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Öğe BER Performance Analysis for NOMA Systems with OTFS Modulation(Ieee, 2023) Umakoglu, Inci; Namdar, Mustafa; Basgumus, Arif; Ozyurt, Serdar; Kulac, SelmanThis study examines the non-orthogonal multiple access (NOMA) system that is modulated with orthogonal time-frequency-space (OTFS), which is a potential waveform candidate that is frequently used in sixth-generation (6G) wireless communication networks and is shown to improve performance in high mobility scenarios. In the proposed OTFS modulated NOMA system, bit error rate performance for near and far users is presented with the help of the message passing detection algorithm.Öğe Bit Error Rate Performance Improvement for Orthogonal Time Frequency Space Modulation with a Selective Decode-and-Forward Cooperative Communication Scenario in an Internet of Vehicles System(Mdpi, 2024) Kulac, Selman; Sahin, MuejdatOrthogonal time frequency space (OTFS) modulation has recently found its place in the literature as a much more effective waveform in time-varying channels. It is anticipated that OTFS will be widely used in the communications of smart vehicles, especially those considered within the scope of Internet of Things (IoT). There are efforts to obtain customized traditional point-to-point single-input single-output (SISO)-OTFS studies in the literature, but their BER performance seems a bit low. It is possible to use cooperative communications in order improve BER performance, but it is noticeable that there are very few OTFS studies in the area of cooperative communications. In this study, to the best of the authors' knowledge, it is addressed for the first time in the literature that better performance is achieved for the OTFS waveform transmission in a selective decode-and-forward (SDF) cooperative communication scenario. In this context, by establishing a cooperative communication model consisting of a base station/source, a traffic sign/relay and a smart vehicle/destination moving at a constant speed, an end-to-end BER expression is derived. SNR-BER analysis is performed with this SDF-OTFS scheme and it is shown that a superior BER performance is achieved compared to the traditional point-to-point single-input single-output (SISO)-OTFS structure.Öğe Büyük Ölçekli Mimo Sistemlerde Pilot Kirliliğini Azaltmaya Yönelik Çağdaş Yaklaşımlar(Osman SAĞDIÇ, 2022) Köse, Esra Cansu; Yayılkan, Abdulkadir; Kulac, Selman; İlk, HakkıBüyük Çoklu Giriş Çoklu Çıkış (MIMO), gelecekte mobil ağlar için yüksek veri kapasitesi talebini karşılamak için umut verici bir teknolojidir. MIMO sistemlerinde kanal durum bilgisinin (CSI) elde edilmesi, enerji ve spektrum verimliliği sağlar. Bu nedenle, CSI'nin doğruluğu çok önemlidir. Zaman Bölmeli Çift Yönlendirme (TDD), Massive MIMO sistemlerinde CSI elde etmek için iyi bir alternatif yöntemdir. CSI elde etmek için pilot diziler kullanılır. Pratikte, her kullanıcı terminaline farklı bir pilot dizisi atamak mümkün değildir. Özellikle Massive MIMO sistemlerinde farklı hücrelerde aynı pilot dizilerin kullanılması pilot kontaminasyonu sorununa neden olmaktadır. Bu sorunu azaltmak için birçok çalışma yapılmıştır. Bu çalışmada, pilot kontaminasyonunun nedenleri tartışılmakta ve pilot kontaminasyonunu ortadan kaldırmak veya azaltmak için literatürde önerilen yöntemler sunulmaktadır. Ayrıca, Massive MIMO'da pilot kontaminasyonla ilgili güvenlik durumu ve gelecekteki sistemlerde önemli olabilecek diğer ilgili konular vurgulanmıştır.Öğe Çok Girişli Çok Çıkışlı Sistemler için Güç Tahsisi Algoritmaları(Osman SAĞDIÇ, 2021) Dikmen, Osman; Kulac, SelmanÇok büyük çok girişli çok çıkışlı sistem (Massive MIMO) beşinci nesil (5G) ve ötesi kablosuz iletişim teknolojilerinin performanslarını geliştirmek için önemli bir sistem olarak hala geçerliliğini korumaktadır. Spektrum verimliliği (SE), enerji verimliliği (EE) bu performanslar arasındadır. Son zamanlarda birbirleriyle bağlantılı cihazların artması, internet of things (IoT) sistemlerin gün geçtikçe yayılması ve buna rağmen kaynakların sınırlı olmasından dolayı çeşitli performans geliştirmeleri kaçınılmaz olmuştur. Massive MIMO ile birlikte bu tür iyileştirmeleri gerçekleştirmek için çeşitli çalışmaların olduğu görülmektedir. Özellikle spektrum verimliliği ve enerji verimliliği için birçok araştırmalar mevcuttur. Çünkü enerji konusu ve bant genişliği problemi ilk olarak çözülmesi ve geliştirilmesi gereken konular arasındadır. Son yıllarda bu iki problemin çözümüne yönelik güç tahsisi algoritmalarına odaklanıldığı anlaşılmaktadır. Bu çalışmada, güç tahsisi algoritmaları hakkındaki araştırmalar incelenmiştir. Çalışmaların temel noktaları üzerinde durulmuştur. Ayrıca temel güç tahsisi algoritmaları arasında yer alacak üç farklı güç tahsisi algoritmasının birbirleri arasında kıyaslaması spektrum verimliliği açısından gerçekleştirilmiştir.