29 May 2014 at 13:30 - Colloquium: "Design, implementation and functional extensions to the Delay Tolerant Payload Conditioning (DTPC) protocol", Ioannis Alexiadis
Summary:
The main objective of this talk is to present the extension of the DTN architecture by integrating a reliable transport protocol in order to provide end-to-end services. The DTN architecture and the accompanying Bundle Protocol propose a means for data communications on potentially heterogeneous networks, employing store-and-forward message routing, and aiming to overcome the issues that arise from the high propagation delays and limited connectivity that usually characterize such networks. The DTN architecture currently does not have a transport layer providing end-to-end services, such as those common in most terrestrial networks, leaving this functionality up to the application. In this presentation, we highlight the benefits of having an additional layer of application-independent protocol, offering transparent application data conditioning services end-to-end and we introduce the Delay Tolerant Payload Conditioning (DTPC) protocol, a novel protocol that realizes this layer. DTPC protocol is an expandable, connectionless, reliable, sequenced transport protocol which extends the DTN architecture in a fashion that accords with the end-to-end principle, enabling the following services: (a) controlled aggregation of application data units, with application-specific elision, (b) reliable end-to-end transmission of data, based on positive acknowledgments and retransmissions, (c) in-order delivery and (d) duplicate suppression.
13 May 2014 at 16:30 - Colloquium: "ALPINE sensor network programming abstractions and tools", Dr. Eli Katsiri
Summary:
The ALPINE research project has a special focus on the investigation of the bidirectional relationship between large scale urban development and the natural habitat of man, fauna and flora. In this talk I will discuss some of the research chalenges that arise in the scope of the ALPINE research project, when designing a sensor network architecture that is tailored to environmental management. The proposed architecture is application-driven and comes together with a software suite of high-level, reactive and energy-efficient programming abstractions. Distributed, real-time monitoring applications can be programmed with the help of these tools instructing the sensor network to monitor continually in real time both the physical world and/or man-made infrastructure such as hydrological networks and proximity to public roads, in order to detect situations of interest of arbitrary complexity, e.g., that there is a sudden drop of pressure in a water pipe causing potential shortage in some part of the city or that a stressed bear trying to cross the highway at a location where there is inadequate fencing leading to possible fatalities.
09 April 2014 at 13:30 - Colloquium: "LEDBAT performance in sub-packet regimes", Dr. Ioannis Komnios
Summary:
Wireless Community Networks in the developing world satisfy the basic needs of remote users to information access. However, community networks in developing regions usually rely on low-bandwidth backhaul links that are shared amongst a large user base, driving these links to sub-packet regimes where the per-flow throughput is less than one packet per RTT. TCP performance significantly degrades in such conditions, resulting in severe unfairness and high packet loss rates. In this presentation, we investigate the performance of scavenger transport methods, namely LEDBAT and its fair modification fLEDBAT, in the sub-packet regime of shared backhaul links in developing regions. Our intention is to explore the feasibility of using such scavenger transport methods for uploading content over bandwidth constrained backhauls. Our findings show that LEDBAT achieves higher link efficiency and fairness compared to TCP in a variety of sub-packet regime scenarios. When TCP and LEDBAT flows share the same link in the sub-packet regime, LEDBAT flows are more aggressive, consuming more resources than TCP. Therefore, we conclude that a more conservative strategy after consecutive timeouts and shared bottleneck detection mechanisms need to be incorporated into the core LEDBAT algorithm, in order to correctly adjust its congestion window in the sub-packet regime.
11 March 2014 at 14:00 - Colloquium: "DTN Sensor Data Carrier - Problem Description and Requirements Phase", Sotirios-Angelos Lenas
Summary:
Ubiquitous sensing, enabled by Wireless Sensor Network (WSN) technologies, is now a part of modern everyday living. Internetworking all those WSN technologies under a unified network architecture would facilitate the efficient exchange and transfer of information between sensors and data collectors. Such an approach could finally lead in improving both the accuracy of the measurements and the understanding of the respective indicators. In this talk, Sotiris will present how Delay Tolerant Networking can help towards that direction based on the architecture's ability to provide reliable data communication across heterogeneous/failure-prone networks, which also present communication interruptions. The requirements of such a system are finally described with respect to the network interfaces that the architecture needs to support and a first set of environmental sensors that would be incorporated is presented.
21 February 2014 at 12:00 - Colloquium: "Performace evaluation of routing algorithms in ad-hoc networks based on connectivity maps", Eirini Kalogeiton
Summary:
In this presentation, a range of mechanisms for the extension and the enhancement of the routing algorithm CARPOOL, which is mainly used in DTN networks, are presented. The first improvement of the algorithm is the replication of two copies of a message from the sender as well as the routing of these copies through different paths in the network. Afterwards, an extra element is added, that includes the recalculation of a route of a message, when necessary. Finally, by exploiting the unscheduled link that two mobile nodes have, the message forwarding between these two nodes is now feasible. The proposed routing algorithm CARPOOL v2 appears to have significant advantages over its earlier version as far as the throughput is concerned. In particular, the CARPOOL v2 algorithm succeeds in decreasing not only the latency of the message but also the necessary hop counts that a message has to pass through in order to reach its final destination, fact that contributes to the increment of the throughput.
11 February 2014 at 14:00 - Colloquium: "A DTN-based architecture for the dissemination of high volumes of space-data", Sotiris Diamantopoulos
Summary:
As space missions such as the Sentinels and Euclid are scheduled to launch in the near future, robust networking mechanisms will need to be in place in order to transfer huge volumes of space data produced on board to interested parties in a timely and efficient fashion. In this work we study the applicability of DTN as a supportive mechanism for the dissemination of space data from storage locations to end-users. Furthermore, we propose a DTN-based communication model to support low-earth orbit earth observation missions, comparing it against CFDP.
