Telfor Journal Vol.10 No.2 (2018)
Content
Editorial 
Editor-in-Chief:
Prof. Dr Đorđe Paunović
Characterization of Nonlinearities in a Class-J Power Amplifier
B. Bukvić and M. M. Ilić
- Topic:
- Radio Communications
- Abstract
- We characterize the nonlinearities of our previously designed 10 W class-J power amplifier with a carrier at 1.5 GHz. We employ numerical simulations and real time adjacent channel power ratio (ACPR) measurements on the fabricated prototype. The measurements are performed for a wideband code division multiple access (WCDMA) signal with 10.5 dB peak-to-average power ratio (PAPR) and 3.84 MHz bandwidth.
- Keywords
- ACPR, class-J, high-efficiency, microwave power amplifier, nonlinearities.
- Full Text
- Characterization of Nonlinearities in a Class-J Power Amplifier
- Page(s)
- 70-73
- Doi
- 10.5937/telfor1802070B
Real-time Internet of Things Architecture for Wireless Livestock Tracking
B. Risteska Stojkoska, D. Capeska Bogatinoska, G. Scheepers, and R. Malekian
- Topic:
- Radio Communications
- Abstract
- Automatic livestock tracking is necessary for countries facing stock theft problems, like South Africa and Kenya. This paper presents a conceptual design of architecture for real-time wireless livestock tracking based on Internet of Things paradigm. It is a hierarchical model consisting of three building blocks, where the first block is represented with wireless sensor network. Additionally, we have developed a low-power device for livestock tracking in an outdoor environment. The animal tracking device (AnTrack) is self-sustainable with a watertight solar panel(s), designed as a collar to be worn by the animals. A detailed analysis of the AnTrack power consumption proves that the device is capable to generate enough supply power, even when there is no sunshine for a week. This device can be used as a robust building block of future real-time Internet of Things livestock tracking solutions.
- Keywords
- livestock tracking architecture, Internet of Things, animal collar.
- Full Text
- Real-time Internet of Things Architecture for Wireless Livestock Tracking
- Page(s)
- 74-79
- Doi
- 10.5937/telfor1802074R
Suitability of Variance Shift Keying for Real Conditions
R. I. Sokolov and R. R. Abdullin
- Topic:
- Signal Processing
- Abstract
- This paper investigates the possibility of real-life using the brand new type of digital modulation, which implies the transmission of white Gaussian noise whose variance changes in time. That modulation has been entitled as variance shift keying. The signals obtained on its basis have a high level of transmission security, and they even cannot be detected by standard means of matched filtering. However, the paper suggests the decision on how to process these signals at the receiver site. It is proposed to use a specially developed optimal receiver, whose restoration quality appears to be better in comparison with the conventional cumulative receiver. The digital simulation of propagation in frequency selective media has shown the signal with variance shift keying is possible to be used in real conditions since its distribution of instantaneous amplitudes remains Gaussian.
- Keywords
- NULLcumulative receiver, free space propagation, inconstant variance, matched filter, optimal receiver, signal hiding, signal interception, variance shift keying, white Gaussian noise.
- Full Text
- Suitability of Variance Shift Keying for Real Conditions
- Page(s)
- 80-85
- Doi
- 10.5937/telfor1802080S
Analyses of Decimation Filter Stopband Attenuation Influence on Subjective Quality of Audio Signals
N. Petrović, M. Bjelić, J. Ćertić, M. Stanojević, and D. Šumarac Pavlović
- Topic:
- Multimedia
- Abstract
- Decimation is a frequently used technique in audio signal processing. This paper investigates the influence of the values of stopband attenuation of decimation filters on the subjective perception of resulting audio signals. In practice, the demands for stopband attenuation of these filters are quite rigorous. The paper examines how justified these demands are from the psychoacoustic point of view. Basic procedure within such a research is a subjective test. Aside from objective parameters, the subjective evaluation is a method that can give insight into the characteristics of audio signal processing under testing. Results of subjective testing of the influence of different values of stopband attenuation on the perceptibility of interfering signal are presented for various audio signals. Two types of interfering signals were used in the subjective test. To increase the validity of psychoacoustic test, the probability of false detection of differences is measured by presenting subjects with equivalent signals. The results of subjective testing can prove to be useful in the design process of decimation filters for audio system applications.
