Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/11

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Author: search.filters.author.Baştürk, İlhanWoS Q: search.filters.wosQuartile.N/A

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Now showing 1 - 9 of 9
  • Conference Object
    Citation - WoS: 2
    Citation - Scopus: 2
    Gezgin Rölelerin Dfbçe Tabanlı Hücresel Ağ Performansına Etkisi
    (Institute of Electrical and Electronics Engineers Inc., 2014) Baştürk, İlhan; Özbek, Berna
    OFDMA-based mobile relay enhanced cellular networks which have lower infrastructure cost and larger coverage areas are important technologies for the next generation communication systems since they allow to communicate at higher data rates. However, it is required to develop efficient radio resource management algorithms in order to reveal these advantages. Thus, in this study, relay selection and resource allocation algorithms are proposed for the mobile relay enhanced cellular networks. It is revealed that the number of satisfied users and the data rate of the cell-edge users that are far from the base station and have lower channel gains are increased by using mobile relays with the proposed algorithms.
  • Conference Object
    Çoklu Kullacılı Çgtç-dfbçe Sistemleri için Adil Kaynak Paylaşımı
    (IEEE, 2011) Baştürk, İlhan; Özbek, Berna
    In this study, the user selection at the base station and resource allocation algorithms are presented for multiuser multipleinput single-output orthogonal frequency division multiple access (MU-MISO OFDMA) systems when the number of users in a cell is much more than the number of transmitter antennas. A fair resource allocation algorithm is proposed in order not to victimize the users far from the base stations. In general, Shannon capacity has been shown as the performance measure for MU-MISO-OFDMA systems. In this paper, the bit error rate (BER) is used as an performance metric instead of the Shannon capacity since, increasing the system capacity does not automatically yield the best performance in terms of error rates. It is also shown that the proposed algorithm provides fairness by calculating the fairness index. © 2011 IEEE.
  • Conference Object
    Ofdm Sistemler için Pilot Tabanlı Yinelemeli Kanal Kestirimi
    (IEEE, 2008) Baştürk, İlhan; Özbek, Berna
    In this study, pilot-based iterative channel estimation, which use virtual pilots, is proposed for OFDM systems In order to find final channel estimates, instead of averaging the group estimates, which are found by virtual pilots, it is proposed to combine them by taking into account their reliabilities that are calculated by using probability density function. Then the proposed method is compared to Expectation-Maximization (EM) algorithm with respect to performance and computational complexity. The performance results are given in terms of Bit Error Rate (BER) and Mean Squared Error (MSE). ©2008 IEEE.
  • Conference Object
    Stbc-ofdm Sistemler için Em Tabanlı Kanal Kestirim Başarımı
    (Institute of Electrical and Electronics Engineers Inc., 2009) Baştürk, İlhan; Özbek, Berna
    Bu çalışmada Uzay-zaman blok kodlu dikgen frekans bölmeli çoğullama sistemleri için Beklenti- Enbüyükleme algoritması yardımıyla frekans alanında her bir alttaşıyıcı için ayrı ayrı kanal katsayılarının kestirildiği bir algoritma önerilmiştir. Başlangıç kanal kestirimi olarak pilot sembollerden yararlanılmış ve bant genişliğinin verimli kullanılması için az sayda pilotla ardışıl kanal kestirimi yapılmıştır. Önerilen algoritma zaman alanında kanal katsayılarını Beklenti-Enbüyükleme algoritmasıyla kestiren ve hesaplama sırasında matris tersi işlemine ihtiyaç duyan algoritma ile karşılaştırılmış ve herhangi bir performans kaybı olmadan karmaşıklığı azalttığı gözlenmiştir. Her iki algoritma için bilgisayar benzetimleri yapılarak, başarımları bit hata oranı, en küçük karesel hata ve Beklenti-Enbüyükleme algoritmasında kullandıkları döngü sayıları ile incelenmiştir.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Dfbçe Tabanlı Kablosuz Ağlarda Kullanıcı Röleler için Uzaklık Bazlı Seçim
    (Institute of Electrical and Electronics Engineers Inc., 2016) Baştürk, İlhan; Özbek, Berna
    Düşük kurulum maliyetine ve geniş kapsama alanına sahip kullanıcı-rölelerle geliştirilmiş dikgen frekans bölmeli çoklu erişim (DFBÇE) tabanlı kablosuz ağlar, yüksek veri hızlarına iletişime olanak sağlamaları açısından gelecek nesil iletişim sistemlerinde önemli bir yer tutmaktadır. Kullanıcı-röleli sistemlerde kullanıcı sayısına paralel olarak artan röle sayısı performansı arttırmaktadır. Tüm kullanıcıların röle olma durumu performans açısından olumlu bir durum olmasına rağmen sinyalleşme yükünü ve dolayısıyla karmaşıklığı çok arttırdığı için pratik sistemlere uygun olmayabilir. Bu nedenle, bu çalışmada performans ve sinyalleşme yükü arasındaki ödünleşimi dengelemek için kullanıcı-röle adayları belirli bir alanda uzaklığa dayalı olarak seçilmiş ve sonuçlar benzetimler yapılarak değerlendirilmiştir.
