Mobile Computing Group - News & Events

3rd International Workshop on Wireless Network Measurement
International workshop on Wireless Traffic Measurements and Modeling
Science and Technology Week

Date: 28 June - 5 July, 2006
Research demostration: Anastasia Katranidou, Scientist under research training at ICS-FORTH
Location: Seminar room I - FORTH
Place: Zappeio - Athens
Title: Cooperative Location-sensing system (CLS) demo

Abstract:

Positioning is a critical component of the mobile and pervasive computing. The Mobile Computing Activity at FORTH designed and evaluated the Cooperative Location-Sensing (CLS) system that adaptively positions wireless-enabled devices using the existing communication infrastructure (WiFi access points) without the need of specialized hardware or training. CLS employs the peer-to-peer paradigm enabling hosts to cooperate and share positioning information. It also allows the easy incorporation of external information (e.g., maps and spatial information, mobility patterns) to improve its accuracy.

URLs:

Actual demo: http://www.ics.forth.gr/mobile/software/CLS.demo.6.06.wmv
Presentation: http://www.ics.forth.gr/mobile/CLS_presentation.ppt
Web page: http://www.ics.forth.gr/news/science-technology_week.html

Ericsson Award of Excellence in Telecommunications for Elias Raftopoulos' undergraduate thesis on : Short-term traffic forecasting in a campus-wide wireless network
Postdoctoral Position in the Mobile Computing Activity at FORTH

We have a postdoctoral research position available at the Institute of Computer Science of the Foundation for Research and Technology - Hellas (FORTH) in Greece.

The focus is on the area of measurements, modeling, and performance analysis on wireless networks. It is a 1-year position (possible renewal at the end of the term). Candidates must have finished their Ph.D. and have deep experience on 802.11 and wireless networking. Also, they must be proficient at reading, speaking, and writing in English.

Interested candidates should send their vita, and arrange to have two letters of reference sent directly to Maria Papadopouli via email (mgp@ics.forth.gr)

Mobile Computing Seminar Lecturer Series

Speaker: Prof. John S. Baras
Date: Wendesday, 30 July 2008
Place: "Mediterranean Studies" Seminar Room, FORTH, Heraklion, Crete
Title: Physical Layer Authentication
Organizer/Host: Prof. Maria Papadopouli
Lecture time: 15:00 - 16:30

Abstract:

Authentication is the process where claims of identity are verified. Most mechanisms of authentication (e.g., digital signatures and certificates) exist above the physical layer, though some (e.g., spread spectrum communications) exist at the physical layer often with an additional cost in bandwidth. We introduce a general analysis and design framework for authentication at the physical layer where the authentication information is transmitted concurrently with the data. By superimposing a carefully designed secret modulation on the waveforms, authentication is added to the signal without requiring additional bandwidth, as do spread spectrum methods. The authentication is designed to be stealthy to the uninformed user, robust to interference, and secure for identity verification. The tradeoffs between these three goals are identified and analyzed in block fading channels. We describe further extensions to OFDM and multicarrier wireless devices. Finally, both simulation results and experimental results from laboratory implementation of these new schemes are given that demonstrate the potential of this new authentication technique.

Bio:

John S. Baras, Lockheed Martin Chair in Systems Engineering B.S. in Electrical Eng. from the Nat. Techn. Univ. of Athens, Greece, 1970; M.S. and Ph.D. in Applied Math. from Harvard Univ. 1971, 1973. Since 1973 with the Electrical and Computer Engineering Department, and the Applied Mathematics Faculty, at the University of Maryland College Park. Faculty member in the Department of Computer Science and Fischell Department of Bioengineering. He was the founding Director of the Institute for Systems Research (ISR) from 1985 to 1991. Since 1991, has been the Director of the Maryland Center for Hybrid Networks (HYNET). Fellow of the IEEE and a Foreign Member of the Royal Swedish Academy of Engineering Sciences. Received the 1980 George Axelby Prize from the IEEE Control Systems Society and the 2006 Leonard Abraham Prize from the IEEE Communications Society. Professor Baras' research interests include control, communication and computing systems.

