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Scientific Papers


Kos, A., Pristov, D., Sedlar, U. Sterle, J., Volk, M., Vidonja, T., Bajec, M., Bokal, D., Bešter, J.Open and scalable IoT platform and its applications for real time access line monitoring and alarm correlation. Lect. notes comput. sci. Volume 7469: pp. 27-38.
Keywords: IoT platform, Access line monitoring, Event correlation, Real-time

We present an open intelligent communication platform that can be used to support various usage scenarios related to future internet of things. Its purpose is twofold: to support fusion of large amounts of data, irrespective of their source or structure and to provide users or devices with semantically analysed and enriched data according to their needs and context. Using the platform, users are able to access enriched data, receive warnings and notifications about events recognised by the system. We present applications for the real time access line monitoring and alarm correlation that respond to telecommunications operators’ needs in the field of proactive line measurement in enabling the helpdesk and field technical teams to pinpoint the cause of service degradations.

Peternel, K., Pogačnik, M., Tavčar, R., Kos, A.A presence-based context-aware chronic stress recognition system. Sensors, 12 (11): 15888-15906.
Keywords: Presence, Chronic stress, Context awareness, Embedded sensors, Hidden Markov models, Health monitoring

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.

Sedlar U., Volk M., Sterle J., Kos A., Sernec R.Contextualized monitoring and root cause discovery in IPTV systems using data visualization. IEEE Network, 01/2012, 26 (6):40-46.
Keywords: Contextualization, Data vizualization, IPTV, Monitoring systems, QoS, QoE

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.

Požrl, T., Kunaver, M., Pogačnik, M., Košir, A., Tasič, J. F. Improving human-computer interaction in personalized TV recommender. Electr. comput. eng. (Shiraz), 36 (E1): 19-36.
Keywords: User modeling, recommender system, content-based filtering, human-computer interaction, user satisfaction, recommendation explanation

In today’s world of numerous sources of multimedia content, recommender systems help users find relevant content items. In our research the reasoning behind the recommendations generated by such systems was explored to check whether presenting users with explanations of recommended content increases their trust in the system. A content-based recommender for TV content has been developed which focuses on items attribute values. The system predicts users’ ratings by classifying the vector of similarities between the user model and the items attributes. Users’ trust is increased by identifying attribute values that are the most relevant for them. Users’ feedback to the identified attribute values was used to improve the performance of the recommender algorithm. Tests in our experimental platform showed that the developed algorithms produce good results. The accuracy of the system was around 75% in the basic version and it further increased in the enhanced, while the identification of relevant attribute values achieved 86% precision

Umberger, M., Humar, I. Energy savings of refrigerators in shopping centers with adaptive control and real-time energy management systems. Prz. Elektrotech., 88 (6): 327-331.
Keywords: Refrigeration systems, Energy saving, Adaptive control system, Real-time EMS

Refrigeration systems are the largest energy consumers in shopping centers, offering great potential for energy saving. In the paper we analyze the savings gained with an adaptive control system and a real-time energy management system, used to control different parameters and individual procedures remotely by a trained person. The results of two experiments show savings around 14.5 % by using an adaptive control
system and additional 7.8 % by using real-time energy management system.

Humar, I., Podnar, M. Implementation and performance evaluation of IGMP snooping supporting multicast functionality on Linux-based Ethernet switches. Telecommun. syst. (online): 1-14.
Keywords: IGMP snooping, Multicast, Performance evaluation, CPU load, Frame loss ratio, Frame delay

The objective of this work was to implement Internet Group Management Protocol snooping to support multicast functionality on Linux-based Ethernet switch and carry out its performance evaluation. The implementation of the new functionality required modifications and improvements of two segments of the operating system: some parts of kernel and the user space management software. Algorithms and data structures, used for building multicast table, have been implemented in order to improve switching logic, which is now based on entries in the multicast table. Performance evaluation has been performed in a dedicated environment using a traffic analyzer, able to generate different types of traffic and traffic loads. The results are given for combinations of different loadings and numbers of target ports and prove that the implementation does not only decrease overall network load by reducing redundant broadcast flooding, but also increase the performance of switch by eliminating unnecessary frame forwarding, which eventually leads to lower frame losses and shorter queuing delays.


