The cybersecurity industry faces a significant skills gap, with a shortage of qualified professionals to meet the growing demand for cyber talent. Although there is a wide variety of cybersecurity professional trainings available, these trainings use different approaches and the certificates obtained are not compatible with each other. Contrary to the United States, there is no European Authority responsible for approving these trainings. The situation becomes even more complex when considering sector-specific trainings. This paper sheds light on the certification landscape regarding relevant, organisations and bodies at the international and European level. The standards, the criteria, and the processes regarding professional certifications are discussed. The manuscript concludes with a proposal of a sector-agnostic schema for a cybersecurity professional training programme.

Cybersecurity constitutes an urgent need in today's digital environment. Nowadays, the Cybercrime landscape changes in a hectic and a rapid way. Cyberattacks pose a huge problem which asks for urgent and professional solutions. As a result, a great need in the world labor market for Cybersecurity specialists, professionals and practitioners has arisen. Vocational Education and Training (VET) graduates must be able to respond to the labor markets calls for specific cybersecurity skills and expertise. Despite this universally accepted situation, the Greek vocational schools do not offer such a specialty. In this paper, a CyBOK compliant Cybersecurity syllabus for inclusion in the ICT curricula of the Greek Vocational schools is proposed. This proposal aims to shorten the gap between the Greek labor market needs and the quantity of available practitioners - professionals. In addition to the syllabus, a roadmap on the next steps to integrate this proposal into the Greek VET is outlined.

The challenges of teaching programming have led to the development of various models, approaches, and tools which attempt to overcome a variety of obstacles. In this article, we explore the application of Noam Chomsky's theory of transformational grammar (TG) to the teaching of programming languages ​​(PLs). In the context of the comparative teaching (CT) of programming languages, we propose a model for exploiting TG's deep structure (DS) and surface structure (SS)., using the technology of Cloud Compilers (CC). We design a theoretical framework for the comparative teaching of programming languages, starting from the deep structure of the computational problem. Through this process, we develop the solution algorithm and transform it to its surface structure, implementing it in various programming languages. The writing, compilation and execution of programs is implemented through the online CC programming environments, within the framework of organized remote labs, where no local installation is required on the user's part and they are free to use. This paper contributes to the scientific debate on issues related to the teaching of computer programming by providing a new model for teaching programming languages, called the Comparative Learning Model (CLM).

There is great potential in the introduction of gamified, interdisciplinary learning approaches in various education environments. This paper explores the effectiveness of Musical Mastermind, a gamified educational tool combining music education and computational thinking to promote interdisciplinary learning. The game, which uses a microcontroller-based LED matrix, challenges students to decode musical sequences, bridging artistic creativity and logical problem-solving. Rooted in the constructivist and experiential learning theories, Musical Mastermind integrates gamification into education, aligning with STEAM principles to foster holistic skill development. The game combines music theory and coding, encouraging exploration, problem-solving, and collaboration. The study was conducted in a seventhgrade classroom using the micro:bit, a cost-effective microcontroller. The students began with an introduction to music and coding, and then created and decoded musical sequences while engaging in collaborative gameplay. A mixedmethods approach was employed, utilizing pre-and post-test assessments, observational analyses, and feedback surveys to evaluate learning outcomes. Results showed significant improvements in music theory comprehension, computational thinking, and problem-solving skills. The students demonstrated high levels of engagement, teamwork, and perseverance, with increased motivation and a stronger connection between music and technology.

NERO represents a sophisticated Cybersecurity Ecosystem comprising five interconnected frameworks designed to deliver a Cybersecurity Awareness initiative, as advocated by ENISA as the optimal method for cultivating a security-centric mindset among employees to mitigate the impact of cyber threats. It integrates activities, resources, and training to nurture a culture of cybersecurity. NERO primarily equips SMEs with a repository of Cyber Immunity Toolkits, a Cyber Resilience Program, and Gamified Cyber Awareness Training, all accessible through a user-friendly Marketplace. The efficacy and performance of this concept will be affirmed through three distinct use case demonstrations across various sectors: Improving Patient Data Security in Healthcare with Cybersecurity Tools, Enhancing Supply Chain Resilience in the Transportation and Logistics Industry through Cybersecurity Awareness, and Elevating Financial Security via Enhanced Cybersecurity Awareness and Tools.

The challenge of connecting and combining sustainability with ICT education is crucial for enhancing transformative learning toward sustainable development (SD). This enhancement can be achieved through integrating aspects of sustainability issues into ICT curricula. Therefore, it is essential to ensure that the ICT teachers possess the necessary knowledge, understanding, skills, and values to enable the inclusion of sustainability education in their learning practices. In this direction, this study explores the Greek ICT teachers’ perceptions and perceived barriers toward embedding sustainability into the secondary education ICT curricula. For this reason, secondary school ICT teachers completed an online questionnaire concerning education for SD and its implementation in the ICT field. Their responses revealed that the ICT teachers have a rather deficient level of understanding and awareness about the concept of sustainability and green informatics. On the other hand, the findings indicated that the ICT teachers have a positive perception toward the inclusion of green informatics into the ICT secondary curricula. They highlighted the need to implement a teacher's training ICT module that is geared towards integrating education for SD across the secondary ICT curricula within the Greek educational system. In addition, they suggested the provision of educational sustainability-related content (books, scientific journals, etc.) at schools.

The work addresses the significance of robotics in education, emphasizing its role in enhancing STEM skills through programming and sensory feedback. Scratch, a multimedia programming environment, is highlighted as a tool for robotic projects. Within Scratch, this work discusses data representation, distinguishing between visible and transparent data, focusing on transparent data. To evaluate how data are used in Scratch by novice programmers, this work also proposes an evaluation framework using the Structure of the Observed Learning Outcome (SOLO) taxonomy.

In today's dynamic educational environment, gamification has emerged as a powerful approach to captivate students and elevate their learning experiences. This paper aims to demonstrate the potential of a gamified teaching experience as a transformative educational strategy by utilizing the Global Positioning System, Google Maps, and Geolocation in a location-based game, following a multi-disciplinary approach that successfully combines History, Sciences, Technology, Engineering, Mathematics, Language, and Arts. Examining the specific case of Rhodes' Old (Medieval) Town, the paper provides insights into how adventure, technology, and multidisciplinary learning can create a dynamic, interactive, and engaging educational environment in an outdoor setting.

The use of educational games based on augmented reality (AR) is a modern approach to supporting programming logic and algorithmic thinking. The purpose of this paper is present the design, development and evaluation of an augmented reality educational game application, under the name “D-Buggy, the AR Bot”. This application intends to support the Informatics course of Greek High Schools. The application introduces students to the concept of algorithms and programming logic and requires the use of mobile devices. More specifically, the structure, functions and tools used to develop the “D-Buggy, the AR Bot” and the evaluation of this first version of the application by specialists in terms of effectiveness, efficiency and user satisfaction are presented.

Over the last decade, It has been illustrated by many modern pedagogical theorists that the contemporary learning process must be meticulously updated by incorporating digital tools that may transform the educational context to the core. Serious games may form immersive experiences that positively boost the players’ engagement as they interact in a computer-generated environment that includes educational elements. This paper aims to review the development and consequent incorporation of a serious game, i.e. a game designed with an underlying intent to educate or inform), into the school curricula (high school, senior high school). “Build to Green” is a single-touch controlled, explorative, and educational gameplay that seeks to teach students how to build a smart city from scratch while coping with radical elements that may allow them to create a unique digital smart ecosystem based on crucial notions of today's society, such as sustainability, recycling, minimization of energy footprint, green economy, open innovation, and cloud computing. Our primal vision is to be able to link this innovative gameplay with certain school subjects (e.g., Mathematics, Geography, Computer Science, Social Science, and Economics) and corresponding learning outcomes.

The Internet of Things (IoT) optimizes remote operations in Cyber-Physical Systems (CPS) by enabling real-time bidirectional communication with cloud services, thus supporting efficient management. However, this increases security risks. Ensuring strong remote user authentication is crucial. This paper presents a Multi-Factor Authentication (MFA) system using Time-based One-Time Passwords (T-OTP) for securing user access at the edge layer of CPS. We validate the system through test cases in smart buildings and Industrial IoT (IIoT) scenarios, demonstrating its broad applicability in enhancing secure remote management of critical systems.