Efficient Routing in Intermittently Connected Mobile Networks

Speaker: Thrasyvoulos (Akis) Spyropoulos
Date: Thursday, 12 April 2007
Place: Mediterranean Studies" Seminar Room, FORTH, Heraklion, Crete
Organizer/Host: Prof. Maria Papadopouli
Lecture time: 13:30 - 15:00

Abstract:

Communication networks (wired or wireless) have traditionally been assumed to be connected at least most of the time. However, emerging wireless applications such as emergency response, peer-to-peer wireless, smart environments, VANETs, etc. coupled with node heterogeneity and volatile links (due to wireless propagation phenomena and node mobility) will likely change the typical conditions under which such networks operate. In fact, in such scenarios, networks may be mostly disconnected, i.e., most of the time, end-to-end paths connecting every node pair do not exist. Under such conditions, a number of assumptions made by commonly used protocols break. Arguably though, one of the most challenging problems in this context is that of routing, as traditional routing protocols fail to deliver any data when no end-to-end paths exist. To overcome this problem "opportunistic routing" algorithms have been proposed. In this talk we'll explore the problem space of mobility-assisted, opportunistic routing for intermittently connected wireless networks. We will describe a family of protocols that manage to achieve very good performance in terms of both packet delivery and resource usage, under a large range of scenarios. Finally, we will briefly touch upon some issues related to theoretical modeling and analysis of routing in intermittently connected environments.

Bio:

Thrasyvoulos Spyropoulos has received a Ph.D. from the department of Electrical Engineering at the University of Southern California (USC), in May 2006, and a Diploma in Electrical and Computer Engineering from the National Technical University of Athens, Greece, in 2000. In the past, he has also worked at the USC-Information Sciences Institute (ISI) and at the Telecommunications lab at the National Technical University of Athens. His research interests include delay tolerant networks, mobility modeling, wireless networking using directional and smart antennas, and pervasive/ubiquitous computing, and he has been supported by NSF, and DARPA grants. He is currently a post-doctoral researcher at INRIA, Sophia-Antipolis, France.

Χωρητικότητα των ασύρματων δικτύων και πως να την προσεγγίσουμε

Speaker: Λέανδρος Τασιούλας, Πανεπιστήμιο Θεσσαλίας
Date: Πέμπτη, 26 Οκτωβρίου 2006
Place: Aίθουσα Συναντήσεων "Μεσογειακών Σπουδών", ΙΤΕ, Ηράκλειο, Κρήτη
Organizer/Host: Prof. Maria Papadopouli
Lecture time: 13:00-14:00

Abstract:

Ένα πλαίσιο προσδιορισμού της χωρητικότητα ασύρματων δικτύων που κάνει εφικτό τον χαρακτηρισμό της σε δίκτυα με πολύπλοκες αρχιτεκτονικές θα περιγραφεί. Αλγόριθμοι που επιτυγχάνουν λειτουργία στα όρια της χωρητικότητας θα δοθούν. Η πολυπλοκότητα των αλγορίθμων θα συζητηθεί ενώ συγκεκριμένες αρχιτεκτονικές όπου έχουμε χαμηλής πολυπλοκότητας, υλοποιήσιμους αλγορίθμους θα περιγραφούν. Τέλος οι δυνατότητες υλοποίησης σε συγκεκριμένα πρότυπα λειτουργίας ασύρματων δικτύων θα συζητηθούν.

Bio:

O Λέανδρος Τασιούλας είναι καθηγητής Τηλεπικοινωνιών και Δικτύων στο Τμήμα Μηχανικών Η/Υ, Τηλεπικοινωνιών και Δικτύων του Πανεπιστημίου Θεσσαλίας από το 2002. Η έρευνητική του δραστηριότητα τα τελευταία 15 χρόνια έχει σα σκοπό τη δημιουργία δικτύων επικοινωνίας και επεξεργασίας πληροφοριών που επιτρέπουν την ανάκτηση και ανταλλαγή πληροφορίας από οπουδήποτε και με οποιονδήποτε. Τα τρέχοντα ερευνητικά του ενδιαφέροντα είναι σε ασύρματα συστήματα σταθερών και κινητών κόμβων, δίκτυα με αυτόματα αναπροσαρμοζόμενη τοπολογία, παροχή ποιότητας υπηρεσιών σε υβριδικά ασύρματα-ενσύρματα δίκτυα, συστήματα επικοινωνίας πολυμέσων και σε δορυφορικές επικοινωνίες. Ο Δρ. Τασιούλας έχει διευθύνει τη διεξαγωγή μεγάλου αριθμού ερευνητικών προγραμμάτων, για κρατικούς φορείς και για τη βιομηχανία στις ΗΠΑ και την ΕΕ (NSF, AFOSR, ARL ONR, GSRT, IBM, Hughes, etc). Επίσης έχει διατελέσει σύμβουλος σε εταιρίες τηλεπικοινωνιών και πληροφορικής και εμπειρογνώμων σε δικαστικές υποθέσεις παραβίασης πνευματικών δικαιωμάτων και διπλωμάτων ευρεσιτεχνίας.