Sterle J., Volk M., Sedlar U., Bešter J., Kos A. Application-based NGN QoE controller. IEEE commun. mag. 49 (1): 92-101.
Keywords: Next generation networking, Proposals, Protocols, Quality assurance, Quality of service, Servers

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-user’s 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.

Atanasijević-Kunc M., Logar V., Karba R., Papić M., Kos A. Remote multivariable control design using a competition game. IEEE trans. ed., 54 (1): 97-103.
Keywords: Education, multiple-input–multiple-output (MIMO) systems, remote laboratory, terms-competition game, virtual laboratory

In this paper, some approaches to teaching multi variable control design are discussed, with special attention being devoted to a step-by-step transition to e-learning. The approach put into practice and presented here is developed through design projects, from which one is chosen as a competition game and is realized using the E-CHO system, Matlab, and a laboratory pilot plant. All the preparations for the game can be completed using a remote virtual and actual laboratory device, while the final competition evaluation takes place in the laboratory in order to preserve personal contacts between the students and the staff. The methods described, comprising all the important e-education elements, were found to stimulate the students’ interest and speed up the learning process, and are directly extendable to different forms of courses suitable for new forms of study and education promotion, including lifelong education.

Humar I., Podnar M. Implementation and performance evaluation of IGMP snooping supporting multicast functionality on Linux-based Ethernet switches. Telecommunication systems. Online First.
Keywords: IGMP snooping, Multicast, Performance evaluation, CPU load, Frame loss ratio, Frame delay

The objective of this work was to implement Internet Group Management Protocol snooping to support multicast functionality on Linux-based Ethernet switch and carry out its performance evaluation. The implementation of the new functionality required modifications and improvements of two segments of the operating system: some parts of kernel and the user space management software. Algorithms and data structures, used for building multicast table, have been implemented in order to improve switching logic, which is now based on entries in the multicast table. Performance evaluation has been performed in a dedicated environment using a traffic analyzer, able to generate different types of traffic and traffic loads. The results are given for combinations of different loadings and numbers of target ports and prove that the implementation does not only decrease overall network load by reducing redundant broadcast flooding, but also increase the performance of switch by eliminating unnecessary frame forwarding, which eventually leads to lower frame losses and shorter queuing delays.


Stegel T., Sterle J., Sedlar U., Bešter J., Kos A. SCTP multihoming provisioning in converged IP-based multimedia environment. Comput. commun. 33 (14): 1725-1735.
Keywords: SCTP, Transport layer multihoming, Path control, NAT, NATFW NSLP

The latest evolution and successful deployment of different access technologies have resulted in end-users having the ability of combining different fixed and wireless technologies into a superior network service. Increasingly bandwidth-hungry multimedia applications are the first to utilize all benefits that multihomed user terminals offer in a way of connection persistence, reliability and fault tolerance, seamless handovers between points of attachments (PoA) and bandwidth aggregation. Stream control transmission protocol (SCTP) is, considering the advantages of integrated multihoming support, possible bandwidth aggregation and high reliability in addition to other attractive features like multistreaming, partial reliability and optional unordered delivery, a viable transport protocol for provisioning of demanding services in the converged IP-based multimedia environment with guaranteed operator-grade reliability and quality. But despite numerous advantages, the use of SCTP is still mainly limited to operators’ services, while end-user terminals have still not yet adopted SCTP as a common transport protocol. As we point out in this article, this is mainly due to widely deployed network address translation (NAT) and firewall (FW) middleboxes and very common use of default routing at the end-user terminals, which results in issues at setting up and maintaining of a fully operational multihomed SCTP association. In this article we introduce two novel solutions that overcome these issues with the use of NAT/firewall NSIS signaling layer protocol (NATFW NSLP). First solution relies on dynamic address reconfiguration SCTP extension and the second one on SCTP endpoints’ routing table synchronization. Interface between NATFW NSLP and SCTP has been designed and implemented in Linux environment, using Linux kernel SCTP (LKSCTP). Test results clearly show the benefits of our approach with a successful deployment of a resilient multihomed SCTP association in distributed NAT environment. Single point of failure is successfully avoided, even though default routing and asymmetrical multihoming is used. Additionally, our solution can realize an immediate failover if a fatal error occurs at a traversed middlebox, and offer disjoint network paths for possible bandwidth aggregation. These advanced features are of vital importance for dynamic end-to-end resource availability and satisfactory service quality for clients with heterogeneous access technologies.

