and Ph.D. degree in electronic engineering from the University of L’Aquila, L’Aquila, Italy, in 1993 and 1997, respectively. Since February 1997 he has been with the Department of Electrical Engineering, at the University of L’Aquila, where he currently holds the position of Associate Professor. His current research interests are mainly focused on wireless communication systems with emphasis on wireless sensor networks and ultra wide band communication techniques. He is involved in major national and European research projects in the field of wireless systems. He is member of the Executive Committee of the Center of Excellence DEWS and serves as Chairman of the Board of Directors of WEST Aquila S.r.l., a Spin-off R&D Company of the University of L’Aquila and Center of Excellence DEWS, founded in December 2004. Riccardo Minutolo works in Thales Italia in the R&D department. He graduated in Electronic Engineering in the University of L’Aquila, in 1999. He joined Thomson-csf in 1999 working as junior engineer in the Radio propagation, interference and software development. In that period he gained expertise in HF, VHF, UHF, SHF radio propagation. In 2002 he joined Thales Italy (ex-Thomson-csf) working in the ad hoc networking area. In 2002 he was the National coordinator of a 3 years European international project (Euclide UWB). The Euclide UWB project aimed to study and research the potentiality of the emerging UWB technology for civil security and military purposes. Since 2002 his major areas of interest are: radio propagation, UWB physical layer, MAC and networking. Mauro Montanari was born in 1950 in Rimini and graduated in Electronic Engineering at Bologna University in 1974. He joined in 1976 Telettra, a national telecommunication company, working since the beginning in Defence R&D activities. His first experience was in the field of advanced automatic antenna matching unit in HF band. Afterwards he mastered, staying for several time periods in TRW—Redondo Beach/California, the technical issue of protecting radio communications through Spread Spectrum communications systems, in view of an important application to a new generation of tactical radio systems in VHF frequency band. On this topic he is co-author, with Prof. S. Pupolin of Padua University, of the book “Spread Spectrum Communications Systems” Collana Scientifica Telettra). From 1991 to 1998 he was responsible of the R&D Department within the Defence Division of Alcatel Italia (formerly Telettra) and in this position he managed several R&D projects: (i) Triservice Digital Network for the Italian MOD, in cooperation with Selenia Communications; (ii) SCRA (Single Channel Radio Access) and network management system for the Italian Army tactical network (SOTRIN) as a partner of Catrin Consortium; (iii) A new generation of radio equipment in HF band for fixed applications; (iv) High speed HF modem, according to several NATO waveforms; (v) HF fixed network for Italia Ministry of Foreign Affairs; (vi) Wide band Interception and jamming systems in HF band. Since 1999, he is responsible, within Thales Italia SpA—Land and Joint Systems Division, of Advanced Studies area with the task of promoting in the company new emerging technologies, specifically in the field of Wireless LAN, Tactical Internet, sensor networks, Ultra Wide Band for military applications and plasma antennas. This role includes establishing relations with most Thales R&D centres located in Europe and promoting new cooperative activities in new advanced technological areas. He also manages scientific relation with several Italian Universities. Fortunato Santucci (S’93–M’95–SM’00) was born at L’Aquila, Italy, in 1964. He received the laurea degree and the Ph.D. degree in Electronic Engineering from the University of L’Aquila, Italy, in 1989 and 1994, respectively. In 1989 he was with Selenia Spazio S.p.a., Rome, working on VSAT networks design. In 1991–1992 he was at the Solid State Electronics Institute (I.E.S.S.) of the National Research Council (C.N.R.), Rome, doing research on superconductor receivers for millimeter wave satellite systems. Since 1994 he has been with the Department of Electrical Engineering, University of L’Aquila, where he currently holds the position of Associate Professor. In 1996 he was a visiting researcher at the Department of Electrical and Computer Engineering of the University of Victoria, BC, Canada, where he researched on CDMA networks. His current research activity is focused on communication theory, access control and radio resource management in wireless systems, with special emphasis on technologies for networked embedded systems. He has participated in major national and European research programs in wireless mobile communications and coordinates research programs funded by industrial partners. He has been a reviewer for major technical journal in telecommunications and a session chairman in various conferences. He currently serves as an Editor for the IEEE Transactions on Communications and Kluwer Telecommunications Systems. He has been/is in the TPC of several conferences in communications. He is a Senior Member of the IEEE and is a member of the Communications Theory Committee. He is in the Executive Committee of the Center of Excellence DEWS at the University of L’Aquila and in the Executive Committee of CNIT.     