Έχει δημοσιεύσει πάνω απο 180 εργασίες, και έχει επιβλέψει την διδακτορική έρευνα 14 φοιτητών. Η ερευνητική δραστηριότητα του Δρ. Τασιούλα έχει τιμηθεί με διακρίσεις οπως: βραβείο καλύτερης εργασίας στο συνέδριο επικοινωνίας υπολογιστών της ΙΕΕΕ, INFOCOM94, βραβείο διακεκριμένου νέου ερευνητή του εθνικού ιδρύματος ερευνών (NSF) 1995 και του Ινστιτούτου Ερευνών Ναυτικού (ΟΝR) ΗΠΑ 1997, βραβείο Ιδρύματος Μποδοσάκη στην περιοχή των παράλληλων και κατανεμημένων υπολογιστικών συστημάτων 1999. Ο Δρ. Τασιούλας ήταν υπεύθυνος έκδοσης στην περιοχή των τηλεπικοινωνιακών δικτύων για το ΙΕΕΕ Trans. on Information Theory και μέλος της εκδοτικής επιτροπής του ΙΕΕΕ/ACM Trans. on Networking, ενώ συμμετέχει τακτικά στην οργάνωση των σημαντικότερων συνεδρίων πάνω σε τηλεπικοινωνίες και δίκτυα (ISIT, INFOCOM, MOBICOM, MOBIHOC). Έχει διατελέσει Καθηγητής στο Πανεπιστήμιο Ιωαννίνων την περίοδο 1999-2002, Αναπλ. Καθηγητής στο Univ. of Maryland 1995-2002, Επικ. Καθηγητής στο Polytechnic University της Ν. Υόρκης την περίοδο 1991-1995 και επισκέπτης ερευνητής στην IBM Research, Yorktown Heights, NY. Aπο το 2002 είναι ερευνητής καθηγητής στο Πανεπιστήμιο του Maryland.Ο Δρ. Τασιούλας πήρε το δίπλωμα Ηλεκτρολόγου Μηχ απο το Πανεπιστήμιο Θεσσαλονίκης το 1987 και τα MSc, PhD Electrical Engineering απο το Univ. of Maryland 1989, 91 αντίστοιχα.

Services Science: An emerging discipline for business and computing Research

Speaker: Dr. Sairamesh T.J. Watson Research Lab @ IBM
Date: Thursday, September 14th, 2006
Place: Mediterranean Studies" Seminar Room, FORTH, Heraklion, Crete
Organizer/Host: Prof. Maria Papadopouli
Lecture time: 15:00-17:00

Abstract:

With the ever increasing role of the Internet and Web for Businesses, there is shift in the way communication and collaboration within and across the Enterprise boundaries is being done for improving products and services for the end-consumers. Over the last few decades, with new advances in the internet, internet-based technologies, social and busi-ness communities, open systems and globalization, there has been a fundamental shift in the way enterprises and governments are being managed. Centralized and monolithic organisations are being transformed into networked collections of businesses, collaborating and sharing services with partners worldwide in order to produce goods and new services faster, cheaper, and better. Enterprises which have traditionally focused on building everything in-house (e.g. Automotive or electronics) have now embraced partnering with specialists and service providers from multiple overlapping business ?ecosystems? in order to provide critical, core, and peripheral products and services to their customers. There also been a shift in the way services are being offered and consumed by partners in a supply -chain. There is more emphasis on utilizing and leveraging the lower-cost specialized and niche services be-ing offered by partners and suppliers in a complex supply-chain. Many traditional in-house business functions are being sourced from suppliers small and large for enabling the production of the final goods and services for the end consumer. In this talk I will also cover the role of Technology such as Web Services, Mobile Services, Mobile applications, Collaboration, Social networks and others that are forming the foundations for services creation and delivery. Within Europe there are many initiatives (e.g. NESSI) being launched in the area of Services and I will briefly mention the initiatives and efforts.

