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 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 bitsConference 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.Editorial Citation - WoS: 6Citation - Scopus: 6Applications 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.Article Citation - WoS: 3Citation - Scopus: 6Decoding of Lt-Like Codes in the Absence of Degree-One Code Symbols(Electronics Telecommunications Research inst, 2016) Gazi, Orhan; Abdulkhaleq, Nadhir I.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.Article Citation - WoS: 10Citation - Scopus: 30The Role of Delay and Connectivity in Throughput Reduction of Cooperative Decentralized Wireless Networks(Hindawi Ltd, 2015) Gazi, Orhan; Sadkhan, Sattar B.; Alkhayyat, AhmedWe proposed a multiple relay selection protocol for decentralized wireless networks. The proposed relays selection protocol aims to address three issues: (1) selecting relays within the coverage area of the source and destination to ensure that the relays are positioned one hop away from the destination, (2) ensuring that the best node (best relays with less distance and attenuation from the destination) access the channel first, and (3) ensuring that the proposed relays selection is collision-free. Our analysis also considers three important characteristics of decentralized wireless networks that are directly affected by cooperation: delay, connectivity, and throughput. The main goal of this paper is to demonstrate that improving connectivity and increasing number of relays reduce the throughput of cooperative decentralized wireless networks; consequently, a trade-off equation has been derived.Article Citation - WoS: 17Citation - Scopus: 22Turbo Product Codes Based on Convolutional Codes(Wiley, 2006) Yilmaz, Ali Ozgur; Gazi, OrhanIn this article, we introduce a new class of product codes based on convolutional codes, called convolutional product codes. The structure of product codes enables parallel decoding, which can significantly increase decoder speed in practice. The use of convolutional codes in a product code setting makes it possible to use the vast knowledge base for convolutional codes as well as their flexibility in fast parallel decoders. Just as in turbo codes, interleaving turns out to be critical for the performance of convolutional product codes. The practical decoding advantages over serially-concatenated convolutional codes are emphasized.