28 January 2014 at 14:00 - Colloquium: "Predicting Queueing Delays in Delay Tolerant Networks with Application in Space", Nikos Bezirgiannidis
Summary:
We present a study of queueing delays experienced in Delay Tolerant Networks with topology based on deterministic contact plan schedules. We examine a generic scenario and propose a sampling procedure that extracts measurements of queueing rates and queue lengths. Sampling queueing information is transmitted to network nodes, which then form time series and can be used to forecast future queueing rates. Through simulations we show that the introduced method can be useful for DTNs with predetermined contact schedules, such as the Interplanetary Internet, providing accurate end-to-end delivery delay predictions.
10 January 2014 at 14:00 - Colloquium: "SPICE Testbed: A DTN Testbed for Satellite and Space Communications", Dr Giorgos Papastergiou
Summary:
In this presentation, we will present an overview of SPICE testbed, a state-of-the-art Delay Tolerant Networking testbed for satellite and space communications deployed at the Space Internetworking Center. The core of the testbed relies on the Bundle Protocol and its architecture has been designed to support multiple DTN implementations and a variety of underlying and overlying protocols. SPICE testbed is equipped with specialised hardware components for the accurate emulation of space links and ground stations, such as Portable Satellite Simulator (PSS) and CORTEX CRT system, as well as protocols and mechanisms specifically designed for space DTNs. Performance and functionality evaluations on SPICE testbed show that it is an ideal platform to evaluate newly developed mechanisms in a variety of space communication scenarios.
10 December 2013 at 13:00 - Colloquium: "DUTH at TREC 2013 Contextual Suggestion Track", Dr George Drosatos
Summary:
In this presentation/seminar we give an overview of our participation in the TREC 2013 Contextual Suggestion Track. We present an approach for context processing that comprises a carefully designed and fine-tuned POI (Point Of Interest) data collection technique, a crowdsourcing approach to enrich our data collection and two radically different approaches for suggestion processing (a k-NN clustering-based and a Rocchio-like). In the context processing, we collect POIs from three popular place search engines, Google Places, Foursquare and Yelp. The collected POIs are enriched by adding snippets from the Google and Bing search engines using crowdsourcing techniques. In the suggestion processing, we propose two methods. The first submits each candidate place as a query to an index of rated examples and scores it based on the top-$k$ user's ratings. The second method is based on Rocchio's algorithm and uses the rated examples per profile to generate a personal query which is then submitted to an index of places. The track evaluation shows that both approaches are working well; especially the Rocchio-like approach looks very promising since it scores almost firmly above the median and achieves the best results in almost half of the judged context-profile pairs.
19 November 2013 - Colloquium: "Traffic shaping for enabling less-than-best effort services at the edges of broadband connections", Sotirios-Angelos Lenas
Summary:
Broadband connection sharing constitutes a network resource pooling technique that could evolve toward supporting the establishment of the “Free Internet for All” notion. This technique could be implemented through the User-Provided Network model in which any end-user device (e.g. ADSL Access Points) could behave as supplier of Internet connectivity. In this talk, Sotiris will elaborate on the behavior of such a system from a queue-management perspective. Towards that direction, he will present a numerical analysis that takes into consideration both the high variability of broadband link speeds and different packet-size distributions. The talk will conclude with an introduction to a new hybrid packet-scheduling scheme that enables the application of Less-than-Best Effort services at the connection edges.
12 November 2013 - Colloquium: "CARPOOL: Extending Free Internet Access over DTN in Urban Environments", Ioannis Komnios
Summary:
In order to address the challenge of digital exclusion, we introduce an access method based on message ferrying that enables free delay-tolerant Internet access to all. Targeting an urban scenario, where means of public transport, such as buses and trams, follow a predefined route and schedule, we utilise a priori knowledge about their current location to extend Internet access provided by hotspots to users and areas that are not typically covered. In this presentation, we explore how the deployment of DTN-capable nodes can extend free Internet coverage in metropolitan areas, we depict the inefficiency of existing DTN routing protocols in highly-dense environments and we propose Connectivity plAn Routing PrOtOcOL (CARPOOL), a reference routing protocol to support our claims. CARPOOL exploits the connectivity plan of public transportation, achieving high delivery ratio with minimum overhead.
18 October 2013 - Colloquium: "Interoperability testing and network performance evaluation of the major DTN implementations", Nikolaos Kouvelas
Summary:
In this presentation, Nikos will give an overview of his study regarding DTN implementations interoperability and network performance. The study is conducted over a large variety of DTN implementations including the most well-known implementations such as DTN2, ION, IBR-DTN and Postellation along with older ones such as ContikiDTN, SPINDLE and DTNLite. Several trade-offs in the performance and the overall behavior of the different implementations are revealed and a guide on selecting the appropriate implementation per application requirements is presented.
18 October 2013 - Colloquium: "Interconnecting Heterogeneous Devices in Ad-Hoc Networks with Mobile Users", Dimitris Mastoras
Summary:
In this presentation, Dimitris will present his study on interconnecting heterogeneous devices under a unified mobile network. For this purpose, Dimitris designed and implemented a Mobile Ad-Hoc Network consisting of portable devices such as mobile phones, Laptops and Raspberry Pis. To address the problems that occurred in communication, due to the mobility and limited resources of nodes, Delay Tolerant Networking was incorporated into the network. After the implementation of the network, several realistic scenarios of communication between the various devices were investigated.