Efficient heuristics for data broadcasting on multiple channels

The problem of data broadcasting over multiple channels consists in partitioning data among channels, depending on data popularities, and then cyclically transmitting them over each channel so that the average waiting time of the clients is minimized. Such a problem is known to be polynomially time solvable for uniform length data items, while it is computationally intractable for non-uniform length data items. In this paper, two new heuristics are proposed which exploit a novel characterization of optimal solutions for the special case of two channels and data items of uniform lengths. Sub-optimal solutions for the most general case of an arbitrary number of channels and data items of non-uniform lengths are provided. The first heuristic, called Greedy+, combines the novel characterization with the known greedy approach, while the second heuristic, called Dlinear, combines the same characterization with the dynamic programming technique. Such heuristics have been tested on benchmarks whose popularities are characterized by Zipf distributions, as well as on a wider set of benchmarks. The experimental tests reveal that Dlinear finds optimal solutions almost always, requiring good running times. However, Greedy+ is faster and scales well when changes occur on the input parameters, but provides solutions which are close to the optimum. This work has been supported by ISTI-CNR under the BREW research grant. Stefano Anticaglia received the bachelor’s degree in Computer Science from the University of Perugia (Italy) in 2005. At present, he is a student in the master’s of Computer Science of the University of Perugia. Ferruccio Barsi received the doctor engineering degree from the University of Pisa, Italy, in 1969. From 1969 to 1992 he has been with he National Council of Research at the Istituto di Elaborazione dell’Informazione, Pisa. Since 1992, he is a Full Professor of Computer Science in the Mathematics and Computer Science Department of the University of Perugia, Italy. His main contributions are in the areas of computer architecture, error-control coding, systems diagnosis, VLSI design, digital signal processing, and computer graphics. He is currently involved in researches concerning network security and wireless communications. Alan Bertossi was born in London (England) in 1956. He got the Laurea Degree summa cum laude in Computer Science from the University of Pisa (Italy) in 1979. Afterwards, he worked as a System Programmer and Designer. From 1983 to 1994 he was with the University of Pisa as a Research Associate first, and later as an Associate Professor. From 1995 to 2002 he was with the University of Trento (Italy), as a Full Professor. Since 2002, he has been with the Department of Computer Science of the University of Bologna (Italy), as a Professor of Computer Science. His main research interests are the computational aspects of high-performance, parallel, VLSI, distributed, fault-tolerant, and real-time systems. He has published about 40 refereed papers on international journals, as well as several papers in international conferences, workshops, and encyclopedias. He has authored a book (on design and analysis of algorithms, in Italian) and he served as a guest coeditor for special issues of Algorithmica, Discrete Applied Mathematics, and Mobile Networks and Applications. He is a member of the editorial board of Information Processing Letters. His biography is included in the 1999 edition of Who’s Who in the World and in the 2000 edition of Who’s Who in Science and Engineering. Since 1999, he has been a scientific collaborator at the Institute of Information Sciences and Technologies of the Italian National Research Council (ISTI-CNR, Pisa, Italy). During 2001–2003, he was the national coordinator of an Italian research project on algorithms for wireless networks. Lucio Iamele received the bachelor’s degree in Computer Science from the University of Perugia (Italy) in 2004. At present, he is working at Noranet (Italy) as a system programmer and designer. M. Cristina Pinotti received the Dr. degree cum laude in Computer Science from the University of Pisa, Italy, in 1986. During 1987–1999 she was a Researcher with the National Council of Research at the Istituto di Elaborazione dell’Informazione, Pisa. From 2000–2003 she was an Associate Professor at the University of Trento. From 2004, she is a Full Professor at the University of Perugia. In 1994 and 1995 she was a Research Associate at the Department of Computers Sciences, University of North Texas, Denton, TX. In 1997 she visited the Department of Computer Science, Old Dominion University, Norfolk, VA (USA). Her research interests are in wireless networks, sensor networks, design and analysis of algorithms, data broadcasting, channel assignment problems, graph coloring, multiprocessor interconnection networks, design and analysis of parallel algorithms, parallel data structures, distributed computer arithmetic, residue number systems, VLSI special purpose architectures. She has published about 50 refereed papers on international journals, in international conferences and workshops. She has been a guest co-editor for special issues of Mobile Networks and Applications, Wireless Networks and Journal of Parallel and Distributed Computing. She is a member of the editorial board of International Journal of Parallel, Emergent and Distributed Systems.     