Debeljak M., Matjačić Z., Vidmar G., Bešter J., Pogačnik M., Zupan A. A method for selection of appropriate assistive technology for computer access. Int. j. rehabil. res., 33 (4): 298-305.
Keywords: /

Assistive technologies (ATs) for computer access enable people with disabilities to be included in the information society. Current methods for assessment and selection of the most appropriate AT for each individual are nonstandardized, lengthy, subjective, and require substantial clinical experience of a multidisciplinary team. This manuscript presents and evaluates an objective approach to test and select an appropriate AT for computer access for people with disabilities. Six user interfaces (standard keyboard, mini and large joystick, mini and large trackball, and head-operated mouse and keyboard) were tested on the control group of 29 people without disabilities and on 63 people with neuromuscular and muscular diseases, using purpose-built software for testing the speed of sentence typing. Different criteria for selecting the optimal AT were tested and compared with the skilled clinician’s choice. The learning curves of the people with disabilities proved to follow those of the healthy controls, but with lower performance. Daily computer use was not associated with AT selection, but corresponded nearly perfectly to the level of functional ability of upper limbs. Agreement between clinician’s choice and learning-based AT selection was noteworthy, but far from perfect. If partial agreement was taken into account, that is, AT was considered as an ordinal variable based on the corresponding functional ability level, and the second best learning-based choice was taken into account, the agreement was high for highest median typing speed as AT selection criterion. In conclusion, the developed method for AT assessment and selection seems to be an efficient guide for an unskilled clinician to choose an appropriate AT.

Volk M., Sterle J., Sedlar U., Kos A. An approach to modeling and control of QoE in next generation networks. IEEE commun. mag. 48 (8): 126-135.
Keywords: Communication system control, Context modeling, Estimation, Monitoring, Network servers, Next generation networking, Production facilities, Proposals, Protocols, Quality assurance, Quality of service, Web server

In this article an approach to QoE modeling and QoE assurance is presented. Employing objective end-to-end QoE modeling, a QoE estimation algorithm is proposed and applied to a service enabler of an NGN SDE to provide a QoE assurance service. The proposed QoE model is context-aware and comprises a comprehensive set of quality-related parameters available throughout various information factories of the NGN, accessible by employing standardized procedures within the NGN SDE. Design principles, methodology, as well as simulation results and comparative analyses are given. A QoE assurance service solution is presented as a use case proposal that operates as a proactive in-service QoE controller, followed by results of a real-world laboratory implementation.

Ge X., Cao, C., Jo M., Chen M., Hu. J., Humar I. Energy efficiency modelling and analyzing based on multi-cell and multi-antenna cellular networks. Trans. internet inf. syst. 4(4): 560-574.
Keywords: Energy efficiency, cellular network, multi-cell, multi-antenna, Markovian chain

In this paper, the relationship between the energy efficiency and spectrum efficiency in a two-cell cellular network is obtained, and the impact of multi-antenna on the energy efficiency of cellular network is analyzed and modeled based on two-state Markovian wireless channels. Then, the energy efficiency of multi-cell cellular networks with co-channel interference is investigated. Simulation results verify the proposed model and the energy-spectrum efficiency tradeoffs in cellular networks with multi-antenna and co-channel interference.

Umberger M., Lumbar S., Humar I. Modeling the influence of network delay on the user experience in distributed home-automation networks. Information systems frontiers. Online First.
Keywords: Quality of experience – Home-automation system and services – Network delay – Subjective QoE assessment – Objective QoE assessment model

Today’s modern home-automation systems and services (HASS) frequently communicate over public telecommunications networks, such as the Internet. Unfortunately, these communication networks do not usually provide sufficient quality (i.e., a predictable delay), which is generally assured in fieldbus HASS networks. Consequently, the user-perceived quality of experience (QoE) cannot be maintained at a satisfactory level when using different HASS devices communicating over an IP-based network. The data transferred over the Internet can experience a non-negligible delay that can have a considerable influence on the QoE. For this reason, the main goal of our research was to measure the influence of the network delay on a subjective QoE assessment, while interacting with some frequently used HASS tasks. The results show that users are satisfied if the delay is kept below 0.8 s, and that they can tolerate delays of over 2 s (depending on the level of the HASS task interactivity). Since such a user-perceived subjective QoE assessment is both time-consuming and expensive we also propose objective QoE assessment models to represent the influence of network delay on a subjective QoE assessment for various HASS tasks.


