Janez Bester

A survey on clustering algorithms for vehicular ad-hoc networks

In the past few years we are witnessing increased interest in the research of inter-vehicle communications. Due to vehicle specific movement patterns new algorithms and solutions have to be developed. Clustering is a technique for grouping nodes in geographical vicinity together, making the network more robust and scalable. This article presents an overview of proposed clustering algorithms for use in vehicular ad-hoc network (VANET). We survey different clustering algorithms and highlight their objectives, features, specialties and possible limitations. Varieties of different approaches have been observed whereby typically each one focuses on different performance metric. Diverse are also complexities of algorithms and the input data they use and relay on. With this article, readers can have a more thorough and delicate understanding of ad hoc clustering and the research trends in this area. The most promising solutions show the significance of reused concepts from the field of social network analysis.

Introduction to the Artificial Neural Networks

An Artificial Neural Network (ANN) is a mathematical model that tries to simulate the structure and functionalities of biological neural networks. Basic building block of every artificial neural network is artificial neuron, that is, a simple mathematical model (function). Such a model has three simple sets of rules: multiplication, summation and activation. At the entrance of artificial neuron the inputs are weighted what means that every input value is multiplied with individual weight. In the middle section of artificial neuron is sum function that sums all weighted inputs and bias. At the exit of artificial neuron the sum of previously weighted inputs and bias is passing trough activation function that is also called transfer function (Fig. 1.).

Routing in ISL networks considering empirical IP traffic

Next-generation satellite networks are expected to provide a variety of applications with diverse performance requirements, which will call for the development of adaptive routing procedures supporting different levels of services. In this paper, we propose traffic class dependent (TCD) routing, which has the potential to differentiate between traffic classes using different optimization criteria in route calculation. The performance of TCD routing is evaluated for different traffic scenarios using an empirical traffic source model derived from the real backbone Internet traffic trace and compared with results obtained with equivalent Poisson traffic as a reference point. In addition, TCD routing is compared with a simple single service routing procedure, which does not make any distinction between traffic classes. Performance analysis, in terms of average packet delay, normalized data throughput, and normalized link load, reveals improved routing resulting from traffic class differentiation, regardless of the traffic scenario considered. The performance measures based of aggregate traffic flow show no significant difference between routing of empirical and equivalent Poisson traffic.

IPTV Systems, Standards and Architectures: Part II - Quality-Assured Provisioning of IPTV Services within the NGN Environment

IPTV represents a solution for interactive television-like services. As the NGN has gained attention for the IP multimedia service delivery platform, IPTV has been recognized as the way to provide the key value-added services. However, IPTV differs from typical NGN-based voice and data services by the fact that it combines three conceptually unfamiliar (until now) components: streamed video, Web services, and NGN-based service control. Another difference is in the sense of the quality-assured service delivery that in the case of IPTV is much stricter for two reasons: it is more challenging to meet an end users satisfaction in the case of television services, and there are issues of quality- assured provisioning of real-time multimedia services in an environment that is best-effort in its nature. In this article, possible approaches to NGN- based IPTV services assurance are presented from the QoE and QoS viewpoints. Current environments and an overview of the standardization efforts are given. A proposal for a fully NGN-integrated quality-assured IPTV provisioning model is presented with an associated converged profile structure. The service-aware quality assurance approach is argued. The article investigates further NGN service delivery enhancements for quality-assured provisioning of IPTV services that until now remained unresolved. The objective of this article is to present the design of a realistic quality assurance model, establish the associated framework for NGN-based IPTV services delivery, and contribute to discussions and research activities. At the same time, the conclusions and the proposed models will serve as a framework for future efforts in our laboratory NGN testbed.

Number of microvesicles in peripheral blood and ability of plasma to induce adhesion between phospholipid membranes in 19 patients with gastrointestinal diseases

It was recently shown that the plasma protein-mediated attractive interaction between phospholipid membranes could in the budding process cause adhesion of the bud to the mother membrane [J. Urbanija, N. Tomsic, M. Lokar, A. Ambrozic, S. Cucnik, M. Kanduser, B. Rozman, A. Iglic, V. Kralj-Iglic, Coalescence of phospholipid membranes as a possible origin of anticoagulant effect of serum proteins, Chem. Phys. Lipids 150 (2007) 49-57]. Since in the in vivo conditions the budding of cell membranes leads to the release of microvesicles into the circulation, a hypothesis was put forward that the ability of plasma to cause adhesion between membranes supresses the microvesiculation process. In the present work, this hypothesis was tested in a population of 19 patients with gastrointestinal diseases. The number of microvesicles in peripheral blood of patients was determined by flow cytometry while the ability of plasma to cause adhesion between membranes was determined by adding patients plasma to the suspension of giant phospholipid vesicles created by electroformation method, and measuring the average effective angle of contact between the adhered vesicles. Statistically significant negative correlations between the number of microvesicles and the average effective angle of contact (Pearson coefficient -0.50, p=0.031) and between the number of microvesicles per number of platelets and the average effective angle of contact (Pearson coefficient -0.64, p=0.003) were found, which is in favor of the above hypothesis. Patients with gastrointestinal cancer had larger number of microvesicles (difference 140%, statistical significance 0.033) and smaller average effective angle of contact (difference 20%, statistical significance 0.013) compared to patients with other gastrointestinal diseases.

