Telfor Journal Vol.9 No.2 (2017)
Content
Editorial
Editor-in-Chief:
Prof. Dr Đorđe Paunović
Performance Evaluation of Software Routers with VPN Features
H. Redžović, A. Smiljanić, and B. Savić
- Topic:
- Telecommunications Networks
- Abstract
- This paper presents implementation and analysis of the VPN software router which is based on Quagga and strongSwan open-source software tools. We validated the functionalities of strongSwan and Quagga in realistic environment which include scenarios with link failures. Also, we measured and analyzed the performance of encryption and hash algorithms supported by strongSwan software, in order to advise an optimal VPN configuration that provides the best performance.
- Keywords
- IPsec protocol, Quagga, Software Routers, Software VPN Solutions, strongSwan.
- Full Text
- Performance Evaluation of Software Routers with VPN Features
- Page(s)
- 74-79
- Doi
- 10.5937/telfor1702074R
Performance of a TV white space database with different terrain resolutions and propagation models
A. M. Fanan, N. G. Riley, M. Mehdawi, and O. Alfahad
- Topic:
- Radio Communications
- Abstract
- Cognitive Radio has now become a realistic option for the solution of the spectrum scarcity problem in wireless communication. TV channels (the primary user) can be protected from secondary-user interference by accurate prediction of TV White Spaces (TVWS) by using appropriate propagation modelling. In this paper we address two related aspects of channel occupancy prediction for cognitive radio. Firstly we investigate the best combination of empirical propagation model and spatial resolution of terrain data for predicting TVWS by examining the performance of three propagation models (Extended-Hata, Davidson-Hata and Egli) in the TV band 470 to 790 MHz along with terrain data resolutions of 1000, 100 and 30 m, when compared with a comprehensive set of propagation measurements taken in randomly-selected locations around Hull, UK. Secondly we describe how such models can be integrated into a database-driven tool for cognitive radio channel selection within the TVWS environment.
- Keywords
- Path loss, Diffraction, Propagation Model, Spectrum Measurement, TVWS, Cognitive Radio.
- Full Text
- Performance of a TV white space database with different terrain resolutions and propagation models
- Page(s)
- 80-85
- Doi
- 10.5937/telfor1702080F
DSP implementation of surround speaker virtualizer for sound bar systems
N. Kaprocki, J. Kovačević, R. Pečkai Kovač, and M. Malko
- Topic:
- Signal Processing
- Abstract
- This paper describes one solution for an implementation of the surround speaker virtualization module for a digital signal processor in a sound bar system. The main problem in this system, which consists of a decoder, a renderer and a post-processing module, is complex processing of sound in real-time. In order to achieve real-time execution of these operations and offer customers an affordable product, sound bar system is implemented on an embedded platform. A detailed overview of the system architecture and available resources is given, as the development of modules in an embedded system requires optimal resource usage. Furthermore, numerous challenges and constraints of real-time system programming are presented through the implementation of surround virtualization module, an integral part of the post-processing block. The merits of the proposed architecture are fortified with the measured usage of limited processor resources, and evaluation results confirm that real-time execution of the proposed solution is achieved.
- Keywords
- audio processing, DSP, real-time, sound bar, surround sound, virtualization.
- Full Text
- DSP implementation of surround speaker virtualizer for sound bar systems
- Page(s)
- 86-91
- Doi
- 10.5937/telfor1702086K
Sparse Representation of FHSS Signals in the Hermite Transform Domain
M. Brajović, A. Draganić, I. Orović, and S. Stanković
- Topic:
- Signal Processing
- Abstract
- Signal sparsity is exploited in various signal processing approaches. Signal compression, classification, coding, as well as the recently introduced compressed sensing are some examples where the possibility to represent a signal sparsely determines the efficiency of the applied processing technique. However, the possibility of a sparse signal representation in a transform basis is highly dependent on the signal nature. Therefore, finding a suitable basis where the signal exhibits a compact support is a challenging task. In this paper, the Hermite Transform (HT) is considered as a sparsity domain for the FHSS wireless communication signals. The transform coefficients sparsification is done by optimizing the scaling factor and time-shift of basis functions. The optimization is done by minimizing the concentration measure of HT coefficients. The theory is verified by numerical examples with synthetic FHSS signals.
- Keywords
- FHSS signals, signal sparsity, sparsification, Hermite transform domain.
