In this web page you can find information on my professional and research activities. I was born in Arta and I work as a teacher of Informatics in Secondary and Post-compulsory Secondary Education. I received my undergraduate degree in Electrical and Computer Engineering in 2001 from the National Technical University of Athens and my MSc and PhD in Informatics from the Informatics Department of the Athens University of Economics and Business in 2003 and 2011 respectively.
Aikaterini Christopoulou, Emmanouel Giakoumakis, Vassilis Zafeiris, Vasiliki Soukara, 2011. Automated Refactoring to the Strategy Design Pattern. Submitted to Information and Software Technology Journal, Elsevier B.V.
Vassilis Zafeiris, Emmanouel Giakoumakis. Optimized Traffic Flow Assignment in Multi-Homed, Multi-Radio Mobile Hosts. In Elsevier Computer Networks, Vol. 55, Issue 5, 2011, Elsevier B.V.(pdf)
Vassilis Zafeiris, Emmanouel Giakoumakis. An Agent-based Perspective to Handover Management in 4G Networks. In Wireless Communications and Mobile Computing Journal, Vol. 8, Issue 7, 2008, John Wiley and Sons Ltd.(pdf)
Christos Doulkeridis, Vassilis Zafeiris, Kjetil N�rv�g, Michalis Vazirgiannis, Emmanouel Giakoumakis. Context-based Caching and Routing for P2P Web Service Discovery. Distributed and Parallel Databases special issue on Context-aware Web services, Vol. 21, Issue 1, pages 59-84, February 2007, Springer.
Yannis Stavrakas, Manolis Gergatsoulis, Christos Doulkeridis, Vassilis Zafeiris. Representing and Querying Histories of Semistructured Databases Using Multidimensional OEM. In Information Systems, Vol. 29, Issue 6, pages 461-482, September 2004, Elsevier.
Vassilis E. Zafeiris and Emmanouel A. Giakoumakis, 2008. Towards flow scheduling optimization in Multihomed Mobile Hosts. In Proceedings of IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC’08), IEEE.
Vassilis E. Zafeiris and Emmanouel A. Giakoumakis, 2008. Mobile Agents for Flow Scheduling Support in Multihomed Mobile Hosts. In Proceedings of International Wireless Communications and Mobile Computing Conference, 2008. (IWCMC’08), pages 261-266, IEEE.
Vassilis Zafeiris, Emmanouel Giakoumakis, 2005. An Agent-based Architecture for Handover Initiation and Decision in 4G Networks. In Proceedings of 6th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM’05), Taormina, Italy, June 2005.
Vassilis Zafeiris, Christos Doulkeridis, Petros Belsis and Ioannis Chalaris, 2005. Agent-mediated Knowledge Management in Multiple Autonomous Domains. In AAMAS 2005 Workshop on Agent Mediated Knowledge Management (AMKM’05), Utrecht, Netherlands, July 2005.
Christos Doulkeridis, Vassilis Zafeiris, Michalis Vazirgiannis. The Role of Caching and Context-Awareness in P2P Service Discovery. In Proceedings of 6th International Conference on Mobile Data Management (MDM'05), pp.142-146, Ayia Napa, Cyprus, May 9-13, 2005.
Yannis Stavrakas, Manolis Gergatsoulis, Christos Doulkeridis, Vassilis Zafeiris. Accomodating Changes in Semistructured Databases Using Multidimensional OEM. In Proceedings of Advances in Databases and Information Systems (ADBIS'02), 6th East-European Conference, pp.360-373, Bratislava, Slovakia, September 8-11, 2002.
V. Zafeiris, C. Doulkeridis, Y. Stavrakas, and M. Gergatsoulis, 2002. An Infrastructure for Manipulating Multidimensional Semistructured Data. In 1st Hellenic Data Management Symposium (HDMS’02), Athens, Greece, July 2002.
The thesis has been submitted to the Department of Informations of Athens University of Economics and Business under the supervision of Professor E.A. Giakoumakis. The full text of thesis in pdf format is available here.
Multi-radio mobile communication devices are increasingly gaining market share due to the diversity of currently deployed and continuously emerging radio access technologies. Multi-homing support in multi-radio terminals, i.e., simultaneous use of two or more radio interfaces, provides improved user experience through increased bandwidth capacity availability and reliability of wireless access. Furthermore, optimized assignment of application traffic flows to available interfaces and radio access bearer services contributes to economic and power consumption efficiency. The thesis studies the traffic flow assignment problem (TFAP) in a mobile node, multi-homed through a set of different technology radio interfaces. It introduces an analytical formulation for the problem and proves its hardness through reduction from the Multiple Knapsack Problem with Assignment Restrictions. Problem solutions are approximated with a heuristic algorithm that is based on local search and is characterized by efficient execution times for a wide set of realistic problem sizes. The quality of approximation is rather satisfactory and is evaluated through comparison of heuristic and exact solutions for a large set of randomly generated problem instances. Moreover, an evaluation of the approach through simulation supports these findings and provides an estimation of the associated mobility management overhead that is limited and allows real deployment of the decision mechanism.
The employment of advanced network selection (or handover decision) or TFAP algorithms cannot be based solely on an end-host infrastructure. The decision mechanisms require both locally available information (e.g. application traffic requirements, user preferences etc.) and location-based network information that is not practical to be retrieved by the mobile terminal exclusively through active scanning. The reason is that active scanning is time consuming and inefficient in terms of energy consumption. Moreover, reliable and in-time information on resource availability of available access networks may not be provided by a single network operator, e.g., the home operator of a mobile user, as it has no incentives to provide it and consequently let its customers utilize third-party services. In this thesis a system architecture is also proposed for supporting the execution of handover decisions or TFAP algorithms. The architecture spans multiple administrative domains and is based on software agents. The software agents represent the users, the network operators, a Multi-Access Provider (MAP) and the regulatory authority. In the proposed approach, handover or traffic flow assignment decisions are delegated to software agents that are user representatives. Decision making is initiated by user agents that execute either in the terminal or the network, depending on the source of handover triggering events. On the other hand, execution of decision algorithms takes place in the network for saving terminal's usually limited power and computational resources. Performance evaluation of the architecture has been performed through a simulation system with focus on the impact on handover latency. The results are promising for the feasibility of the proposed architecture.
My research interests span the following areas:
Teaching activities since 2003 are summarized in the following table:
|Software Engineering (undergraduate)||Supportive role, part of Phd obligations||Department of Informatics, Athens University of Economics and Business (AUEB)||Spring Semesters from 2003 (S'03) to 2010|
|Analysis and Design of Information Systems (undergraduate)||Supportive role, part of Phd obligations||Department of Informatics, AUEB||Autumn Semester of 2009 (A'09)|
|Introduction to Programming in Java (undergraduate)||Supportive role, part of Phd obligations||Department of Informatics, AUEB||A'07, A'08|
|Information retrieval||Teaching Assistant||Technological Education Institute (TEI) of Athens||A'05, S'06|
|Databases II||Teaching Assistant||TEI of Athens||Acad. years 2005-06, 2007-2010|
|Software Engineering (postgraduate)||Teaching Assistant||MSc in Information Systems (full time program), Department of Informatics, AUEB||A'07-A'10|
|Software Engineering (postgraduate)||Teaching Assistant||MScIS (part time program), Department of Informatics, AUEB||A'09, A'10|
|Introduction to information and communication technologies||Teacher of Informatics||Compulsory education||2007-today|