Integrated component web-based interactive learning systems for engineering

Dynamic web-based learning tools are indispensable in modern teaching, especially considering their capability for interaction on demand as a means of stimulating and engaging students. The experience on which the results reported here are based has grown out of progressive testing of different approaches for publishing technical sketches and mathematical notations from the field of electromagnetics on the web, starting in 1997 with simple static web pages of solved examples. The encouraging results from using and evaluating this educational material and the needs expressed by students for learning from more dynamic and interactive web learning materials that offer the possibility of changing parameters in online calculations motivated a search for new approaches to publishing interactive learning materials on the web. Integration of already developed components for building animations, presenting mathematical equations, and performing online computations with browser scripting led to development of a learning environment where animations are synchronized with corresponding derivations of equations and supported by dynamic, parametric-driven calculations and visualizations that can be integrated with sound and video. The system supports tests and examinations in which the answers are provided as mathematical notations. The use of Mathematical Markup Language (MathML) permits equations in the learning materials to be copied and pasted into most of the popular mathematical software tools for algebraic manipulation or numerical computation. Examples demonstrate how the system can be used with a course on electromagnetics, although the basic approach is applicable in other fields of engineering and natural science.

Application-based NGN QoE controller

In this article, a specification and testbed implementation results of an application-based QoE controller are presented, proposing a solution for objective and context-aware end-to-end QoE control in the NGN networks. The proposed solution bases on standardized NGN service enabler operation principles that allows for efficient in-service QoE estimation and optimization. QoE control is accomplished through context-based QoE modeling, the principal role of which is to provide a detailed description of the circumstances, under which the communication is established and by which the end-users QoE is affected. Implementation results and findings confirm feasibility and efficient design of the QoE controller proposal as well as full compliance with the requirements for its deployment into real-world NGN environments.

Empirical analysis and modeling of peer-to-peer traffic flows

This study presents a detailed flow-level empirical analysis of Peer-to-peer traffic. It is based on 24 hours long traffic traces that were collected on a backbone link in academic environment and in ADSL access. The flows were identified by 5-tuples and were categorized to three main categories: Peer-to-Peer, World-Wide-Web and TCP-big. Four main flow parameters were statistically analyzed: flow interarrival times, size of flows measured in number of packets, size of flows measured in number of bytes, and flow duration. Using the distribution fitting techniques we show that flow interarrival time can be successfully modeled by Weibull distribution, flow size by Pareto distribution and flow duration by log-normal distribution. The key distribution parameters are identified. They indicate a strong resemblance of Peer-to-Peer and TCP-big categories and significantly deviate from the parameters of the World-Wide-Web category. The results can be used in the simulations and other of further studies that involves Peer-to-Peer traffic.

Bringing click-to-dial functionality to IPTV users [web services in telecommunications, part II]

Architecture for click-to-dial over IP television is discussed, utilizing Parlay X Web services to communicate with telephony network elements. The architecture and individual elements of the system are presented in detail, including a gateway to call servers and telephony switches. The implemented system enables IPTV users to establish calls over mobile or fixed phones by pushing a button on their IPTV remote control. Additionally, we describe a method for automatic phone number recognition from live video that communicates the data to IPTV users via Web services architecture, enabling them to initiate a call easily to any number displayed on the video.

Usability Pitfalls of Diabetes mHealth Apps for the Elderly

Diabetes mellitus has high prevalence in the ageing population and is often accompanied by other comorbidities, such as Alzheimers disease, and general disabilities, such as poor eyesight. These comorbidities have redefined ways in which patients use mHealth apps, including diabetes apps. The latter have proven benefits for monitoring blood glucose levels and insulin tracking in the general population. In this paper, we analyse a diabetes monitoring app DeStress Assistant (DeSA), which was developed as a part of an EU project and tested in a hospital setting. Due to the increasing number of older adults, we wanted to ensure the app was suitable for that demographic. Based on a number of supervised tests, we show that the app, which was developed with the help of workshops and feedback from tech-savvy patients and clinicians, is difficult to use by elderly users. We demonstrate that with a small number of changes it is possible to raise the usability of the app in a number of categories. We summarise the lessons learned in the discussion. Our findings demonstrate that special care needs to be taken when developing mHealth apps for the elderly population.