Bio:

Dr. Jakka Sairamesh (Ramesh) has been actively pursuing research in the areas of eBusiness, mobile commerce, Business solutions, economics and dynamics of electronic commerce systems, information and computational economies, electronic marketplaces, information cities and middleware for electronic commerce, and network resource allocation and management. He has many years of experience in modeling and analyzing large-scale systems using economic models. Dr. Jakka Sairamesh has a Ph.D. in Computer Science from Columbia University , New York . He was one of the organizers of the First Conference on Information and Computation Economies, which was held in Charleston , South Carolina , USA , in October 1998, and a co-chair of the 7th DELOS Workshop on Electronic Commerce, which was held in conjunction with the 2nd European Conference on Digital Libraries in Heraklion, Crete , Greece , in September 1998. His current area of interest is in Business Solutions, Real-time systems, Sensor networks, Electronic Marketplaces, Early Warning Systems and others. He has published many papers (conferences, workshops and Journals) in the area of electronic commerce and information economies. He has two distinguished outstanding innovation awards for his contributions to eBusiness and next generation IBM products and solutions.

Avalanche: network coding for large scale content distribution

Speaker: Dr. Pablo Rodriguez Microsoft Research Labs, Cambridge , UK
Date: Thursday, September 7th, 2006
Place: Mediterranean Studies" Seminar Room, FORTH, Heraklion, Crete
Organizer/Host: Prof. Maria Papadopouli
Lecture time: 15:00-17:00

Abstract:

Up until recently, content distribution solutions consisted on placing dedicated equipment at certain places inside or at the edge of the Internet. However, in recent years, a new paradigm for Content Distribution has emerged based on a fully distributed architecture where commodity PCs are used to form a cooperative network and share their resources (storage, CPU, bandwidth). In this talk, we will study a P2P system for content distribution of large files that is based on network coding. With network coding, each node of the distribution network is able to generate and transmit informative blocks of information. This is particularly important in large unstructured overlay networks, where the nodes need to make decisions based on local information only. We will demonstrate the benefits of network coding under different realistic settings, present the results of several live trials, and discuss the implementation overheads and security related problems that need to be overcome to make such solution work.

Bio:

Pablo Rodriguez is a researcher at Microsoft Research, Cambridge . Prior to Microsoft he was a Technical Staff Member at Bell-Labs and also worked for a couple of startups in California (Inktomi, Tahoe Networks). His research interests are in the areas of P2P (Avalanche), Content Distribution, Information Theory and Wireless networks. He holds a Ph.D. from the Swiss Federal Institute of Technology (EPFL). As a result of his work Pablo Rodriguez received several awards including the "Prix de la Recherche" in France , and the "Extraordinary Category Classification in Science" from the USA government.

Planet Scale Software Updates

Speaker: Dr. Thomas Karagiannis, Associate Researcher Microsoft Research at Cambridge
Date: Tuesday, 25th July, 2006
Place: Mediterranean Studies" Seminar Room, FORTH, Heraklion, Crete
Organizer/Host: Prof. Maria Papadopouli

Abstract:

Fast and effective distribution of software updates (a.k.a. patches) to millions of Internet users has evolved into a critical task over the last years. In this talk, we characterize “Windows Update”, one of the largest update services in the world, with the aim to draw general guidelines on how to best design and architect a fast and effective planet-scale patch dissemination system. To this end, we analyze an extensive set of data traces collected over the period of a year, consisting of billions of queries from over 300 million computers. Based on empirical observations and analytical results, we identify interesting properties of today’s update traffic and user behavior. Building on this analysis, we consider alternative patch delivery strategies such as caching and peer-to-peer and evaluate their performance. We identify key factors that determine the effectiveness of these schemes in reducing the server workload and the network traffic, and in speeding-up the patch delivery. Most of our findings are invariant properties induced by either user behavior or architectural characteristics of today’s Internet, and thus apply to the general problem of Internet-wide dissemination of software updates.

QoS In Ad hoc Networks

Speaker: Khaldoun Al Agha, Full Professor at the Paris XI University
Date: Thursday, 13th April, 2006
Place: "Mediterranean Studies" Seminar Room, FORTH, Heraklion, Crete
Organizer/Host: Prof. Maria Papadopouli

Abstract:

In Ad hoc networks, nodes can communicate without any pre-existing infrastructure. Topology is created dynamically and can change upon nodes mobility. Hence, the function of routing becomes very complex. Many protocols are now standardized to calculate routes between a couple of nodes in an ad hoc network. These protocols find shortest routes based on the number of hops between source and destination.

