Telfor Journal Vol.8 No.2 (2016)
Content
Editorial
Editor-in-Chief:
Prof. Dr Đorđe Paunović
CoordSS: An Ontology Framework for Heterogeneous Networks Experimentation
V. Nejkovic, F. Jelenkovic, M. Tosic, N. Milosevic, and Z. Nikolic
- Topic:
- Communication Theory
- Abstract
- Experimenting with HetNets environments is of importance because of the role that such environments have in next-generation cellular networks. In this paper, the CoordSS ontology experimentation framework is proposed with an aim to support experimenting with HetNets environments on wireless networking testbeds. In the framework, domain and system ontologies are adopted for formal representation of the knowledge about the context of the problem. This paper outlines implementation details of ontologies in the CoordSS experimentation framework. The synergy between semantic and cognitive computing is introduced as the theoretical foundation of the paper.
- Keywords
- ontology, semantics, cognitive, computing, spectrum sensing, wireless, networking testbed, LTE-U, Wi-Fi.
- Full Text
- CoordSS: An Ontology Framework for Heterogeneous Networks Experimentation
- Page(s)
- 70-75
- Doi
- 10.5937/telfor1602070N
Spectrum Sensing Experimentation for LTE and WiFi Unlicensed Band Operation
N. Milošević, Z. Nikolić, F. Jelenković, V. Nejković, and M. Tošić
- Topic:
- Communication Theory
- Abstract
- If several different systems operate in the same frequency band, a coordination between them is needed for effective use of the available spectrum. The coordination is especially important if the systems are not designed to operate in such an environment. The very important initial phase of the coordination process is acquiring of the spectrum usage map or spectrum sensing. The paper describes the spectrum sensing experimentation in the unlicensed 5 GHz band during the WiFi or LTE transmission. It describes the experiment workflow and depicts the obtained results. The experiments were performed at NITOS testbed at the University of Thessaly, Greece, and show that it is possible to determine whether WiFi or LTE transmission is sensed. Therefore, based on spectrum sensing it will be possible to coordinate a shared access of WiFi and LTE users in the unlicensed 5 GHz band.
- Keywords
- Cognitive radio, spectrum sensing, unlicensed band, LTE, WiFi.
- Full Text
- Spectrum Sensing Experimentation for LTE and WiFi Unlicensed Band Operation
- Page(s)
- 76-80
- Doi
- 10.5937/telfor1602076M
Outage Analysis of Clustered Cooperative Networks in Generalized Fading and Shadowing
N. Zdravković
- Topic:
- Telecommunications Networks
- Abstract
- In this paper, the outage probability of a noise-limited decode-and-forward wireless cooperative network cluster, subject to the Nakagami-m multipath fading and Gamma shadowing is investigated. The closed-form expression for outage probability, when the network fusion center selects the stronger received transmission out of the maximal ratio combined signal, arriving from the nodes acting as relays, and a repeated signal from the originating node, is derived. Moreover, special cases, in which the generalized fading and shadowing channel is reduced to several familiar propagation environments, are observed. The derived analytical expressions for outage probability are furthermore confirmed by running independent Monte-Carlo simulations. The effects of multipath fading severity and shadowing sharpness, average signal-to-noise ratio values, and network dimension on outage performance are discussed.
- Keywords
- Cooperative networks, decode-and-forward relay, multipath fading, outage probability, shadowing.
- Full Text
- Outage Analysis of Clustered Cooperative Networks in Generalized Fading and Shadowing
- Page(s)
- 81-86
- Doi
- 10.5937/telfor1602081Z
Empirical Analysis of Electric Field Strength Long-Term Variability for GSM/DCS/UMTS Downlink Band
M. Koprivica, M. Petrić, M. Popović, J. Milinković, and A. Nešković
- Topic:
- Radio Communications
- Abstract
- The long-term variability of electric field strength, obtained by band selective measurements for GSM 900MHz, DCS 1800MHz and UMTS 2100MHz downlink band in realistic mobile network environment, is considered in this paper. Intensive measurements were carried out for 7 days at each of 7 different locations in an urban area of Belgrade. The measurement results show that each day can be divided into two distinctive periods: one with higher levels of electric field (9h-23h) and one with lower ones (23h-9h). Regarding the days of the week, the results show that the weekend days are slightly different from the working days. Having in mind the need for determination of values averaged over the defined time period, additional uncertainty stemming from telecommunication traffic and transmitter functionalities must be taken into account. Mentioned uncertainty was determined for different time intervals of averaging: 10s, 30s, 1min, 6min, 15min, 30min, 1h, 3h, 5h, 10h, 14h and 24h. Results show that the uncertainty falls within a range of 4.04 – 12.11% (GSM), 2.71 – 7.92% (DCS) and 4.69 – 14.69% (UMTS), for 6 different categories defined with regard to the days of the week and the specific day periods.