Reduced Impact of Induced Gate Noise on Inductively Degenerated LNAs in Deep Submicron CMOS Technologies

Designers of radio-frequency inductively-degenerated CMOS low-noise-amplifiers have usually not followed the guidelines for achieving minimum noise figure. Nonetheless, state-of-the-art implementations display noise figure values very close to the theoretical minimum. In this paper, we point out that this is due to the effect of the parasitic overlap capacitances in the MOS device. In particular, we show that overlap capacitances lead to a significant induced-gate-noise reduction, especially when deep sub-micron CMOS processes are used.Paolo Rossi was born in Milan, Italy, in 1975. He received the Laurea degree (summa cum laude) in electrical engineering from the University of Pavia, Pavia, Italy, in 2000, where he is currently working toward the Ph.D. degree. His research interests are in the field of analog integrated circuits for wireless transceivers in CMOS and BiCMOS technology, with particular focus on the analysis and design of LNA and mixer for multi-standard applications.Francesco Svelto received the Laurea and Ph.D. degrees in electrical engineering from the University of Pavia, Pavia, Italy, in 1991 and 1995, respectively. From 1996 to 1997, he held a grant from STMicroelectronics to design CMOS RF circuits. In 1997, he was appointed Assistant Professor at the University of Bergamo, Italy, and in 2000, he joined the University of Pavia, where he is an Associate Professor. His current research interests are in the field of RF design and high-frequency integrated circuits for telecommunications. Dr. Svelto has been a member of the technical program committee of the IEEE Custom Integrated Circuits Conference since 2000 and the Bipolar/BiCMOS Circuits and Technology Meeting (BCTM) since 2003, and the European Solid State Circuits Conference in 2002. He served as Guest Editor of the March 2003 special issue of the IEEE Journal of Solid-State Circuits, of which he is currently an Associate Editor.Andrea Mazzanti was born in Modena (Italy) in 1976. He received the Laurea degree (summa cum Laude) in Electrical Engineering from the University of Modena and Reggio Emilia, Modena, Italy in 2001. Since 2001 he is pursuing his PhD in Electrical Engineering at University of Modena and Reggio Emilia, Italy. His major research interest are modelling of microwave semiconductor devices and design of CMOS RF integrated circuits, with particular focus on low noise oscillators and analog frequency dividers. During the summer of 2003 he was with Agere Systems, Allentown, PA as an internship student, working on the design of an highly integrated CMOS FM transmitter.Pietro Andreani received the M.S.E.E. from the University of Pisa, Italy, in 1988. He joined the Dept. of Applied Electronics, Lund University, Sweden, in 1990, where he contributed to the development of software tools for digital ASIC design. After working at the Dept. of Applied Electronics, University of Pisa, as a CMOS IC designer during 1994, he rejoined the Dept. of Applied Electronics in Lund as an Associate Professor, where he was responsible for the analog IC course package between 1995 and 2001, and where he received the Ph.D. degree in 1999. He is currently a Professor at the Center for Physical Electronics, ØrstedDTU, Technical University of Denmark, Kgs. Lyngby, Denmark, with analog/RF CMOS IC design as main research field.     

Optimization of lithographic masks using genetic algorithms

Due to its cost effectiveness and reliability, wet-chemical etching of silicon is still one of the key technologies for producing bulk-silicon microstructures. In this paper we present an approach for the design of advanced mask sets for anisotropic, wet-chemical etching of silicon. The optimization method of genetic algorithms is used to derive suitable masks for cases where geometrically calculated compensation structures fail. The underlying etch simulation is described as well as the optimization algorithm itself. Design tasks of current research projects are used as examples to illustrate the advantage of using the presented tool. Udo Triltsch was born in Bergisch Gladbach, Germany, in 1976. He received the Dipl.-Ing. degree for Mechanical Engineering from the Technical University of Braunschweig, Germany, in 2002. He is currently working towards his Ph.D. at the Institute for Microtechnology, Braunschweig, Germany. His research interests include: design methodology for MEMS, process simulation and knowledge management. Anurak Phataralaoha was born in Bangkok, Thailand, in 1973. He received the B. Eng. degree for Production Engineering from KMUTT, Thailand in 1995 and Dipl.-Ing. degree for Mechanical Engineering from Technical University of Clausthal, Germany in 2002. He is currently working towards his Ph.D. at the Institute for Microtechnology, Braunschweig, Germany. His research interests include: 3D-tactile sensors, micro machining for silicon, Tribological micro guide. Stephanus Büttgenbach obtained the Diploma and Ph.D. degrees in physics from the University of Bonn, Germany, in 1970 and 1973, respectively. From 1974 to 1985, he was with the Institute of Applied Physics of the University of Bonn, working on atomic and laser spectroscopy. In 1983, he was promoted to Professor of Physics. From 1977 to 1985, he was also a Scientific Associate at CERN in Geneva, Switzerland. In 1985, Dr. Büttgenbach joined the Hahn-Schickard-Society of Applied Research at Stuttgart as Head of the Department of Microtechnology, where he worked on micromechanics, laser microfabrication, and resonant sensors. From 1988 to 1991, he was the Founding Director of the Institute of Micro and Information Technology of the Hahn-Schickard-Society. In 1991, Dr. Büttgenbach became Professor of Microtechnology at the Technical University of Braunschweig. His current research centers on the development and application of micro sensors, micro actuators, and micro systems. Currently, he is Vice President of the Technical University of Braunschweig, where his areas of responsibility are research and technology transfer. Dima Straube was born in Berlin, Germany, in 1977. He received the Dipl.-Ing. degree for Civil Engineering from Technical University of Berlin, Germany, in 2002. He is currently working towards his Ph.D. at the Institute for Engineering Design, Braunschweig. His research interests include: design methodology for MEMS, computer aided design and tolerance management. Hans-Joachim Franke was born in Helmstedt, Germany, on February 14, 1944. He received his diploma in mechanical engineering (Dipl.-Ing.) from the Technical University of Braunschweig, Germany, in 1969. From 1969 to 1976 he was research assistant of Prof. Roth at the Institute for Engineering Design. In 1976 he received his Ph.D. degree in mechanical engineering. From 1976 to 1988 he had diverse executive positions at the KSB-AG in Frankenthal, Germany, a company, which produces pumps and valves. Since 1988 he has been the director of the Institute for Engineering Design of the Technical University of Braunschweig. His research interests are in the areas of design methodology, computer aided design and machine elements.     

