Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
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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.Publication Hierarchical Control With Partial Observations: Sufficient Conditions(IEEE, 2011) Boutin, Olivier; Komenda, Jan; Masopust, Tomas; Schmidt, Klaus Werner; Van Schuppen, Jan H.In this paper, hierarchical control of both monolithic and modular discrete-event systems under partial observations is studied. Two new conditions, called observation consistency and local observation consistency, are proposed. These conditions are sufficient for the preservation of observability between the original and the abstracted plant. Moreover, it is shown that both conditions are compositional, that is, they are preserved by the synchronous product. This property makes it possible to use hierarchical and decentralized supervisory control for discrete-event systems with partial observations.Publication On parallelized serially concatenated codes(IEEE, 2007) Gazi, Orhan; Yılmaz, A. ÖzgüerSerial concatenated codes show very good performance at low signal to noise ratios. However, large decoding delays due to long input frame lengths constitute a major disadvantage for these type of codes. In this study we introduce a new class of concatenated convolutional codes which are very suitable for parallel decoding, thus have much less decoding delays and also show comparable performance to that of classical serial concatenated convolutional codes. The analytical upper bound expressions for performance of the proposed structures are derived using the uniform interleaver concept.Publication Hierarchical decision making and decision fusion(IEEE, 2007) Beldek, Ulaş; Leblebicioğlu, KemalIn this study, a hierarchical decision making structure possessing a decision fusion technique is proposed in order to solve decision making problems efficiently. The proposed structure mainly depends on effects of the decisions made in the lower levels to decisions in the upper levels up to an activation degree. The proposed hierarchical structure is used for detecting the fault degrees for single and multiple fault scenarios artifically generated in a four tank system. The results obtained demonstrate the effectiveness of the proposed hierarchical decision making structure.Publication Developing growing hierarchical structures for decision making(IEEE, 2007) Beldek, Ulaş; Leblebicioğlu, KemalThis study is about developing a hierarchical approach for decision-making problems. The development is done on a representative decision-making problem. A hierarchical decision making approach which enables fusion of decisions of previous and current levels is proposed. The agents that determine the decisions at different hierarchy levels is accomplished by utilizing a genetic algorithm.Publication Analysis of delay factors for voice over WiMAX(IEEE, 2008) Şafak, A.; Preveze, B.This paper presents the results of our computer simulation for delays experienced by voice packets over WiMAX 802.16e protocol running over an enterprise packet network connected to public internet. In the simulation we analyzed the effect of packet size, core network link speed, internet service provider link speed, wireless network link speed, wireless distance, base station range, and distance in internet parameters that effect the amount of delay in a WiMAX embedded IP network. In this study, all the delay parameters are fixed to their default values and current parameter values are changed so that the delay is varied between minimum and maximum values in uniformly distributed 100 steps and the delay is plotted in each step. Total fixed delays can be considered as minimum delay and variable delay corresponds to the maximum delay that can occur under the given conditions. All other fixed and variable delay parameters such as switching delays, packetization delays, contention delays and the delays caused by buffers etc. are also taken into account. The results indicate that among these delays WiMAX base station range and the number of base stations play the most decisive role.Publication Design of irregularly shaped patch antennas by using the multiport network model(IEEE, 2008) Şener, Göker; Alatan, Lale; Kuzuoğlu, MustafaBook Part Review On The Modified Theory of Physical Optics(IEEE, 2018) Başdemir, Hüsnü DenizIn this review, modified theory of physical optics approach to the diffraction problem is revisited. The important aspects of the method are explained and steps for the usage of the method are revealed. Also, historical progress of the method is mentioned.Publication Use of matrix pade approximation in the analysis of ırregularly shaped patch antennas with multiport network model(IEEE, 2009) Şener, Göker; Alatan, Lale; Kuzuoğlu, MustafaA new procedure for implementing the multiport network model for analyzing two-dimensional microwave circuits is proposed. The proposal procedure leads to more efficient evaluation of impedance matrices than the procedure known earlier. The computational efforts in the two procedures are compared.Publication Propagation of optical flat-topped gaussian beams in satellite links(IEEE, 2009) Kamacıoğlu, Canan; Altay Arpalı, Serap; Baykal, Yahya; Yazgan, ErdemPropagation of optical flat-topped Gaussian beams in earth-satellite optical communication links is investigated where part of the link is turbulent atmosphere. Flat-topped Gaussian source field is obtained by superposing many Gaussian beams of different source size. Starting with the flat-topped Gaussian incidence at the earth surface, the average intensity at the satellite is formulated by using the extended Huygens Fresnel principle. For the structure constant variation versus height, Hufnagel-Valley model is employed in the vertical and slant paths. The received average intensity is numerically calculated and the effects of the source and medium parameters on the received average intensity profile are examined for different zenith angles. In earth-satellite optical communications links, the advantages of using flat-topped Gaussian beams as compared to Gaussian beams are scrutinized.