When extending the routing function to take into account quality of service parameters such delay, available bandwidth, loss probability, etc., the problem becomes more and more complex. In this seminar, we present works that we proposed in this topic that permits to find routes offering quality of service by using the OLSR protocol for ad hoc networks.

Bio:

After working at the university of Versailles and INRIA, Khaldoun Al Agha is now Full Professor at the Paris XI University. He created and conducts the Networking group within the LRI Laboratory (Laboratory of Research in Computer-Science). Khaldoun Al Agha takes an active part in various research projects in the field of network mobility. Its research relates to the resource allocation in cellular networks (GSM, GPRS, UMTS) and on IP network mobility (Mobile IP, ad hoc networks ...). Khaldoun Al Agha develops his research within several national and international projects and cooperation.

Network Measurements in the Dark: Characterizing the Unknown

Speaker: Thomas Karagiannis, Dept. of Computer Science and Engineering University of California , Riverside
Date: Monday, 27th February, 2006
Place: S.Orphanoudakis Seminar Room - FORTH
Organizer/Host: Prof. Maria Papadopouli

LECTURE 1 Time: 12:00-13:00

Abstract:

The increased popularity of IEEE 802.11 WLANs has led to dense deployments in urban areas. Such high density leads to sub-optimal performance unless the interfering networks learn how to optimally share the spectrum. This paper proposes a set of novel fully distributed algorithms that allow (i) multiple interfering 802.11 WLANs to select their operating frequency in a way that minimizes global interference, and (ii) clients to choose their Access Point so that the bandwidth of all interfering networks is shared optimally. The proposed algorithms rely on Gibbs’ sampler and optimize global network performance based on local information. They do not require explicit coordination among the wireless devices. We establish the mathematical properties of the proposed algorithms and study their performance using analytical, event-driven simulations. Our results strongly motivate the need for self-organization strategies in wireless access networks. We discuss implementation requirements and show that significant benefits can be gained even within incremental deployments and in the presence of non-cooperating wireless clients.

LECTURE 2 Time: 16:00-17:00

Abstract:

Recently, peer-to-peer (P2P) networks have emerged as an attractive solution to enable large-scale content distribution without requiring major infrastructure investments. While such P2P solutions appear highly beneficial for content providers and end-users, there seems to be a growing concern among Internet Service Providers (ISPs) that now need to support the distribution cost. In this work, we explore the potential impact of future P2P file delivery mechanisms as seen from three different perspectives: i) the content provider, ii) the ISPs, and iii) individual content consumers. Using a diverse set of measurements including BitTorrent tracker logs and payload packet traces collected at the edge of a 20,000 user access network, we quantify the impact of peer-assisted file delivery on end-user experience and resource consumption. We further compare it with the performance expected from traditional distribution mechanisms based on large server farms and Content Distribution Networks (CDNs).

While existing P2P content distribution solutions may provide significant benefits for content providers and end-consumers in terms of cost and performance, our results demonstrate that they have an adverse impact on ISPs' costs by shifting the associated capacity requirements from the content providers and CDNs to the ISPs themselves. Further, we highlight how simple "locality-aware" P2P delivery solutions can significantly alleviate the induced cost at the ISPs, while providing an overall performance that approximates that of a perfect world-wide caching infrastructure.

Bio:

http://www.cs.ucr.edu/~tkarag/papers/resume.pdf

Self organization of Interfering 802.11 Wireless Access Networks

Speaker: Dr. Dina Papagiannaki, Intel Research in Cambridge , UK
Date: Monday, July 25th, 2005 3pm
Place: Mediterranean Studies Conference Room
Organizer/Host: Prof. Maria Papadopouli

Abstract:

The increased popularity of IEEE 802.11 WLANs has led to dense deployments in urban areas. Such high density leads to sub-optimal performance unless the interfering networks learn how to optimally share the spectrum. This paper proposes a set of novel fully distributed algorithms that allow (i) multiple interfering 802.11 WLANs to select their operating frequency in a way that minimizes global interference, and (ii) clients to choose their Access Point so that the bandwidth of all interfering networks is shared optimally. The proposed algorithms rely on Gibbs’ sampler and optimize global network performance based on local information. They do not require explicit coordination among the wireless devices. We establish the mathematical properties of the proposed algorithms and study their performance using analytical, event-driven simulations. Our results strongly motivate the need for self-organization strategies in wireless access networks. We discuss implementation requirements and show that significant benefits can be gained even within incremental deployments and in the presence of non-cooperating wireless clients.

