Mühendislik Fakültesi

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Citation - Scopus: 1
A New Companding Technique for Papr Reduction in Ofdm Communication Systems
(2011) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
One of the major disadvantages of OFDM communication systems is their high peak-to-average power ratio (PAPR) which degrades system performance when nonlinear power amplifiers are employed. Among the proposed PAPR tech- niques companding is favorable due to its simplicity and easy of implementation. In this article, using the arctan- gent function we propose a new compading technique for PAPR reduction. We compare the proposed technique to the previously suggested exponential companding, and μ- law companding methods. Via computer simulations it is verified that the proposed technique is better than exponen- tial and μ-law companding methods for PAPR reduction.
A sequential coding approach for short length lt codes over awgn channel
(IEEE, 2017) Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Luby 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 (AWGN) 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 memory-based-RSD (MBRSD) even when supported by belief propagation-pattern recognition (BP-PR) technique.
Citation - Scopus: 2
A Tutorial Introduction to VHDL Programming
(Springer Singapore, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
This book helps readers create good VHDL descriptions and simulate VHDL designs. It teaches VHDL using selected sample problems, which are solved step by step and with precise explanations, so that readers get a clear idea of what a good VHDL code should look like. The book is divided into eight chapters, covering aspects ranging from the very basics of VHDL syntax and the module concept, to VHDL logic circuit implementations. In the first chapter, the entity and architecture parts of a VHDL program are explained in detail. The second chapter explains the implementations of combinational logic circuits in VHDL language, while the following chapters offer information on the simulation of VHDL programs and demonstrate how to define data types other than the standard ones available in VHDL libraries. In turn, the fifth chapter explains the implementation of clocked sequential logic circuits, and the sixth shows the implementation of registers and counter packages. The book’s last two chapters detail how components, functions and procedures, as well as floating-point numbers, are implemented in VHDL. The book offers extensive exercises at the end of each chapter, inviting readers to learn VHDL by doing it and writing good code. © Springer Nature Singapore Pte Ltd. 2019.
Citation - WoS: 0
Citation - Scopus: 1
Analysis of parallel decodable turbo codes
(Ieice-inst Electronics information Communications Eng, 2012) Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Turbo codes suffer from high decoding latency which hinders their utilization in many communication systems. Parallel decodable turbo codes (PDTCs) are suitable for parallel decoding and hence have low latency. In this article, we analyze the worst case minimum distance of parallel decodable turbo codes with both S-random interleaver and memory collision free Row-Column S-random interleaver. The effect of minimum distance on code performance is determined through computer simulations.
Citation - WoS: 6
Citation - Scopus: 6
Applications of Cognitive Radio Networks: Recent Advances and Future Directions
(Sage Publications inc, 2016) Kim, Sung W.; Gazi, Orhan; Pan, Miao; Joshi, Gyanendra Prasad; Gazi, Orhan; He, Jianhua; Coupechoux, Marceau; 102896; Elektronik ve Haberleşme Mühendisliği
Citation - WoS: 4
Citation - Scopus: 4
Bounds for generalized gamma distributed fading channels
(Ieee-inst Electrical Electronics Engineers inc, 2011) Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this article, upper bounds for the outage probability and moment generating functions of the fading channels with alpha - mu distribution are derived. The proposed upper bound for the moment generating function is used in the performance evaluation of M - PSK communication systems. The derived expressions are simple to use and do not require complex software tools to evaluate. We verified the proposed expressions via numerical computations.
Citation - Scopus: 0
Channel Coding Theorem
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will discuss the channel coding theorem in details. Channel coding theorem can be accepted as a milestone in electronic communication field. For this reason, it is very critical for a communication engineer to comprehend the channel coding theorem very well. In many information theory books, or in many lecture notes delivered in classes about information theory, channel coding theorem is very briefly summarized, for this reason, many readers fail to comprehend the details behind the theorem. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 7
Citation - Scopus: 8
Collision free row column s-random interleaver
(Ieee-inst Electrical Electronics Engineers inc, 2009) Gazi, Orhan; Gazi, Orhan; Yilmaz, A. Oezguer; 102896; Elektronik ve Haberleşme Mühendisliği
Parallel decodable turbo codes (PDTCs) are suitable for concurrent decoding and hence have low latency. Memory collision issue is an important problem met during parallel processing. In this article, we propose a collision free interleaver for parallel processing operations. The performance of PDTCs is analyzed with the proposed random interleaver preventing the memory collision problem. Distance spectra of PDTCs with the proposed interleaves are computed and compared to those with S-random interleaver.
Citation - Scopus: 0
Concept of Information, Discrete Entropy and Mutual Information
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will try to explain the concept of information, discrete entropy and mutual information in details. To master on the information theory subjects, the reader should have a knowledge of probability and random variables. For this reason, we suggest to the reader to review the probability and random variables topics before studying the information theory subjects. Continuous entropy and continuous mutual information are very closely related to discrete entropy and discrete mutual information. For this reason, the reader should try to understand very well the fundamental concepts explained in this chapter, then proceed with the other chapters of the book. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 3
Citation - Scopus: 6
Decoding of LT-like codes in the absence of degree-one code symbols
(Electronics Telecommunications Research inst, 2016) Abdulkhaleq, Nadhir I.; Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Luby transform (LT) codes were the first practical rateless erasure codes proposed in the literature. The performances of these codes, which are iteratively decoded using belief propagation algorithms, depend on the degree distribution used to generate the coded symbols. The existence of degree-one coded symbols is essential for the starting and continuation of the decoding process. The absence of a degree-one coded symbol at any instant of an iterative decoding operation results in decoding failure. To alleviate this problem, we proposed a method used in the absence of a degree-one code symbol to overcome a stuck decoding operation and its continuation. The simulation results show that the proposed approach provides a better performance than a conventional LT code and memory-based robust soliton distributed LT code, as well as that of a Gaussian elimination assisted LT code, particularly for short data lengths.
