Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
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Article The Research and Design of Multi Relays in Cooperative Communication System Based on Polar Codes(2021) Hadi Hadı, Ali Sameer; Gazi, OrhanIn this paper, we propose a method to increase the performance of cooperative communication using polar codes. For this purpose, we consider non-line-of sight (NLOS) cooperative communication scheme where destination node does not receive signal from source directly. The relay nodes use decodes and forward approach. We propose a voting scheme for the relay nodes, which share information among them. It is shown by the simulation results that the proposed approach significantly improves the performance of relayed communication.Article Odak Dışı Beslemeli Silindirik Parabolik Reflektör Antenlere Ait Işıma İntegralinin Optimizasyonu(2005) Yalçın, Uğur; Umul, Yusuf ZiyaBu çalışmada, ( , ,z ρ 0 φ0 ) koordinatlarına yerleştirilmiş çizgisel akım kaynağıyla beslenen, z eksenine paralel sonsuz uzun mükemmel iletken içbükey silindirik parabolik reflektör antenden saçılma problemi göz önüne alınmıştır. İlk olarak, Hertz vektörüne ait yüzey ışıma integrali Fiziksel Optik (FO) yöntemi kullanılarak belirlenmiştir. Bu integral ifadesin de görülen Green fonksiyonu tanımlanmış ve yüzeye ait normal birim vektörü ile yüzeye gelen toplam magnetik alan bileşeninin vektörel çarpımı elde edilmiştir. Daha sonra bu ifadeler ışıma integralinde yerine yazılmış ve integralin ' z katı hesaplanmıştır. Neticede, FO ışıma integrali sadece ' φ katına bağlı olarak ifade edilebilmiştir. Elde edilen integral ifadesinden faydalanılarak anten sistemine ait ışıma diyagramları, ilgili parametrelerin çeşitli değerleri için polar koordinatlarda çizdirilmiş ve böyle bir anten sisteminin tasarımı için en optimum durum araştırılmıştır. Çalışmada silindirik parabolik reflektör antenin çalışma frekansı 2 (GHz) olarak seçilmiştirArticle Fast Calculation of Polar Code Bits and Frozen-Bit Locations(2021) Genç, Fatih; Gazi, OrhanIn this paper, we show that encoding operation for the polar codes can be achieved without the employment of the generator matrix, and all the polar code bits can be generated at the same time using a number of tree-encoding structures running in parallel. Since encoding matrix is not used in the implementation of the polar encoders in digital electronic devices, hardware space is saved, and low complexity hardware applications are achieved. Besides, we also proposed a method for the calculation of split channel parameters, such as Bhattacharyya bounds or average-bit-error probabilities of the transmitted bits using a tree-based structure. Moreover, the proposed structure enables to calculate the probability of bit-error values of all the transmitted bits at the same time in a parallel manner and decide the locations of data and frozen bits very rapidly.Article High Performance Low Latency Parallel Successive Cancelation Decoder Structures for Polar Codes(2020) Alrataim, Abdelkareim; Gazi, OrhanPolar codes are decoded using successive cancellation (SC) algorithm where likelihood ratios (LRs) for data bits are calculated in a sequential manner, and decisions are made using the calculated LRs. During the decoding of an information bit, the decision results for the predecessor bits are used, and a wrongly decided predecessor bit has negative effect on the accurate calculation of the LR for the information bit being decoded. In SC algorithm, when LR=1, the information bit is decoded as u ̂_i=0, however, such a decision has 50% of chance of being correct. In this paper, we propose improved polar decoders utilizing a number of SC decoders. We consider the case of LR=1, and propose polar decoder structures for the more accurate calculation of the LRs of the successor bitsArticle Diffraction Theory of Waves by Resistive Surfaces(2010) Umul, Yusuf Ziya; Yalçın, UğurDiffraction of scalar plane waves by resistive surfaces are investigated by defining a new boundary condition in terms of the Dirichlet and Neumann conditions. The scattering problems of waves by a resistive half-plane and the interface between resistive and perfectly magnetic conducting half-planes are examined with the developed method. The resulting fields are plotted numerically. The numerical results show that the evaluated field expressions are in harmony with the theory.Article Comparative Analysis of Early Studies on Turkish Whistle Language and a Case Study on Test Conditions(2018) Özaydın, SelmaThis paper examines the early studies on Turkish Whistle Language and it argues that they have some controversial results. The study considers these issues need to be discussed and searched again in terms of linguistic and phonetic form. Unfortunately, there are few research studies on Turkish whistle language and most of them were performed nearly fifty years ago despite the fact that this language still has been used in Kuskoy