Yazar "Uysal, Murat" seçeneğine göre listele

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    Adaptive relay selection method for asynchronous amplify and forward cooperative communications
    (IEEE, 2016) Çelik, Yasin; Odabaşıoğlu, Niyazi; Uysal, Murat
    In this paper, we propose a new adaptive relay selection method named as Adaptive Best Relay Assessment (ABRA) for cooperative communication with amplify and forward (AF) relaying. ABRA is based on two relay selection criteria which are cascaded channel gain coefficient and cascaded time offset in source-relay-destination (S-R-D) channel. Our simulation results demonstrate that the channel gain coefficient is the best criteria at low signal-to-noise ratio (SNR) regimes and time offset at high SNR regimes. Therefore, we combine these two criteria to select best relay for all SNR values. Finally, ABRA achieves the best bit error rate (BER) performance in asynchronous AF cooperative communications for three different path gain ratios 30 dB, 0 dB, and -30 dB.
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    Joint time offset and fading channel coefficient estimation for cooperative communication systems
    (2013) Çelik, Yasin; Odabaşıoğlu, Niyazi; Uysal, Murat
    In this paper, we investigate joint channel gain and time offset estimation for two different data aided methods in cooperative communication with amplify-And-forward (AF) relaying. First one is the Cascaded Estimation (CE) method which channel gain, and time offset consisting of both source-to-relay, and relay-to-destination links are estimated at the destination terminal, second one is Disintegrated Estimation (DE) method which channel gain, and time offset are estimated seperately at the relay for source-to-relay link, and at the destination for relayto- destination link. Both of the proposed joint estimators are based on Expectation-Maximization (EM) algorithm and, produce a low-complexity solution of itaretive maximum likelihood (ML) estimation. It was observed by the bit error rate (BER) curves, the proposed methods provide good performances with lowcomplexity. © 2013 IEEE.
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    On the performance of SC-FDE schemes with decision feedback equalizer for visible light communications
    (IEEE Computer Society, 2015) Çelik, Yasin; Kızılırmak, Refik Çaglar; Odabaşıoğlu, Niyazi; Uysal, Murat
    In this paper, we investigate the two single carrier frequency domain equalization (SC-FDE) techniques, namely on-off keying single carrier frequency domain equalization (OOK-SC-FDE) and decomposed quadrature optical (DQO)-SC-FDE, under realistic channel conditions with a practical LED model for visible light communications (VLC). We first compare their performances under dynamic range constraints of the LEDs and observe lower peak-to-average power ratio (PAPR) for SC-FDE schemes as compared to orthogonal division multiplexing (OFDM) techniques. We further introduce decision feedback equalizer (DFE) for SC-FDE schemes and demonstrate performance improvement in multi-tap indoor VLC channels. © 2015 IEEE.