Empowering young adults to protect our planet starts in their school era and moves forward to the community. By engaging pupils in sustainability-based learning, they become environmentally conscious young people. In order to explore pupils' knowledge of sustainability and the intention to deal with “Green Informatics” in Greece, we collected pupils-generated data from learning activities and conducted a research via a questionnaire after delivering a computer science course. The course was based on the Moodle platform, where pupils engaged in sustainability. The results indicate the pupils' positive perceptions related to green informatics and the integration of sustainability into the CS curricula. These results highlight the necessity for redesigning the primary and secondary education curricula in order to increase pupils' sustainability and environmental awareness. In addition, the pupils suggest the introduction of awareness activities in an inclusive manner so that these activities may provide a learning path towards environmental sustainability for the whole school community.

Robotics is being increasingly used in order to engage pupils in STEM, in which computer programing can also be taught. This paper, as part of a larger research approach within Robotics and STEM where visual programming languages are used and proposes a set of evaluation criteria on data assessment in Scratch based on the SOLO taxonomy. The data evaluation is influenced by their form, the types and symbolism of their content, the ways in which they are used, their actors, their degree of visibility, the organization of simple and multimedia data, their processing, and their naming. The types and symbolism of their content, as well as the ways in which they are used, are investigated in this work. For each considered factor, a categorization is made using the SOLO taxonomy levels. The teachers can use this categorization as a tool to either assess their students' performance using quantifiable criteria (in matters pertaining to the factors mentioned above) or to create their own teaching paths, thereby building a mental scaffolding that aids in the efficient and effective learning of new material.

In this paper we propose a methodology for intrusion detection of attacks originating from WiFi networks, along with WiFi-NID, a WiFi Network Intrusion Detection tool, developed to automate the detection such attacks at the 802.11 networks. In particular, WiFi-NID has the ability to detect and trace possible illegal network scanning attacks, which originate from attacks at the WiFi access layer. A penetration testing methodology is defined, in order to discover the environmental security characteristics, related with the current configuration of the devices connected to the 802.11 network. The methodology covers known WiFi attacks such as deauthentication attacks, capturing and cracking WPA-WPA/2 handshake, captive portal and WPA attacks, mostly based on various open source software tools, as well as on specialized hardware. For the validation process, a testbed is set based on realistic scenarios of WiFi network topologies.

The education of Vocational Education and Training (VET) students on various topics related to the programming of personalized electronic devices beyond a strong theoretical foundation requires a broad hands-on experience as well. This paper proposes such a hands-on didactic application that can be integrated with the design of the extension of the curriculum of the Specialty “Technical Applications of Informatics” for the course “Computer Programming” of the Greek VET educational system. In particular, this paper explores how a program that identifies unsolicited (spam) Short Message Services (SMSs) using modern Natural Language Processing (NLP) techniques can be integrated into the teaching practice. First, we cover the theoretical background for the necessity of the intervention and the overall framework that is required to understand and ensure the correctness of the techniques used. Then, we demonstrate how the implementation of an artificial neural network can be used effectively to solve this particular problem. To achieve all the above, we have designed and proposed a teaching scenario that on the one hand approaches the new advanced communication technologies, and, on the other hand, operates within the cognitive limits of secondary technical education.

According to Wirth, “a program is algorithm plus data”. This association of algorithm and data also occurs at the micro-scale of a command, where the program is represented by a single command plus a data representation. This paper proposes to map the degrees of complexity of the command, data processing and data structuring to the levels of the SOLO taxonomy in order to create tool for evaluating code which is used in visual programming environments. This tool allows the teacher to assess the degree of the student’s understanding of the use of a command, and the complexity of that command. The ability of the teacher to measure the weight of each command, allows him to design alternative teaching spiral paths, from a simple command to the most complex ones. The work in this paper is part of a broader project to evaluate visual programming code – with Scratch as the chosen visual programming language.

The goal of this paper is to propose a framework in order to automate the environmental vulnerability assessment of communication protocols and networked services in operational environments. Initially, a network security ontology is defined, to model the environmental characteristics related with the current security status of available communication protocols channels within an examined infrastructure. The functionality of this infrastructure is presented by an ontology. All active communication services are initially identified and enumerated using a combination of different information gathering tools. Then by combining passive scanning and active security analysis tools each active communication service is assessed to output an environmental security score. This score may be utilized in vulnerability scoring systems such as CVSS, to properly adjust relevant scores and to identify implementation or configuration weaknesses in real environments. By using a test environment that involves various networks and communication protocols, we validate the proposed framework and we provide concrete examples for popular communication protocols.

In this paper we examine traditional and novel software models for critical IoT applications. We propose a hybrid cellular IoT model that offers optimizations with respect to automated network management, re-configuration and optimized performance. This hybrid model utilizes the fog/edge computing model and can satisfy better the requirements of time-sensitive IoT applications.

The transformation of the digital economy into an opportunity for women goes through complexities related to political, economic, social, cultural, customary, and family issues. As a consequence, the vulnerable groups of women are closer to acquiring the skills needed to access jobs but, on the other hand, these are unstable and shallow digital jobs that do not guarantee their exit from employment exclusion. In this article, data collected by the program "WOMEN4IT-20" are presented, followed by a discussion on delving into the prospects and plans of the program for the immediate future. The article concludes that women have equal access to the digital economy, as the digital age belongs to women equally.

This article presents the synchronous and asynchronous administrative tools that were mostly engaged in Digital Learning at the second phase of the COVID-19 lockdown. Apart from eLearning tools, this article also presents the necessary administrative tools and techniques that can support DL in public schools and especially in junior high schools. These administrative tools can be used in conjunction with the “my-school” platform, which contributes to distance learning by enhancing the database of the participating teachers and students to provide crucial student-school communications.

The majority of systems rely on user authentication on passwords, but passwords have so many weaknesses and widespread use that easily raise significant security concerns, regardless of their encrypted form. Users hold the same password for different accounts, administrators never check password files for flaws that might lead to a successful cracking, and the lack of a tight security policy regarding regular password replacement are a few problems that need to be addressed. The proposed research work aims at enhancing this security mechanism, prevent penetrations, password theft, and attempted break-ins towards securing computing systems. The selected solution approach is two-folded; it implements a two-factor authentication scheme to prevent unauthorized access, accompanied by Honeyword principles to detect corrupted or stolen tokens. Both can be integrated into any platform or web application with the use of QR codes and a mobile phone.

The Vocational Education and Training (VET) curriculum aims to provide students with the necessary skills to make them employable and successful in their specialties. Therefore, an increasing number of VET curricula are employing various resources to equip students with 21stcentury skills such as critical thinking, creativity, communication, collaboration, and information literacy. In this paper, we explore the key dimensions of active learning for empowering and enriching Collaboration, Individual Empowerment, and Development of the apprentices’ learning processes through Teaching and Learning Analytics (TLA), in a Learning Management System (LMS) for VET apprenticeships. We describe in detail “how TLA can “work” in a VET environment, and we present how we organize the TLA methodology inside the proposed LMS.

BadUSB is a critical vulnerability which has not yet been successfully addressed. BadUSB attacks are based on reprogramming the firmware of a USB device. This paper presents Spyduino, a properly programmed Arduino appearing as a Human Interface Device (HID), which can operate in most of the common operating systems (OSs). Spyduino exploits the BadUSB vulnerability in order to gain access to sensitive data and send information to the cloud via FTP. In this implementation, Spyduino is embedded in a USB keyboard and sends sensitive OS and user information to an FTP server without user permission. Various countermeasures are discussed and potential extensions are presented.

The use of mobile devices in secondary education is an emerging trend which introduces new ways of teaching and learning when applied according to the respective educational and legal regulations. In this study, we focus on the design, development, presentation and evaluation of an application, named “EduApp”, which uses smartphones and tablets and which is addressed to secondary education teachers and students, during or outside the classroom settings. The ulitmate goal of EduApp is to support any lesson by providing interaction and collaboration between all the involved in the education process. In this paper, we present the technical and usability evaluation by experts that we performed before the implementation of the first version of EduApp in real classroom conditions. The evaluation results indicate, among others, a stable and easy to use application that does not increase the users' cognitive load.

