Browsing by Author "Gazi, Orhan"

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A Sequential Coding Approach for Short Length LT Codes over A WGN Channel
(2017) Abdulkhaleq, Nadhir Ibrahim; Gazi, Orhan; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 (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.
A sequential coding approach for short length lt codes over awgn channel
(IEEE, 2017) Abdulkhaleq, Nadhir Ibrahim; Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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: 1
Analysis of Parallel Decodable Turbo Codes
(Ieice-inst Electronics information Communications Eng, 2012) Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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) Pan, Miao; Joshi, Gyanendra Prasad; Gazi, Orhan; He, Jianhua; Coupechoux, Marceau; Kim, Sung W.; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - WoS: 4
Citation - Scopus: 4
Bounds for Generalized Gamma Distributed Fading Channels
(Ieee-inst Electrical Electronics Engineers inc, 2011) Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 - WoS: 7
Citation - Scopus: 8
Collision Free Row Column S-Random Interleaver
(Ieee-inst Electrical Electronics Engineers inc, 2009) Yilmaz, A. Oezguer; Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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 - WoS: 3
Citation - Scopus: 6
Decoding of Lt-Like Codes in the Absence of Degree-One Code Symbols
(Electronics Telecommunications Research inst, 2016) Gazi, Orhan; Abdulkhaleq, Nadhir I.; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
Dijital Mantık Devrelerinin Tasarımı
(Seçkin Yayıncılık, 2018) Gazi, Orhan; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - WoS: 1
Citation - Scopus: 1
The Effect of Error Propagation on the Performance of Polar Codes Utilizing Successive Cancellation Decoding Algorithm
(Advanced Electromagnetics, Geeps-supelec, 2019) Gazi, Orhan; Andi, Alia A.; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, we discuss and analyze the effect of error propagation on the performance polar codes decoded using the successive cancellation algorithm. We show that error propagation due to erroneous bit decision is a catastrophic issue for the successive cancellation decoding of polar codes. Even a wrong decision on a single bit may cause an abundance of successor bits to be wrongly decoded. Furthermore, we observe that the performance of polar codes is significantly improved if even single bit errors are detected and corrected before the decoding of successor bits.
Fast Calculation of Polar Code Bits and Frozen-Bit Locations
(2021) Genç, Fatih; Gazi, Orhan; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In 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.
Citation - WoS: 5
Fast Decodable Turbo Codes
(Ieee-inst Electrical Electronics Engineers inc, 2007) Gazi, Orhan; Yilmaz, A. Ozgar; 102896; 111575; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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: 9
Fast Decoding of Polar Codes Using Tree Structure
(inst Engineering Technology-iet, 2019) Gazi, Orhan; Andi, Alia A.; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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.
High Performance Low Latency Parallel Successive Cancelation Decoder Structures for Polar Codes
(2020) Alrataim, Abdelkareim; Gazi, Orhan; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Polar 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 bits
The Implementation of a Successive Cancellation Polar Decoder on Xilinx System Generator
(Ieee, 2017) Colak, Ayse; Gazi, Orhan; Arli, A. Cagri; 206005; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Polar coding is the first kind of the capacity achieving codes which are defined for binary-input discrete memoryless channels initially. Parallel processing property of the FPGA allows to decode faster with a margin of complexity. Xilinx System Generator as a practical tool to construct decoding designs in shorter time is a fact. In this study, FPGA implementation of decoding polar codes through Xilinx System Generator is shown.
Information Theory for Electrical Engineers
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - Scopus: 1
Information theory perspective of polar codes and polar encoding
(Springer Science and Business Media B.V., 2019) Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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) Arlı, A. Çağrı; Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Low Latency Hybrid Structures Involving Convolutional Product Like Codes and Space Time Codes
(Springer, 2017) Al-Kattan, Ahmed A. S.; Gazi, Orhan; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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: 2
Mathematical Modeling of Stochastic Resonance Systems
(Ieee, 2018) Gazi, Orhan; Arli, A. Cagri; 102896; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Knowledge of at which condition in a nonlinear threshold system stochastic resonance phenomena occurs, can be important in noise introduced threshold systems. A new method for mathematical modeling of stochastic resonance systems is introduced. The proposed approach can be used for the modeling of many other phenomenons. It's shown that using the mathematical model developed for stochastic resonance systems it's possible to estimate the optimum noise variances necessary for the occurrence of the stochastic resonance. The accuracy of the estimated noise variances are verified by the simulation results.
Matlab Uygulamalı Sayısal Sinyal İşleme
(Seçkin Yayınevi, 2019) Gazi, Orhan; 06.02. Elektronik ve Haberleşme Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Kitap, gördüğü yoğun ilgi sonucunda kısa sürede 2. Baskısını yapmıştır. Bu kitapta sayısal sinyal işleme konularını Matlab uygulamaları ile ele alınmıştır. Bunun için ilk olarak Matlab komutlarını kısa ve öz bir şekilde anlatılmıştır. Daha sonra sayısal sinyal işlemenin temel konuları olan örnekleme, analog sinyallerin örneklerinden yeniden oluşturulması, örnek azaltma, örnek arttırma, ayrık Fourier dönüşüm ve analog ve sayısal filtre tasarımı konularının Matlab uygulamaları yapılmıştır. Kitap, lisans düzeyindeki üniversite öğrencileri için hazırlanmış olmasının yanı sıra bunun dışında sinyal işlemeyle ilgilenen herkes de bu kitaptan faydalanabilir. Unutulmamalıdır ki bir mühendis kendisini teorik bilgilerin pratikte uygulamalarını yaparak geliştirebilir. Bu kitap, sinyal işlemede geçen teorik bilgilerin yazılım olarak uygulamalarını içermektedir.