Collaborators:

Bruno Kauffmann, Franc?ois Baccelli, Augustin Chaintreau, and Christophe Diot

Bio:

Dina Papagiannaki received her first degree in electrical and computer engineering from the National Technical University of Athens, Greece, in 1998, and her PhD degree from the University College London, U.K., in 2003. Her thesis work was awarded the CHPC/BCS Distinguished Dissertations Award 2003 for the best PhD thesis in the area of Computer Science in the British Isles . From 2000 to 2004, she was a member of the IP research group at the Sprint Advanced Technology Laboratories, CA, U.S.A. She is currently with Intel Research in Cambridge , UK . Her research interests are in Internet measurements, modeling of Internet traffic, network design and provisioning, infrastructure and mesh wireless networks. A complete publications record can be found at http://www.cambridge.intel-research.net/~kpapagia/.

Seminar Lecture Series

7/10/2005
Bazaars, Services, and Systems Session
Speaker: Tziatzios Achilleas
Time: 15:00
Location: G100 ICS-FORTH
23/9/2005
16/9/2005
A Unified Energy-Efficient Topology for Unicast and BroadcastMulti-Radio, Multi-Channel Communication Session
Speaker: Pantelias Manolis
Time: 15:00
Location: G100 ICS-FORTH
8/8/2005
Improving Accuracy in End-to-end Packet Loss Measurement
Speaker: Raftopoulos Hlias
Time: 14:00
Location: G100 ICS-FORTH
4/8/2005
4/8/2005
On Power-Law Relationships of the Internet Topology
Speaker: Moudatsos Mihalhs
Time: 13:00
Location: G100 ICS-FORTH
20/1/2005
TNL presentation: Mesh Networking Problems & perspective
Speaker: Vangelis Angelakis
Time: 11:00
Location: Mediterranean Studies Room, ICS-FORTH
25/11/2004
Performance Anomaly of 802.11b
Speaker: Petros Politopoulos
Time: 14:00
Location: Mediterranean Studies Room, ICS-FORTH
25/11/2004
ns-2 lecture
Speaker: Despoina Triantafylidou
Time: 14:00
Location: Mediterranean Studies Room, ICS-FORTH
9/11/2004
Tutorial on Kalman and Particle Filters
Speaker: Dr. Haris Baltzakis
Time: 15:00
Location: RA201 (white buildings) UoC
4/11/2004
Three Papers on Mobile User Localization
Speaker: Anastasia Katranidou
Time: 13:00
Location: G100 ICS-FORTH
21/10/2004
An Introduction to Game Theory : part II
Speaker: Vagelis Angelakis
Time: 12:30
Location: G100 ICS-FORTH
14/10/2004
An Introduction to Game Theory : part I
Speaker: Vagelis Angelakis
Time: 13:00
Location: G100 ICS-FORTH

Mobile Computing Distinguished Lecturer Series

Census and Survey of the Visible Internet

Speaker: Prof. Christos Papadopoulos
Date: Thursday, May 24th, 2007
Time: 12:00-14:00
Place: Mediterranean Studies Seminar Room, FORTH , Heraklion, Crete
Organizer/Host: Prof. Maria Papadopouli

Abstract:

Many Internet topology studies have appeared in the literature. However, such studies have, for the most part, ignored the population of hosts. While many hosts are hidden behind firewalls and NATs, there is much to be learned from examining the population of "visible" Internet hosts -- one can better understand network growth and accessibility to help assess vulnerabilities, deployment of new technologies, and improve network models. This paper is, to our knowledge, the first attempt to measure the population of visible Internet edge hosts. We measure hosts in two ways: via periodic Internet censuses, where we query all accessible Internet addresses every few months, and via surveys of a small fraction of the responsive address space, probing each address every 11 minutes for one week. These approaches are complementary: a census is effective at evaluating the Internet as a whole, while surveys validate the census and allow observation of the lifetime of typical address occupancy.