LoRaWAN is a recently proposed MAC layer protocol which manages communications between LoRa-based gate-ways and end-devices. It has attracted much scientific attention due its physical layer characteristics, but mainly due to its versatile configuration parameters. However, it is known that LoRaWAN-based transmissions suffer from extensive collisions due to the unregulated access to the medium. For this reason, various techniques that alleviate the burst of collisions have been proposed in the literature. In this paper, we deal with the problem of fast data delivery in LoRa-based networks. We model a network where transmissions follow a Poisson process. We compute the average packet success probability per Spreading Factor (SF) assuming orthogonal transmissions. We, then, formulate an SF optimization problem to maximize the success probability given an amount of data per node and a maximum data collection time window. We show - both theoretically and using simulations - that the overall success probability can be improved by approximately 100% using optimal SF assignments. We validate our findings using a 10-node testbed and extensive experiments. Despite that experiments reveal the existence of inter-SF interference, our solution still provides the best performance compared to other LoRaWAN configurations.

Recently, D/DoS attacks have been launched by zombie IoT devices in smart home networks. They pose a great threat to network systems with Application Layer DDoS attacks being especially hard to detect due to their stealth and seemingly legitimacy. In this paper, we propose ForChaos, a lightweight detection algorithm for IoT devices, which is based on forecasting and chaos theory to identify flooding and DDoS attacks. For every time-series behaviour collected, a forecasting-technique prediction is generated, based on a number of features, and the error between the two values is calculated. In order to assess the error of the forecasting from the actual value, the Lyapunov exponent is used to detect potential malicious behaviour. In NS-3 we evaluate our detection algorithm through a series of experiments in flooding and slow-rate DDoS attacks. The results are presented and discussed in detail and compared with related studies, demonstrating its effectiveness and robustness.

Blended and computer supported collaborative learning (CSCL) are contemporary trends that are constantly and rapidly evolving. In parallel, digital games are considered to be excellent tools for teaching and learning and offer an engaging and interesting way of participating and learning. For example, games like Kahoot! can be a very good choice for teaching university students. In this study, we leverage Kahoot!'s features by implementing in the learning process the Quiz and Jumble types of games, during the laboratory part of the "Web Technologies" course. Also, we use the Challenge feature to assign homeworks for further engagement. Finally, we gather the students' opinions about this blended type of teaching and learning by using a suitably adjusted questionnaire. The results are very positive since students think of Kahoot! as a useful learning tool.

The IEEE 802.15.4 Time Slotted Channel Hopping (TSCH) networks suffer considerably from the high interference caused by the presence of nearby external devices, such as from the presence of IEEE 802.11b/g/n Access Points. Frequency hopping and blacklisting of radio channels that temporarily or consistently present bad performance are the two main approaches to cope with interference and increase the chances of successful packet delivery. However, the blacklisting of a number of channels and the scheduling of transmissions so that two or more neighboring links do not use the same frequency at the same time is a challenging problem, since in IEEE 802.15.4 TSCH many parallel transmissions may occur. Blacklisting algorithms may be applied either locally or globally in IEEE 802.15.4 networks. In this paper, we first present the weaknesses of a localized blacklisting solution presented in the literature for multi-hop networks, and we propose a new distributed solution to overcome these issues. Both analytical and simulation evaluation under heavy interference show the superiority of the proposed scheme. In particular, the packet delivery ratio is improved while achieving minimum delay.

Time Slotted Channel Hopping (TSCH) has been proposed in various wireless protocols as a solution to combat external interference, path-loss fading and static jamming attacks. However, since TSCH algorithms generate a deterministic and periodic pattern of channel hops, they are still subject to jamming attacks. Proactive randomization of the channel generation process could provide a good solution against jamming attacks, however due to the strict time constraints of the timeslots, practical solutions should be very efficient. In this paper, we propose R-TSCH, a randomized radio channel generation algorithm that can be used to proactively protect wireless nodes from jamming attacks. Based on a cryptographic hash function and a secret key, R-TSCH produces a new pseudo-random channel sequence, which looks as truly random to anyone who has no access to the key. Our simulation results show that the attacked links of the TSCH network enhanced with the proposed mechanism can achieve an over 90% Packet Reception Rate (PRR) in presence of multiple jammers.

One of the most recent and reliable MAC protocols for low-rate wireless personal area networks is the IEEE802.15.4-TSCH. The formation of an IEEE802.15.4-TSCH network depends on the periodic transmission of Enhanced Beacons (EBs), and, by extension, on the scheduling of EB transmissions. In this paper, we present and analyze a negative phenomenon that can occur in most of the autonomous EB scheduling methods proposed in the literature. This phenomenon, which we call full collision, takes place when all the neighboring EB transmissions of a joining node collide. As a consequence, a node may not be able to join the network fast, consuming a considerable amount of energy as well. In order to eliminate collisions during EB transmissions, and, thus, to avoid the occurrence of this phenomenon, we propose a novel autonomous collision-free EB scheduling policy. The results of our simulations demonstrate the superiority of our policy compared to two other recently proposed policies.

In this paper we present some important factors affecting peer assessment of student presentations in a graduate course. The course was titled “Advanced Information Systems” and was offered during the autumn semester of the academic year 2015-16 by the University of Piraeus. The sixty-one postgraduate students taking the course participated in this research. Students cooperated in groups of two or three in order to present a topic selected from a textbook relevant to the material that had already been taught in the class. Participants had to attend their peers' presentations and assess them using a single-page questionnaire. The questionnaire contained 19 closed five-point Likert scale questions plus some demographic questions. This peer assessment was also compared to the instructor's assessment who used the same questionnaire. The research revealed that: a) students' grades span a very narrow range in the grading scale (0-5), i.e., from 3.5 to 4.5; b) male students graded their peers more generously (higher) than female students; c) elder students graded their peers more generously than younger students; d) peer assessment grades did not depend on whether the students had to make a presentation or they had to do a simulation project; e) students who had already presented graded their peers more generously than those who had not presented yet; and finally, f) students gave different grades to the members of each group.

This paper aims to investigate, classify and establish appropriate benchmarks for visual programming codes. For the present study we have relied on the use of the Scratch-2 visual programming language. Scratch-2 is very popular as an introductory programming language at primary education and at the first years of secondary education in Greece. Initially, an evaluation framework, named VPLEF (Visual Programming Languages Evaluation Framework), is constructed based on several selected criteria. Since the observation of the visual code is not easy in the programming environment, we adopted the codOrama tool for a more consistent representation of the Sctrach-2 codes, aiming to identify the code characteristics, which were then associated with the evaluation criteria. We focuson the evaluation criteria of user interactivity, communication and parallelism-linearity of VPLEF and on two groups of commands, namely on “Control” and Event”, in conjunction with the system arguments. The study of the aforementioned entities leads us to a set of specified relationships of each of these three criteria with the command/argument combinations. Finally, an evaluation process is proposed to quantify the contribution of each combination to a specific criterion.

Collaborative learning has become an increasingly popular method of engaging students in the learning process. The activities included in this type of learning focus on the interaction that occurs between users when they are working in groups and they often incorporate solutions to real life problems. Collaborative software development to support this process has grown in popularity over the last years. In this paper, we evaluate software tools that are used in Collaborative Learning and investigate how these software tools can affect the learning process and to what extent they have influenced the educational process. In this study we focus on contemporary collaborative trends, their unique characteristics, and their assimilation and implementation to education and we propose learning activities that exploit their advantages. The results, among others, depict the significant extent of new technological achievements' effect on the educational process.

The purpose of this article is to investigate how to design and organize Science, Technology, Engineering and Mathematics (STEM) courses for students of Technical Vocational Education and Training (TVET). Our work has been triggered by the fact that the Greek government following European standards for training has enacted a two-hour STEM course for the first class of the technical high schools. Through an enriched learning environment, we analyze the teaching mechanisms as well as the actions that should be implemented with the intention of supporting vocational educational students to acquire the best preparation for the STEM courses. We present several learning strategies that utilize educational technologies in order for the students and the teachers of TVET to achieve the optimum adaptation.