Čorović S., Bešter J., Miklavčič D. An e-learning application on electrochemotherapy. Biomed. eng. online 8(26): 15 str.
Keywords: /

The e-learning application we present in this article provides educational material on electrochemotherapy and its underlying principles such as cell and tissue electroporation. The e-learning application is developed to provide an interactive educational content in order to simulate the “hands-on” learning approach about the parameters being important for successful therapy. The e-learning application together with the interactive e-learning environment is available to the users to provide collaborative and flexible learning in order to facilitate knowledge exchange among the experts from different scientific fields that are involved in electrochemotherapy. The modular structure of the application allows for upgrade with new educational content collected from the clinics and research, and can be easily adapted to serve as a collaborative e-learning tool also in other electroporation-based treatments such as gene electrotransfer, gene vaccination, irreversible tissue ablation and transdermal gene and drug delivery. The presented e-learning application provides an easy and rapid approach for information, knowledge and experience exchange among the experts from different scientific fields, which can facilitate development and optimisation of electroporation-based treatments.

Pavlič J.I., Mareš T., Bešter J., Janša V., Daniel M., Iglič A. Encapsulation of small spherical liposome into larger flaccid liposome induced by human plasma proteins. Comput. methods biomech. biomed. eng. 12 (2): 147-150.
Keywords: /

We show that human plasma can induce the encapsulation of small spherical liposomes into larger flaccid liposomes. To explain the observed phenomena, it is proposed that the orientational ordering of charged plasma proteins induces attractive interaction between two like-charged liposome surfaces in close contact. It is observed that the encapsulation of the spherical liposome is possible only if the membrane of the target liposome is flexible enough to adapt its shape to the shape of the spherical liposome. In the theoretical model, the shapes of the two agglutinated liposomes are determined by minimisation of the sum of the adhesion energy and the membrane elastic energy. In the simulations, the membrane of liposomes is considered as an elastic structure and discretised via the finite element method using spring elements. It is shown that the observed agglutination of liposomes and encapsulation of smaller spherical liposomes into larger flaccid liposomes may be explained as a competition between the membrane deformation energy and the membrane adhesion energy.

Kos A., Volk M., Bešter J. Quality assurance in the IMS-based NGN environment. Handbook of research on wireless multimedia: quality of service and solutions, Hershey, New York, Information Science Reference, 2009:240-257.
Keywords: Multimedia Technologies & Networking, Multimedia Technology

Commonly understood as the next generation networks (NGN), a composite environment of proven telecommunications and Internet-oriented mechanisms has become generally recognized as the telecommunications environment of the future. However, the nature of the NGN environment presents several complex issues regarding quality assurance that have not existed in the legacy environments (e.g., multi-network, multi-vendor, and multi-operator IP-based telecommunications environment, distributed intelligence, third-party provisioning, fixed-wireless and mobile access, etc.). In this chapter, a serviceaware policy-based approach to NGN quality assurance is presented, taking into account both perceptual quality of experience and technology-dependant quality of service issues. The respective procedures, entities, mechanisms, and profiles are discussed. The purpose of the presented approach is in research, development, and discussion of pursuing the end-to-end controllability of the quality of the multimedia NGN-based communications in an environment that is best effort in its nature and promotes end user’s access agnosticism, service agility, and global mobility.

Umberger M., Humar I., Kos A., Guna J., Žemva A., Bešter J. The integration of home-automation and IPTV system and services. Comput. stand. interfaces. 31 (4): 675-684.
Keywords: Home automation,
IP network,
User interface

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.

Krenker A., Volk M., Sedlar U., Bešter J., Kos A. Bidirectional artificial neural networks for mobile-phone fraud detection. ETRI J., 31 (1): 92-94.
Keywords: Bidirectional artificial neural networks (bi-ANN), fraud detection, mobile telecommunications.

We propose a system for mobile-phone fraud detection based on a bidirectional artificial neural network (bi-ANN). The key advantage of such a system is the ability to detect fraud not only by offline processing of call detail records (CDR), but also in real time. The core of the system is a bi-ANN that predicts the behavior of individual mobile-phone users. We determined that the bi-ANN is capable of predicting complex time series (Call_Duration parameter) that are stored in the CDR.