- Keywords
- Subjective testing, Decimation, Filters, Psychoacoustics, Placebo, Critical bands.
- Full Text
- Analyses of Decimation Filter Stopband Attenuation Influence on Subjective Quality of Audio Signals
- Page(s)
- 86-90
- Doi
- 10.5937/telfor1802086P
An Extended Evaluation of Schema Issues Advisor in the Azure SQL Database
D. Dundjerski, S. Lazić, M. Tomašević, and D. Bojić
- Topic:
- Software Tools and Applications
- Abstract
- The analysis of the telemetry data in Azure SQL database has revealed that most of the problems affecting the customers are due to the schema inconsistency errors. An assumption has been made that direct e-mail notifications sent to the customers about the current problems could significantly shorten time to resolve them. The prospective benefits are first validated by sending e-mail recommendations manually. Then, in an iterative way, the schema issue advisor that detects anomalies and automatically sends the appropriate notifications to the customers is implemented on top of Azure resources. Finally, an extended evaluation has confirmed the expected benefits of direct communications with the customers.
- Keywords
- Azure SQL database platform, Schema issue advisor, Feature validation and testing, Cloud services.
- Full Text
- An Extended Evaluation of Schema Issues Advisor in the Azure SQL Database
- Page(s)
- 91-96
- Doi
- 10.5937/telfor1802091D
Identity Provider Deployment Based on Container Technology
M. S. Eremija, N. R. Ilić, M. Cvetanović, J. Protić, and Z. Radivojević
- Topic:
- Software Tools and Applications
- Abstract
- Identity Providers are an integral part of Identity Federations. Many different and complex technologies are needed to create an Identity Provider. In order to be able to fully utilize all the benefits of Identity Federations, adequate hardware resources are needed for Identity Provider deployment. Containers address the complexity and resources issues, while enabling faster deployment and keeping the functionalities and core concepts intact at the same time. Containers cannot be perceived as a replacement for virtual machines or bare metal servers, as they are meant to co-exist and have already found a wide range of use cases. This paper proposes using containers for easier implementation of Identity Providers, while lowering resource usage and complexity imposed by deployment requirements.
- Keywords
- Containers, Docker, Identity Federations, SAML, Single Sign-On.
- Full Text
- Identity Provider Deployment Based on Container Technology
- Page(s)
- 97-101
- Doi
- 10.5937/telfor1802097E
Design and Implementation of a Configurable System for Managing X509 Certificates
M. B. Vukasovic, B. S. Veselinovic, and Z. S. Stanisavljevic
- Topic:
- Software Tools and Applications
- Abstract
- In this paper a design and an implementation of a configurable system for managing the X509 certificates is described. The X509 certificates are one of the most important standards used today in a large number of different authentication mechanisms. As such, they represent one of the important topics at the Computer Security course at the School of Electrical Engineering, University of Belgrade. The system described in this paper has been used within the practical project at the Computer Security course. It provides the ability to generate, sign, and manipulate X509 certificates and it’s implemented in such a way that the graphical user interface (GUI) is completely separated from the logic. This way of implementation relaxes the students from GUI programming and enables them to concentrate on programming the part related to the certificates – security part of the project. The system has been successfully used at the course in the previous school year and the new and improved version is going to be used in this school year.
- Keywords
- Authentication, Computer Security, Information Security, E-learning Software Systems, X509 Certificates.