This paper presents the Open Models Laboratory (OMiLAB), a modeling method engineering space destined for education and research in the domain of conceptual modeling. Besides a short description of the lab's conceptualization lifecycle and how it is employed for educational purposes, the paper outlines three application examples from business process management, from education, and information systems security as they were presented in a workshop held during the IEEE EDUCON 2017 conference.

In this paper, we extend previous work on the use of ontologies as a tool in teaching geometry. As ontologies gather the information in a well-organized form, where relations between geometrical objects are exposed and explained, we took advantage of the properties of the circle's central and inscribed angles, we connected them to the notion of the right angled triangle and created the liaison between the two ontologies of the circle and the right angled triangle. The students undertook activities that allowed them to observe, cooperate, speculate, verify and connect geometrical meanings with mathematical concepts. This process allowed the students to realize that mathematics is a subject worthy of exploration and not just the memorization of properties of a geometrical object.

In this paper we review previous works done with respect to Conference Key Distribution Systems (CKDS). We focus on the system proposed by Kim et al. and we propose improvements on that scheme a) from the perspective of security and anonymity, b) from the perspective of efficient calculation of the Lagrange polynomial coefficients, and c) from the perspective of adaptation into the dynamic wireless ad hoc network. The security of the proposed scheme is based on the difficulty of computing discrete logarithms over elliptic curves, the intractability of inverting a one-way hash function and the pseudo-randomness of user coordinates. We demonstrate the effectiveness of the proposed scheme through the analysis of characteristic attack scenarios.

A major advantage of wirelessly powered devices is the use of wire-free and sometimes battery-free nodes that can operate for extremely long times. However, to achieve infinite network lifetime a set of chargers is needed to periodically transmit energy to the nodes through the emission of RF signals. In this paper, we study the problem of finding the optimal number of chargers so that a group of nodes can operate without using power sources other than wireless charging. We show that this problem is equivalent to the set-cover problem which is NP-Complete. We propose an efficient heuristic that bypasses the high computational cost of finding the overlapping segments of the harvesting sensor disks and we compare to optimal and non-optimal set-cover solutions. The results show significant performance gains in terms of execution time while keeping the number of chargers close to the optimal.

In this paper we explore ways that the semantic web may provide a different perspective on the educational process in the field of Mathematics. First, we present a general overview of ontologies and the use of the semantic web in the field of mathematics. Then, we analyze a particular geometry problem using semantics, and we point out the added value of semantics to the teaching process in comparison to the traditional teaching techniques. Finally, we present the applicability of the presented concept in a wider setting within the education procedures.

As network complexity and heterogeneity have increased dramatically in the last decade, modern policy-based management techniques for adaptive routing decisions regarding path selection optimization and intelligent path control are necessary. In this paper, we analyze the application performance requirements, and the event-based management options for adaptive routing. Then, we propose an innovative model to monitor the appropriate indicators with the suitable detectors, which improves the dynamic routing performance. We present the design and implementation of Performance-based and Event-Management Routing (PEMR) model and we validate the proposed model by enforcing the appropriate adaptive routing policies and decisions. PEMR can resolve failed or poorly performance paths into alternative routing paths automatically and it can adapt quickly to dynamic network conditions. Besides, we can avoid any conflicting policies (i.e. traffic load distribution versus cost minimization, path availability versus response time), and facilitate the optimum path selection.

In this paper, we propose a highly modular cross-layer architectural solution for the design and implementation of self-protected and self-organized Mobile Ad hoc NETworks (MANETs). In the absence of infrastructure we exploit the capabilities provided by cooperation towards autonomic and informed decision-making of the ad hoc nodes. The proposed generic framework flexibly combines local operational and global cooperative components. We highlight the details of the clustering sub-layer designed with intruder detection capability. Simulation results show the applicability and the effectiveness of the proposal in the MANET environment.

This paper describes a file storage service for elearning platforms using object oriented logic in a cloud computing environment. The service can be used by an academic community giving users the ability to store remotely and access their personal files with no security compromises. The Learning Research Management (LRM) innovative system is introduced and a technological assessment of this system is proposed and implemented using a statistical evaluation process. The conducted process is based on the perceptions from using the system by the involved student population. This process leads to an iterative decision making phase to further improve the system.

Unisuite is an integrated suite of applications for the creation and management of e-learning. It consists of three state-of-the-art stand-alone entities, Unibook, Uniboard and UniPM, which communicate via smart interfaces. In this paper, the techntechnological and operational innovationsical characteristics of Unisuite are presented. The technological and operational innovations are analyzed and potential extensions and improvements are presented.

In this paper we propose a secure anonymous voting scheme (SAnoVS) for re-clustering in the ad-hoc network. SAnoVS extends our previous work of degree-based clustering algorithms by achieving anonymity and confidentiality of the voting procedure applied to select new cluster heads. The security of SAnoVS is based on the difficulty of computing discrete logarithms over elliptic curves, the intractability of inverting a one-way hash function and the fact that only neighboring nodes contribute to the generation of a shared secret. Furthermore, we achieve anonymity since our scheme does not require any identification information as we make use of a polynomial equation system combined with pseudo-random coordinates. The security analysis of our scheme is demonstrated with several attacks scenarios.

In broadcast systems a central server collects client queries for a given set of data items and schedules the next broadcast accordingly. Since anonymity has been shown to promote user participation, the client queries do not contain a client ID. However, this choice leaves ample room for service misuse. This paper identifies a number of prospective attacks and quantifies their impact on the performance of the system. A novel query filtering mechanism named Sensor Swarm is introduced to tackle these attacks. Extensive simulations show that the proposed scheme can ensure smooth system operation even under heavy attacks. Thus, a broadcast system that employs the Sensor Swarm filtering scheme can sustain excessive client misbehavior before resolving to Turing tests or compromising user anonymity.

In this paper, an integrated framework is proposed which covers synchronous and asynchronous education using several Web 2.0 tools and which takes into account several existing principles, views and strategies. Furthermore, this framework embeds self-evaluation mechanisms that are based on the performance of students, on answers to appropriately structured questionnaires and on the on-line monitoring of the supporting platform's parameters.

Text-based passwords, despite their well-known drawbacks, remain the dominant user authentication scheme implemented. Graphical password systems, based on visual information such as the recognition of photographs and / or pictures, have emerged as a promising alternative to mitigate reliance on text passwords. Nevertheless, despite the advantages offered they have not been widely used in practice since many open issues need to be resolved. In this paper we propose a novel graphical password scheme, NAVI, where the credentials of the user are his username and a password formulated by drawing a route on a predefined map. We analyze the strength of the password generated by this scheme and present a prototype implementation in order to illustrate the feasibility of our proposal. Finally, we discuss NAVI's security features and compare it with existing graphical password schemes as well as text-based passwords in terms of key security features, such as password keyspace, dictionary attacks and guessing attacks. The proposed scheme appears to have the same or better performance in the majority of the security features examined.

ABSTRACT The TwoHop trust framework is a collaborative system for computing trust towards service providers in a peer‐to‐peer network. TwoHop participants share their trust information so that peers without prior interaction may establish indirect trust relationships. TwoHop imposes a limit of two hops on trust delegation chains, which allows for increased efficiency in the trust calculation process. In addition, it provides multiple edges between nodes in the trust graph, allowing for the existence of both service evaluations and recommendations for service evaluators. In this paper, we present an improved version of the TwoHop trust calculation algorithm along with a formal description of its model of trust. We evaluate its key characteristics against those of other trust frameworks and compare it with the EigenTrust algorithm and to an improved version of the PeerTrust algorithm in terms of performance. Our simulation results indicate the robustness of our design against dishonest participants and its ability to scale to accommodate the needs of large peer‐to‐peer networks. Copyright © 2011 John Wiley & Sons, Ltd.

The ever-increasing use of information systems and networks in every aspect of our lives has made possible the transfer of data to a wide range of different users and applications. In recent years, several architectures and models have been proposed in order to limit access to resources and ensure that data are available only to authorized users, programs or processes. These models in most cases are not dynamic and the permissions assigned to users are granted based on a static policy. A mechanism that will allow exception access to data, for example to medical information, in case of an emergency is needed. In current systems, emergency access techniques are not well defined and are used in an ad hoc manner on top of the access control mechanisms implemented without using parameters such as time, location or hierarchy of the actors involved in the system. In this paper, we present a model that provides both a normal access control based on roles and also a mechanism that is used in order to provide exception access to data in case of an emergency. The proposed emergency access mechanism is time aware and takes into account the mobility and location of users, also it grants exception access with a controlled manner in case of an emergency utilizing role hierarchies.

