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, İlhanPublisher: search.filters.publisher.Institute of Electrical and Electronics Engineers Inc.

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Now showing 1 - 8 of 8
  • Conference Object
    Ofdm Sistemleri için Pilot Tabanlı Em Kanal Kestirim Başarımı
    (Institute of Electrical and Electronics Engineers Inc., 2007) Baştürk, İlhan; Özbek, Berna; Özbek, Berna; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this work, pilot-based Expectation-Maximization (EM) channel estimation for OFDM systems are studied by considering different pilot placements. In the first method, the pilot symbols are distributed at certain locations in the OFDM time-frequency lattices to find appropriate initial values. In the second method, the pilot symbols are placed in the first OFDM symbol and then a sequential channel estimation is applied. These two methods are compared and the performances are studied in terns of mean square error and bit error rate. Moreover, the number of iterations used in the algorithm are given to compare the complexity of the methods.
  • 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; Özbek, Berna; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    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
    Stbc-ofdm Sistemler için Em Tabanlı Kanal Kestirim Başarımı
    (Institute of Electrical and Electronics Engineers Inc., 2009) Baştürk, İlhan; Özbek, Berna; Özbek, Berna; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    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; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    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; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    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: 9
    Radio Resource Management for Ofdma-Based Mobile Relay Enhanced Heterogenous Cellular Networks
    (Institute of Electrical and Electronics Engineers Inc., 2013) Baştürk, İlhan; Özbek, Berna; Özbek, Berna; Tan, Ahmet Serdar; Zeydan, Engin; Ergüt, Salih; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this paper, we focus on the radio resource management problem for the Orthogonal Frequency Division Multiple Access (OFDMA)-based mobile relay-enhanced het erogenous cellular networks. We combine mobile relaying and data offloading scenarios to increase the capacity of the system and cope with the mobile data traffic volume that is increased by the number of wireless subscribers accessing mobile data services. We propose network interface selection, relay selection and resource allocation solutions for this scenario and show effect of relaying and data offloading on the system capacity and on the ratio of satisfied users. © 2013 IEEE.
  • 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; Özbek, Berna; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    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; Özbek, Berna; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    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.