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Article Citation - WoS: 4Citation - Scopus: 6On the Classification of Modulation Schemes Using Higher Order Statistics and Support Vector Machines(Springer, 2022) Coruk, Remziye Busra; Gokdogan, Bengisu Yalcinkaya; Benzaghta, Mohamed; Kara, AliThe recognition of modulation schemes in military and civilian applications is a major task for intelligent receiving systems. Various Automatic Modulation Classification (AMC) algorithms have been developed for this purpose in the literature. However, classification with low computational complexity as well as reasonable processing time is still a challenge. In this paper, a feature-based approach along with various classifiers is employed based on statistical features as well as higher-order moments and cumulants. An over-the-air (OTA) recorded dataset consisting of four analog and ten digital modulation schemes are used for testing the proposed method at 0-20 dB SNR. The overall accuracy for quadratic Support Vector Machine (SVM) is found to be as high as 98% at 10 dB. The comparison of the results with other AMC papers published in the literature indicates that the proposed method present higher accuracy, especially for realistic channel induced OTA dataset.Article Citation - WoS: 29Citation - Scopus: 36Massive Mimo Systems for 5g: a Systematic Mapping Study on Antenna Design Challenges and Channel Estimation Open Issues(inst Engineering Technology-iet, 2021) Benzaghta, Mohamed; Rabie, Khaled M.The next generation of mobile networks (5G) is expected to achieve high data rates, reduce latency, as well as improve the spectral and energy efficiency of wireless communication systems. Several technologies are being explored to be used in 5G systems. One of the main promising technologies that is seen to be the enabler of 5G is massive multiple-input multiple-output (mMIMO) systems. Numerous studies have indicated the utility of mMIMO in upcoming wireless networks. However, there are several challenges that needs to be unravelled. In this paper, the latest progress of research on challenges in mMIMO systems is tracked, in the context of mutual coupling, antenna selection, pilot contamination and feedback overhead. The results of a systematic mapping study performed on 63 selected primary studies, published between the year 2017 till the second quarter of 2020, are presented. The main objective of this secondary study is to identify the challenges regarding antenna design and channel estimation, give an overview on the state-of-the-art solutions proposed in the literature, and finally, discuss emerging open research issues that need to be considered before the implementation of mMIMO systems in 5G networks.Research Project Yansımaları Kullanarak Emisyon Kaynaklarının Yer Tespiti(2021) Tabakcıoğlu, Mehmet Barış; Benzaghta, Mohamed; Imran, Md Abdullah Al; Taş, Sümeyra; Kara, Ali; Maiga, Bamoye; Dalveren, YaserBu projede, deniz yüzeyi ve çevresindeki girinti çıktının çok olduğu bölgeler (kıyılar, koylar, adaların yoğun bölgeler vb.) başta olmak üzere, yansımaların olduğu tüm (askeri/sivil) operasyonel ortamlarda, yansımaların kullanılması suretiyle bir temas alıcısı (geniş bant pasif alıcı) tarafından emisyon kaynaklarının konumlarının tespit edilmesine yönelik yöntem ve araçlar geliştirilmiştir. Geliştirilen yöntemde, öncelikli olarak pürüzlü/düzensiz (rough and irregular) araziler üzerindeki saçılma merkezlerinin kestirimi yapılmaktadır. Bunu yapabilmek için, sayısal harita bilgileri bilinen ve yöntemin çalıştırılması öngörülen bölgelerde (örneğin, Ege Denizi ve çevresi), temas alıcısında var olan ölçüm yeteneklerinin de yardımıyla, emisyon kaynağına (radar vericisi) yönelik parametreler (darbe genişliği, hüzme açısı gibi) kullanılarak yansıma olan muhtemel bölgelerin sınırları belirlenmektedir. Ardından, muhtemel saçılma merkezleri belirlenerek, arazi kesitleri üzerinde radyo yayılım kayıpları, yüksek frekanslı teknikler (GTD/UTD) ve dalga yayılım etkileri (yansıma, kırınım) kullanan bir ışın izleme algoritmasıyla hesaplanmaktadır. Ayrıca, geliştirilen ışık izleme algoritması ile, saçılma merkezlerinin çok yollu yayılımın kaynağı olma olasılıkları