Purpose The purpose of this paper is to introduce a new tool which detects, prevents and records common web attacks that mainly result in web applications information leaking using pattern recognition. It is a cross‐platform application, namely, it is not OS‐dependent or web server dependent. It offers a flexible attacks search engine, which scans http requests and responses during a webpage serving without affecting the web server performance. Design/methodology/approach The paper starts with a study of the most known web vulnerabilities and the way they can be exploited. Then, it focuses on those web attacks based on input validation, which are the ones the new tool detects through pattern recognition. This tool acts as a proxy server having a simple GUI for administration purposes. Patterns can be detected in both http requests and responses in an extensible and manageable way. Findings The new tool was compared to dotDefender, a commercial web application firewall, and ModSecurity, a widely used open source application firewall, using over 200 attack patterns. The new tool had satisfying results for every attack category examined having a high percentage of success. Results for stored XSS could not be achieved since the other tools are not able to search and detect them in http responses. The fact that the new tool is very extensible, it makes it possible for future work to be done. Originality/value This paper introduces a new web server plug‐in, which has some advanced web application firewall features with a flexible attacks search engine which scans http requests and responses. By scanning http responses, attacks such as stored XSS can be detected, a feature that cannot be found on other web application firewalls.

Purpose The paper proposes looking at the automation of the incident response (IR) process, through formal, systematic and standardized methods for collection, normalization and correlation of security data (i.e. vulnerability, exploit and intrusion detection information). Design/methodology/approach The paper proposes the incident response intelligence system (IRIS) that models the context of discovered vulnerabilities, calculates their significance, finds and analyzes potential exploit code and defines the necessary intrusion detection signatures that combat possible attacks, using standardized techniques. It presents the IRIS architecture and operations, as well as the implementation issues. Findings The paper presents detailed evaluation results obtained from real‐world application scenarios, including a survey of the users' experience, to highlight IRIS contribution in the area of IR. Originality/value The paper introduces the IRIS, a system that provides detailed security information during the entire lifecycle of a security incident, facilitates decision support through the provision of possible attack and response paths, while deciding on the significance and magnitude of an attack with a standardized method.

The advent of Wireless Body-Area Sensor Networks (WBASNs) technologies enables the autonomic and remote collection of realtime physiological data related to the health status of patients with chronic diseases. At the same time the advances in wireless communication systems make possible the "anywhere, anytime" delivery of such data to medical staff and caregivers in order to allow them to easily monitor and quickly respond in emergencies. In this paper, we propose a system architecture that utilizes the IMS (IP Multimedia Subsystem) and the HL7 (Health Level Seven) technologies to implement a mobile and interoperable healthcare system to support WBASNs in a healthcare environment.

Abstract While the traditional data shipping systems use physical information to organize data, a newer data caching technique maintains both associated answers (data items) of previous queries and their meaning (purpose). This form of information description is called semantic description, and it makes it possible to reason about and derive knowledge from the given description. In a distributed heterogeneous environment, such as the mobile environment, the semantic data caching paradigm is an important technique for improving the performance of wireless data dissemination systems. Data caching performance depends heavily on the replacement policy being used for the cache management. However, future location uncertainty, limited client resources and frequent client disconnections make cache management a challenge. This paper proposes a future location‐aware cache replacement policy to manage a semantic cache. The proposed replacement policy uses the validity of the data fetched from the server and the neighboring locations to decide which of the cache entries is less likely to be needed in the future, and therefore a good victim for eviction when cache space is needed. The replacement policy's preference for cached items to be evicted is modeled as a general function that declines with distance between the mobile user's current location and the candidate for replacement cached item's bound location. For better efficiency, the overall replacement granularity is dynamically achieved along three levels: ring, cell and data item. Simulation study of the proposed approach shows that it outperforms both the least recently used (LRU) and furthest away replacement (FAR) schemes, where only temporal locality is considered. Moreover, the proposed scheme is easier to implement than other research and development proposals. Copyright © 2008 John Wiley & Sons, Ltd.

Communications are increasingly relying on peer-to-peer models of interaction in which all participating entities have the same level of authority. Such models allow developed systems to overcome single points of failure, since there is no central management of security parameters. In order to select trustworthy service providers, peers in such environments require collaborative metrics that build trust relationships based on evidence of previous interactions. In this paper, we present a collaborative metric and an algorithm for the evaluation of trust in peer-to-peer networks called TwoHop. Our proposal requires no central management and scales to accommodate the fundamental need for growth that characterises peer-to-peer systems. Our experimental analysis and simulation results indicate the robustness of our design against dishonest participants and its ability to flexibly accommodate the needs of majorities.

Object replacement strategies are considered as key performance factors of a web proxy caching application. Several algorithms have been proposed, analyzed and simulated during the last decade, in order to decide upon the champion one. In this paper, we recommend the methodology of Data Envelopment Analysis as a powerful tool, with a complementary activity to that of trace driven simulation, which is able to discover the set of the `good-enough' replacement strategies ­ i.e. strategies that exhibit good results for the basic performance metrics ­ under a variety of simulated workloads. Web caching; proxy; replacement; strategies/policies; Data Envelopment Analysis; I.

Cache management in a real world mobile user system is too complex to allow for an analytical evaluation through a realistic mobility model. The recently proposed location-dependent applications request the design of simulation and the development of internet benchmarks. This paper presents the design of a random walk simulator that captures the movement of mobile users in Personal Communications Services (PCS) networks. A novel mathematical model is used and the validity of the data fetched from the server to identify a reduced subset of neighboring cells used to simulate the data caching computing paradigm for mobile computing. We demonstrate the capabilities of the simulator by simulating three key cache management replacement policies and measure the cache hit ratio performance.

Data retention refers to the legal obligation of Internet service providers (ISPs) to retain the communication data of their subscribers for a certain period, in order to enable the legal investigation of possible crimes. However, the retention of communication data increases the security threats against the privacy of theirs subscribers. In this paper we explore the privacy issues of data retention in Internet communications. We also describe possible security mechanisms which may thwart these threats and minimize the risks against user privacy.

Information systems are slowly, but steadily, affecting every aspect of our life. For the last few years, their application and penetration in the e-government sector has been constantly increasing. Governmental organisations and citizens alike place a great amount of expectations concerning improved, quality and secure enterprise services in e-government platforms. This effort, however, needs coordinated support from all the different stakeholders in the domain, which in turn requires that a common vehicle of communication must be developed and used. This vehicle is the information system's architecture. In this paper, we present a framework for modelling distributed systems architectures which has been standardised by ISO and we apply it to the design of the enterprise specification of an e-government platform, which is under development. We analyse the process of modelling a system and continue by proposing an extension to the modelling concepts of the framework with terminology specifically tailored for and inspired by the e-government domain. Several open research issues are identified and analyzed.

In this paper, we introduce a 2-level distributed database architecture combined with the Group Registration (GR) location tracking strategy to be used in 3G wireless networks. With this strategy, the total location management cost is reduced by updating the location of MTs (Mobile Terminals) in an RA with a single route response message to the HSS (Home Subscriber Server). The Location Registration and Call Delivery procedures are presented in detail. The extensive analysis of the numerical results shows that the GR strategy integrated with a 2-level distributed databases architecture in 3G networks can achieve a significant reduction of the total cost per call arrival, as well as, a reduction of the call delivery latency, compared to the corresponding costs of the distributed databases without the GR strategy and the GR strategy without distributed databases.

Purpose Security information management systems (SIMs) have been providing a unified distributed platform for the efficient management of security information produced by corresponding mechanisms within an organization. However, these systems currently lack the capability of producing and enforcing response policies, mainly due to their limited incident response (IR) functionality. This paper explores the nature of SIMs while proposing a set of requirements that could be satisfied by SIMs for the efficient and effective handling of security incidents. Design/methodology/approach These requirements are presented in a high‐level architectural concept and include policy visualization, system intelligence to enable automated policy management, as well as, data mining elements for inspection, evaluation and enhancements of IR policies. Findings A primitive mechanism that could guarantee the freshness and accuracy of state information that SIMs provide in order to launch solid response alarms and actions for a specific incident or a series of incidents is proposed, along with a role based access control administrative model (ARBAC) based on a corporate model for IR. Basic forensic and trace‐back concepts that should be integrated into SIMs in order to provide the rich picture of the IR puzzle are also examined. Practical implications The support of policy compliance and validation tools to SIMs is also addressed. Originality/value The aforementioned properties could greatly assist in automating the IR capability within an organization.

