Detailed Publication List

This article discusses the problems that arise when standard Internet protocols such as TCP are used over wireless links. We review wireless link characteristics with case studies drawn from commercial Wireless LANs and Cellular Telephony systems. We discuss problems with Internet protocols when employed over these systems, such as degraded TCP performance when wireless errors are interpreted as congestion losses. We survey various proposed approaches to mitigating such problems and examine their applicability. Finally, we look at the future of wireless systems and the new challenges that they will create for Internet protocols, and state some goals for further protocol enhancement and evolution, pointing out the need for better protocol integration across layers. [J.4] IPMulticast GroupManagement for Point-to-Point Local Distribution, George Xylomenos and George C. Polyzos, Computer Communications, vol. 21, no. 18, 1998, pp. 1645–1654. Abstract: We examine the applicability of existing IP multicast mechanisms for Point-to-Point links such as wired and wireless telephone lines. We identify problems such as overhead due to IGMP leave latency and unnecessary probing of hosts, both important issues for power constrained mobile hosts and low bandwidth wireless links. We propose alternative mechanisms that preserve the IP multicasting model but employ join/leave messages to track group membership. We describe the implementation requirements of ourmechanisms and compare them to existing oneswith respect to performance, mobile power efficiency, interoperability, robustness and implementation complexity, demonstrating that the join/leave approach is uniformly superior for this environment. [J.3] TheMultimedia Multicasting Problem, Joseph C. Pasquale, George C. Polyzos and George Xylomenos, ACM Multimedia Systems, vol. 6, no. 1, 1998, pp. 43–59. Abstract: This paper explores the problems associated with the multicasting of continuous media to support multimedia group applications. The interaction between multicasting and the delivery of multiple time-correlated continuous-media streams with real-time delay requirements poses various new and interesting problems in research on communication protocols and architectures. We describe these problems, and identify where the opportunities are for effective solutions, all in the context of providing an overview of the current state of research in multimedia multicasting. The issues we discuss include quality of service, resource reservations, routing, error and traffic control, heterogeneity, and the use of hierarchical coding and open-loop control techniques. [J.2] IP Multicast for Mobile Hosts, George Xylomenos and George C. Polyzos, IEEE Communications Magazine, vol. 35, no. 1, 1997, pp. 54–58. Abstract: We present alternative designs for efficiently supporting multicast for mobile hosts on the Internet. Methods for separately supporting multicasting and mobility along with their possible interactions are briefly described, and then various solutions to the combined problem are explored. We examine three different multicast delivery mechanisms and compare them based on their efficiency and impact on host protocol software. [J.1] Evaluation and SelectionCriteria for Software Requirements Specification Standards, E.A. Giakoumakis and George Xylomenos, IEE/BCS Software Engineering Journal, vol. 11, no. 5, 1996, pp. 307–319. Abstract: Various organisations have published proposals to prescribe the form and content of software requirements specification documents; the standards were designed to support the specific needs of these organisations and the intricacies of their development projects. To help third parties in taking advantage of this body of work, a set of criteria are proposed and discussed that can be used to evaluate such standards, according to the unique characteristics of specific combinations of organisations and software development projects, and then the question of how the criteria can be applied in an evaluation, selection and tailoring process, depending on the circumstances, is discussed. Finally, the criteria are demonstrated by applying them on some published standards, to help interested organisations to preselect those that seem most appropriate for their needs. Refereed Conferences [C.75] Multimodal Assessment of Network Music Performance, Konstantinos Tsioutas, Konstantinos Ratzos, George Xylomenos and Ioannis Doumanis, Proceedings of the Workshop on Multimodal Affect and George Xylomenos Annotated Publication List 9 Aesthetic Experience (MAAE) 2021. Abstract: The most common method of assessing the Quality of Musician’s Experience (QoME) in Network Music Performance (NMP) is to perform a subjective study, where the participants evaluate their experience via questionnaires. Translating experiences intometrics is not an exact science, though: in our recent study on the effects of audio delay and quality in the QoME of NMP, the responses