Energy efficient node-to-node authentication and communication confidentiality in wireless sensor networks

A distributed Wireless Sensor Network (WSN) is a collection of low-end devices with wireless message exchange capabilities. Due to the scarcity of hardware resources, the lack of network infrastructures, and the threats to security, implementing secure pair-wise communications among any pair of sensors is a challenging problem in distributed WSNs. In particular, memory and energy consumption as well as resilience to sensor physical compromise are the most stringent requirements. In this paper, we introduce a new threat model to communications confidentiality in WSNs, the smart attacker model. Under this new, more realistic model, the security features of previously proposed schemes decrease drastically. We then describe a novel pseudo-random key pre-deployment strategy ESP that combines all the following properties: (a) it supports an energy-efficient key discovery phase requiring no communications; (b) it provides node to node authentication; (c) it is highly resistant to the smart attacker.We provide both asymptotic results and extensive simulations of the schemes that are beingproposed. This work was partially funded by the WEB-MINDS project supported by the Italian MIUR under the FIRB program, and by the PRIN 2003 “Web-based Management and Representation of Spatial and Geographic Data” program from the Italian MIUR. Roberto Di Pietro is partially funded by ISTI-CNR, WNLab, Pisa, with a Post-doc grant under the IS-MANET program. Roberto Di Pietro received the Ph.D. in Computer Science from the University of Roma “La Sapienza”, Italy, in 2004. He received the Bs. and Ms. degree in Computer Science from the University of Pisa, Italy, in 1994. Since 1995 he has been working for the technical branch of the Italian Army and the Internal Affairs Ministry. His main research interests include: security for mobile ad hoc and wireless networks, security for distributed systems, secure multicast, applied cryptography and computer forensics. Luigi V. Mancini received the PhD degre in Computer Science from the University of Newcastle upon Tyne, UK, in 1989, and the Laurea degree in Computer Science from the University of Pisa, Italy, in 1983. From 2000, he is a full professor of Computer Science at the Dipartimento di Informatica of the University of Rome “La Sapienza”. Since 1994, he is a visiting research professor of the Center for Secure Information Systems, GMU, Virginia, USA. Currently he is the advisor of six Ph.D students. His current research interests include: computer network and information security, wireless network security, fault-tolerant distributed systems, large-scale peer-to-peer systems, and hard-real-time distributed systems. He published more than 60 scientific papers in international conferences and journals such as: ACM TISSEC, IEEE TKDE, IEEE TPDS, and IEEE TSE. He served in the program committees of several international conferences which include: ACM Conference on Computer and Communication Security, ACM Conference on Conceptual Modeling, ACM Symposium on Access Control Models and Technology, ACM Workshop of Security of Ad-hoc and Sensor Networks, IEEE Securecomm, IEEE Conference on Cluster Computing. He is also the program chair of the first two editions of the IEEE Workshop on Hot Topics in Peer-to-Peer Systems held in 2004 (Volendam, Holand) and in 2005 (San Diego, California). Currently, he is a member of the Scientific Board of the Italian Communication Police force, and the director of the Master degree program in Computer and Network Security of the University of Rome “La Sapienza”, Italy. Alessandro Mei received the Laurea degree in computer science from the University of Pisa, Italy, in 1994, and the PhD degree in mathematics from the University of Trento, Italy, in 1999. In 1998, he was at the Department of EE-Systems of the University of Southern California, Los Angeles, as a visiting scholar for one year. After holding a postdoctoral position at the University of Trento, in 2001 he joined the Faculty of Science of the University of Rome "La Sapienza", Italy, as an assistant professor of computer science. His main research interests include security of distributed systems and networks, algorithms for parallel, distributed, and optical systems and reconfigurable computing. He was presented with the Best Paper Award of the 16th IEEE International Parallel and Distributed Processing Symposium in 2002, the EE-Systems Outstanding Research Paper Award of the University of Southern California for 2000, and the Outstanding Paper Award of the Fifth IEEE/ACM International Conference on High Performance Computing in 1998. He is a member of the ACM and the IEEE and, from 2005, he is an Associate Editor of IEEE Transactions on Computers.     