In a mobile wireless environment, the latency (time-delay) observed by a user before s/he receives up-to-date information may be high because of the limited available bandwidth. An efficient prefetching strategy must be tailored to the competing goals of keeping latency low (which requires more prefetching) and reducing resource waste in a mobile environment, which is characterized by scarce bandwidth and resource-poor user devices. Current research is based on the tangent velocity approach, which is effective only within a short time interval and has a high cost of continuous geometric estimations.This paper proposes a cache management method that maintains the mobile terminal's cache content by prefetching data items with maximum benefit and evicting cache data entries with minimum benefit. The data item benefit is evaluated based on the user's query context defined as a set of constraints (predicates), which define both the movement pattern and information context requested by the mobile user. A context-aware cache is formed and maintained using a set of neighboring locations (we call the prime list) restricted by the validity of the data fetched from the server. Simulation results show that the proposed strategy using different levels of granularity can greatly improve the system performance in terms of cache hit ratio.

While the traditional data shipping systems use physical information to organize data, a newer data caching technique maintains both associated answers (data items) of previous queries and their meaning (purpose). This form of information description is called semantic description, and it makes it possible to reason about and derive knowledge from the given description. In a distributed heterogeneous environment, such as the mobile environment, the semantic data caching paradigm is an important technique for improving the performance of wireless data dissemination systems. Data caching performance depends heavily on the replacement policy being used for the cache management. However, future location ambiguity, limited client resources and frequent client disconnections make cache management a challenge. This paper proposes a future location-aware cache replacement policy to manage a semantic cache. The proposed replacement policy uses the validity of the data fetched from the server and the neighboring locations to decide which of the cache entries is less likely to be needed in the future, and therefore, a good candidate to be evicted when cache space is needed. The replacement policy's preference for cached items to be evicted is modelled as a general function that declines with distance between the cell the candidate for replacement's cached item is bounded to and the query's bound cell. For better efficiency the overall replacement granularity is dynamically achieved along three levels: ring, cell and data item. Simulation study of the proposed approach shows that it outperforms both the least recently used (LRU) and furthest away replacement (FAR) schemes, where only temporal locality is considered. Moreover, the proposed scheme is easier to implement than the industry standard policies

In mobile networks, the location of a mobile user needs to be traced for successful and efficient call delivery. In existing cellular networks, as a mobile user changes his/her location area (LA), a location registration request is sent to the home location register (HLR) to update the user profile to point to the new LA. With a large number of mobile subscribers, this conventional registration strategy will incur a high volume of signaling traffic. We propose a new location registration strategy, called Group Registration (GR), which efficiently reduces the location registration cost by reporting location changes to the HLR for multiple mobile terminals (MTs) in a single location update request message. Specifically, the IDs of the MTs newly moving into an LA are buffered and sent to the HLR for location update in the route response message of the next incoming call to any MT in the LA. An analytic model is developed and numerical results are presented. It is shown that the proposed GR strategy can achieve significant cost reductions compared to the conventional strategy and the local anchor strategy over a wide range of system parameters. Moreover, the GR strategy results in a much smaller call delivery latency than the local anchor strategy.

Existing MANET authentication schemes cannot fully protect nodes from well-known impersonation attacks. Although these schemes cryptographically link an entity to a claimed identity, the actual entity is never linked to the physical node device. However, the link is implicitly assumed. This shortcoming may be easily exploited within a MANET setting, due to the broadcast nature of the access medium. In this paper we propose a multifactor authentication framework that extends the cryptographic link, binding an entity to a physical node device. This is achieved by using two distinct authentication factors; certified keys and certified node characteristics. Although the proposed framework requires additional sensing capabilities from the MANET nodes, it provides the additional confidence level required for node authentication in critical applications.

Recent work on key establishment for sensor networks has shown that it is feasible to employ limited elliptic curve cryptography in sensor networks through hybrid protocols. We propose a hybrid key establishment protocol for uniform self-organized sensor networks. The proposed protocol combines elliptic curve Diffie-Hellmann key establishment with implicit certificates and symmetric-key cryptographic techniques. The protocol can be implemented on uniform networks comprised of restricted functional devices. Furthermore, due to its public-key nature, the protocol is resilient to a wide range of passive and active attacks, such as known-key attacks, as well as attacks against the confidentiality, integrity and authenticity of the communication. The protocol is scalable and efficient for low-capability devices in terms of storage, communication and computational complexity; the cost per node for a key establishment is reduced to one scalar multiplication with a random point, plus one with a fixed point.

The next-generation mobile network will support terminal mobility, personal mobility, and service provider portability, making global roaming seamless. A location-independent personal telecommunication number (PTN) scheme is conducive to implementing such a global mobile system. However, the nongeographic PTNs coupled with the anticipated large number of mobile users in future mobile networks may introduce very large centralized databases. This necessitates research into the design and performance of high-throughput database technologies used in mobile systems to ensure that future systems will be able to carry efficiently the anticipated loads. This paper proposes a scalable, robust, efficient location database architecture based on the location-independent PTNs. The proposed multitree database architecture consists of a number of database subsystems, each of which is a three-level tree structure and is connected to the others only through its root. By exploiting the localized nature of calling and mobility patterns, the proposed architecture effectively reduces the database loads as well as the signaling traffic incurred by the location registration and call delivery procedures. In addition, two memory-resident database indices, memory-resident direct file and T-tree, are proposed for the location databases to further improve their throughput. Analysis model and numerical results are presented to evaluate the efficiency of the proposed database architecture. Results have revealed that the proposed database architecture for location management can effectively support the anticipated high user density in the future mobile networks.

In this paper, a new location registration strategy - group registrations for mobile networks is proposed, in which instead of sending a location registration request to the home location register (HLR) for each registration area (RA) change of a mobile terminal (MT), the identifications of the MTs newly moving into an RA are buffered and sent to the HLR for location registration when the next incoming call to the RA occurs, i.e., the buffered MT identifications are forwarded to the HLR in the route response message of the call. Upon RA change, a forwarding pointer is set up from the MT's local anchor to its new visitor location register (VLR), so that incoming calls to the MT can be delivered before the MT's local anchor is changed to its current VLR via the next group registration. An analytic model is developed and numerical results are presented. It is revealed that compared to the conventional RA-based location registration scheme, the group registration strategy can achieve a significant cost savings over a wide range of system parameters.

The development of efficient quality of service (QoS) routing algorithms in a high-speed network environment is a very important and at the same time very difficult task due to the need to provide divergent services with multiple QoS requirements. Heuristic algorithms based on Lagrange relaxation techniques have been proposed to resolve the contradiction between the time complexity and the quality of solution. We investigate the performance of two heuristic algorithms, LR/spl I.bar/DCLC and NR/spl I.bar/DCLC, for the delay-constrained least-cost (DCLC) routing problem. Algorithm LR/spl I.bar/DCLC is based on linear relaxation, while algorithm NR/spl I.bar/DCLC, which is proposed in this paper, is based on nonlinear relaxation. A large number of simulations demonstrate that even though both algorithms have very good performance, NR/spl I.bar/DCLC can obtain much better solutions than LR/spl I.bar/DCLC by running Dijkstra's (1959) algorithm on average a few more times, especially in the case when the optimal solutions are hard to find.

The problem of finding a path with two additive constraints is called a multi-constrained path (MCP) problem in the literature. In this paper, we explore the MCP problem based on the idea of single mixed weight. Given two infeasible paths, it can be theoretically proved that a better path can possibly be found if we choose an appropriate parameter to construct the mixed weight. An approximate algorithm is thus proposed to solve the MCP problem. A large number of experiments on networks of different sizes demonstrate that this algorithm can make a correct judgment whether there is a feasible path or not with a very high probability. On the other hand, the time complexity of this algorithm is very small since it only needs to execute Dijkstra's algorithm a limited number of times even for a network of relatively large size.