- Keywords
- electromagnetic fields, GSM, DCS, UMTS, base station, human exposure, long-term variability, measurement uncertainty.
- Full Text
- Empirical Analysis of Electric Field Strength Long-Term Variability for GSM/DCS/UMTS Downlink Band
- Page(s)
- 87-92
- Doi
- 10.5937/telfor1602087K
Interference Estimation in Wireless Mobile Random Waypoint Networks
L. Irio, D. Oliveira, and R. Oliveira
- Topic:
- Radio Communications
- Abstract
- It is well known that the stochastic nature of the interference deeply impacts the performance of emerging and future wireless communication systems. In this work we consider an ad hoc network where the nodes move according to the Random Waypoint mobility model. Assuming a time-varying wireless channel due to slow and fast fading and, considering the dynamic path loss due to the mobility of the nodes, we start by characterizing the interference distribution caused to a receiver by the moving interferers located in a ring. For this purpose, we consider a receiver located at the center of the simulated region. Based on the distribution of the interference’s power, we evaluate different methodologies to estimate the power of the interference in real-time. Results achieved with a Maximum Log-likelihood estimator (MLE) and a Probability Weighted Moments (PWM) estimator are compared. The accuracy of the results achieved with the proposed methodologies in several simulations show that they may used as an effective tool of interference power estimation in future wireless communication systems, exhibiting high accuracy even when the number of samples is low.
- Keywords
- Interference Estimation, Ad Hoc Networks, Mobility.
- Full Text
- Interference Estimation in Wireless Mobile Random Waypoint Networks
- Page(s)
- 93-97
- Doi
- 10.5937/telfor1602093I
Design of Wideband Printed Antenna Array in Corner Reflector with Cosecant Square-Shaped Beam Pattern
M. Milijić, A. Nešić, B. Milovanović, and I. Radnović
- Topic:
- Applied Electromagnetics
- Abstract
- The paper presents a wideband printed antenna array with a cosecant square-shaped beam pattern. The array is with four symmetrical pentagonal dipoles as radiating elements operating at the second resonance. The apex of the corner reflector is at a distance λ0/2 from antenna array. Orchard Elliott’s methods and genetic algorithm are used for synthesizing the proposed antenna. A symmetrical tapered feed network of impedance transformers enables a required distribution. Simulated and measured results show that proposed antenna model has a 15 dBi gain and side lobe suppression around 20 dB in E-plane at the frequency of 10 GHz.
- Keywords
- Printed antenna array, Cosecant square radiation pattern, Symmetric printed technique, Feeding network.
- Full Text
- Design of Wideband Printed Antenna Array in Corner Reflector with Cosecant Square-Shaped Beam Pattern
- Page(s)
- 98-103
- Doi
- 10.5937/telfor1602098M
Analysis of TLM Air-vent Model Applicability to EMC Problems for Normal Incident Plane Wave
N. J. Nešić and N. S. Dončov
- Topic:
- Applied Electromagnetics
- Abstract
- In this paper, the shielding properties related to a protective metal enclosure with airflow aperture arrays are numerically analyzed. As a numerical model, a TLM method, either in a conventional form based on fine mesh to describe apertures presence or enhanced with the compact air-vent model is employed. The main focus in the paper is on examining the limits of applying the compact air-vent model for EMC problems solving. Namely, various values for the distance between neighboring apertures in the TLM air-vent models as well as the air-vent thicknesses are analyzed. Specifically, the analyses are conducted for a normal incident plane wave, vertically and horizontally polarized.
- Keywords
- Enclosure, fine TLM mesh, hexagonal apertures, plane wave, round apertures, shielding effectiveness, TLM Air-vent model.
- Full Text
- Analysis of TLM Air-vent Model Applicability to EMC Problems for Normal Incident Plane Wave
- Page(s)
- 104-109
- Doi
- 10.5937/telfor1602104N
Animation Content in Frame Analysis
G. J. Zajić, M. D. Vesić, A. M. Gavrovska, and I. S. Reljin
- Topic:
- Multimedia
- Abstract
- Animation frame content is analyzed in this paper. The animation found in frame/video content is usually characterized by specific color distribution and texture. The existence of animation within a frame can be described by carefully selected features. We analyzed both fully and partially animated frames. Here, we present our initial results related to automatic animation interpretation using different types of video sequences.
- Keywords
- Video, frame, animation, features, content interpretation, color, texture.