- Full Text
- Design and Implementation of a Configurable System for Managing X509 Certificates
- Page(s)
- 102-107
- Doi
- 10.5937/telfor1802102V
Experiences in the Teaching of the DataFlow Paradigm: Lessons Learned
N. Trifunovic, M. Kotlar, O. Andric, P. Trifunovic, S. Stojanovic, M. Cvetanovic, Z. Radivojevic, M. Punt, N. Korolija, and V. Milutinovic
- Topic:
- Software Tools and Applications
- Abstract
- The DataFlow paradigm has been existing for a long time, but good enough enabling technologies have been made available only very recently. The teaching of a different from the mainstream paradigm, such as the DataFlow paradigm, encounters a few problems. If a new paradigm is presented among experienced professionals, the presentation is often received with resistance. If a new paradigm is presented before students, the presentation is always received with enthusiasm, especially if tools and libraries that support the paradigm do exist. In order to overcome the problem with introducing the new paradigm, a series of courses was organized for Universities in the USA and Europe, to teach the DataFlow paradigm, using the Maxeler approach as the baseline for practical work. The course is organized in three different levels: (A) full-hour presentation that includes introducing the programming model with hands-on examples, which is most appropriate for research groups at Universities (B) a certified full-day short-course that students could use as an extension to diploma, (C) full-semester course for credits that is part of graduation requirement. This paper discusses different methods and their results, which could be used in order to efficiently introduce any different from the mainstream paradigm. The results presented in this paper are for 10 universities in the group A, 10 in the group B, and 10 in the group C. Where appropriate, the findings are backed with statistics data.
- Keywords
- Big data, Dataflow, Paradigm shift, Sea of gates, Teaching.
- Full Text
- Experiences in the Teaching of the DataFlow Paradigm: Lessons Learned
- Page(s)
- 108-111
- Doi
- 10.5937/telfor1802108T
Experience-Oriented Conceptual Space for Designing the System with Software
P. Sosnin
- Topic:
- Software Tools and Applications
- Abstract
- The design of any system with software is a behavioral process that encompasses a certain area of the physical space on the definite interval of time. The space of designing is useful for expressing in forms of the corresponding models. The paper presents a reflection of an operational space onto a conceptual space CS(t) that is experience-oriented. It can be achieved via question-answer interactions of designers with an accessible experience and it, in its turn, will facilitate increasing the success of designing.
- Keywords
- Conceptual space, designing, question-answering, project task, software engineering.
- Full Text
- Experience-Oriented Conceptual Space for Designing the System with Software
- Page(s)
- 112-117
- Doi
- 10.5937/telfor1802112S
Design of Fully Homomorphic Encryption by Prime Modular Operation
S. Shihab Hamad and A. Makki Sagheer- Topic:
- Software Tools and Applications
- Abstract
- The meaning of cloud computing is the Information Technology (IT) model for computing, which consists of all the IT components (software, hardware, services and, networking) that are needed to enable the delivery and development of cloud services through a private network or the internet. In cloud computing, the client (user) puts his data in the cloud, and any computations on his stored data will be implemented in the cloud. Security is the main thing in cloud computing because a service provider can access, intentionally change or even delete the stored data. To protect data that is stored in the cloud, it is necessary to use an encryption system that can perform computations on the encrypted data. The scheme that allows executing several computations on the encrypted message without decrypting the message is called homomorphic encryption. The implementation of fully homomorphic encryption over the integer (DGHV scheme) and a Simple Fully Homomorphic Encryption Scheme Available in Cloud Computing (SDC Scheme), are slow in execution time because all of them convert the message to a binary format and then encrypt it. Therefore, we propose another scheme called Fully Homomorphic encryption based on a prime modular operation, this scheme encrypts the message character by character by using a prime secret key without converting that character into a binary format. As a result, we compute the time complexity and compare the execution time among the three schemes and analyse the security of the three schemes.
- Keywords
- Cloud Computing, Cryptosystem, Fully Homomorphic Encryption, Information Security.
