Telfor Journal Vol.3 No.1 (2011)

Content

Editorial HyperLink
Editor-in-Chief: Prof. Dr Đorđe Paunović

Service Provider Revenue Dependence of Offered Number of Service Classes

V. Radonjić and V. Aćimović-Raspopović
Topic:
Telecommunications Policy
Abstract
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.
Full Text
HyperLink Service Provider Revenue Dependence of Offered Number of Service Classes
Page(s)
2-7

What University Students Do (or Don’t) Know about Security in their Mobile Phones

I. Androulidakis and G. Kandus
Topic:
Telecommunications Services
Abstract
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.
Full Text
HyperLink What University Students Do (or Don’t) Know about Security in their Mobile Phones
Page(s)
8-12

Semantic Synchronization of Key Registers in a Model for Drinking Water Resources Management

M. K. Banjanin, D. Ćulum-Мiladinović, G. Drakulić, and B. Drašković
Topic:
Telecommunications Services
Abstract
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.
Full Text
HyperLink Semantic Synchronization of Key Registers in a Model for Drinking Water Resources Management
Page(s)
13-18

CQ Switch Analysis under Traffic Overload

M. Radonjić, I. Radusinović, I. Maljević, and D. Banović
Topic:
Telecommunications Networks
Abstract
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.
Full Text
HyperLink CQ Switch Analysis under Traffic Overload
Page(s)
19-22

Network Topology Availability Analysis

M. Cabarkapa, D. Mijatovic, and N. Krajnovic
Topic:
Telecommunications Networks
Abstract
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.
Full Text
HyperLink Network Topology Availability Analysis
Page(s)
23-27

Implementation of Order-wire Functionality in IRITEL NG-SDH devices

P. Mićović, P. Knežević, M. Ilić, D. Katanić, and S. Crnobrnja
Topic:
Telecommunications Networks
Abstract
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.
Full Text
HyperLink Implementation of Order-wire Functionality in IRITEL NG-SDH devices
Page(s)
28-32

An Empirical Study of the EDCA QoS Mechanism for Voice over WLAN

M. T. Koprivica , M. M. Ilić, A. M. Nešković, and N. J. Nešković
Topic:
Radio Communications
Abstract
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.
Full Text
HyperLink An Empirical Study of the EDCA QoS Mechanism for Voice over WLAN
Page(s)
33-38

M-RATS: Mobile-based Radio Access Technology Selector for Heterogeneous Wireless Environment

A. Tudzarov and T. Janevski
Topic:
Radio Communications
Abstract
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.
Full Text
HyperLink M-RATS: Mobile-based Radio Access Technology Selector for Heterogeneous Wireless Environment
Page(s)
39-42

Analysis of Coexisting GPON and NG-PON1 (10G-PON) Systems

M. D. Mraković and P. S. Matavulj
Topic:
Optical Communications
Abstract
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).
Full Text
HyperLink Analysis of Coexisting GPON and NG-PON1 (10G-PON) Systems
Page(s)
43-48

Scheduling Issues in ECOFRAME Optical Packet Switched Ring

B. Ušćumlić, A. Gravey, P. Gravey, and M. Morvan
Topic:
Optical Communications
Abstract
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.
Full Text
HyperLink Scheduling Issues in ECOFRAME Optical Packet Switched Ring
Page(s)
49-53

Computer Game Lugram - Version for Blind Children

B. Lučić, N. Vujnović Sedlar, and V. Delić
Topic:
Software Tools and Applications
Abstract
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.
Full Text
HyperLink Computer Game Lugram - Version for Blind Children
Page(s)
54-59

Architecture of a System for Interactive Training and Testing in Algorithms and Data Structures

M. Milivojević, Đ. Đurđević, and M. Tomašević
Topic:
Software Tools and Applications
Abstract
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.
Full Text
HyperLink Architecture of a System for Interactive Training and Testing in Algorithms and Data Structures
Page(s)
60-65

Semantic Search Engine as Tool for Clinical Decision Support in Register for Acute Coronary Syndrome

P. Kostić, D. Novičić, S. Blesić, Z. Vasiljević, J. Grujić Milanović, S. Pavlović, and S. Milanović
Topic:
Software Tools and Applications
Abstract
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.
Full Text
HyperLink Semantic Search Engine as Tool for Clinical Decision Support in Register for Acute Coronary Syndrome
Page(s)
66-71

Comparison of the Event-Related Desynchronization during Self-Paced Movement and when playing a Nintendo Wii Game

Nikola Šobajić and Andrej Savić
Topic:
Signal Processing (Student Paper)
Abstract
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.
Full Text
HyperLink Comparison of the Event-Related Desynchronization during Self-Paced Movement and when playing a Nintendo Wii Game
Page(s)
72-76