A user location information distribution strategy is proposed for mobile systems. Local anchors (LAs), replicated databases and forwarding pointers are applied in an integrated way that greatly reduces the location update rate and the call delivery cost incurred by location tracking. In particular, the visitor location registers (VLRs) associated with a user's home and workplace are selected as the user's LAs, which are connected by a forwarding pointer chain. When the user changes their registration area (RA) within a local signal transfer point (LSTP) region, the new location is reported to the home location register (HLR) and to the replicas. In the call delivery procedure, if a call orginates from one of the LAs or replicas, the HLR does not need to be queried. An analytic model is developed and numerical examples are given to compare the performance of the proposed scheme, the standard scheme, the replication scheme and the local anchoring scheme. The results show that the proposed strategy outperforms the other three strategies over a wide range of system parameters.

We have elsewhere developed a general method called the stable state analysis technique to determine constraints that the weights in the Hopfield energy function must satisfy so that valid solutions of high quality can be always obtained. In this paper, the effectiveness of this method is demonstrated through a reinvestigation of the capability of the Hopfield neural net (HNN) to solve the traveling salesman problem (TSP). A large number of experiments on 10-city TSPs demonstrate the proposed method can obtain results comparable to those obtained using simulated annealing, while the mean error of achieved solutions to a 51-city TSP is about 15% longer than the optimal tour, which is much better than that of solutions obtained through other HNN-based methods.

This paper introduces a distributed hierarchical database architecture for location management in global personal communications system (PCS) networks with the location-independent numbering plan. The proposed structure consists of a number of database subsystems, each of which is a three-level tree structure and is connected to the others only through its root. Due to the localized nature of calling and mobility patterns, this scheme effectively reduces the database loads and signaling traffic incurred by the location update and call delivery procedures. Moreover, based on the flat numbering plan, two memory-resident access structures-the memory-resident direct file and the T-tree are proposed for the location databases to further improve the database throughput. Analytical models and numerical examples are presented to evaluate the response time and the storage capacity required for each location database. Results show that our method can produce a high-throughput database system, which is crucial for the deployment of high-capacity PCS systems in the future. In addition, modifications to the data structure, the insert algorithm, and the delete algorithm for the T-tree are proposed to enhance the performance of the T-tree.

Several working or experimental management systems use expert systems techniques for fault management purposes. Although the effort in the area is still growing, most of the expert fault management systems developed were built in an ad-hoc and unstructured basis simply transferring the knowledge of the human expert into an automated system. However, to meet future challenges, a theoretical foundation for fault management must be established aiming to bridge the gap between the working systems and research, and to provide a general structured model easily expandable to future networks. In this paper an algorithm is proposed to simplify the set of clustered alarms. This algorithm is based on the techniques widely used in the logic design field to simplify switching functions. The performance of the proposed algorithm is analyzed and the results are compared to those of a traditional algorithm.

Mobility tracking is to keep track of the users locations for call delivery. In standards, such as IS-41 and GSM, the two level hierarchy of location databases is used: the home location register (HLR) and the visitor location register (VLR). As the number of mobile subscribers increases, the HLR may become the system bottleneck. To alleviate the burden on the HLR, a number of auxiliary strategies based on the HLR-VLR architecture have been proposed. These strategies include the forwarding strategy (FS), the anchoring strategy (AS), the caching strategy (CS), and the replication strategy (RS). However, each of these strategies is only suitable for a certain type of users with a specific range of call to mobility ratios (CMRs). In reality, a user may change his/her mobility patterns frequently. To cope with such time-varying mobility patterns efficiently, an integrated strategy is proposed. In particular, the VLRs associated with a user's home and workplace, where the user spends considerable time periods, are selected as the user's local anchors (LAs), which are connected by a forwarding pointer chain. The VLRs from which relatively high call rates to the user originate are selected as the replicas. When the user changes registration area (RA) within a local signal transfer point (LSTP) region, the new location is updated at one of the LAs. Otherwise, the new location is reported to the HLR and the replicas. In the call delivery procedure, if a call originates from one of the LAs or replicas, the HLR does not need to be queried. An analytic model that can capture actual user mobility characteristics is used for performance evaluation. Results show that in terms of the end-to-end call setup delay and location update delay, the proposed strategy outperforms the standard scheme used in GSM and IS-41, the RS scheme, and the AS scheme over a wide range of system parameters.

This paper introduces a location-based locating strategy for Personal Communication Services (PCS) systems. In the proposed scheme, location updates are based on the value of a movement counter. The update of the movement counter is based on information on the locations visited by a mobile terminal (MT) since the last location update. In particular, the cell identifiers and the corresponding movement counter values are maintained in the MT for a part of the visited cells since the last location update. When the MT enters a cell whose identifier is not stored in the MT, the movement counter increases by one. If the movement counter reaches the update threshold, a location update is triggered; otherwise, the cell identifier and the corresponding movement counter value are stored in the MT. When the MT enters a cell whose identifier is in the MT, the movement counter is assigned with the counter value kept in the MT for this cell, and all cells with greater counter values in the MT are removed. The proposed scheme allows the dynamic selection of the update threshold according to each user's calling and mobility patterns. Analytical and simulation models have been developed to compare the proposed scheme with both the movement-based scheme and the distance-based scheme. Results demonstrate that when the call-to-mobility ratio (CMR) is low, the proposed scheme can achieve a significant cost reduction compared to the movement-based scheme. For example, when the CMR is 0.01, a savings of around 25% in the optimal total cost per call arrival is achieved with the proposed scheme. Moreover, the proposed scheme is easier to implement than the distance-based scheme.

Routing algorithms are required to guarantee the various quality of service (QoS) characteristics requested by the wide range of applications supported by broadband integrated services digital networks (B-ISDN). However, it is known that such a routing problem, with two or more additive or multiplicative QoS metrics in any possible combination is NP-complete. We propose a heuristic approach based on fuzzy logic. For each metric, a fuzzy membership function is defined to reflect the QoS requirements from that metric. A fuzzy-inference rule base is implemented to generate the fuzzy cost of each path based on the crisp values of the different metrics possibly used in the network links. The proposed approach is tested with different loads and the effect on different measures of performance is analyzed. Simulation results demonstrate the capability of this approach to increase the throughput and utilization of the communication network, and provide a fair distribution of different connection requests.

This paper presents two location tracking strategies (LS-I and LS-II) for personal communications services (PCS) systems. In the proposed schemes, the movement history of a mobile terminal (MT) since the last location update is taken into account in making a location update decision. In particular, before reaching the update threshold the movement counter is increased only after the MT visits a new cell. When the MT revisits a cell since the last location update, in the LS-I scheme the counter remains unchanged, while in the LS-II scheme the counter is assigned with the old counter value when the MT visited this cell last time. Analytic and simulation results demonstrate that when the call-to-mobility ratio (CMR) is low, the proposed schemes can achieve a significant cost reduction compared to the movement-based scheme.

Fault management is used to detect, isolate, and repair problems in communication networks. Alarms are considered an external manifestation of faults occurring inside the managed network. These faults may affect the network's hardware and software components. Alarm correlation identifies the relationships between reported alarms to produce a new, smaller list of alarms. This allows operators to quickly and more accurately to identify the root cause of problems and resolve them faster. Temporal reasoning, reasoning about time, plays a critical role in monitoring network alarms. In this paper, a fuzzy-logic model is proposed for finding the temporal relation between events for correlation purposes. A fuzzy-inference rule base is used to integrate fuzzy membership functions to determine the "best" temporal relation between events. The proposed model is compared to the traditional crisp temporal reasoning.

Routing algorithms are required to guarantee the various quality-of-service (QoS) characteristics requested by the wide range of applications supported by Broadband Integrated Services Digital Networks (B-ISDNs). In this paper the routing problem is formulated as a fuzzy multiobjective optimization model. The fuzzy approach allows for the inclusion and evaluation of several criteria simultaneously. The proposed model takes into consideration the balancing of the load in the network to avoid link saturation and hence the possibility of congestion. The efficiency and applicability of the model are tested under different load conditions by studying several measures of performance.