10 October 2013 - Colloquium: "Deploying the "Space-Data Routers" architecture to emulate realistic scenarios", Sotirios Diamantopoulos
Summary:
In the framework of the "Space-Data Routers" project, DUTH is developing a DTN overlay to enhance the dissemination of space data. In the final part of the project, the implemented architecture will be evaluated in terms of the impact it will have on the scientific community, based on realistic scenarios. In this colloquium the most important scenarios, as selected by the "Space-Data Routers" consortium, are presented and the DTN-overlay deployment specifics are discussed. Furthermore, we assess the impact of the proposed architecture on the aforementioned scenarios.
17 September 2013 - Colloquium: "Simulations of space missions", Maria Tsioumani
Summary:
The Satellite Tool Kit (STK) was used to perform simulations of space missions in order to gather realistic information of the respective communication channels. In particular, STK was used to perform link budget analysis of each communication link involved and calculate the contact periods among the communicated elements. This information (such as bandwidth, PER, propagation delay and connectivity schedule) constituted a set of network parameters that were imported in either a network simulator or in our DTN testbed, where actual data transferring among space elements was simulated/emulated and the performance of various network protocols and mechanisms was evaluated. In our study we considered complex communicating systems consisting of several space elements, such as satellites, ground stations, landers and rovers, targeting mainly on Mars communications.
17 July 2013 - Colloquium: "Multicasting on Delay Tolerant Networks: The IMC-BSS Approach", Sotirios-Angelos Lenas
Summary:
Bundle Multicasting refers to the act of delivering the same bundle to a group of nodes, which are all part of the same network and are interested for the same piece of information, in a single transmission from the source. That means that the source won't issue separate bundle transfers but the network itself will automatically create copies in other network elements, such as routers, only when the topology of the network requires it. This group of nodes is called "multicast group" and all of them have to register to the same "multicast endpoint", an endpoint that is not known to have exactly one member. For this purpose the Interplanetary Overlay Network platform defines the Interplanetary Multicast scheme (IMC) and the destination endpoint ID of a multicast group must be a URI formed in the “imc” scheme (e.g., imc:913.11). Forwarding a bundle to all members of the multicast group is the responsibility of all the multicast-aware nodes of the network and is based on a single multicast spanning tree overlaid onto the dtnet.
Reliably transferring a piece of information into all the destination nodes constitutes a great challenge since end-to-end delivery of data can fail in many ways, at different layers of the stack. When delivery fails, we can either accept the communication failure or retransmit the data. In this talk, Sotiris will elaborate on how Bundle Streaming Service (BSS) could be used is such a scheme to provide reliability in an efficient way by taking advantage of the sophisticated forwarding functionalities employed by BSS.
06 June 2013 - Colloquium: "A Study of Queueing Delay in Delay Tolerant Networks with Application in Space", Nikolaos Bezirgiannidis
Summary:
We present a study of queueing delays in Delay Tolerant Networks with topology based on deterministic contact plan schedules. We examine a generic scenario and propose a sampling procedure that extracts queue length information from an outbound queue. Sampling data is then used to calculate the enqueueing rates for all transmitting nodes that contribute to this queue, as well as the dequeueing data rate. Extracted rate measurements are stored in a database and can be used in an administrative framework to predict future enqueueing and dequeueing rates, using a time series forecasting procedure. Finally, a pair of introduced algorithms exploit rate predictions in order to estimate the expected queue lengths and bundle queueing delays at specific future times. The proposed method can be effective in Space communications, in the upcoming Solar System Internet.
25 April 2013 - Colloquium: "Offload 3G networks traffic through Delay Tolerant Networks", Fani Tsapeli
Summary:
The rapidly increasing popularity of mobile devices with networking capabilities (e.g. smartphones or tablets) results in increasing demand for 3G services. This demand is expected to increase more in the near future. Cellular network providers should increase their network capacity in order to be able to handle the mobile traffic (for example by upgrading to 4G). However, the continuously increasing demands will induce again overloading problems. In this presentation, I will discuss alternative 3G offloading methods that are based on utilizing the available WiFi hotspots and or the delay tolerant architecture.
16 April 2013 - Colloquium: "Towards a new ESA mission: Tuning the communication protocols", Sotirios Diamantopoulos
Summary:
Euclid is a joint ESA-NASA mission to map the geometry of the dark Universe. Featuring a state-of-the-art high image quality camera as its main scientific payload, it is expected to generate huge volumes of data daily that will need to be transferred to Earth as fast as possible, since the on-board memory of the satellite is limited. The networking technology that will be used on Euclid is still an open issue, especially as far as the CFDP protocol and its tuning are concerned. This presentation will provide some insight on the requirements, open issues and solutions proposed during my 3-month internship at the European Space Operations Centre (ESOC).
10 April 2013 - Colloquium: "Mobile ICN-DTN-Assisted services using satellites for safety and security (MIDAS^3)", Ioannis Komnios
Summary:
Universal Internet Access is one of the fundamental requirements today and is being currently addressed at the European level via the Digital Agenda for Europe as well as globally. MIDAS^3 directly addresses the need for providing Universal Internet Access irrespective of geography, socio-economic and technological barriers, creating an enabler for connecting the people, content, clouds and things. Such an enabler can play a crucial role in safety and security in societies.
MIDAS^3 is a universal communication platform that encompasses a working set of protocols, systems, services and tools to enable tighter integration of satellite and terrestrial communications, aiming at providing seamless accessibility, security and safety to societies. The architecture combines two emerging architecture and connectivity approaches: Information Centric Networking (ICN) and Delay Tolerant Networking (DTN) as a unified architecture. Such a unified architecture aggressively seeks to widen the connectivity options beyond what is currently pursued in the game around digital inclusion. Smart and flexible satellite capacity mechanisms are used to provide the notion of flexible Quality of Service. Finally, we demonstrate how local government organizations can provide a range of public services from low priority free Internet access to communities utilizing the unused capacity in satellite networks to high priority communications for safety and security.
