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Article Citation - WoS: 11Citation - Scopus: 15A Study on the Performance Evaluation of Wavelet Decomposition in Transient-Based Radio Frequency Fingerprinting of Bluetooth Devices(Wiley, 2022) Almashaqbeh, Hemam; Dalveren, Yaser; Kara, AliRadio frequency fingerprinting (RFF) is used as a physical-layer security method to provide security in wireless networks. Basically, it exploits the distinctive features (fingerprints) extracted from the physical waveforms emitted from radio devices in the network. One of the major challenges in RFF is to create robust features forming the fingerprints of radio devices. Here, dual-tree complex wavelet transform (DT-CWT) provides an accurate way of extracting those robust features. However, its performance on the RFF of Bluetooth transients which fall into narrowband signaling has not been reported yet. Therefore, this study examines the performance of DT-CWT features on the use of transient-based RFF of Bluetooth devices. Initially, experimentally collected Bluetooth transients from different smartphones are decomposed by DT-CWT. Then, the characteristics and statistics of the wavelet domain signal are exploited to create robust features. Next, the support vector machine (SVM) is used to classify the smartphones. The classification accuracy is demonstrated by varying channel signal-to-noise ratio (SNR) and the size of transient duration. Results show that reasonable accuracy can be achieved (lower bound of 88%) even with short transient duration (1024 samples) at low SNRs (0-5 dB).Article Citation - WoS: 5Heterogeneity in Classes: Cooperative Problem-Solving Activities Through Cooperative Learning(Fac Teacher Education, 2014) Cigdemoglu, Ceyhan; Kapusuz, Kamil Yavuz; Kara, AliTeachers, from primary schools to college, experience challenges regarding both increased class sizes and a greater diversity of students having a broad spectrum of abilities, interests, needs, and goals. The aim of this paper is to investigate the effect of cooperative learning through Cooperative Problem-Solving (CPS) activities on homogenous and heterogeneous grouping in an engineering course. As a mixed method design, the study utilized both quantitative and qualitative data. The participants, 47 engineering students selected conveniently, were enrolled in a communication systems course. The analysis of the quantitative data indicated that no significant difference (p=.791) exists between the ways in which the students in homogenous and the students in heterogeneous group understand communication systems. In order to reveal the perceptions of students regarding the implementation, they were interviewed at the end of the semester. The qualitative data obtained from these interviews suggests that students prefer heterogeneous to homogenous grouping. The findings also imply that further research should concentrate on heterogeneous grouping strategies and more detailed qualitative data in order to reveal what kind of patterns emerge from students' interactions in different groupings.Conference Object Citation - WoS: 1Characterization of Satellite Transponder Impairments Based on Simulations with Test Data(Ieee, 2015) Ulubey, Orhan; Gulgonul, Senol; Kara, AliA satellite transponder simulator based on actual test data of TURKSAT 3A satellite has been developed to analyze degradation in multicarrier scenarios. Communication impairment sources through a transponder are explained in conjunction with a methodology defined to characterize total degradation resulting from them. Several transponder utilization scenarios are studied with respect to total degradation and optimum operation conditions are demonstrated.Article Citation - WoS: 4Citation - Scopus: 8Remote Rf Laboratory Requirements: Engineers' and Technicians' Perspective(Anadolu Univ, 2007) Cagiltay, Nergiz Ercil; Aydin, Elif Uray; Kara, Ali; Department of Electrical & Electronics Engineering; Software EngineeringThis study aims to find out requirements and needs to be fulfilled in developing remote Radio Frequency (RF) laboratory. Remote laboratories are newly emerging solutions for better supporting of e-learning platforms and for increasing their efficiency and effectiveness in technical education. By this way, modern universities aim to provide lifelong learning environments to extend their education for a wider area and support learners anytime and anywhere when they need help. However, as far as the authors concern, there is no study investigating the requirements and needs of remote laboratories in that particular field in the literature. This study is based on electrical engineers' and technicians' perspectives on the requirements of a remote laboratory in RF domain. Its scope covers investigation of the participants' perceptions toward computer mediated communication and it attempts to answer the questions: which studying strategies are preferred by the learners and what kind of RF laboratory content should be provided. The analysis of the results showed that, geographic independence, finding quickly the elements of past communication and temporal independence are declared as the most important advantages of computer-mediated communication. However, reading significant amount of information is a problem of these environments. In the context of how to show the content, respondents want to see shorter text on the screen. Therefore the instructions should include little amount of text and must be supported with figures and interactive elements. The instructional materials developed for such learner groups should support both linear and non-linear instructions. While analyzing the content to be provided, we have seen that, most of the participants do not have access to high level equipments and traditional experiments are considered as the necessary ones for both engineers and technicians.Article Citation - WoS: 3Citation - Scopus: 3Modeling and Measurement of Human Body Blockage Loss at 28 Ghz(Taylor & Francis Ltd, 2023) Benzaghta, Mohamed; Gokdogan, Bengisu Yalcinkaya; Coruk, Remziye Busra; Kara, AliMillimeter-wave (mm-Wave) spectrum is an essential enabler to the fifth generation (5G) wireless technology. Humans are one of the most noticeable blockers that cause temporal variation in indoor radio channels. This paper presents human blockage measurements at 28 GHz, with several humans of different sizes. The effect of the crossing orientations of the human bodies is investigated for three different transmitter heights. A human blockage model based on the