  • Conference Object
    Citation - Scopus: 2
    Resource Allocation for User-Relay Assisted Miso-Ofdma Networks
    (Institute of Electrical and Electronics Engineers Inc., 2015) Baştürk, İlhan; Özbek, Berna
    The next generation cellular networks request higher capacity and coverage that user-relay assisted Orthogonal Frequency Division Multiple Access (OFDMA) networks are costeffective solutions to meet these demands. These networks can be enriched with multiple antennas in order to obtain a diversity gain to combat signal fading and to achieve more capacity gain without increasing the bandwidth or transmit power. However, radio resource management (RRM) such as relay selection and resource allocation (RA) is important in such a multi-user, multirelay and multi-antenna environment to fully take advantage of multiple-input single-output (MISO)-OFDMA based user-relay assisted cellular networks. Thus, we propose a RA algorithm for these networks to reveal the benefits of the combination of userrelaying and multiple antennas technologies and compare the proposed scheme with existing schemes in terms of percentage of satisfied users and cell-edge users' data rate.
  • Conference Object
    Citation - Scopus: 5
    Queue-Aware Resource Allocation for Ofdma-Based Mobile Relay Enhanced Networks
    (VDE Publishing House, 2013) Baştürk, İlhan; Özbek, Berna; Le Ruyet, Didier
    Mobile relay assisted OFDMA networks that are considered as a good candidate in future deployment scenarios for coverage extension and lower deployment costs are promising solutions for provision of ubiquitous high-data-rate services in wide coverage areas. However, it is required to design efficient resource allocation algorithms to exploit these opportunities. Thus, this paper designs an heuristic resource allocation algorithm based on the queue and channel state information of the users for mobile relay enhanced OFDMA networks. The proposed queue aware algorithm is appropriate for the realistic scenarios and use system resources efficiently. Numerical results revealed that the mobile-relay enhanced scheme improves coverage and assisting users having unfavorable channel conditions such as cell-edge users by increasing the data rate compared to existing fixed-relay enhanced and non-relaying schemes. © VDE Verlag GMBH.
  • Conference Object
    Citation - Scopus: 2
    Fairness Aware Resource Allocation for Downlink Miso-Ofdma Systems
    (Institute of Electrical and Electronics Engineers Inc., 2012) Baştürk, İlhan; Özbek, Berna
    In this paper, a resource allocation problem for downlink multiple input-single output orthogonal frequency division multiple access (MISO-OFDMA) systems is investigated. The problem is defined as maximizing the minimum user rate with the constraints of total power and bit error rate (BER). Since it is difficult to obtain the optimal solution to this problem, a suboptimal but efficient solution is proposed based on zero forcing beamforming (ZFBF) to reduce computational complexity. The proposed algorithm is a fairness aware radio resource allocation algorithm that shares the resources equally among the users who has different distances from the Base Station (BS). The simulation results show that the proposed algorithm satisfies the fairness criterion having higher data rates compared to the existing algorithms. © 2012 IEEE.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 3
    Iterative Em-Based Channel Estimation for Stbc-Ofdm
    (Institute of Electrical and Electronics Engineers Inc., 2009) Baştürk, İlhan; Özbek, Berna
    In this paper, an iterative EM based channel estimation algorithm is studied for STBC-OFDM systems. Compared to the time domain EM based channel estimation algorithm which needs matrix inversion, a frequency domain EM based channel estimation algorithm is proposed by estimating the channel coefficients for each subcarrier. The proposed channel estimation algorithm decreased the complexity without sacrificing the performance. The time domain and proposed frequency domain EM based channel estimation algorithms are compared in terms of bit error rate (BER), mean square error (MSE) and the number of iterations used in the EM algorithm.