TELFOR is the abbreviation for the Telecommunications Forum, a long lasting scientific, engineering and professional event which started in 1993 in Belgrade, Serbia. Initial idea was to establish a new modest national scientific conference in Telecommunications and related areas. During the years, that idea evolved in such a way that today TELFOR is a huge regional international conference, having also its several other parallel tracks, like special presentations of companies, presentations and papers of invited experts, exhibition of telecommunications hardware, software, systems and services, then seminars, tutorials, round tables, etc. During TELFOR’s existence several thousands of scientific papers were presented and published, quite a number of them being with a considerable quality and important results.
Having such resources at disposal, establishing a new scientific journal, the TELFOR Journal, was a very natural next step for several reasons:
- Authors with favourable TELFOR reviewers’ assessments would have additional chances to improve and expand their initial ideas;
- Editorial board would have a wide set of prospective invited authors;
- After some time of existence, one could expect that TELFOR Journal would attract independent authors to submit their papers to be considered for publishing.
The history of TELFOR Journal is not a long one. The first volume consisting of two issues was published during the TELFOR 2009 conference in November 2009. That first volume of the Journal was intended to present a selection of the improved and expanded versions of the best scientific papers presented at Telecommunications Forum 2008.
The second volume of the TELFOR Journal, again with two issues, was electronically published before the TELFOR 2010 conference, in November 2010. Printed copies were realized slightly later. This is the third volume, based on the selected, expanded and improved results from the TELFOR 2010 conference.
After three years of existence one can easily conclude that TELFOR Journal is already a recognizable scientific publication in the region of south-east Europe. The impressions of the scientific and research community were positive, both with respect to the Journal scientific quality and the very nice design.
The TELFOR Journal is published in the English language, with both electronic and printed versions, minimally with the two issues per year. Having in mind that recent studies have shown that freely available papers are cited more often, Editorial board decided that electronic version will be once again free of charge.
The TELFOR Journal is an IEEE co-supported publication and it is following all the IEEE rules, procedures, and consequently the scientific quality.
The large spectrum of TELFOR Journal topics accounts for the rapid convergence through telecommunications towards the information and knowledge society. The Journal provides a medium for exchanging research results and technological achievements accomplished by the scientific community from academia and industry.
Editor-in-Chief
Prof. Dr Đorđe Paunović
In this paper possible applications of responsive pricing scheme and Stackelberg game for pricing telecommunication services with service provider as a leader and users acting as followers are analyzed. We have classified users according to an elasticity criterion into inelastic, partially elastic and elastic users. Their preferences are modelled through utility functions, which describe users’ sensitivity to changes in the quality of service and price. In the proposed algorithm a bandwidth management server is responsible for performing automatic optimal bandwidth allocation to each user’s session while maximizing its expected utility and the overall service provider’s revenue. The pricing algorithm is used for congestion control and more efficient network capacity utilization. We have analyzed different scenarios of the proposed usage-based pricing algorithm. Particularly, the influence of the number of service classes on price setting in terms of service provider’s revenue and total users’ utility maximization are discussed. The model is verified through numerous simulations performed by software that we have developed for that purpose.
Keywords: service class, user’s elasticity, Stackelberg equilibrium, responsive pricing.
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Subject Category: Telecommunications Policy
Page(s): 2-7
We surveyed a pool of 433 students at the University of Banja Luka in Bosnia and Herzegovina during April 2010, examining users’ perceptions about mobile phones security. The main research hypothesis validated was that users are unaware of the necessary measures to avoid a possible unauthorized access and/or sensitive data retrieval from their phones and that they lack proper security education. Most of the results proved to be non-country specific, revealing that users feel mobile phone communication is not secure. We further present the results about users’ security practices regarding mobile phone usage.
Keywords: mobile phone security, mobile phone usage, security practices, user interface security, questionnaire survey.