- Full Text
- Animation Content in Frame Analysis
- Page(s)
- 110-114
- Doi
- 10.5937/telfor1602110Z
Error Concealment using Data Hiding in Wireless Image Transmission
A. Akbari, H. Danyali, M. Trocan, and B. Granado
- Topic:
- Multimedia
- Abstract
- The transmission of image/video over unreliable medium like wireless networks generally results in receiving a damaged image/video. In this paper, a novel image error concealment scheme based on the idea of data hiding and Set Partitioning In Hierarchical Trees (SPIHT) coding is investigated. In the encoder side, the coefficients of wavelet decomposed image are partitioned into “perfect trees”. The SPIHT coder is applied to encode each per-fect tree independently and generate an efficiently compressed reference code. This code is then embedded into the coefficients of another perfect tree which is located in a different place, using a robust data hiding scheme based on Quantization Index Modulation (QIM). In the decoder side, if a part of the image is lost, the algorithm extracts the embedded code for reference trees related to this part to reconstruct the lost information. Performance results show that for an error prone transmission, the proposed technique is promising to efficiently conceal the lost areas of the transmitted image.
- Keywords
- Wireless networks, Error Concealment, Data hiding, SPIHT, Image transmission.
- Full Text
- Error Concealment using Data Hiding in Wireless Image Transmission
- Page(s)
- 115-120
- Doi
- 10.5937/telfor1602115A
Analysis of CPU and GPU Implementations of Convolution Reverb Effect
M. J. Mišić, D. V. Nikolov, and M. V. Tomašević
- Topic:
- Software Tools and Applications
- Abstract
- Rapid development of modern central processing units (CPUs) and graphics processing units (GPUs) has allowed a significant increase in computing power for different engineering applications. Audio signal processing is an example of such a computationally demanding application. Fast Fourier Transform (FFT) is often a core part of these processing algorithms, and it is efficiently implemented on the CPUs and GPUs through available libraries. In this paper, we present an implementation of the convolution reverb effect using OpenMP and FFTW library on the CPU, and CUDA and cuFFT library on the GPU. Implemented effect is tested with the set of four different audio signals and ten impulse responses of different lengths. We observed speedups in the range of 2 to 3 times over CPU implementation. The results of the analysis are briefly discussed with emphasis on the benefits and drawbacks of using GPUs in such an application.
- Keywords
- convolution reverb, CUDA, graphics processing units, OpenMP, parallel programming.
- Full Text
- Analysis of CPU and GPU Implementations of Convolution Reverb Effect
- Page(s)
- 121-126
- Doi
- 10.5937/telfor1602121M
Reconfigurable Virtual Environment for Multi-robot Operations and its Application in Education
M. M. Lutovac, Z. Dimić, S. Mitrović, A. Stepanović, and V. Kvrgić
- Topic:
- Software Tools and Applications
- Abstract
- This paper presents the development of reconfigurable virtual environment for programming, control, simulation, and monitoring of multiple robots and its application in the process of education. During the development special attention is devoted to the fulfillment of the modularity, scalability, and openness that represent the basic requirements of reconfigurability. The reconfigurability of the virtual laboratory can be considered from two aspects: as a possibility of reconfiguring operating mode and as a possibility of reconfiguring virtual robots and virtual laboratory. It represents an integrated environment for programming, control, simulation and monitoring of multiple robots with continuous adjustment to the real laboratory environment and robots’ usage. With the possibility to adjust the virtual environment in accordance with the students’ foreknowledge and experience by combining different operating modes and virtual environments, from the educational viewpoint, it is expected that the proposed solution will improve the process of gaining knowledge.
- Keywords
- Education, Reconfigurability, Robot programming, Virtual laboratory.
- Full Text
- Reconfigurable Virtual Environment for Multi-robot Operations and its Application in Education
- Page(s)
- 127-132
- Doi
- 10.5937/telfor1602127L
The TELFOR Journal appreciates the support received from the reviewers. The following is the alphabetic list of the reviewers who have submitted one or more reviews for the current volume of the TELFOR Journal.
Aleksej Avramović, Marko Barjaktarović, Živko Bojović, Milan Čabarkapa, Jelena Ćertić, Zoran Čiča, Goran Dimić, Dejan Drajić, Dušan Drajić, Radivoje Đurić, Octavian Fratu, Ana Gavrovska, Nataša Gospić, Stevica Graovac, Milan Ilić, Predrag Ivaniš, Miloš Janjić, Milica Janković, Milun Jevtić, Nenad Jevtić, Branka Jokanović, Miloš Jovanović, Nenad Jovičić, Venceslav Kafedziski, Nenad Kojić, Nenad Korolija, Miroslav Lutovac, Branko Malešević, Marija Malnar, Vera Marković, Roman Marsalek, Nenad Milošević, Bratislav Milovanović, Veljko Napijalo, Bojana Nikolić, Zorica Nikolić, Angelina Njeguš, Milorad Paskaš, Đorđe Paunović, Milica Pejanović-Djurišić, Lucian Andrei Perisoara, Grozdan Petrović, Vladimir Petrović, Dragan Radojević, Vasa Radonić, Siniša Ranđić, Lazar Saranovac, Aleksandra Smiljanić, Mirjana Stojanović, Mile Stojčev, Željen Trpovski, Miloš Živanov.