Statistically assisted routing algorithms (SARA) for hop count based forwarding in wireless sensor networks

The main goal of this paper is to provide routing–table-free online algorithms for wireless sensor networks (WSNs) to select cost (e.g., node residual energies) and delay efficient paths. As basic information to drive the routing process, both node costs and hop count distances are considered. Particular emphasis is given to greedy routing schemes, due to their suitability for resource constrained and highly dynamic networks. For what concerns greedy forwarding, we present the Statistically Assisted Routing Algorithm (SARA), where forwarding decisions are driven by statistical information on the costs of the nodes within coverage and in the second order neighborhood. By analysis, we prove that an optimal online policy exists, we derive its form and we exploit it as the core of SARA. Besides greedy techniques, sub–optimal algorithms where node costs can be partially propagated through the network are also presented. These techniques are based on real time learning LRTA algorithms which, through an initial exploratory phase, converge to quasi globally optimal paths. All the proposed schemes are then compared by simulation against globally optimal solutions, discussing the involved trade–offs and possible performance gains. The results show that the exploitation of second order cost information in SARA substantially increases the goodness of the selected paths with respect to fully localized greedy routing. Finally, the path quality can be further increased by LRTA schemes, whose convergence can be considerably enhanced by properly setting real time search parameters. However, these solutions fail in highly dynamic scenarios as they are unable to adapt the search process to time varying costs. Michele Rossi was born in Ferrara, Italy on October 30th, 1974. He received the Laurea degree in Electrical Engineering (with honors) and the Ph.D. degree in Information Engineering from the University of Ferrara in 2000 and 2004, respectively. Since 2000 he has been a Research Fellow at the Department of Engineering of the University of Ferrara. During 2003 he was on leave at the Center for Wireless Communications (CWC) at the University of California San Diego (UCSD), where he did research on wireless sensor networks. In November 2005 he joined the Department of Information Engineering of the University of Padova, Italy, where he is currently an Assistant Professor. Michele Rossi is currently part of the EU funded Ambient Networks and eSENSE projects. His research interests include: TCP/IP protocols over wireless networks, performance analysis of link layer retransmission techniques, routing and access selection in heterogeneous wireless networks and MAC/routing algorithms for wireless sensor networks. Michele Zorzi was born in Venice, Italy, in 1966. He received the Laurea degree and the Ph.D. degree in Electrical Engineering from the University of Padova, Italy, in 1990 and 1994, respectively. During the Academic Year 1992/93, he was on leave at the University of California, San Diego (UCSD), attending graduate courses and doing research on multiple access in mobile radio networks. In 1993, he joined the faculty of the Dipartimento di Elettronica e Informazione, Politecnico di Milano, Italy. After spending three years with the Center for Wireless Communications at UCSD, in 1998 he joined the School of Engineering of the University of Ferrara, Italy, and in 2003 joined the Department of Information Engineering of the University of Padova, Italy, where he is currently a Professor. His present research interests include performance evaluation in mobile communications systems, random access in mobile radio networks, ad hoc and sensor networks, and energy constrained communications protocols. Dr. Zorzi from 2003 to 2005 was the Editor-In-Chief of the IEEE Wireless Communications Magazine, and currently serves on the Editorial Boards of the IEEE Transactions on Communications, the IEEE Transactions on Wireless Communications, the IEEE Transactions on Mobile Computing, the Wiley Journal of Wireless Communications and Mobile Computing and the ACM/URSI/Kluwer Journal of Wireless Networks. He was also guest editor for special issues in the IEEE Personal Communications Magazine (Energy Management in Personal Communications Systems) and the IEEE Journal on Selected Areas in Communications (Multi-media Network Radios). Ramesh R. Rao was born in Sindri, India, where he completed his undergraduate work at the Regional Engineering College of the University of Madras in Tiruchirapalli, obtaining a BE (Honors) degree in Electronics and Communications in 1980. He completed his graduate work at the University of Maryland, College Park, Maryland where he received his M.S. and Ph.D. Professor Rao is currently a Professor at the University of California, San Diego (UCSD) at the department of Electrical and Computer Engineering in the Irwin and Joan Jacobs School of Engineering, where he has been a member of the faculty since 1984. Professor Rao is the former director of UCSD’s Center for Wireless Communications (CWC), and currently serves as the Qualcomm Endowed Chair in Telecommunications and Information Technologies, and as the Director of the San Diego Division of the California Institute of Telecommunications and Information Technology [Cal-(IT)²]. As Director of the San Diego Division of Cal-(IT)², he leads several interdisciplinary and collaborative projects. His research interests include architectures, protocols and performance analysis of computer and communication networks, and he has published extensively on these topics. Since 1984, Professor Rao has authored over 100 technical papers, contributed book chapters, conducted a number of short courses and delivered invited talks and plenary lectures. He is currently supervising both masters and doctoral students.     