Our findings include trends in address occupancy, an upper bound on the number of servers and an analysis of firewalled addresses and firewall block size. Joint work with John Heidemann, Yuri Pryadkin, Ramesh Govindan and Joseph Bannister.

Bio:

Christos Papadopoulos is currently an associate professor at Colorado State University . He received his Ph.D. in Computer Science in 1999 from Washington University in St. Louis , MO. His interests include network security, router services, multimedia protocols and reliable multicast. His current work includes signal processing techniques for network attack detection and participation in the PREDICT program to collect network traces for security research.

Selected Topics in Security and Cooperation of Wireless Networks

Speaker: Prof. Jean-Pierre Hubaux, EPFL
Date: Friday, 11 May 2007
Time: 13:00-15:00
Place: Mediterranean Studies Seminar Room
Organizer/Host: Prof. Maria Papadopouli

Abstract:

In this talk, we will develop some of the chapters of the graduate textbook "Security and Cooperation in Wireless Networks", written by L. Buttyan and J.-P. Hubaux, to appear this fall at Cambridge University Press.

The full book can be downloaded from http://secowinet.epfl.ch/.

The addressed chapters will be:

  • Security of upcoming wireless networks (Chapter 2), with an emphasis on vehicular networks
  • Securing neighbor discovery (Chapter 6)
  • Privacy protection (Chapter 8)
  • Selfish behavior in wireless networks, application of game theory (Part III and Appendix B).

Bio:

Jean-Pierre Hubaux joined the faculty of EPFL in 1990; he was promoted to full professor in 1996. His research activity is focused on wireless networks, with a special interest in security and cooperation issues.

He has been strongly involved in the National Competence Center in Research named "Mobile Information and Communication Systems" (NCCR/MICS), since its genesis in 1999; this center is often nicknamed "the Terminodes project". In this framework, he has notably defined, in close collaboration with his students, novel schemes for the security and cooperation in multi-hop wireless networks, vehicular networks, and sensor networks; in particular, he has devised new techniques for key management, secure positioning, and incentives for cooperation in such networks. He has also made several contributions in the areas of power management in sensor networks and of group communication in ad hoc networks.

He has recently written, with Levente Buttyan, a graduate textbook entitled "Security and Cooperation in Wireless Networks".

He is a member of the steering committee of IEEE Transactions on Mobile Computing and an associate editor of Foundations and Trends in Networking. He is the chairman of the steering committee of ACM Mobihoc. He has been serving on the program committees of numerous conferences and workshops, including SIGCOMM, Infocom, Mobicom, Mobihoc, SenSys, WiSe, and VANET. He is a member of the Federal Communications Commission (ComCom), the "Swiss FCC".

He held visiting positions at the IBM T.J. Watson Research Center and at the University of California at Berkeley .

He was born in Belgium , but spent most of his childhood and youth in Northern Italy . After completing his studies in electrical engineering at Politecnico di Milano, he worked 10 years in France with Alcatel, where he was involved in R&D activities, primarily in the area of switching systems architecture and software.

More information: http://people.epfl.ch/jean-pierre.hubaux

Network Coding and Scheduling in Wireless Networks

Speaker: Prof. Anthony Ephremides
Date: Thursday, June 2nd, 2005 3pm
Place: Mediterranean Studies Conference Room
Organizer/Host: Prof. Maria Papadopouli

Bio:

Anthony Ephremides received his B.S. degree from the National Technical University of Athens (1967), and M.S. (1969) and Ph.D. (1971) degrees from Princeton University , all in Electrical Engineering. He has been at the University of Maryland since 1971, and currently holds a joint appointment as Professor in the Electrical Engineering Department and the Institute of Systems Research (ISR). He is co-founder of the NASA Center for Commercial Development of Space on Hybrid and Satellite Communications Networks established in 1991 at Maryland as an off-shoot of the ISR.

He was a Visiting Professor in 1978 at the National Technical University in Athens , Greece , and in 1979 at the EECS Department of the University of California , Berkeley , and at INRIA, France. During 1985-1986 he was on leave at MIT and ETH in Zurich , Switzerland . He was the General Chairman of the 1986 IEEE Conference on Decision and Control in Athens , Greece . He has also been the Director of the Fairchild Scholars and Doctoral Fellows Program, an academic and research partnership program in Satellite Communications between Fairchild Industries and the University of Maryland . He won the IEEE Donald E. Fink Prize Paper Award (1992). He has been the President of the Information Theory Society of the IEEE (1987), and served on the Board of the IEEE (1989 and 1990).