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Subject Category: Telecommunications Services
Page(s): 8-12
Research was oriented to spatial-cadastral information-presentation system (SCIPS) and its application to the process of drinking water resources management, with the aim of improving the quality and availability of spatial and other relevant data about these resources. Authors define a model of drinking water resources management on a SCIPS platform, which improves the efficiency of information exchange in the individual interactions of social, government and private participants witch supply users with drinking water. The model is oriented to achieving a high level of availability and multiple uses of data in a wider geographic area based on the principles of cooperation, coordination and collaboration of various elements in a drinking water distribution system. Application of that model, in which key registers are semantically synchronized, may provide more rational and more sustainable usage of drinking water resources and avoiding of potential conflicts of interest or jurisdiction over those resources.
Keywords: Drinking Water Resources, Information Communication Technologies, Interoperability, Ontological Engineering, Semantic Synchronization of the Key Registers, Spatial-Cadastral Information-Presentation System, Spatial Data, Spatial Information Infrastructure.
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Subject Category: Telecommunications Services
Page(s): 13-18
An analysis of 2x2 crossbar packet switch with buffers at crosspoints and round robin scheduling algorithm is presented in this paper. The analysis is performed for a non-admissible traffic pattern, where output ports are overloaded. The case of full offered load is observed and output ports are loaded with packets that have different arrival probabilities. In addition to the parameters that are commonly observed in such an analysis (throughput and average packet delay), memory requirements for the implementation of the buffer, as well as fair representation when servicing the buffer - the so-called fairness are also analyzed. The results show that even for a switch with a small number of ports very large buffers should be implemented, if we want to achieve satisfactory performance under traffic overload.
Keywords: Average cell latency, Crossbar switch, Fairness, Scheduler, Throughput.
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Subject Category: Telecommunications Networks
Page(s): 19-22
In this paper the availabilities of some network topologies are analyzed and calculated. Software based on exact All-terminal Graph reduction Algorithm is developed and applied. Results, conclusions and solutions are presented, demonstrated and discussed.
Keywords: availability, network, topology.
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Subject Category: Telecommunications Networks
Page(s): 23-27
This paper describes the implementation of order-wire functionality in NG-SDH devices ODS2G5 and OTS622 IRITEL. The paper also describes the operation of order-wire in networks with arbitrary topologies, as well as the configuration of order-wire functionality by using network management software SUNCE. The presented solution for order-wire functionality is compared with VoIP solutions. The paper shows that the presented solution provides fast reaction to network failures, while keeping the implementation simple.
Keywords: NG-SDH, order-wire, VoIP, network management, reliability.
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Subject Category: Telecommunications Networks
Page(s): 28-32
An empirical analysis of EDCA QoS mechanism defined in IEEE 802.11e standard is presented in this paper. Measurements were carried out in controlled laboratory conditions, with and without configured QoS. Mean and maximum delay, jitter and packet loss were measured in voice communications between two clients, first competing with best effort clients, and then competing with voice clients. The results show that QoS mechanism brings significant improvements in the transmission of voice, which is especially significant in the case of highly loaded network.
Keywords: EDCA, IEEE 802.11e, QoS, VoWLAN.
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Subject Category: Radio Communications
Page(s): 33-38
Wireless heterogeneous environments are a common reality today and will be so even more in the future. This paper is focused on providing a wireless access selection method for the future mobile terminals that will use naturally inspired algorithms for best network selection. The novel algorithm uses mobile terminal measurements from different radio access technologies within a given time window. The network selection is based on specified criteria, whose number can be increased as needed. Each criterion is modeled with a membership function associated with Fuzzy Logic controllers, which are optimized by using Particle Swarm Optimization. Each criterion is weighted, with the aim to assign the influence on the decision for a radio access network. Hence, our proposed algorithm implements past knowledge of the service performances of available wireless networks used by the mobile, to make a decision for network selection on given time intervals. The main contribution in the algorithm for wireless access network selection is in the usage of nature inspired algorithms, such as Particle Swarm Optimization – PSO, for optimization of Fuzzy Logic controllers, as well as usage of a Genetic Algorithm for optimization of decision making based on multi-criteria inputs. The simulation analysis has shown that the proposed algorithm gives a better probability of satisfied users compared to other existing wireless network selection algorithms.
