Person: ACAR, YUSUF
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Dr. Öğr. Üyesi
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ACAR
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YUSUF
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Publication Metadata only Generalised prefix for space-time block-coded orthogonal frequency division multiplexing wireless systems over correlated multiple-input multiple-output channels(Inst Engineering Technology-Iet, Michael Faraday House Sıx Hılls Way Stevenage, Hertford Sg1 2Ay, England, 2014-06-12) Yıldız, Hakan; Cooklev, Todor; Doğan, Hakan; ACAR, YUSUF; 253657; 237377; 41066Space-time block coding (STBC) orthogonal frequency division multiplexing (OFDM) is known to improve the reliability of broadband communication over wireless links. However, this technique suffers from a performance loss when the multiple-input multiple-output (MIMO) channel is correlated. This study addresses this problem. A STBC-OFDM system is proposed that is based on convolution that is skew-circular, rather than circular. This skew-circular convolution leads to one additional degree of freedom. The additional parameter can be optimised leading to improved performance for MIMO channels that are correlated. The skew-circular convolution is achieved via the introduction of a generalised prefix. The simulation results are given, illustrating the performance improvement of the proposed STBC-OFDM system. Furthermore, the proposed system is shown to be robust when channel state information is known not precisely, but imperfectly.Publication Metadata only Performance Improvement for Correlated 4x4 MIMO-OFDM Systems by Generalized Prefix Approach(IEEE, 345 E 47Th St, New York, Ny 10017 Usa, 2013) Cooklev, Todor; Doğan, Hakan; Yıldız, Hakan; ACAR, YUSUF; 237377; 41066; 253657Antenna correlation limits the multiplexing gain achieved by practical MIMO-OFDM systems and degrades the performance significantly. Recently, investigations are focused to reduce the antenna correlation by the designing new antenna structures. Differently, in this paper, we propose the generalized prefix approach to solve problem for correlated MIMO-OFDM system. It is shown that the proposed generalized prefix for 4x4 MIMO-OFDM exhibits a gain of about 8 dB over the conventional 4x4 MIMO-OFDM system at BER = 10(-4)Publication Metadata only Generalized Prefix Approach for Alamouti Coded OFDM Systems over Gaussian Channels Correlated in Space(IEEE, 345 E 47Th St, New York, Ny 10017 Usa, 2014) Yıldız, Hakan; Cooklev, Todor; Doğan, Hakan; ACAR, YUSUF; 237377; 253657; 41066In this ivorkt, generalized frelix (GP) lbr space time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems is considered in the presence of correlated channel. The 2x2 STBC case, in practice, lead to significant correlation among the spatial signatures and reduce the systems performance. There are several structures to reduce correlation. To solve this problem, we propose the generalized prefix that has low computational complexity. It is shown that the proposed generalized prefix thr 2x2 STBC-OFDNI outperforms the conventional 2:c2 STBC-OFDNI system.Publication Metadata only High-Performance Mimo Ofdm Wireless Systems With Generalized Prefix(IEEE, 345 E 47Th St, New York, Ny 10017 Usa, 2013) Yıldız, Hakan; Cooklev, Todor; Doğan, Hakan; ACAR, YUSUF; 237377; 41066Consumers require increasing data rates and therefore it is important to develop techniques that increase the spectrum efficiency. MIMO OFDM is a fundamental technology for high data rate wireless systems. Correlation among the different spatial streams is the main factor limiting the spectral efficiency. All practical MIMO OFDM wireless systems use cyclic prefix (CP). In this paper we propose a novel prefix for MIMO OFDM wireless systems, referred to as generalized prefix. This generalized prefix provides additional degree of freedom, which can be optimized and provides improved performance for correlated MIMO channels.