The Role of HAPs in Supporting Multimedia Broadcast and Multicast Services in Terrestrial-Satellite Integrated Systems

New-generation telecommunications systems are expected to meet the rising user exigencies of mobility and ubiquitous access to multimedia services. As a consequence, 3GPP consortium has introduced the Multimedia Broadcast and Multicast Service (MBMS) concept into 3G/beyond-3G networks. Supporting MBMS in next generation hybrid wireless platforms becomes a challenging issue due to high traffic load deriving from both signaling message exchange and data transmission between multicast sources (BM-SC) and end users. Therefore, in this context, key research issues are surely: effective exploitation of the limited radio spectrums available, coordination of users accessing radio resources, as well as provisioning of desired QoS guarantees. Given the high mobility profiles typical of UMTS users, it clearly appears that the cited target performance can only be achieved through networking solutions based on an overlapped terrestrial-HAP-satellite coverage. An inter-working scenario where HAPs operate in synergy with the UMTS terrestrial and satellite segments seems to be the most promising solution to provide mobile users with MBMS services. Our work, dealing with architectural design options, takes into account many metrics relevant to aspects, such as: frequency allocation, costs in terms of resource utilization, signaling traffic load, number and location of customers, reliability, possible retransmission paths, user mobility, and QoS.Giuseppe Araniti received a degree in Electronic Engineering from the University of Reggio Calabria, Italy, in 2000. He received the Ph.D. in Electronic Engineering from the same University, in March 2004. He is currently a junior researcher at the D.I.M.E.T., of the University of Reggio Calabria, Italy. His major area of research is the traffic and resource management in third and fourth generation mobile radio systems.Antonio Iera graduated in Computer Engineering at the University of Calabria, Italy, in 1991 and received a Master Diploma in Information Technology from CEFRIEL, Italy, in 1992 and a Ph.D. degree from the University of Calabria, Italy, in 1996.Since 1997 he has been with the University of Reggio Calabria, Italy, first as an Assistant Professor and then as an Associate Professor. Currently, he is Professor at the same University. His research interests include Personal Communications Systems, Enhanced Wireless and Satellite Systems.Antonella Molinaro received a degree in Computer Engineering from the University of Calabria, Italy, in 1991, a Master degree in Information Technology from CEFRIEL, Italy, in 1992, and a Ph.D. degree from the University of Calabria, Italy, in 1996. Since 1998 she has been an Assistent Professor first at the University of Messina and then at the University of Calabria. She is currently an Associate Professor at the University Mediterranea of Reggio Calabria, Italy. Her interests include mobile radio systems and inter-working wireless-wired networks.     

Programmable CNN Analogue Chip for RD-PDE Multi-Method Simulations

Cellular Non Linear Networks can be useful applied for the solution of several types of Partial Differential Equations (PDEs). This paper will describe an analogue circuit implementation for the simulation of one-dimensional Reaction-Diffusion PDE with the possibility to set different boundary conditions as well as to select different discretization methodologies. Fausto Sargeni was born in Riano (ROMA) in 1961. He received the Dipl. Eng. degree in Electronic Engineering at the University of Rome “La Sapienza" in 1987. In 1989 he jointed the Dept. of Electronic Engineering at the University of Rome “Tor Vergata" as Assistant Professor. In 1998 he became Associate Professor. His research interests include analog VLSI circuits for non linear circuits and high-speed interconnections. Vincenzo Bonaiuto was born in Rome, Italy, in 1962. He received the Dipl. Eng. degree in Electronic Engineering at the University of Rome “La Sapienza". In 1997 he received the the Ph.D. in Telecommunication and Microelectronics. In 1996 he jointed the Electronic Engineering Dept. as Assistant Professor at the University of Rome “Tor Vergata” and, in 2002, he became Associate Professor. His main research interests are in the area of non linear circuits, Artificial Neural Networks analogue/digital VLSI circuits implementation.     