26 March 2013 - Colloquium: "Bundle Streaming Service", Sotirios-Angelos Lenas
Summary:
Data streaming over Delay-Tolerant Networks (DTN) is a challenging task considering jointly the specific characterisics of DTN environments, the demanding nature of streaming applications and their wide applicability. Sotiris will present his work on Bundle Streaming Service (BSS), a framework, specifically designed for Delay Tolerant Networks, that supports the delivery of streaming media in DTN bundles. After a short discussion on the challenges that the DTN area presents and on the research efforts so far focusing on data streaming over DTNs, Sotiris will elaborate on how BSS achieves reliable delay-tolerant streaming while improving the reception and storage of data streams through efficient forwarding techniques and the exploitation of the inherent Bundle Protocol mechanisms.
11 March 2013 - Colloquium: "Setting up a DTN testbed", Ioannis Alexiadis
Summary:
In this presentation we provide an overview of the SPICE testbed equipment and then delve into the details of the installation and configuration process, the challenges we faced, and how it is currently used in DTN related experiments.
25 February 2013 - Colloquium: "Multi-objective Contact Graph Routing Mechanism", Sotirios Diamantopoulos
Summary:
The Multi-Objective Contact Graph Routing (MOCGR) mechanism is an extension of the Contact Graph Routing (CGR) algorithm. A sophisticated algorithm is used to provide available routes towards the destination, exploiting contact information available to all nodes participating on the overlay. This information is then coupled with a number of routing criteria embedded on the bundle protocol header by the transmitting node allowing the algorithm to calculate the best available route depending on the sender requirements.
11 February 2013 - Colloquium: "Message Ferry Routing in Delay Tolerant Networks", Ioannis Komnios
Summary:
This presentation summarizes the existing routing protocols that have been proposed for Delay Tolerant Networks and achieve maximum performance when message ferries are used. Message Ferrying approach is a mobility-assisted approach which utilizes a set of special mobile nodes, called message ferries, to provide communication service for nodes in the deployment area. The applicability of specific routing protocols, which have been introduced for space environments, for terrestrial networks that utilize message ferries is investigated.
28 January 2013 - Colloquium: "Bundle Delivery Time Estimation: a tool for predicting arrival time of space bundles.", Nikolaos Bezirgiannidis
Summary:
We present a method for predicting delivery time of bundles in space internetworks. The bundle delivery time estimation (BDTE) tool exploits contact graph routing (CGR), predicts bundle route, and calculates plausible arrival times along with the corresponding probabilities. Latency forecasts are performed in an administrative node with access to an instrumentation database (DB) appropriate for statistical processing. Through both analysis and experimentation, we demonstrate that estimates of bundle earliest plausible delivery time and destination arrival probabilities can be provided.
14 January 2013 - Colloquium: "DTN Queue Management", Sotirios-Angelos Lenas
Summary:
Even though the Bundle Protocol seems to be the prevalent candidate architecture for delay-tolerant applications, some practical issues hinder its wide deployment. One of the functionalities that require further research and implementation is DTN queue management. The main topic of the forthcoming discussion will be the newly-proposed DTN Queue Management Architecture, aka DTQM. Following a short discussion on the issues that affect queue-management strategies in DTN (loss of connectivity and extended delays), Sotiris will present DTQM attributes and how connectivity status is integrated into buffering and forwarding policy, eliminating the possibility of stored data to expire and promoting applications that show potential to run smoothly.
17 December 2012 - Colloquium: "Separating transport from other services provided by Delay-Tolerant Payload Conditioning", Ioannis Alexiadis
Summary:
DTPC is an application service protocol operating on top of Bundle Protocol, that offers delay-tolerant support for several end-to-end services to applications, such as aggregation, elision, in-order delivery, retransmissions and duplicate suppression. In this presentation we discuss the potential benefits of allowing applications to request aggregation/elision functionality separately from transport-like functionality.
7 December 2012 - Colloquium: "New technologies in energy and transport", Dr. Spyros Kiartzis
Summary:
Dr. Kiartzis will present the need to develop new technologies in order to face current technical dead ends and challenges related to energy and transportations. The policies that will be implemented will recognize and support the need for a smooth and gradual mutation into a world of reduced carbon emissions. The solution will not be univocal, will consist of a mixture of actions and policies on energy, transportations and the environment, with basic conditions of security of supply and economic sustainability.
Short Bio:
Spyros Kiartzis is Deputy Director of Alternative Energy Sources in Hellenic Petroleum SA. He received his Diploma and Ph.D. in Electrical and Computer Engineering from the School of Engineering and his degree on Economics from the School of Law and Economics both from the Aristotle University of Thessaloniki.
Upon graduation, he joined the Aristotle University of Thessaloniki as a researcher and later as an instructor. Following a period in the construction sector he served as a part-time Power Systems instructor at the Dept. of Mechanical Engineering of the University of Western Macedonia. Since 2012 he lectures in the MSc in Energy Systems of International Hellenic University. His research interests are in industrial power systems, in renewable energy, in energy economics and in energy sector deregulation policy.
He joint the Hellenic Petroleum SA in 2001 where he held a range of posts in maintenance and project construction sections before becoming Deputy Director of Alternative Energy Sources in 2008. He is also member of the Board of Directors of the Hellenic Petroleum Renewable Energy Sources SA (subsidiary of Hellenic Petroleum Group). He has served as member of the Board of Directors of EKO Bulgaria SA (subsidiary of Hellenic Petroleum Group) and has participated in the Project Management Team for the construction of a 390 MW Combine Cycle Power Plant.