Sedlar U., Zebec L., Bešter J., Kos A. Bringing click-to-dial functionality to IPTV users. IEEE commun. mag. 46 (3): 118-125.
Keywords: Automatic control , Control systems , IPTV , Network servers , Service oriented architecture , Switches , TV , Telecommunication switching , Telephony , Web services

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.

Peternel B., Kos A. Broadband access network planning optimization considering real copper cable lengths. IEICE trans. commun. E91-B (8): 2525-2532.
Keywords: broadband, copper network, remote DSLAM, xDSL, FTTx, optimization, tree structure, dynamic programming

Broadband access network planning strategies with techno-economic calculations are important topics, when optimal broadband network deployments are considered. This paper analyzes optimal deployment combination of digital subscriber line technologies (xDSL) and fiber to the home technologies (FTTx), following different user bandwidth demand scenarios. For this reason, optimal placement of remote digital subscriber line multiplexer (RDSLAM) is examined. Furthermore, the article also discusses the economy of investments, depending on certain investment threshold and the reach of different xDSL technologies. Finally, the difference between broadband network deployment in a characteristic urban and rural area in Republic of Slovenia, in terms of required optical cable dig length per household is shown. A tree structure network model of a traditional copper access network is introduced. A dynamic programming logic, with recursion as a basis of a tree structure examination and evaluation of optimal network elements placement is used. The tree structure network model considers several real network parameters (e. g.: copper cable lengths, user coordinates, node coordinates). The main input for the optimization is a local loop distance between each user and a candidate node for RDSLAM placement. Modelling of copper access networks with a tree structure makes new extensions in planning optimization of broadband access networks. Optimization of network elements placement has direct influence on efficiency and profitability of broadband access telecommunication networks.

Janšar R., Šuštar V., Frank M., Sušanj P., Bešter J., Manček Keber M., Kržan M. Iglič A. Number of microvesicles in peripheral blood and ability of plasma to indicate adhesion between phospholipid membranes in 19 patients with gastrointestinal diseases. Blood cells mol. diseases. 41 (1): 124-132.
Keywords: Microvesicles, Microparticles, Cancer, gastric, Tumor progression, Procoagulant

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. Tomšič, M. Lokar, A. Ambrožič, S. Čučnik, M. Kandušer, B. Rozman, A. Iglič, V. Kralj-Iglič, 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 patient’s 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.

Volk M., Guna J., Kos A., Bešter J. Quality-assured provisioning of IPTV services within the NGN environment. IEEE commun. mag. 46 (5): 118-126.
Keywords: IPTV , Laboratories , Next generation networking , Proposals , Quality assurance , Quality of service , Standardization , Streaming media , TV , Web services

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 user’s 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.

Savić D., Bešter J., Pustišek M., Tomažič S., Potorti F., Furfari F. CostGlue : simulation data exchange in telecommunications. Simulation.84(4): 157-168.
Keywords: simulation, measurements, data, archiving, HDF

Exchanging simulation data among simulation practitioners is, to a great extent, hindered by the use of different kinds of data formats in simulation software packages. The purpose of the CostGlue project is to facilitate the exchange of simulation data in the field of telecommunications. We propose a common data interchange format and a data exchange model for raw simulation data, metadata and post-processing data. Based on this model, we additionally propose a framework, CostGlue, designed for packaging simulation output data into the common interchange format, launching post-processing plugins and exporting data into input formats for various third party tools. As a proof of concept we have implemented the framework as a software package and released it as free software.

Humar I., Gradišar M., Turk T. The impact of color combinations on the legibility of a Web page text presented on CRT displays. Int. j. ind. ergon.38 (11/12): 885-899.
Keywords: Color combinations, Computer display, Legibility, Luminance contrast, Color difference, Polarity