Dr. Ephremides' interests are in the areas of communication theory, communication systems and networks, queueing systems, signal processing, and satellite communications.

His email address is: tony@eng.umd.edu.

Anthony Ephremides
Electrical Engineering Department and Institute of Systems Research University of Maryland College Park, MD 20742

Robust overload response during traffic or network misbehavior in wireless ad-hoc networks

Speaker: Prof. Leandros Tassiulas
Date: Thursday, May 19th, 2005 at 2pm
Place: Mediterranean Studies Conference Room
Organizer/Host: Prof. Maria Papadopouli

Abstract:

Unpredictability in traffic load variations, link capacity fluctuations, topology modifications, node failures or other types of intentional misbehavior may lead the network in overload conditions. Instantaneous system response in those stressful situations is essential for effective crisis management in the system. In this talk we study the operation of the network in overload. The notion of superflow is introduced as a generalization of flow where flow conservation at the nodes need not necessarily hold. Super flows facilitate accurate modeling of overload situations where the traffic generation intensity may temporarily exceed the capacity at different localities of the network. We propose as a measure for overload response the vector of backlog build up at the various network nodes when the network changes operational mode to overload. Optimization of that measure has as an effect most balanced allocation of the overload to the different network nodes. that manner for instance the time to buffer overflow is maximized We show that in the space of overload vectors there is one that is lexicographically minimal, thus most balanced and we characterize it. Furthermore we show that that vector is the unique solution for a wide class of optimization problems with objective function that is the sum of nondecreasing functions of the node overloads. Furthermore we characterize the class of most balanced superflows as those achieving most balanced overflow vectors. The characterization of most balanced superflows reveals certain structural properties of the network and helps to identify regions that experience the maximum stress from the current distribution of traffic intensity irrespectively of what the routing policy might be.

Finally we show how to achieve most balanced overflow through a simple distributed algorithm.

Bio:

Leandros Tassiulas is Professor in the Dept of Computer Engineering and Telecommunications at the University of Thessaly Greece since 2002 and Research Professor at the University of Maryland College Park . His research activity over the last fifteen years is towards the development of communication and information processing networks that facilitate access and exchange of information among multiple entities. Current research and teaching topics include wireless mobile communications, ad-hoc networks, smart antennas, sensor networks, high speed networked environments. He was Assistant Professor at Polytechnic University, NY, 1991-1995, Associate Prof. at the University of Maryland , College Park until 2002 (on leave 2000-2002) and Professor of Computer Science at the University of Ioannina Greece 1999-2002. He obtained the Diploma in Electrical Engineering from the University of Thessaloniki, Greece in 1987, and the M.S. and Ph.D. degrees in Electrical Engineering from the University of Maryland , College Park in 1989 and 1991 respectively. He has been Associate Editor for Communication Networks for IEEE Transactions on Information Theory and an editor for IEEE/ACM Transactions on Networking. His received a National Science Foundation (NSF) Research Initiation Award in 1992, an NSF CAREER Award in 1995, the Office of Naval Research Young Investigator Award in 1997 and the INFOCOM `94 best paper award. In 1999, he was awarded the "Bodossaki Foundation Academic Prize" in the field: Applied Science: Theories, Technologies and Applications of Parallel and Distributed Computing Systems.

He represents Greece in the 6th framework program of the European Union, as national expert in telecommunications.

Distinguished Lecturer Series Schedule 2005-2006

19/05/2005
Robust overload response during traffic or network misbehavior in wireless ad-hoc networks
Speaker: Leandros Tassiulas
Time: 14:00
Location: Mediterranean Studies Room, ICS-FORTH
Organizer/Host: Prof. Maria Papadopouli
2/06/2005
Network Coding and Scheduling in Wireless Networks
Speaker: Anthony Ephremides
Time: 15:00
Location: Mediterranean Studies Room, ICS-FORTH
Organizer/Host: Prof. Maria Papadopouli

Invited Talks

Analysis of the Wireless Access, Association Patterns, and Information Locality in a Campus

(This presentation requires the free Apple QuickTime Player which can be downloaded from the following link: www.apple.com/quicktime/download)

Conditions of Use | Privacy Policy