He also serves as member of the Board or Consultant in technical and financial sector. He is a senior member of IEEE, a member of the Conference International des Grands Reseaux Electriques a Haute Tension (CIGRE) and a member of the Society of Professional Engineers of Greece.
9 November 2012 - Colloquium: "Admission to an organization and structure of a successful self-presentation", Dr. Konstantinos Georgiadis
Summary:
During the first part of his presentation Dr. Georgiadis will explain to us how Human Resources Department functions. He will develop not only the goals and aspirations but also the challenges for a young engineer in the job market. Then, he will analyze the procedures followed in a company in order to choose the right personnel that will meet the current business needs and he will give us advice on how to present ourselves. The seminar will conclude with a real interview.
Short Bio:
Dr. Georgiadis is working as a human resources manager in Sunlight S.A. company. He graduated from the Economics Department (U.O.M) and the JF Kennedy School of Government (Harvard). He has a Master in Business Administration and a Ph.D. in Strategic Management and the Psychology of Human Resources (Bath). Moreover, he holds an Executive Diploma, as a scholar of Kokkalis Foundation. He has experience in consulting services and he specializes in human resources management, governance practices in connection with the company's performance, control costs, fluctuations in the company's size and liquidity effects in corporate and in research he focuses on work behavior.
13 June 2012 - Colloquium: "Delay-Tolerant Communication with Content-Centric Networks", Carlos Anastasiades
Summary:
Content-Centric Networking (CCN) is a promising approach for mobile ad-hoc communication, because routing is not based on specific forwarding nodes but content names. If an individual forwarder becomes unavailable, any node in vicinity that has overheard the content transmission or holds the corresponding content may replace the former forwarder's functionality. CCN can therefore support location-based and delay-tolerant content delivery. In this talk, we will present application scenarios, requirements and research challenges of delay-tolerant content-centric communication.
30 May 2012 - Colloquium: "PacketEconomy: a mechanism for best effort user-controlled QoS", Aris-Remous Koutsiamanis
Summary:
In this work, we apply a common economic tool, namely money, to coordinate network packets. In particular, we present a network economy, called PacketEconomy, where ordinary network packets can self-regulate their access to network resources by mutually trading their positions in a router queue. Queue positions and money are exchanged directly between the packets while the routers simply carry out the agreed trades. This work describes the network model, the client and server model and the router model used as well as the pairing algorithms and trading method at a high level. Finally, we also highlight problematic issues and areas for potential application.
25 May 2012 - Colloquium: "Erasure Coding in Space Communications", Giorgos Papastergiou
Summary:
Erasure coding has attracted the attention of space research community due to its potential to present an alternative or complementary solution to ARQ schemes. Giorgos Papastergiou discussed the potential of erasure coding in space communications and provided an overview of the proposed approaches for the incorporation of erasure codes within the CCSDS DTN protocol stack.
17 May 2012 - Colloquium: "Graph Representation of Deterministic Delay Tolerant Networks", Dr Diego Borsetti
Summary:
Dr Borsetti provided an overview of the available graph representation methods of deterministic delay-tolerant networks. In particular, the following methods were presented:
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DTN Graph
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Space-Time Graph
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Cyclic Mobispace
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Event-driven Graph
09 May 2012 - Colloquium: "Utility Based Routing", Fani Tsapeli
Summary:
Utility-based replication is one of the most prominent solutions for Delay-Tolerant Networks, as far as routing is concerned. In this colloquium, we will present and discuss the recent advances on the field of utility-based replication routing.
30 April 2012 - Colloquium: "Satellite Toolkit (STK): Software to model, analyze and visualize space, defense and intelligence systems", Souzana Makaratzi, MSc Candidate, DUTH
Summary:
STK is a physics-based software geometry engine that accurately displays and analyzes land, sea, air, and space assets in real or simulated time. Users can model the time-dynamic position and orientation of vehicles and the characteristics and pointing of payloads aboard the assets. STK also determines spatial relationships between an asset of interest and all of the objects under consideration and then assess the quality of these relationships. The presentation starts with the capabilities of STK and then continues with some exercises that include the problem statement and the solution for each one. In this way is provided a basic understanding of the capabilities that are part of the STK software suit.
12 March 2012 - Colloquium: "Study and Evaluation of HTTP load balancing techniques on the Internet", Sotirios Kontogiannis, PhD Candidate, DUTH
Summary:
Increasing utilization of web based applications and implementation of more and more services over HTTP, lead to the building of more efficient web servers and services. Focusing on further improvements of web servers’ performance, distributed web architectures consisting of web server farms were introduced and load balancing architectures were deployed. Such distributed web architecture is the cluster-based web system, comprised of a farm of web server nodes joined together as a single unity.
This presentation focuses on adaptive and content aware load balancing algorithms for cluster-based web systems. The algorithms presented do try to improve overall system performance and scalability in cases of heterogeneous conditions due to network resources and/or processing capabilities limitations of web cluster nodes.
6 February 2012 - Colloquium: "Authenticated Key Exchange (AKE) in Delay Tolerant Networks", Sofia-Anna Menesidou, PhD Candidate, DUTH
Summary:
Key exchange is considered to be a challenging problem in Delay Tolerant Networks (DTNs) operating in space environments. We investigate the options for integrating key exchange protocols with the Bundle Protocol. We demonstrate this by using a one-pass key establishment protocol. In doing so, we also highlight the peculiarities, issues and opportunities a DTN network maintains, which heavily influences the underlying security solution.
