Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Conference Object Yazılım Tabanlı Radyolarda Karşılıklı Kanal Özelliğinin İncelenmesi(Institute of Electrical and Electronics Engineers Inc., 2016) Uslu, Merve; Tuğrel, Halim Bahadır; Karabulut Kurt, Güneş; Özbek, BernaKablosuz haberleşme sistemlerinde, kanal kestirimi çok önemli bir yer tutmaktadır. Bu çalışmada A ve B, iki haberleşme düğümü olduğu varsayıldığında, A düğümünden B düğümüne olan kanal için elde edilen kanal katsayıları ile, B düğümünden A düğümüne olan kanal için elde edilen kanal katsayılarının benzerliği incelenmiştir. Karşılıklı kanal özelliğinden dolayı bu kanalların birbirine benzer çıkmaları beklenmektedir. Bu çalışmada, laboratuvar ortamında yazılım tabanlı radyo kitleri kullanılarak karşılıklı kanal özelliği test ortamında test edilmiş, bu iki kanal katsayılarının genlik ve faz ortalama değerleri karşılaştırılmıştır.Conference Object Citation - WoS: 1Citation - Scopus: 2Implementation of Pre-Fft Beamforming in Mimo-Ofdm(Institute of Electrical and Electronics Engineers Inc., 2016) Gökçeli, Selahattin; Uslu, Merve; Karabulut Kurt, Güneş; Özbek, Berna; Alakoca, Hakan; Durmaz, Mehmet AkifIn this study, real-time software defined radio implementation of the point to point multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) system using pre-fast Fourier transform (pre-FFT) beamforming technique in both the transmitter and the receiver is done for the first time in the literature. By taking benefit of the MIMO system's spatial multiplexing property, the performance of the implemented pre-FFT beamforming approach is demonstrated in terms of bit error rate and error vector magnitude measurements. As a result of the test results, the effect of the beamforming methods on the performance of communication systems are clearly observed.Conference Object Citation - Scopus: 7Pilot-Symbol Iterative Channel Estimation for Ofdm-Based Systems(Institute of Electrical and Electronics Engineers Inc., 2005) Özbek, Berna; Le Ruyet, Didier; Panazio, CristianoIn this paper, we propose a pilot-symbol-aided iterative channel estimation for coded OFDM-based systems. We use the symbol APP provided by the channel decoder to form groups of virtual pilots. According to their reliabilities, we combine these groups to improve the channel estimation. We also compare the proposed algorithm with the EM algorithm. Orthogonal frequency division multiplexing (OFDM) based systems are strong candidates for an air interface of future fourth-generation mobile wireless systems which provide high data rates and high mobility. In order to achieve the potential advantages of OFDM-based systems, the channel coefficients should be estimated with minimum error. The channel estimation can be improved using more pilot symbols [1]. However, it causes data rate reduction or bandwidth expansion. Therefore, spectrally efficient channel estimation techniques should be considered. In this case, the iterative techniques provide an improvement on the channel estimator performance without requiring additional pilots.Article Citation - WoS: 1Citation - Scopus: 7The Adaptive Channel Estimation for Stbc-Ofdm Systems(İstanbul Üniversitesi, 2005) Özbek, Berna; Yılmaz, ReyatIn this paper, we propose adaptive channel estimation methods based on LMS and RLS for orthogonal STBC-OFDM systems with three transmit antennas. The performance of the proposed algorithms is obtained in the frequency selective channels using Hiperlan/2 characteristics.