Yazar "Seyman, Muhammet Nuri" seçeneğine göre listele

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    Adaptive arrangement of cyclic prefix length for MC-CDMA systems via multi-objective bat algorithm
    (Springer London Ltd, 2018) Seyman, Muhammet Nuri
    Multi-carrier multiplexing systems, used in high bit rate communication applications, are more affected by the time- or frequency-dependent fading effects incurring in the channel than the single-carrier systems. When the fading effects at multi-carrier systems are not taken into consideration, inter-carrier interference or inter-symbol interferences that cause bit error rate increase at the receiver would occur. In order to eliminate these interference effects, the cyclic prefix is used in MC-CDMA systems, which are the kind of multi-carrier systems. However, determining how long the CP length is to be used will directly affect both the error and the capacity performance of the system. In this study, multi-objective bat algorithm is proposed for the adaptive arrangement of the CP lengths according to the channel conditions. Contrary to the standard CP determination methods, not only the bit errors are minimized, but also the maximization of the channel capacity is provided by the utilization of MOBA.
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    Ateş böceği algoritması kullanarak MC-CDMA sistemlerinde çevrimsel ön takı uzunluğunun belirlenmesi
    (2017) Seyman, Muhammet Nuri
    Çok taşıyıcılı kod bölmeli çoklu erişim gibi yüksek hızlarda veri iletimini sağlayan çok taşıyıcılı haberleşme sistemlerinde semboller arası girişim ve kanallar arası girişimi önlemek için çevrimsel ön takıdan faydalanılır. Bu yüzden çevrimsel ön takı uzunluğunun uygun bir şekilde belirlenmesi, sadece hata performansını artırmayacak aynı zamanda da sembol enerjisindeki azaltmaları da engelleyecektir. Bu çalışmada çevrimsel ön takı uzunluklarının belirlenmesi için yeni bir meta-sezgisel algoritma olan ateş böceği algoritması önerilmiştir. Önerilen bu algoritmayı kullanarak, Genetik Algoritmalar ve 1/8 oranlı çevrimsel ön takı kod uzunluklu sistemlere göre daha iyi bit hata oranları elde edilmiştir. Parametre sayısının az ve performansının Genetik Algoritmalara göre yüksek olması nedeniyle bu algoritma çok taşıyıcılı kod bölmeli çoklu erişim sistemlerinde çevrimsel ön takı boyutlarının adaptif olarak belirlenmesinde kullanılabilir
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    Channel estimation based on neural network in space time block coded MIMO-OFDM system
    (Academic Press Inc Elsevier Science, 2013) Seyman, Muhammet Nuri; Taspinar, Necmi
    In this study, we propose feed-forward multilayered perceptron (MLP) neural network trained with the Levenberg-Marquardt algorithm to estimate channel parameters in MIMO-OFDM systems. Bit error rate (BER) and mean square error (MSE) performances of least square (LS) and least mean square error (LMS) algorithms are also compared to our proposed neural network to evaluate the performances. Neural network channel estimator has got much better performance than LS and LMS algorithms. Furthermore it doesn't need channel statistics and sending pilot tones, contrary to classical algorithms. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.
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    Cooperative spectrum sensing method for MC-CDMA systems in cognitive radio networks
    (Ieee, 2018) Yilmazel, Rustem; Seyman, Muhammet Nuri
    The development of wireless communication networks has made spectrum management more compulsory. Different systems such as Multi-carrier code division multiple access (MC-CDMA) have to be adapted for cognitive radio technology to solve this problem. In this article, cooperative spectrum sensing technique, which is one of the spectrum sensing techniques, is adapted to MC-CDMA technology. This method can be used to decrease the mathematical density of the obtained spectral characteristics or to get better the probability of detection. Cognitive radio has made it possible to make spectrum perception more effective and reduce the possibility of false perception. The aim is to increase the likelihood that an unauthorized user will be able to identify the presence of a licensed user by cooperating with each other. The theoretical value and the simulated result are compared and then the results are interpreted according to the changing signal-to-noise ratios (SNRs).
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    Determination of the cyclic prefix length in MC-CDMA using firefly algorithm
    (Pamukkale Univ, 2017) Seyman, Muhammet Nuri
    Cyclic prefix is utilized to prevent intermho) interference and inter currier interference M multi currier communication,systems such us multi -carrier code division multiple access that provides high speed data transmission, Therefore determination of the cyclic prefix Length properly, not only increases the error performance but also prevents the reduction in symbol energy. In this tvork, the fire fly algorithm which is a new metu-heuristic algorithm, is proposed to determine the CP length, By using the proposed algorithm, the better bit error rate in comparison with Genetic Algorithms and 1/8 rate cyclic prefix systems was obtained. Due to the less parameters and high performance of this algorithm over Genetic Algorithms; it can he used in multi currier cock division multiplexing systems to determine the cyclic prefix length adoptively.