16 January 2012 - Colloquium: "Detection of Learner's Affective State Based on Mouse Movements", Georgios Tsoulouhas, PhD Candidate, DUTH
Summary:
Nowadays it is generally accepted that the use of the computer can to greatly improve the learning process. The Adaptive Educational Hypermedia Systems (AEHS) developed increasingly trying to help the student - user To get the knowledge they need to be delivered efficiently. Studies have shown that the emotional state of the user during a monitoring module plays an important role the effectiveness of the learning process.
For example, if a presentation of a lesson causes feeling of boredom to the student, then the student will be able to attend the course and time will roll ineffective. Therefore the possibility can the system - computer to detect status of the student is very important as it may be adapted and to stimulate the student to change the mood and the pique their interest back. We present a method for detecting a sense of boredom based on hand movements of the student and therefore mouse movements.
19 December 2011 - Colloquium: "Experience-Driven Procedural Content Generation", Georgios Giannakakis, Associate Prof. at University of Copenhagen
Summary:
Procedural content generation (PCG) is an increasingly important area of technology within modern human-computer interaction (HCI) design. Personalization of user experience via affective and cognitive modeling, coupled with real-time adjustment of the content according to user needs and preferences are important steps towards effective and meaningful PCG. Games, the semantic web, interface and software design are amongst the most popular applications of automated content generation. This talk will go through a taxonomy of PCG algorithms and will introduce a framework for PCG driven by computational models of user experience. This approach, named Experience-Driven Procedural Content Generation (EDPCG), is generic and applicable to any content-intensive application. The approach’s effectiveness will be demonstrated via dissimilar successful game applications.
12 December 2011 - Colloquium: "Electrodynamic simulations in the near-earth environment", Theodoros Sarris, Assistant Prof. at DUTH, Department of Electrical and Computer Engineering
Summary:
Near Earth environment constitutes an electromagnetic laboratory that is occupied by complex current systems of million Amperes and dynamic interactions between charged particles with the constantly-changing magnetic field of Earth. Despite the amount of satellites and ground measurements, one of the most novel ways to understand these complex processes is through simulations, which can combine the necessary in-situ measurements in common meaning. In this presentation, we will provide an insight to such simulations that attempt to describe some of the most crucial processes of the magnetic environment of Earth.
23 November 2011 - Colloquium: "User Mobility in Urban Areas as a semi Markov process", Lefteris Mamatas - Senior Engineer at SPICE Center, Alexandra Papadopoulou - Assistant Prof at AUTH
Summary:
User mobility in urban environments may follow certain patterns.For example, walking users pass from high streets or other points of interest with increased probability. Detecting these patterns allows us to introduce efficient opportunistic routing algorithms that can exploit even the slightest communication opportunity.
According the literature, existing user mobility modeling: (i) is usually based on weak theoretical foundations (e.g., assumptions are not evaluated, inappropriate theoretical tools etc), and (ii) does not exploit the recent advances in mathematical modeling.
It is obvious that the limitations of the theoretical tools hinder the expressiveness and applicability of the proposed models. Here, we investigate new and more detailed analytical tools, trading simplicity for expressiveness. We introduce a Semi-Markov model as a theoretical tool of study. We gradually extend the complexity of the proposed model.
21 November 2011 - Colloquium: "Usage assessment of Internet applications", Stavros Valsamidis - PhD Candidate, Democritus University of Thrace.
Summary:
The usage of web applications can be measured with the use of indexes and metrics. However, in e-Learning platforms there are no appropriate indexes and metrics that would facilitate their qualitative and quantitative measurement. The purpose of this presentation is to use existing techniques in a different way, in order to analyze the log file of an LMS and deduce useful conclusions. Three metrics, enrichment, homogeneity and interest for course usage measurement are used. Two algorithms for course classification and suggestion actions are also described. Data mining techniques, such as classification, clustering and association, are applied to the LMS data with the use of the open source software tool Weka. It should be mentioned that even though the scope of the method is on e-Learning platforms and educational content, it can be easily adopted to other web applications such as e-government, e-commerce, e-banking, blogs, etc.
7 November 2011 - Colloquium: "Routing for Opportunistic Networks Based on Probabilistic Erasure Coding", Fani Tsapeli, Engineer at SPICE Center
Summary:
Opportunistic networks exemplify characteristics of delay tolerant networking (DTNs) in environments where contacts appear opportunistically. Common examples of such networks are mobile sensor networks, underwater sensor networks, or transportation networks, where delay tolerance constitutes an inherent property of limited bandwidth or sparse connectivity. Routing in such networks is a particularly challenging problem since it does not simply rely on connectivity to establish optimal routes but rather attempts to exploit windows of connectivity opportunities. This presentation provides a short overview of the problem of routing in opportunistic networks and also presents a novel routing strategy based on erasure coding technique.
31 October 2011 – Colloquium: "Managing P2P Traffic: State-of-the-Art and Future Directions", Roman Dunaytsev, Senior Engineer at SPICE Center
Summary:
Over the last decade, we have witnessed the tremendous growth of P2P file sharing. P2P traffic rapidly became the dominant type of traffic in the Internet and continues to be one of the biggest consumers of network resources. As a result, traffic generated by P2P file sharing applications interferes with delay-sensitive traffic such as VoIP and multimedia streaming, degrading the performance of other applications on the same network. Moreover, built as overlays on top of the existing Internet infrastructure, P2P file sharing networks usually ignore the underlying network topology, thus generating a lot of "unwanted" inter-ISP traffic. Huge amounts of inter-ISP traffic affect the way ISPs do business and force them to either reevaluate their peering agreements with other ISPs or to use special policies when handling P2P traffic. This presentation provides a short overview of different approaches to deal with P2P traffic, identifying those that may provide long-term benefits for both ISPs and users.
