Andrej Kos

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.).

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.

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.

Techniques for performance improvement of VoIP applications

In order to effectively compete in todays telecommunication market, service providers and enterprises are turning towards voice over IP (VoIP) technology. Initially, the goal of using VoIP in enterprises was a better utilisation of internal packet networks and avoiding long-distance toll charges. On the other side service providers need to rollout new revenue generating services quickly. There are many compelling reasons to migrate voice traffic to IP networks, but certain problems must be solved first. This paper introduces important concepts surrounding the performance of VoIP applications in corporate networks and in the Internet. We explain the problem of end-to-end delays, delay jitter, packet reordering and frame erasures and also emerging techniques for solving those problems. This paper focuses on the performance of VoIP applications in wide area networks.

A Presence-Based Context-Aware Chronic Stress Recognition System

Stressors encountered in daily life may play an important role in personal well-being. Chronic stress can have a serious long-term impact on our physical as well as our psychological health, due to ongoing increased levels of the chemicals released in the ‘fight or flight’ response. The currently available stress assessment methods are usually not suitable for daily chronic stress measurement. The paper presents a context-aware chronic stress recognition system that addresses this problem. The proposed system obtains contextual data from various mobile sensors and other external sources in order to calculate the impact of ongoing stress. By identifying and visualizing ongoing stress situations of an individual user, he/she is able to modify his/her behavior in order to successfully avoid them. Clinical evaluation of the proposed methodology has been made in parallel by using electrodermal activity sensor. To the best of our knowledge, the system presented herein is the first one that enables recognition of chronic stress situations on the basis of user context.

Contextualized monitoring and root cause discovery in IPTV systems using data visualization

This article describes the architecture and design of an IPTV network monitoring system and some of the use cases it enables. The system is based on distributed agents within IPTV terminal equipment (set-top box), which collect and send the data to a server where it is analyzed and visualized. In the article we explore how large amounts of collected data can be utilized for monitoring the quality of service and user experience in real time, as well as for discovering trends and anomalies over longer periods of time. Furthermore, the data can be enriched using external data sources, providing a deeper understanding of the system by discovering correlations with events outside of the monitored domain. Four supported use cases are described, among them using weather information for explaining away the IPTV quality degradation. The system has been successfully deployed and is in operation at the Slovenian IPTV provider Telekom Slovenije.

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.

Using presence information for an effective collaboration

Presence service provides users with information about others userspsila availability, willingness to communicate and preferred means of communication. Presence information can serve as an input for innovative applications which act differently depending on the state of the user and their location. In enterprise environments, such information can greatly increase productivity by allowing employees to efficiently manage their meetings, communication and other work-related tasks. In this article, we explain the basic and extended presence system architecture. We demonstrate the architecture for enterprise environment that combines presence information from various sources and provides it to consumers. The central parts of the system are IMS core and presence server. We propose presence server architecture which is Java based and scalable. We present an implementation of presence architecture and demonstrate its usefulness with an application that provides employees with information about coworkerspsila locations and communication capabilities and allows them to instantly start the communication.

The integration of home-automation and IPTV system and services

In this paper we propose the integration of a home-automation system and its services (HASS) with an IPTV system and its services (IPTVSS) to enable convergence at the network-technology and user-interface levels. The convergence at the network-technology level was achieved by using the Internet protocol (IP), and therefore both integrated systems have to provide IP connectivity. To enable communication between the HASS and the IP-based services, we have implemented the WebService/Konnex gateway. The IPTVSS are IP based; therefore, an easy convergence at the network-technology level is possible. The convergence at the user-interface level was achieved by a hardware and software user-interface implementation.