802.11 power-saving mode for mobile computing in Wi-Fi hotspots: Limitations,enhancements and open issues

Nowadays Wi-Fi is the most mature technology for wireless-Internet access. Despite the large (and ever increasing) diffusion of Wi-Fi hotspots, energy limitations of mobile devices are still an issue. To deal with this, the standard 802.11 includes a Power-Saving Mode (PSM), but not much attention has been devoted by the research community to understand its performance in depth. We think that this paper contributes to fill the gap. We focus on a typical Wi-Fi hotspot scenario, and assess the dependence of the PSM behavior on several key parameters such as the packet loss probability, the Round Trip Time, the number of users within the hotspot. We show that during traffic bursts PSM is able to save up to 90% of the energy spent when no energy management is used, and introduces a limited additional delay. Unfortunately, in the case of long inactivity periods between bursts, PSM is not the optimal solution for energy management. We thus propose a very simple Cross-Layer Energy Manager (XEM) that dynamically tunes its energy-saving strategy depending on the application behavior and key network parameters. XEM does not require any modification to the applications or to the 802.11 standard, and can thus be easily integrated in current Wi-Fi devices. Depending on the network traffic pattern, XEM reduces the energy consumption of an additional 20–96% with respect to the standard PSM. This work has been carried out while A. Passarella was with the Department of Information Engineering of the University of Pisa. Giuseppe Anastasi is an associate professor of Computer Engineering at the Department of Information Engineering of the University of Pisa, Italy. He received the Laurea (cum laude) degree in Electrical Engineering, and the Ph.D. degree in Computer Engineering, both from the University of Pisa, in 1990 and 1995, respectively. His research interests include mobile and pervasive computing, ad hoc and sensor networks, and power management. He is a co-editor of the book Advanced Lectures in Networking (LNCS 2497, Springer, 2002), and has published more than 60 papers in the area of computer networking and pervasive computing, both in international journals and conference proceedings. He is a member of the editorial board of the Journal of Ubiquitous Computing and Intelligence (JUCI), and is currently serving as Vice Program Co-Chair for the IEEE MASS 2007 conference. He has served as general chair for IEEE WoWMoM 2005, Workshops Chair for IEEE PerCom 2006 and IEEE WoWMoM 2006, and program chair for several international workshops. He has also served on the Technical Program Committee of many international conferences. He is a member of the IEEE Computer Society. Marco Conti is a research director at IIT, an institute of the Italian National Research Council (CNR). He co-authored the book “Metropolitan Area Networks” (Springer, 1997) and is co-editor of the book “Mobile Ad Hoc Networking” (IEEE-Wiley 2004). He published in journals and conference proceedings more than 180 research papers related to design, modeling, and performance evaluation of computer-network architectures and protocols. He served as TPC chair of IEEE PerCom 2006, and of the IFIP-TC6 Conferences “Networking2002” and “PWC2003”, and as TPC co-chair of ACM WoWMoM 2002, WiOpt ’04, IEEE WoWMoM2005, and ACM MobiHoc2006. He served as general co-chair of IEEE WoWMoM 2006 and as general chair of ACM REALMAN 2006. Currently, he is serving as general chair of IEEE MASS 2007. He is Associate Editor of Pervasive and Mobile Computing Journal, and he is on the editorial board of: IEEE Transactions on Mobile Computing, Ad Hoc Networks journal and Wireless Ad Hoc and Sensor Networks: An International Journal. Enrico Gregori received the Laurea in electronic engineering from the University of Pisa in 1980. In 1981 he joined the Italian National Research Council (CNR) where he is currently a CNR research director. He is currently the deputy director of the CNR institute for Informatics and Telematics (IIT). In 1986 he held a visiting position in the IBM research center in Zurich working on network software engineering and on heterogeneous networking. He has contributed to several national and international projects on computer networking. He has authored more than 100 papers in the area of computer networks and has published in international journals and conference proceedings and is co-author of the book “Metropolitan Area Networks” (Springer, London 1997). He was the General Chair of the IFIP TC6 conferences: Networking2002and PWC2003 (Personal Wireless Communications) and IEEE Pervasive Computing and Communication (PERCOM) 2006. He served as guest editor for the Networking2002 journal special issues on: Performance Evaluation, Cluster Computing and ACM/Kluwer Wireless Networks Journals. He is a member of the board of directors of the Create-Net association, an association with several Universities and research centers that is fostering research on networking at European level. He is on the editorial board of the Cluster Computing, of the Computer Networks and of the Wireless Networks Journals. His current research interests include: Ad hoc networks, Sensor networks, Wireless LANs, Quality of service in packet-switching networks, Evolution of TCP/IP protocols. Andrea Passarella is a Researcher at the IIT Institute of the National Research Council (CNR), Italy. Before joining IIT, he was a Research Associate at the Computer Laboratory of the University of Cambridge, UK. He received the Ph.D. and M.S. Degrees in Computer Engineering, both from the University of Pisa, Italy, in 2005 and 2001, respectively. His current research is mostly on opportunistic and delay-tolerant networking. More in general, he works on ad hoc and sensor networks, specifically on p2p systems, multicasting, transport protocols, and energy-efficient protocols. His research interests also include mesh networks and wireless access to the Internet. He is Co-Editor of the book “Multi-hop Ad hoc Networks: From Theory to Reality” (Nova Science, 2007). He was TPC Vice-Chair for IEEE REALMAN 2005, ACM REALMAN 2006, and IEEE MDC 2006. He served and is currently serving in the TPC of several international conferences, including IEEE PerCom 2006/07 and IEEE WoWMoM 2006/07, and workshops. He is an Associate Technical Editor for IEEE Communications Magazine. He is a member of ACM SIGMOBILE.     