23 May 2011 – Colloquium: "Electronic Governance and Local Administration", Maria Spanou, MSc, Head of Administrative and Financial Services, Municipality of Xanthi
Summary:
The introduction of modern technologies in Public Administration and especially in local governance has followed a really slow pace in Greece. Only during the last years we have identified the role of Information and Communication Technologies for change and modernization of Public Administration and we have made some serious efforts for their application. Electronic Governance is the revolution of the 21st century. However, redesigning the legislation framework and changing the behavior of both citizen and civil servants is required.
16 May 2011 – Colloquium: "Infrastructure-Assisted Geo-Routing for Cooperative Vehicular Networks", Dr Diego Borsetti
Summary:
Cooperative vehicular systems require the design of reliable and efficient multi-hop networking protocols to achieve their foreseen benefits. Although many geo-routing protocols have been proposed in the literature, few contributions have analysed the benefits that road side infrastructure units could provide to successfully route data from source to destination. In this context, we propose a novel infrastructure-assisted routing approach designed to improve the end-to-end performance, range and operation of multi-hop vehicular communications by exploiting the reliable interconnection of infrastructure units. The conducted investigation shows that the proposed infrastructure-assisted routing approach achieves its objectives, and reduces the routing overhead compared to other greedy position-based geo-routing protocols. Finally, in order to obtain the maximum benefits from the proposed infrastructure-assisted routing approach, optimal infrastructure deployment strategies are investigated.
4 Apr 2011 – Colloquium: "Wired and Wireless Methods for Controlling a 5-DOF Robotic Arm", Apostolos Koutsokalis, Konstantinos Manolis, Athanasios Vellios, Yiannis S. Boutalis, Savvas A. Chatzichristofis
Summary:
Here we present an open-source Graphical User Interface (GUI) that works under the Windows OS (XP or later version) used for controlling a five-degrees-of-freedom robotic arm, including both a virtual remote controller and a command parser. We also provide a control method using a wireless natural-physics controller that translates human-hand movements to commands for the robotic arm. Authors of this paper are using modern console game controllers that have built-in accelerometers and IR sensors. The resulting methods are tested on Eurobtec’ s IR52c.
4 Apr 2011 – Colloquium: "An Open Source Set of Libraries to Control a 5-DOF Robotic Arm", Christos Mavrakis, Themistoklis Kyrgos, Savvas A. Chatzichristofis
Summary:
In this presentation we will introduce a new, open-source, lightweight software library that implements solutions to the Direct and Inverse kinematics problem for a 5-degrees-of-freedom robotic arm in general. In addition, a library for low level communication with the IR25c robotic arm has been developed, that can be used with the previously mentioned library and allows for easy manipulation of the robot. Both libraries are open source software, provided under the GNU General Public License and are designed with modularity in mind, so that they can be used together or separately in large projects.
21 Mar 2011 – Colloquium: "Computational tools for describing and designing complex systems", Assistant Prof. Georgios Syrakoulis
Summary:
In this presentation we will present the computational tools used in the Electronics laboratory for describing and designing complex systems. In particular, Cellular Automata (CA) will be presented, which are mathematical models of physical systems where space and time have distinct sjze and local interactions. CA present some interesting characteristics, such as massive parallelis, local interactions, simplified cells and rising computation. For this reason, CA have been used as models of physical systems and processes, as well as electronic systems architectures. During this presentation, we will present CA applications for describing and designing complex systems, starting from the 1980s till today, which have been developed from different research teams of our Department.
14 Mar 2011 – Colloquium: "Ecoinformatics: Software engineering challenges for the environment's sake", Dr Ioannis N. Athanasiadis
Summary:
Ecoinformatics is the science of information in Ecology and Environmental Sciences. Its aim is to provide languages (common to both humans and computers) that enable the documentation of Nature and facilitate its interpretations. Ecoinformatics is a discipline of applied informatics and is an excellent realistic testbed for demonstrating computer science innovations. It raises new challenges for computing as complexity, uncertainty and scaling issues of natural systems form a demanding application domain.
This talk will present the principles of ecoinformatics, outline speaker's experience from past research projects in Europe, and present challenges for future research and collaborations with the Electrical and Computer Engineering Dept of Democritus University of Thrace.
28 Feb 2011 – Colloquium: "Presentation of work on Software Technologies and Computation Systems Security"
During this colloquium, two groups of students of the department of Electrical and Computer Engineering will present their work on Software Technologies and Computation Systems Security, accordingly.
21 Feb 2011 – Colloquium: "Artificial vision: applications in robotic systems", Assistant Prof. Antonios Gasteratos
Abstract
In this presentation we will demonstrate the results of the research projects, in which Assistant Prof. Gasteratos was project coordinator or were completed under his guidance in the Department of Production and Management Engineering during the last five years. In particular, these projects include Rescuer FP6-IST-511492, ViewFinder FP6-IST-2006-045541, Acroboter FP6-IST-2006-045530 and Infra FP7-ICT-SEC-2007-1-225272. The projects were funded by the European Commision within the 6th and 7th Framework Programmes.
21 Jan 2011 – Colloquium: "Short presentation of research work of SPICE researchers"
During this colloquium, researchers at the Space Internetworking Center will briefly present their research advances and future plans.