This paper describes the impact of color combinations on the legibility of a Web page text presented on a calibrated cathode ray tube display. Four hundred and sixty-eight participants tested the legibility of 56 color combinations, compounded of elementary Web safe colors, with a visual performance task. In the task, the participants were asked to identify 21 uppercase alphabetic characters, selected and presented in conformance with the Snellen chart. The number of correctly identified characters was recorded as objective-dependent measure for each color combination. The impacts of color combination, luminance contrast, color difference, and polarity on the legibility were studied. According to the analysis of variance test, color combinations significantly affected the number of correctly identified characters. The obtained results showed that more than 90-year-old Le Courier legibility table is not appropriate for integrative color computer displays. Consequently, a new legibility table is proposed. The influences of both luminance contrast and color difference were investigated by means of the logarithmic and the second-degree polynomial regression model. A second-degree polynomial model proved as appropriate describing the legibility in dependence of luminance contrast. A second-degree polynomial model and logarithmic model proved as appropriate describing the legibility in dependence of color difference. The analysis of influence of polarity on legibility showed that, generally, dark backgrounds lead to better results for colors with greatest luminance contrast.

Volk M., Štular M., Bešter J., Kos A., Tomažič S. IP multimedia subsystems (IMS). Encyclopedia of wireless and mobile communications, Taylor & Francis Group, Auerbach Publications, 2008(1): 462-572.
Keywords: IP multimedia subsystem, multimedia services, next-generation networks, service delivery platform, universal mobile telecommunications system

IP multimedia subsystem (IMS) represents a standardized next-generation reference system to provide an overlay global open service delivery platform (SDP) that enables provisioning of converged multimedia services.


Ambrožič J., Kos A., Bešter J. Robust power line modem synchronization using signal phase measurement. Meas. sci. technol. 18 (8): 2686-2695.
Keywords: /

Intelligent automatic meter reading and automatic meter management systems that collect, communicate and process data from different meters, i.e. electricity, gas, water, etc, form an important building block of smart and efficient environments. When using power line modems for communications, achieving fast and accurate synchronization is one of the key issues. This paper provides a novel contribution of phase measurements of the power line signal for robust synchronization purposes. Phase calculation is based on an extended Goertzel algorithm providing zero crossing information and reducing the negative effects of noise and disturbances. With relatively small complexity and low implementation costs it assures sufficient accuracy and speed of convergence. Practical realization on a low-cost microprocessor is discussed. The whole solution has been field-tested and measurements proved that it is highly efficient and very suitable for large quantity deployment.

Kunaver M., Požrl T., Pogačnik M., Tasič J.F. Optimisation of combined collaborative recommender systems. AEÜ, Int. j. electron. commun. 61 (7): 433-443.
Keywords: User modelling, Personalisation, Collaborative recommendation, Hybrid recommender systems

A new approach to collaborative user modelling is presented in this paper. We have developed a framework that can be used for easy testing of different concepts. We have also introduced three different areas where collaborative modelling can be further improved. For the first phase of testing, we have created a hybrid system based on three different collaborative recommender techniques. Since this system implements multiple collaboration techniques, we decided to call this approach Combined Collaborative Recommender. Although each prediction technique can produce adequate results, we have proved that the combination of these techniques into a unified system provides a much more stable system. It should also be pointed out that these analyses were done using a very large dataset (more than 2 million ratings) providing reliable results. Results of these optimisations are presented along with pointers for further development.


Humar I., Sinigoj A.R., Bešter J., Hagler M.O. Integrated component web-based interactive learning systems for engineering. IEEE trans. ed.48 (4): 664-675.
Keywords: Animation, Education, Electromagnetic fields, Equations, Learning systems, Publishing, Systems engineering and theory, Testing, Visualization, Web pages

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.

Pogačnik M., Tasič J.F., Meža M., Košir A. Personal content recommender based on a hierarchical user model for the selection of TV programmes. User model. user-adapt. interact. 15(5): 425-457.
Keywords: Hierarchical user model, multimedia, support vector machines, TV programmes, updating of the user model, user modeling

In this paper we present our approach to user modeling for a personalized selection of multimedia content tested on a corpus of TV programmes. The idea of this approach is to classify content (TV programmes) based on the calculation of similarities between the description of content and the user model for each description attribute. Calculated similarities are then combined into a classification decision using the Support Vector Machines. The basis for the calculation of similarities is a hierarchical structure of the user model, overlaid upon a taxonomy of TV programme genres. Preliminary results show that it works well with a varying quality of content descriptions including incomplete genre classification and arbitrary number of description attributes. The evaluation of the system performance was based on content described using the TV-Anytime standard, but the approach can be adapted for search of other types of content with multi-attribute descriptions.