da hesaplanabilmektedir. Geliştirilen yöntemin sonraki aşamasında, saçılma merkezleri yer tespit/konumlamada kullanılmak üzere yapay sensör olarak belirlenmektedir. Belirlenen yapay sensörler, çoklu sensör uygulaması için literatürde bilinen bir Varış Zaman Farkı (VZF: Time Difference of Arrival-TDOA) konumlama tekniğinde kullanılmaktadır. Yöntemin son aşamasında ise TDOA tekniği ile elde edilen pozisyonlar ile saçılma merkezlerinin çok yollu yayılımın kaynağı olma olasılıkları ağırlıklı ortalama alma yönteminde kullanılarak emisyon kaynağının konumu/pozisyonu kestirilmektedir. Bu şekilde, temas alıcısı ile birlikte yansımaların yapay sensör olarak kullanılması suretiyle, tek bir alıcı ile sabit emisyon kaynaklarının konumlanması yapılabilmektedir. Geliştirilen yöntemin kestirim doğruluğu ve uygulanabilirliği yüksek çözünürlüklü (DTED2) sayısal harita verileri ile gerçekçi senaryolar üzerinde benzetimler yapılarak değerlendirilmiştir. Elde edilen sonuçlar, geliştirilen yer tespit yönteminin elektronik harp uygulamalarında genel olarak uygulanabilir olduğunu doğrulamaktadır.Article Citation - WoS: 1Citation - Scopus: 2A Miniaturized Multi-Layer Microstrip Antenna for Linear Wireless Sensor Network Monitoring Systems(Gazi Univ, 2022) Kara, Ali; Aydın, Elif; Benzaghta, Mohamed; Er, Burak; Bilgin, GulsimaThis article presents a sub-GHz ISM band microstrip patch antenna based on the use of multi-layer compact structure, which overcomes the shortcomings of typical microstrip antennas such as low gain and high resonant frequency. The antenna was simulated using an electromagnetic simulator, ANSYS HFSS, and fabricated on two different substrates: RT Duroid 5880 and FR4 epoxy with a compact size of 100 x 100 x 8 mm3 (0.29λ × 0.29λ × 0.02λ). The simulated results of the antenna were then compared with the measured ones, and the two were observed to have a reasonable agreement. The proposed antenna operates in the sub-GHz license-free ISM band (862-875 MHz), with a gain value of 2.92 dB. Two prototypes of the proposed antenna were fabricated and used in a Linear Wireless Sensor Networks (LWSNs) monitoring system. Results show that the proposed antenna is a good candidate for those types of LWSNs systems.Article Citation - Scopus: 1A Hybrid-Flipped Classroom Approach: Students' Perception and Performance Assessment(Univ Nac Colombia, Fac ingenieria, 2023) Gokdogan, Bengisu Yalcinkaya; Coruk, Remziye Busra; Benzaghta, Mohamed; Kara, AliThis study presents an improved hybrid-flipped classroom (hybrid-FC) education method based on technology-enhanced learning (TEL) along with diluted classes for a course on probability and random processes in engineering. The proposed system was implemented with the participation of two student groups who alternated weekly between attending face-to-face activities and fully online classes as a sanitary measure during the pandemic. The education model was combined with the flipped classroom (FC) approach in order to improve the quality of learning and address the negative effects of remote education. Before the lessons, the students studied the course material, filled a question form, and then took a low- stake online quiz. Then, the students attended a session where the questions reported in the forms were discussed, and they took an online problem-solving session followed by an individual quiz. Class sessions were available to both online and face-to-face students, as well as in the form of video recordings for anyone who missed lessons. Qualitatively and quantitatively, the proposed education method proved to be more effective and comprehensive than conventional online methodologies. The students' performances were evaluated via quizzes and exams measuring the achievement of the course learning outcomes ( CLOs). Weekly pre/post-tests were applied to examine the students' progress in each topic. Midterm and final exams were planned to measure the level of success for all course topics. Additionally, the students' perception was assessed with questionnaires and face-to-face interviews. A performance assessment showed an apparent increase in the success rate, and the students' perception was found to be positive.