29 Nov 2010 – Colloquium: "Current Advances in 3D Object Retrieval", Ioannis Pratikakis
Abstract
3D object representations have become an integral part of modern computer graphics applications, such as computer-aided design, game development and film production. At the same time, 3D data have become very common in domains such as computer vision, computational geometry, molecular biology and medicine. The rapid evolution in graphics hardware and software development, in particular the availability of low cost 3D scanners, has greatly facilitated 3D model acquisition, creation and manipulation, giving the opportunity to experience applications using 3D models to a large user community. As the number of 3D models is continuously growing fast the problem of creating new 3D models has shifted to the problem of searching for existing 3D models. Thereupon, the development of efficient search mechanisms is required for the effective retrieval of 3D objects from large repositories, both of a single class (such as human faces) and across classes.
This lecture will strive toward presenting the current hot topics in the important research area of 3D Object Retrieval and will put particular emphasis in a novel robust descriptor for retrieval in generic 3D databases as well as a novel part-based representation which enhances retrieval performance by improving the intra-class accuracy.
23 Nov 2010 – Colloquium: "Adaptive and optimization tools for Large-scale actuator/sensor networks", Ilias Kosmatopoulos
Abstract
The inability of existing theoretical and practical tools to scale-ably and efficiently deal with the design, deployment and operation of Large-Scale Networks of Actuators/Sensors (LS-NAS) for complex, uncertain and time-changing large-scale applications, not only leads to an effort-, time- and cost-consuming deployment of LS-NASs, but also prohibits their wide application in areas and applications where they could potentially have a tremendous effect in improving system efficiency and Quality of Services (QoS), reducing energy consumption and emissions, and improving the day-to-day quality of life.
In this presentation, we will briefly present our results on designing and deploying LS-NASs that are capable of:
1. Providing pro-active, arbitrarily-close-to-optimal performance
2. Being intrinsically self-tuneable, able to rapidly and efficiently optimize performance when short- medium- and long-time variations affect the large-scale system
3. Providing efficient, rapid and safe fault-recovery and re-configuration
4. Achieving all the above, while being scalable and modular
Applications to mobile (flying and underwater) sensor networks (EC-funded projects sFLY and NOPTILUS) and energy-positive buildings and traffic control systems (EC-funded projects PEBBLE and AGILE) will be also reported.
01 Nov 2010 – Colloquium: "www.MMRetrieval.net: A Multimodal Search Engine", Dr Konstantinos Zagoris
Abstract
MMRetrieval is an experimental multimodal search engine, which allows multimedia and multi-language queries, and makes use of the total available information in a multimodal collection. All modalities are indexed and searched separately, and results can be fused with different methods depending on
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the noise and completeness characteristics of the modalities in a collection
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whether the user is in a need of high initial precision or high recall.
Beyond fusion, we also provide 2-stage retrieval by first thresholding the results obtained by secondary modalities targeting recall, and then re-ranking them based on the primary modality. The engine demonstrates the feasibility of the proposed architecture and methods on theImageCLEF 2010 Wikipedia collection. Its primary modality is image, consisting of 237434 items, associated with noisy and incomplete user-supplied annotations and the Wikipedia articles containing the images. Associated modalities are written in any combination of English, German, French, or any other undetermined language.
25 Oct 2010 – "Coctail party problem and proposed solutions", Lecturer Nikolaos Mitianoudis
Abstract
Imagine you're at a cocktail party. For you, it is no problem to follow the discussion of your neighbours, even if there are lots of other sound sources in the room: other discussions in English and in other languages, different kinds of music, etc.. You might even hear a siren from the passing-by police car. In this presentation, a brief overview will be given on audio source separation techniques based on Independent Component Analysis (ICA), i.e. the problem of computer-automated extraction of audio sources using microphones that capture an auditory scene. The three most common mixing models will be covered along with the corresponding techniques to recover the audio sources that exist in the mixture and audio examples.
18 Oct 2010 – "The bodyguard", Assistant Prof. Vassilis katos
Abstract
"A pop singer has been receiving threatening notes, and her manager hires a bodyguard known for his good work. The bodyguard ruffles the singer's feathers and most of her entourage by tightening security more than they feel is necessary. The bodyguard is haunted by the fact that he was on Reagan's secret service staff but wasn't there to prevent the attack by Hinckley. Eventually the bodyguard and the singer start an affair, and she begins to believe his precautions are necessary when the stalker strikes close to home." (http://www.imdb.com/title/tt0103855/plotsummary)
In this colloquium -with the help of Kevin and Whitney- we will investigate the basic principles of information systems security.
11 Oct 2010 – "Algorithmic Game Theory", Assistant Prof. Pavlos Efraimidis
Abstract
In this lecture we wil present game theory using the typical dilemma of a prisoner, we wil investigate the idea of Nash equilibrium, as well as the problems that Algorithmic Game Theory can study.
05 Oct 2010 – "Modeling Score Distributions in Information Retrieval & Applications", Lecturer Avi Arampatzis
Abstract
Modeling score distributions in Information Retrieval (IR) is an important theoretical issue which has many practical applications in Distributed Retrieval, Fusion/Meta-search, Filtering, Topic Detection & Tracking, and elsewhere. We review the history of modeling score distributions, focusing on the mixture of Normal-Exponential by investigating the theoretical as well as the empirical evidence supporting its use. We discuss suggested conditions which valid (from an IR perspective) binary mixture models should satisfy. Last, we present our related on-going work on Legal Document Retrieval, and Multi-Modal Image Retrieval.
20 Sep 2010 – "Official presentation of Space Internetworking Center", Prof. Vassilis Tsaoussidis
Abstract
Space Internetworking Center was established on September 1st, 2010 and is situated in the ground floor of the building of Electrical and Computer Engineering of DUTH. Goal of the center is to interconnect the peripherical research areas that can support "Space Internetworking", such as retrieval, transmission and handling of space data.
SPICE project has received research funding from the Seventh Framework Programme of the European Union (Grant Agreement No 264226, FP7-REGPOT-2010-1).