had a high variance and were inconsistent. To strengthen our confidence in the results of the subjective study, we analyzed video recordings of the participants using machine learning. Specifically, we used Facial Expression Recognition (FER) to detect the emotions felt by the participants and then compare them with their questionnaire responses. In addition to pointing out interesting phenomena that were not apparent from the questionnaires, this multimodal analysis showed analogies between the emotions felt (as captured by FER) and the emotions expressed (as captured by the responses). [C.74] Assessing the QoME of NMP via Audio Analysis Tools, Konstantinos Tsioutas and George Xylomenos, Proceedings of the International Conference on Signal Processing andMultimedia Applications (SIGMAP) 2021. Abstract: Analyzing the Quality of Musicians’ Experience (QoME) in Network Music Performance (NMP) typically involves having musicians perform NMP sessions and then assessing their experience via questionnaires. Such subjective studies produce results with wide variances, making the extraction of solid conclusions difficult. For this reason, we complemented a subjective study on the effects of delay in the QoME of NMP with an analysis of the audio captured during the study using automated tools. Specifically, we used signal processing techniques to analyze the captured audio, in order to detect tempo evolution during each performance and examine its correlation with delay. Our results indicate that musicians in real NMP settings are more tolerant to delay than previously thought, holding a steady tempo even with one way delays of 40 ms. [C.73] SecuringNamedDataNetworking routing usingDecentralized Identifiers, Nikos Fotiou, Yannis Thomas, Vasilios A. Siris, George Xylomenos and George C. Polyzos, Proceedings of the IEEE Semantic Addressing and Routing for Future Networks Workshop (SARNET) 2021. Abstract: Named Data Networking (NDN) is a realization of the Information-Centric Networking (ICN) paradigm, where routing is based on content identifiers rather than on network location identifiers. The routing state in NDN can grow exponentially, not only due to the huge number of content identifiers (as opposed to network addresses) but also because it is difficult to detect “fake” routing advertisements. For example, in contrast to IP-based routing, a potentially valid routing entry in NDN can be advertised from multiple network locations, making NDN susceptible to Denial-of-Service attacks at the routing layer. In this paper, we leverage Decentralized Identifiers (DIDs) to build self-verifiable content advertisements. With our solution, any router can verify that a content advertisement originates from an authorized entity, without requiring any trusted third party. We implement our solution and we evaluate it in a scenario where filtering is implemented by the edge routers. We show that our solution reduces fake routing advertisements with minimal computational overhead. [C.72] An empirical evaluation of QoME for NMP, Konstantinos Tsioutas, George Xylomenos and Ioannis Doumanis, Proceedings of the IFIP International Conference on New Technologies, Multimedia and Security (NTMS) 2021. Abstract: For Network Music Performance (NMP), low end-to-end delay is probably the most critical factor affecting the Quality of Musicians’ Experience (QoME), as inflated delays inhibit the synchronization between musicians. Even though customized NMP tools can greatly reduce application-layer delays, generally available Internet connections impose considerable network-layer delays to NMP sessions in wide-area settings. In order to empirically assess the delay tolerance of NMP, multiple pairs of musicians were asked to perform in a controlled network environment, while we varied the end-to-end delay. The musicians were then asked to evaluate a number of metrics. The statistical analysis of the results indicates that the tolerance of actual musicians to delay is higher than previously thought, thus expanding the applicability of NMP to longer distances. [C.71] In-network packet-level caching for error recovery in ICN, Yannis Thomas, George Xylomenos and George C. Polyzos, Proceedings of the International Workshop on Content Caching and Delivery in Wireless Networks (CCDWN) 2020. George Xylomenos Annotated Publication List 10 Abstract: In-network packet-level caching is one of the salient features of Information-Centric NetIn-network packet-level caching is one of the salient features of Information-Centric Networking (ICN) architectures, offering reduced communication latency, sender load, and network traffic. The literature on ICN caching is quite extensive, exploring in depth different aspects of caching, such as the positioning of storage resources in the network, the caching policies of individual caches, as well as the interaction of caching and routing. However, many researchers have questioned the value of innetwork caching, arguing that the limite