- Full Text
- Design of Fully Homomorphic Encryption by Prime Modular Operation
- Page(s)
- 118-122
- Doi
- 10.5937/telfor1802118S
Automatic Complaint Classification System Using Classifier Ensembles
M. Ali Fauzi- Topic:
- Automatic Classification
- Abstract
- Sambat Online is an online complaint system run by the city government of Malang, Indonesia. Because most citizens do not know to which work units (Satuan Kerja Pemerintah Daerah [SKPDs]) their complaints should be sent, the system administrator must manually sort and classify all of the incoming complaints with respect to the appropriate SKPDs. This study empirically evaluated the application of an automated system to replace the manual classification process. The experiments, which used Sambat Online data, involved five individual classification algorithms— Naïve Bayes, Maximum Entropy, K-Nearest Neighbors, Random Forest, and Support Vector Machines—and two ensemble strategies—hard voting and soft voting. The results show that the Multinomial Naïve Bayes classifier achieved the best performance, an 80.7% accuracy value, of the five individual classifiers. The results also indicate that generally all of the ensemble methods performed better than the individual classifiers. Almost all of them had the same accuracy level of 81.2%. In addition, the soft voting strategy had slightly higher accuracy than the hard one when all five classifiers were used. However, when the three best classifier combinations were used, both had the same level of accuracy.
- Keywords
- Ensemble Learning, E-Government, Machine Learning, Hard Voting, Soft Voting, Complaint classification.
- Full Text
- Automatic Complaint Classification System Using Classifier Ensembles
- Page(s)
- 123-128
- Doi
- 10.5937/telfor1802123A
Contactless Controlled Low-cost Robotic System
S. A. Milojević
- Topic:
- Software Tools and Applications (Student Paper)
- Abstract
- This paper presents and depicts a realization of a robotic arm with four degrees of freedom based on cheap components and software for its control with hand gestures. A position of the arm is determined by processing the acquired data from the sensor. The application is developed using free software packages. Results of this project could find use in industrial robotics, therapeutic biofeedback, telemanipulation systems, etc.
- Keywords
- acquisition, LeapMotion, Python, rehabilitation, robot, control.
- Full Text
- Contactless Controlled Low-cost Robotic System
- Page(s)
- 129-133
- Doi
- 10.5937/telfor1802129M
Development of the Game Hangman in Assembly Programming Language
S. Tešanović and P. Mitrović
- Topic:
- Software Tools and Applications (Student Paper)
- Abstract
- This paper describes the realization of the Hangman game in Microsoft Visual Studio, using the assembler programming language, Kip Irvine's and MASM libraries. Knowledge of the work in the software tool is demonstrated, as well as advanced knowledge of assembler and work with library functions. The obtained game uses less CPU time than its realizations in other higher level programming languages.
- Keywords
- irvine32, masm, assembly, hangman, game.
- Full Text
- Development of the Game Hangman in Assembly Programming Language
- Page(s)
- 134-138
- Doi
- 10.5937/telfor1802134T
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.
Marko Barjaktarović, Milan Bjelica, Dragan Bojić, Milan Čabarkapa, Zoran Čiča, Marko Dimitrijević, Borislav Djordjević, Andjela Draganic, Dejan Drajić, Radivoje Đurić, Aleksandar Erdeljan, Slavko Gajin, Roberto Giorgi, Dušan Grujić, Valentina Janev, Milica Janković, Nenad Jevtić, Kosta Jovanović, Nenad Jovičić, Aleksandra Klašnja‐Milićević, Petar Knežević, Mladen Koprivica, Nenad Krajnović, Ivan Luković, Miroslav Lutovac, Maja Lutovac Banduka, Zlatica Marinković, Goran Marković, Miomir Mijić, Nenad Milošević, Vladimir Mladenović, Vladimir Ostojić, Stevan Ostrogonac, Veljko Papić, Milorad Paskaš, Slavche Pejoski, Cristian Perra, Vladimir Petrović, Jelena Popović-Božović, Aleksandar Rakić, Lazar Saranovac, Dejan Simić, Aleksandra Smiljanić, Leonid Stoimenov, Mirjana Stojanović, Olivera Šveljo, Dejan Tošić, Mladen Trikoš, Željen Trpovski, Pavle Vuletić, Marija Zajeganović