This paper addresses the unfairness problems of a DQDB network through a structured access remedial scheme, namely the Dynamic Three-Tier protocol. At low load domains, it retains the original 802.6 (no Bandwidth Balancing Mechanism, (BWB) protocol performance. At heavy loads, it activates a dynamic bandwidth control mechanism, called the Alpha Tuning Mechanism. With the right choice of the α parameter, the match of the service pattern (rendered by the proposed protocol) and the actual demand (or traffic) pattern in the network is achieved. Between these domains, at normal loads, it uses an anticipatory demand function (Δ) to address latency-related unfairness. The proposed protocol's performance is investigated over different load types and load values, with single- and multiple-packet-sized messages. In each scenario, the proposed protocol is capable of delivering better performance over the current 802.6 (with BWB) standard. Its effectiveness and dynamic capabilities are very impressive.

In B-ISDN links have to be described in terms of multiple metrics, thus making routing with multiple requirements an extremely difficult problem to tackle. A fuzzy logic approach is proposed to define a fuzzy cost to reflect the crisp values of the different metrics possibly used in the network links. The fuzzy system is then integrated into a complete routing system. Simulation results demonstrate the capability of this approach to increase the utilization and throughput of the communication network, and provide a fair distribution of calls, while offering a small delay.

We present the Expert Network Designer "END" an automated system for large structured computer network design, modeling, simulation and optimization. Obtaining the network environment from the user END employs the formalized network design experience to recommend the network solutions suitable for such environment, explains why such solutions were chosen, and further ranks and evaluates such solutions using artificial intelligence optimization techniques and engineering simulation tools.

Broadband integrated services digital networks (B-ISDN) support a wide range of applications with diverse traffic characteristics. Routing algorithms are required to guarantee the quality of service (QoS) requested by these traffic classes. In this paper, the routing problem is formulated as a fuzzy multiobjective optimization model. The fuzzy approach allows for the inclusion and evaluation of several criteria simultaneously. The proposed model takes into consideration balancing the load in the network to avoid link saturation and hence the possibility of congestion. The model is tested with different loads and the effect on different measures of performance is analyzed.

Communication network design is becoming increasingly complex, involving making networks more usable, affordable, and reliable. To help with this, we have proposed an expert network designer (END) for configuring, modeling, simulating, and evaluating large structured computer networks, employing artificial intelligence, knowledge representation, and network simulation tools. We present a neural network/knowledge acquisition machine-learning approach to improve the END's efficiency in solving the network design problem and to extend its scope to acquire new networking technologies, learn new network design techniques, and update the specifications of existing technologies.

We propose the use of an artificial neural network (ANN) technique for a rate-based feedback controller in asynchronous transfer mode (ATM) networks. A leaky bucket (LB) mechanism is used for cell discarding, when the traffic violates a predefined threshold. Since the network cannot rely on the user's compliance with its declared parameters, it is extremely difficult to select the best threshold value and depletion rate for the LB. We propose an ANN model which monitors the status of the LB and predicts the possible cell discarding at the LB in the near future. The source rate is regulated to a certain amount depending on the feedback signal "strength" when possible cell discarding is detected. The lower the value carried in the feedback cell, the higher the possibility of cell discarding and, subsequently, the higher the probability that the traffic is regulated to a lower rate. Our model considers the propagation delay time of the feedback signal making our approach more realistic. This mechanism is transparent to the source if the LB is correctly set up and the traffic follows its declared parameters. We use the same trained ANN for different MPEG traces and the results of a simulation study suggest that our mechanisms provide simple and effective traffic management for ATM networks. Cell loss rate due to the congestion shows a two to five times improvement compared with the static approach, while transmission delays introduced by our ANN controller are also smaller than in the static approach. Channel utilization is also improved, showing that our mechanisms provides a better alternative to static feedback controllers.

The alpha tuning mechanism for distributed queue dual bus (DQDB) networks is proposed. This mechanism achieves a match between the users' demand and the resulting protocol's service patterns. The use of a tunable /spl alpha/-parameter (representing some fictitious user population) and access protection lead to a dynamic bandwidth control capability. The inherently position dependent fairness problems of DQDB are overcome, especially at heavy loads. Fairly uniform delays and uniform success rates of transmission are seen for every user. Analysis and simulation studies for different load patterns, show that it outperforms the bandwidth balancing mechanism (BBM). This mechanism may be extended to any unidirectional channel, to achieve demand and service pattern match.

This paper addresses the unfairness problems of a DQDB network through an structured access remedial scheme, viz., the dynamic 3-tier protocol. At low load domains, the original DQDB protocol performance is retained. At heavy loads, a dynamic bandwidth control mechanism, named Alpha Tuning Mechanism, is activated. With the right choice of the /spl alpha/-parameter, it is possible to match the service pattern (in terms of channel bandwidth) offered by the access protocol with the actual demand (or traffic) pattern in the network. At low load domains an anticipatory demand function (/spl Delta/) addresses latency related unfairness. The results demonstrate the effectiveness of this approach.>

Iterative flow control algorithms to achieve a Pareto optimal point have been proposed in the telecommunications literature. In this paper, we present several relaxation and estimation techniques to improve the performance of the algorithms. We also explore several possible implementations that extend support to the proposed analytical models. Simulations of these possible implementations are carried out, and the performance of the flow control algorithms studied. The proposed implementations for the Pareto algorithms achieve optimization of the product of powers of individual user classes. The effect of additional factors like the length of the observation cycle, the structure of the observation cycle, and the relaxation factors are also studied. The simulation results suggest that better convergence is achieved when the observation windows are maintained at the node level and are packet count based. The window size has to be sufficiently long. The relaxation techniques are useful with the right choice of relaxation factors. The greedy algorithms using estimation techniques to achieve complete decentralizability are very appealing.

An analytic hierarchy process (AHP) approach that can be used either for the analysis and comparison of the quality of several telecommunications companies, or for the evaluation of alternate technologies in telecommunications is presented. The method is based on pairwise comparison between several factors that affect the quality of service in a hierarchical structure. Two particular formulations are presented and discussed extensively.>

Pareto optimality is studied in the context of multiclass telecommunications networks with constraints on the maximum allowable user delays. The performance objective of each individual class is the maximization of throughput under a delay constraint. Users share the network on a processor sharing basis. The multiobjective problem that arises is solved via a transformation that leads to a multicriterion linear program. The solution method is outlined by a thorough study of a simple example. Pareto optimal solutions are compared on the basis of fairness given to different configurations and traffic characteristics.>

The Nash equilibrium point for optimum flow control in a noncooperative multiclass environment is studied. Convergence properties of synchronous and asynchronous greedy algorithms are investigated in the case where several users compete for the resources of a single queue using power as their performance criterion. A proof of the convergence of a synchronous greedy algorithm for the n users case is given, and the necessary and sufficient conditions for the convergence of asynchronous greedy algorithms are obtained. Another important contribution is the introduction to the literature and the extension of a not very widely known theorem for the convergence of Gauss-Seidel algorithms in the linear systems theory.>

The Nash equilibrium point for optimum flow control in a noncooperative multiclass environment is studied. Convergence properties of asynchronous as well as synchronous algorithms are investigated. The convergence of a greedy algorithm for the n users case is proved, and necessary and sufficient conditions for the convergence of asynchronous algorithms are obtained. Since asynchronous algorithms do not converge for all values of the weighting factors, one must be careful in their choice. An introduction to the literature and an extension of a not very widely known theorem for the convergence of Gauss-Seidel algorithms in the linear systems theory are given.>

Consideration is given to the problem of optimal flow control in a multiclass telecommunications environment where each user (or class) desires to optimize its performance while being fair to the other users (classes). The Nash (1950) arbitration scheme from game theory is shown to be a suitable candidate for a fair, optimal operation point in the sense that it satisfies certain axioms of fairness and is pareto optimal. This strategy can be realized by defining the product of individuals user performance objectives as the network optimization criterion. This provides the rationale for considering the product of user powers, as has been suggested in the literature. For delay constrained traffic, the constrained optimization problem of maximizing the product of user throughputs subject to the constraints leads to a Nash arbitration point. It is shown that these points are unique in throughput space, and the authors also obtain some convexity properties for power and delays with respect to throughputs in a Jackson network.>