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    Energy Detection Approach for Spectrum Sensing in Cognitive Radio Systems
    (2018) Yılmazel, Rüstem; Seyman, Muhammet Nuri; Tuna, Eyüp
    Because a large number of licensed users have occasionally used their allocated bandwidth in recent years, efficient use of frequency band is a vital issue. While licensed users continue to use this bandwidth for publishing, unused bands can be allocated for reuse to provide broadband network services. These empty bands are described as white space and cover a large part of the bandwidth. It is possible to activate this great potential by cognitive radio technology. In this study, energy detection technique was used to detect unused bands. With this technique, it is determined which frequency band is suitable and there will be done appropriately theassignment of the second user.
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    A Novel Subcarrier Allocation Algorithm for MC–CDMA Systems
    (Slovak Univ Technology, 2016) Seyman, Muhammet Nuri; Sacakli, Bircan
    Multi carrier modulation techniques such as MC-CDMA are used in high-speed communication applications. Due to MC-CDMA being a multiuser in technology, the subcarrier quantity allocated per user decreases in case the quantity of active users increases. Consequently, data rates per user are reduced with the increase in the bit error rate (BER). Efficient allocation of subcarriers to users within the system can aid the overcoming of this problem. This study develops a new algorithm for subcarrier allocation and system performance improvement in terms of BER, and data rates in comparison to other algorithms were ensured.
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    Optimization of pilot tones using differential evolution algorithm in MIMO-OFDM systems
    (2012) Seyman, Muhammet Nuri; Taşpınar, Necmi
    In this paper, we propose a differential evolution (DE) algorithm for optimizing the placement and power of the pilot tones that are utilized by a least square (LS) algorithm for channel estimation in multipleinput and multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. Computer simulations demonstrated that the performance of the LS algorithm was increased by optimizing the pilot tones with the DE algorithm instead of locating them orthogonally. We used the upper bound of the mean square error (MSE) as a fitness function of the DE algorithm for optimization tasks. With the use of an upper bound, it is not necessary to compute the matrix inversion that is needed in computing the MSE.
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    Particle swarm optimization for pilot tones design in MIMO-OFDM systems
    (Springer, 2011) Seyman, Muhammet Nuri; Taspinar, Necmi
    Channel estimation is an essential task in MIMO-OFDM systems for coherent demodulation and data detection. Also designing pilot tones that affect the channel estimation performance is an important issue for these systems. For this reason, in this article we propose particle swarm optimization (PSO) to optimize placement and power of the comb-type pilot tones that are used for least square (LS) channel estimation in MIMO-OFDM systems. To optimize the pilot tones, upper bound of MSE is used as the objective function of PSO. The effects of Doppler shifts on designing pilot tones are also investigated. According to the simulation results, PSO is an effective solution for designing pilot tones.
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    Pilot Tones Optimization Using Artificial Bee Colony Algorithm for MIMO-OFDM Systems
    (Springer, 2013) Seyman, Muhammet Nuri; Taspinar, Necmi
    How to design the pilot tones that are used in channel estimation has a significant effect on the estimation performance. To achieve good performance in least square (LS) algorithm, we propose the artificial bee colony (ABC) algorithm for optimizing the placement of pilot tones in MIMO-OFDM systems. We also derive the upper bound of mean square error of LS estimation with the help of Gerschgorin disc theorem for fitness function of ABC algorithm. The results show that designing pilot tones using the ABC algorithm outperforms other considered placement strategies in terms of high system performance and low computational complexity.
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    Subcarrier Allocation Algorithm Based on Greedy-Like in Multi Carrier Code Division Multiple Access Systems
    (Kaunas Univ Technology, 2017) Seyman, Muhammet Nuri; Demiral, Bircan
    One of the most important issues to be taken into consideration in multi carrier communication systems with multi users is the assignment of the available resources to the users efficiently. Thus, how to determine the number of subcarriers to be allocated to the users has an important role with regards to data rate and error performance of the system when active users are increased in multi carrier system. In this study by using Greedy-Like algorithm, the subcarriers in MC-CDMA systems are optimal allocated to the users and the efficiency of this algorithm compared with other algorithms in terms of bit error and bit rate performance.
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    Symbol detection using the differential evolution algorithm in MIMO-OFDM systems
    (Tubitak Scientific & Technological Research Council Turkey, 2013) Seyman, Muhammet Nuri; Taşpınar, Necmi
    Channel estimation and symbol detection in multiple-input and multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) systems are essential tasks. Although the maximum likelihood (ML) detector reveals excellent performance for symbol detection, the computational complexity of this algorithm is extremely high in systems with more transmitter antennas and high-order constellation size. In this paper, we propose the differential evolution (DE) algorithm in order to reduce the search space of the ML detector and the computational complexity of symbol detection in MIMO-OFDM systems. The DE algorithm is also compared to some heuristic approaches, such as the genetic algorithm and particle swarm optimization. According to the simulation results, the DE has the advantage of significantly less complexity and is closer to the optimal solution.