- Full Text
- Sparse Representation of FHSS Signals in the Hermite Transform Domain
- Page(s)
- 92-97
- Doi
- 10.5937/telfor1702092B
An Automated Environment for Hardware Testing Using PXI Instrumentation and LabVIEW Software
V. D. Ćatić, N. M. Lukić, I. M. Salom, V. P. Ristić, M. M. Kabović, B. Ž. Planić, and N. M. Nenadić
- Topic:
- Applied Electronics
- Abstract
- Reliable and fast testing was a requirement in the serial production of the advanced wireless microphone MIKME. Hence, a system for automatic testing, fully adapted for the product, was developed. The system comprises: 1) a specially designed test fixture – bed-of-nails, on which the device under test is placed, 2) the PXI platform and 3) an application developed in LabVIEW environment. Throughout the design of this system the goal was to achieve maximal automation of the entire test procedure in order to minimize the influence of human factor, and therefore save time and significantly reduce the possibility of error.
- Keywords
- automated hardware testing, LabVIEW, PXI, test procedures, virtual instrumentation.
- Full Text
- An Automated Environment for Hardware Testing Using PXI Instrumentation and LabVIEW Software
- Page(s)
- 98-103
- Doi
- 10.5937/telfor1702098C
Sentiment Classification of Documents in Serbian: The Effects of Morphological Normalization and Word Embeddings
V. Batanović and B. Nikolić
- Topic:
- Software Tools and Applications
- Abstract
- An open issue in the sentiment classification of texts written in Serbian is the effect of different forms of morphological normalization and the usefulness of leveraging large amounts of unlabeled texts. In this paper, we assess the impact of lemmatizers and stemmers for Serbian on classifiers trained and evaluated on the Serbian Movie Review Dataset. We also consider the effectiveness of using word embeddings, generated from a large unlabeled corpus, as classification features.
- Keywords
- comparative evaluation, lemmatization, morphology, sentiment analysis, stemming, word embeddings.
- Full Text
- Sentiment Classification of Documents in Serbian: The Effects of Morphological Normalization and Word Embeddings
- Page(s)
- 104-109
- Doi
- 10.5937/telfor1702104B
Distributed Resource Allocation in Cloud Computing Using Multi-Agent Systems
A. Mazrekaj, D. Minarolli, and B. Freisleben
- Topic:
- ddSoftware Tools and Applications
- Abstract
- The Infrastructure-as-a-Service model of cloud computing allocates resources in the form of virtual machines that can be resized and live migrated at runtime. This paper presents a novel distributed resource allocation approach for VM consolidation relying on multi-agent systems. Our approach uses a utility function based on host CPU utilization to drive live migration actions. Experimental results show reduced service level agreement violations and a better overall performance compared to a centralized approach and a threshold-based distributed approach.
- Keywords
- Cloud computing, live migration, multi-agent systems, utility function, virtual machines.
- Full Text
- Distributed Resource Allocation in Cloud Computing Using Multi-Agent Systems
- Page(s)
- 110-115
- Doi
- 10.5937/telfor1702104M
ERRATA
- Topic:
- ERRATA
- Abstract
- Errata to the July 2017 issue of the Telfor Journal.
- Keywords
-
- Full Text
- ERRATA
- Page(s)
- 116-116
- Related article is available here. link
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, Ružica Bilibajkić, Milan Bjelica, Vesna Blagojević, Zlatko Bundalo, Jelena Ćertić, Miloš Cvetanović, Nebojša Dončov, Vujo Drndarević, Dejan Dunđerski, Milica Đurić-Jovičić, Ana Gavrovska, Dušan Grujić, Predrag Ivaniš, Valentina Janev, Toni Janevski, Milica Janković, Nenad Jevtić, Slobodan Jovičić, Petar Knežević, Nenad Kojić, Goran Kvaščev, Vančo Litovksi, Ivan Luković, Marija Malnar, Goran Marković, Miomir Mijić, Aleksandar Nešković, Milorad Paskaš, Slavche Pejoski, Neda Pekarić-Nađ, Lucian Andrei Perisoara, Slobodan Petričević, Grozdan Petrović, Miloš Petrović, Dragana Prokin, Siniša Ranđić, Branimir Reljin, Andreja Samčović, Mirjana Simić Pejović, Vladimir Slavković, Mirjana Stojanović, Aleksandar Sugaris, Dragana Šumarac Pavlović, Miodrag Tasić, Branimir Trenkić, Željen Trpovski, Verica Vasiljević, Marija Zajeganović