region. Therefore, the findings of these early research studies could give valuable information to start to a new research study on the subject. The first scientific study on Turkish Whistle language was performed by a French scientist R.G. Busnel with his multidisciplinary research team in 1967. Some of this research’s results were published in the book. A Turkish scientist O. Baskan also participated in Busnel’s research group and published a paper on TWsL in 1968. However, some assertions such as people having a tendency to understand the Turkish whistle language with three vowels and three consonants have not been in the research results of R.G. Busnel. In addition, a Turkish scientist D. Aksan in Turkey had performed another research at Kuskoy region with his own team. Their test methods were different from the previous ones. This paper analyzes these research results on a comparative basis and presents the common and conflicted issues to discuss the uncertain points. The comparative evaluation of these past research studies aims to highlight the controversial position of the results on Turkish Whistle Language. In this scope, this paper opens a discussion about the selection of test conditions for an acoustic and linguistic analysis of the Turkish whistle language.Article Scattering of plane waves by a half-plane at the interface of two ısorefractive media(2015) Başdemir, Hüsnü DenizScattering of plane waves by a half-plane at the boundary of two isorefractive media is analyzed. The E-polarization case is taking into account. The results were analyzed numerically and compared with a similar previous study. The results are consistent with each other.Conference Object A Sequential Coding Approach for Short Length LT Codes over A WGN Channel(IEEE, 2017) Abdulkhaleq, Nadhir Ibrahim; Gazi, OrhanLuby Transform (LT) codes which can be considered as one of the first type of rate less codes are introduced to be an efficient erasure code. In such codes a fountain of encoded symbols is continuously transmitted until the successfully delivery of all the data packets. Whenever the receiver collects N noisy encoded symbols the decoding operation starts. Usually belief propagation (BP) algorithm is used to decipher the code and extract the k data symbols. In this paper, short length LT codes are generated using efficient sequential encoding approach (SEA) and performance measurements have been done over additive white Gaussian (A WGN) channel. This coding technique generates its degree in a repeated sequential manner which yields a mutual relation between adjacent codes that will be used in the decoding part. The decoding complexity of the proposed structure is similar to that of the Raptor codes. The simulation results show that the proposed approach has better performance in terms of error floor and successful decoding ratio when compared to LT codes using robust soliton distribution (RSD) and memorybased-RSD (MBRSD) even when supported by belief propagation-pattern recognition (BP-PR) technique.Conference Object İki izorefraktif ortam arasına yerleştirilmiş empedans sınır koşuluna sahip yarım düzlemden düzlemsel dalgaların saçılması(2016) Başdemir, Hüsnü Deniz; Umul, Yusuf Ziyaİki izorefraktif ortamın sınırına yerleştirilmiş empedans sınır koşuluna sahip bir yarım düzlemden düzlemsel dalgaların saçılması incelenir. Elde edilen alan ifadeleri sayısal olarak analiz edilir.Article Photodetector Engineering with Plasmonic Properties(2021) Kurt, Hasan Furkan; Atabey, Tuğba Nur; Dereli, Onat Cavit; Salmanogli, Ahmad; Geçim, H. SelçukIn the article, the main goal is to study the effect of the plasmonic properties on the photocurrent generated by a photodetector. Fundamentally, a typical photodetector is designed and simulated using the finite element methods. To utilize the plasmonic effect, gold nanoparticles with different shape, size and morphology are buried into the intrinsic region. Plasmonic effect is arisen through the interaction of the incoming light with nanoparticles by which electrical properties of the photodetector are manipulated. In fact, using plasmonic nanoparticles not only increases the absorption bandwidth of the incoming light, but also generates a high intensity near-field close to the plasmonic nanoparticles. Those properties strongly affect the generated photocurrent. The simulation results show that using plasmonic nanoparticles significantly enhances the electrical properties of the photodetectors. More importantly, one can easily manipulate the plasmonic properties of the gold nanoparticles through engineering the nanoparticles' size, shape and morphology. Another important phenomenon is plasmon-plasmon interaction inside the photodetector. It is shown that plasmon-plasmon interaction improves the electron-hole generation rate by which the rate of the current generation is severely enhanced. This is the key factor that we want to focus on, to improve the photodetector electrical properties.