Öğe A Comprehensive Review on ISAC for 6G: Enabling Technologies, Security, and AI/ML Perspectives(Ieee-Inst Electrical Electronics Engineers Inc, 2025) Aldirmaz-Colak, Sultan; Namdar, Mustafa; Basgumus, Arif; Ozyurt, Serdar; Kulac, Selman; Calik, Nurullah; Yazici, Mehmet AkifIntegrated sensing and communication (ISAC) has received significant attention over the past five years as a key component of the 6G vision for next-generation communication systems. Starting with the fundamentals of ISAC, we present strategies focused on sensing-centric and communication-centric ISAC systems that satisfy both radar and communication objectives using the same physical hardware and waveform. The communication-centric ISAC focuses primarily on improving communication performance beyond 5G/6G cellular networks and Wi-Fi standards, while also performing additional processing required for detection. On the other hand, the sensing-centric ISAC prioritizes sensing and detection capabilities while incorporating communication functions in the most efficient way possible. In this survey, we present a comprehensive review of both ISAC systems along with new approaches for enabling technologies and highlight unique challenges and existing solutions that are already available. We explore the roles of innovative functions in enabling ISAC, including joint waveform design, edge computing, vehicular sensing and communications, and their practical applications. We then discuss 3GPP standardization efforts related to ISAC as a future direction for the 6G vision. We also outline possible future research directions, with a specific emphasis on security, artificial intelligence, and machine learning.Öğe Extraction of Novel Features Based on Histograms of MFCCs Used in Emotion Classification from Generated Original Speech Dataset(Kaunas Univ Technology, 2020) Pakyurek, Muhammet; Atmis, Mahir; Kulac, Selman; Uludag, UmutThis paper introduces two significant contributions: one is a new feature based on histograms of MFCC (Mel-Frequency Cepstral Coefficients) extracted from the audio files that can be used in emotion classification from speech signals, and the other - our new multi-lingual and multi-personal speech database, which has three emotions. In this study, Berlin Database (BD) (in German) and our custom PAU database (in English) created from YouTube videos and popular TV shows are employed to train and evaluate the test results. Experimental results show that our proposed features lead to better classification of results than the current state-of-the-art approaches with Support Vector Machine (SVM) from the literature. Thanks to our novel feature, this study can outperform a number of MFCC features and SVM classifier based studies, including recent researches. Due to the lack of our novel feature based approaches, one of the most common MFCC and SVM framework is implemented and one of the most common database Berlin DB is used to compare our novel approach with these kind of approaches.Öğe Investigation of Ideal Number User Terminals with Spectrum Efficiency in Next Generation Wireless Communication Systems(Int Information & Engineering Technology Assoc, 2021) Dikmen, Osman; Kulac, SelmanSuppose that a multi-user multiple-input multiple-output (MIMO) system is developed from scratch to equally envelop a defined region with optimal spectrum efficiency (SE) in next generation wireless communication systems such as sixth-generation (6G) and beyond networks. What are the ideal number of user terminals U, number of base stations antennas, and used pilot reuse factor? The purpose of this paper is to address this specific issue. Three interference levels are specified for this. Based on these interference levels, signal-to-interference-and-noise ratios (SINRs) are extracted. Closed-form spectrum efficiency equations are thus obtained. As a function of the base station (BS) antenna number, simulations are carried out considering multiple pilot reuse factors and diverse processing schemes such as Maximum Ratio Combining (MRC) and Zero-Forcing (ZF). From the results, it is understood that U varies according to the processing schemes. Therefore, evaluating the results considering the fixed number of users K will not give an accurate result in determining the design parameters for the next generation communication systems. In general, these results are useful statements that spectrum efficiency is maximized when the ideal number of users U is used in multi-cell systems.Öğe Web Page Information Extraction System by Using Deep Learning(Ieee, 2019) Pakyurek, Muhammet; Sezgin, Mehmet Selman; Kulac, SelmanIn many companies, business units that aim to online sell, need every type of referential data about the market. In order to collect this data which can be group of price, content, survey etc. with a predefined format, websites which sell similar products can be used. The methods used in the data collection process are generally categorized by 3 main groups: 1 Manual 2-Half Manual 3-Auto. Statically coded data collectors (type 1 and type 2) are unable to collect healthy data in the long term and require continuous development and maintenance effort, as Internet pages are dynamic and changes would happen frequently in their page designs. In this study, a data scraping application (type 3) which is not affected by structural changes in web pages was developed. This study aims to obtain data from images of web pages using Deep CNNs.