New Paradigms in Wireless Communication Systems

This paper discusses what a new paradigm can be in wireless communication systems of the twenty-first century. First, it suggests two directions for the new paradigm; one is “micro- and nano-device communication system” which is the projected scenario considering that the entities in source and destination have been shrinking throughout the history of wireless communication systems. The second direction is “networked robot system”, which emerges as a natural extension of mobile ad hoc networking where the networking is closely related to motion control of robots. Secondly, it shows two interesting research topics, “the new communication protocol design” and “signal processing”, respectively, that arise in the wake of the fusion between the two directions in the novel communication paradigm. Finally, it considers a new science of wireless communications in the twenty-first century. Shinsuke Hara received the B.Eng., M.Eng. and Ph.D. degrees in communications engineering from Osaka University, Osaka, Japan, in 1985, 1987 and 1990, respectively. From April 1990 to March 1997, he was an assistant professor in the Department of Communication Engineering, School of Engineering, Osaka University, and from October 1997 to September 2005, he was an associate professor in the Department of Electronic, Information and Energy Engineering, Graduate School of Engineering, Osaka University. Since October 2005, he has been a professor in the Department of Physical Electronics and Informatics, Graduate School of Engineering, Osaka City University. In addition, from April 1995 to March 1996, he was a visiting scientist at Telecommunications and Traffic Control Systems Group, Delft University of Technology, Delft, The Netherlands. His research interests include wireless communications systems and digital signal processing. Hiroyuki Yomo received B.S. degree in communication engineering from Department of Communication Engineering, Osaka University, Osaka, Japan, in 1997, and M.S. and Ph.D. degrees in communication engineering from Department of Electronic, Information, and Energy Engineering, Graduate School of Engineering, Osaka University, Osaka Japan, in 1999 and 2002, respectively. From April 2002 to March 2004, he was a Post-doctoral Fellow in Department of Communication Technology, Aalborg University, Denmark. From April 2004 to September 2004, he was at Internet System Laboratory, NEC Corporation, Japan. Since October 2004, he has been an Assistant Research Professor in Center for TeleInfrastructure (CTIF), Aalborg University, Denmark. His main research interests are access technologies, radio resource management, and link-layer techniques in the area of short-range communication, cellular network, cognitive radio, and sensor network. Petar Popovski received the Dipl.-Ing. in electrical engineering and M.Sc. in communication engineering from the Faculty of Electrical Engineering, Sts. Cyril and Methodius University, Skopje, Republic of Macedonia, in 1997 and 2000, respectively. He received a Ph.D. degree from Aalborg University, Denmark, in 2004. From 1998 to 2001 he was a teaching and research assistant at the Institute of Telecommunications, Faculty of Electrical Engineering in Skopje. He is currently Assistant Professor at the Department of Communication Technology at the Aalborg University. His research interests are related to the PHY-MAC aspects of wireless protocols, wireless sensor networks, random access protocols, and network coding. Kazunori Hayashi received the B.E., M.E. and Ph.D. degrees in communication engineering from Osaka University, Osaka, Japan, in 1997, 1999 and 2002, respectively. He spent 3 months in 2000 at Aalborg University, Denmark, as a Visiting Scholar. Since 2002, he has been with the Department of Systems Science, Graduate School of Informatics, Kyoto University. He is currently an Assistant Professor there. His research interests include digital signal processing for communications systems.