Keywords: Fuzzy Logic, Genetic Algorithm, Optimization, Wireless Networks.
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Subject Category: Radio Communications
Page(s): 39-42
In this paper, the simulation model of coexisting GPON and NG-PON1 (10G-PON) systems is presented, which has been developed for the analysis of feasibility and implementation issues of this coexistence. The aim was to analyze the impact of the most important parameters of the components that are needed for new network elements, on the performance of these coexistent networks. On the basis of the results obtained, the optimal parameters of the new system components were defined.
Keywords: 10 Gb/s, coexistence, GPON (Gigabit Passive Optical Networks), NG-PON (Next Generation PON).
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Subject Category: Optical Communications
Page(s): 43-48
In the metropolitan area, traditional SONET/SDH circuit switched rings are likely to be replaced with optical packet/burst switching technologies. In this paper we consider a slotted WDM optical packet ring operating without resource reservation mechanisms. In such rings, optical packets in transit have priority over traffic to be inserted by the node. Packets to be inserted are thus queued according to their destination, in order to avoid headof- line blocking. We focus on scheduling policies and compare several MaxWeight scheduling policies, including Oldest Packet First (OPF) which emulates FIFO queueing while avoiding head-of-line blocking. We show that there is a trade-off between implementation complexity and fairness, and identify the Largest Virtual Waiting Time First (LVWTF) scheduling policy as presenting both a low complexity and a good fairness performance.
Keywords: fairness, MaxWeight, optical packet ring, scheduling, stability.
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Subject Category: Optical Communications
Page: 49-53
Computer games have undoubtedly become an integral part of educational activities of children. However, since computer games typically abound with audio and visual effects, most of them are completely useless for children with disabilities. Specifically, computer games dealing with the basics of geometry can contribute to mathematics education, but they require significant modifications in order to be suitable for the visually impaired children. The paper presents the results of research and adaptation of the educational computer game Lugram to the needs of completely blind children, as well as the testing of the prototype, whose results are encouraging to further research and development in the same direction.
Keywords: adaptation software, blind children, educational computer games, geometry.
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Subject Category: Software Tools and Applications
Page: 54-59
In this paper we propose the architecture of a new software system for self-directed interactive learning and assessment in the domain of algorithms and data structures. The system extends Visual Simulator of Algorithms (VSA), a tool previously developed at the School of Electrical Engineering, University of Belgrade. The system provides control of trainee's independence level, flexible input data set assignment and configurable automatic assessment of test-taker's actions. The paper describes the architecture of the proposed system and gives relevant implementation details.
Keywords: automatic assessment, interactive training, knowledge testing.
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Subject Category: Software Tools and Applications
Page: 60-65
This paper presents the implementation and use of Semantic Search Engine (SSE) as part of knowledge management system functionalities in Register for Acute Coronary Syndrome (REACS). REACS SSE is part of a clinical decision support system and is used as an aid in decision making in clinical processes related to the care and treatment of patients with Acute Coronary Syndrome (ACS).
Keywords: Semantic search engine, Register, Acute Coronary Syndrome, Knowledge Management, Cardiology.
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Subject Category: Software Tools and Applications
Page: 66-71
We compared pre-movement event-related desynchronization (ERD) of μ rhythm over the primary motor cortex using surface electrodes in a group of five healthy subjects during self-paced wrist movement and the wrist movement when playing a Nintendo Wii. We present a method that uses ERD to detect the onset of movement in single-trial electroencephalographic (EEG) data. This algorithm produced a mean detection accuracy of 83% for the self-paced movement and 75% for the Wii-included sessions, without requiring subject training. This technique can be employed in an EEG-based brain–computer interface due to its high recognition rate and simplicity in computation.
Keywords: Brain-computer interface, Event-related desynchronization (ERD), Electroencephalogram (EEG), Nintendo Wii.
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Subject Category: Student Paper
Page: 72-75