Fresnel diffraction scheme is shown to be applicable in estimating the human blockage loss in indoor radio links considering various body sizes, different crossing orientations, and different transmitter heights. The findings reported in this paper could help improve indoor radio channel models at 28 GHz bands for 5G technologies considering the presence of human body blockages.Conference Object Citation - Scopus: 1Development of a Digital Communications Course Enriched by Virtual and Remote Laboratory Tools(2011) Kara,A.; Kara, Ali; Cagiltay,N.; Çağıltay, Nergiz; Dalveren,Y.; Dalveren, Yaser; Kara, Ali; Çağıltay, Nergiz; Dalveren, Yaser; Department of Electrical & Electronics Engineering; Software Engineering; Department of Electrical & Electronics Engineering; Software EngineeringDigital communications is a basic concept for rapidly growing fields of Electrical, Computer and Electronics Engineering like wireless and mobile communication systems, radar and electronic warfare, telemetry and many signal processing techniques. A re-designed digital communications course with ICT (Information and Communication Technologies) based diverse tools including matlab assignments, remote experiments and interactive simulators is described in this study. First, the objectives of the course, learning outcomes and evaluation methods are described. The re-designed course is offered in the last semester at Atilim University, and performance increase in students is compared with the previous year's offering, and by evaluating the course on a topic-based approach. © 2011 IEEE.Conference Object Citation - WoS: 2New Wavelet-Based Features for the Recognition of Jittered and Stagger Pri Modulation Types(Ieee, 2015) Gencol, Kenan; Kara, Ali; At, NurayIn dense electronic warfare environments, numerous emitters can be active simultaneously and an interleaved stream of pulses in natural time of arrival order is received by the Electronic Support Measures (ESM) receiver. It is the task of the ESM system to de-interleave this mixed pulse sequence and thus to identify the surrounding threatening emitters. In this processing, pulse repetition interval (PRI) modulation recognition has a significant role due to the fact that it can reveal the hidden patterns inside pulse repetition intervals and thus help identify the emission source and its functional purpose. In this paper, we propose new wavelet-based features for the recognition of jittered and stagger PRI modulation types. The recognition of these types are heavily based on histogram features. Experimental results show that the proposed feature set have very high recognition rates and outperform histogram based methods.Conference Object Citation - WoS: 1An Industry Sponsored Undergraduate Research (ur) Experience: Preliminary Study on Fulfillment of Program Outcomes and Industry Requirements(Ieee, 2014) Kapusuz, Kamil Yavuz; Kara, AliThis study presents educational results of an industry sponsored undergraduate research (UR) project. The aim of the study is to show how such project works contribute to students in acquiring qualifications or skills necessary by the industry, and abilities regarding with program outcomes of accreditation organisations. The study is based on quantitative (surveys) and qualitative (self descriptions) data collected from senior students who worked in 9 months UR project sponsored by a company in Radio frequency (RF) and Communications domain. The preliminary results showed that an industry sponsored undergraduate research project may serve to both short term (industry requirements) and longer term (program outcomes) expectations in undergraduate curriculum of engineering departments.Conference Object Citation - WoS: 2Citation - Scopus: 3Design Considerations for Sub-Ghz Multilayer Microstrip Antenna for Near Ground Communication Links in Rural Areas(Ieee, 2017) Bilgin, Gulsima; Yilmaz, Vadi Su; Aydin, Elif; Kara, Ali; Department of Electrical & Electronics Engineering; Electrical-Electronics EngineeringThis paper presents some preliminary results of design and development of sub-GHz multilayer microstip antenna for use in near ground communication applications. In design stage of the antenna, iterative approach was applied. Firstly, a two layer microstrip antenna design process is presented. Next, the corners of the patch were cut, and a vertical wall on all sides of the antenna were introduced. In this way, both the size and resonant freqeuncy can be tuned. Moreover, as an application specific requirement, it is intended to embed this antenna into a metal box in order to protect it from man-made and natural environmental effects. This was also studied, and effects of the embedding ground on the antenna characteristics were examined. It is shown that the designed antenna provides -27dB resturn loss, and 7.3dB peak gain at 915MHz with the dimension of 150x200x13mm. Some preliminary measurements have proven the simulations.Article Citation - WoS: 14Citation - Scopus: 16Reliability of Linear Wsns: a Complementary Overview and Analysis of Impact of Cascaded Failures on Network Lifetime(Elsevier, 2022) Carsancakli, Muhammed Fatih; Imran, Md Abdullah Al; Yildiz, Huseyin Ugur; Kara, Ali; Tavli, BulentLinear Wireless Sensor Networks (LWSNs) are used in applications where deployment scenarios necessitate sensor nodes to be placed over a line topology. However, such a deployment raises reliability concerns because almost all the nodes in the network are critical with respect to the survivability of the LWSN. It is possible that an LWSN can stay connected even if a subset of the nodes are eliminated, yet, the potential reduction in Network Lifetime (NL) due to such an occurrence can be significant. In this study, after presenting a concise survey of the literature on LWSN reliability, we present an elaborate optimization framework to model the operation of an LWSN, which is built upon a comprehensive system model. Our framework encompasses three transmission power and packet size assignment strategies, which are instrumental in characterizing LWSN behavior. Furthermore, we utilized two-node failure models (i.e., random and coordinated) to assess the vulnerability of LWSNs from multiple perspectives. The results of this study reveal that the impact of coordinated node failures on NL is more severe than the impact of random node failures to such extent that in strongly connected LWSNs, the percentage decrease in NL due to coordinated node failures can be more than a magnitude higher than the NL decrease due to random node failures.