Citation - Scopus: 0
Entropy for Continuous Random Variables Discrete Channel Capacity, Continuous Channel Capacity
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will study the entropy concept for continuous random variables. The capacity of both continuous and discrete channels will be inspected in details. The capacity formula for additive white Gaussian channel is to be derived and the factors that affects the capacity of the additive white Gaussian channel will be elaborated. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 5
Fast decodable turbo codes
(Ieee-inst Electrical Electronics Engineers inc, 2007) Gazi, Orhan; Gazi, Orhan; Yilmaz, A. Ozgar; 102896; 111575; Elektronik ve Haberleşme Mühendisliği
Decoding delay is an important consideration for the use of turbo codes in practical applications. We propose a new structure for turbo codes which is very suitable for parallel decoding. It is shown by union bound analysis and simulation results that the proposed system performance is comparable to that of the classical turbo codes.
Citation - WoS: 5
Citation - Scopus: 8
Fast decoding of polar codes using tree structure
(inst Engineering Technology-iet, 2019) Andi, Alia A.; Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this study, the authors first propose a tree structure for the successive cancelation (SC) decoding of polar codes. The proposed structure is easy to implement in hardware and suitable for parallel processing operations. Next, using the proposed tree structure, they propose a technique for the fast decoding of polar codes. With the proposed method, it is possible to decode all the information bits simultaneously at the same time, i.e. in parallel. Lastly, they introduce an improved version of the proposed high-speed decoding algorithm. The proposed high-speed decoding approach and its improved version are simulated on the computer environment and their bit error rate performances are compared to the performance of the classical SC method.
Citation - Scopus: 11
Forward Error Correction via Channel Coding
(Springer International Publishing, 2019) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
This book provides a comprehensive explanation of forward error correction, which is a vital part of communication systems. The book is written in such a way to make the subject easy and understandable for the reader. The book starts with a review of linear algebra to provide a basis for the text. The author then goes on to cover linear block codes, syndrome error correction, cyclic codes, Galois fields, BCH codes, Reed Solomon codes, and convolutional codes. Examples are provided throughout the text. Provides a comprehensive treatment of forward error correction Includes examples through the book, which are solved in steps, making them easier to understand Ideal for researchers, professionals and students. © Springer Nature Switzerland AG 2020.
Citation - Scopus: 0
Information theory for electrical engineers
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Information theory perspective of polar codes and polar encoding
(2019) Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Polar codes are one of the recently discovered capacity achieving channel codes. What makes the polar codes different from other channel codes is that polar codes are designed mathematically and their performance are mathematically proven. © Springer Nature Singapore Pte Ltd. 2019.
Karar Yayılım Algoritması ile Kutup Kodlarının Çözümlenmesi
(2018) Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Citation - WoS: 0
Citation - Scopus: 0
Low latency hybrid structures ınvolving convolutional product like codes and space time codes
(Springer, 2017) Gazi, Orhan; Gazi, Orhan; Al-Kattan, Ahmed A. S.; 102896; Elektronik ve Haberleşme Mühendisliği
In this paper, we propose new joint serially concatenated communication structures constructed from convolutional product codes and space time codes. The proposed structures are suitable for parallel processing operations and they have very low decoding latencies compared to their classical counterparts. Use of multi-antennas increases the spectral efficiency of the joint structures.
Citation - Scopus: 1
Mathematical modelling of polar codes, channel combining and splitting
(Springer Science and Business Media B.V., 2019) Gazi, O.; 102896
In Chap. 2, we explained the decoding of polar codes in a clear and trivial manner. However, in most of the engineering sciences, it is critical to mathematically formulate the theories or techniques invented. © Springer Nature Singapore Pte Ltd. 2019.
Citation - WoS: 26
Noise-Aided Belief Propagation List Decoding of Polar Codes
(Ieee-inst Electrical Electronics Engineers inc, 2019) Arli, A. Cagri; Gazi, Orhan; Gazi, Orhan; 102896; 206005; Elektronik ve Haberleşme Mühendisliği
Noise can help weak information bearing signal to be detected in nonlinear systems by the use of stochastic perturbation. In this letter, we propose a novel belief propagation list (BPL) decoder that relies on artificial noise. The proposed decoder is constructed by using parallel independent BP decoders. Noise with different powers are added to different BP decoders that runs in parallel, and the output of the decoder that pass the early detection and termination criteria check is considered as the recovered data. Adding small amount of noise enables the decoder to handle un-converged errors. The obtained results show that the performance of noise-aided BPL decoder is much better than the performances of BP, successive cancelation (SC), and successive cancelation list (SCL) decoders, and it is a bit behind of cyclic redundancy check aided SCL in terms of bit-error rate performance.

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