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Öğe Antenna selection for decode and forward based MIMO cooperative networks [Çöz ve ilet temelli MIMO işbirlikli a?lar için anten seçimi](IEEE Computer Society, 2014) Aydin E.; Ilhan H.; Özdemir Ö.In this paper, a cooperative system structure that utilizes decode and forward (DF) method with antenna selection based on the signal to noise ratio (SNR) have been proposed. In order to decrease performance degradation due to error propagations in DF based wireless cooperative networks and increase the error performance of the system, selection combining (SC), classical maximal ratio combining (MRC), cooperative-maximal ratio combining (C-MRC) and link adaptive regeneration (LAR) techniques have been utilized at destination. Error performance analyses of the considered structures are investigated using optimal decision rules determined theoretically for the corresponding relaying strategy. © 2014 IEEE.Öğe Differential modulation based network coded cooperative communications [Farksal Modülasyon Kullanan A? Kodlamali Işbirlikli Iletişim](Institute of Electrical and Electronics Engineers Inc., 2015) Karabulut M.A.; Ilhan H.; Özdemir O.Multiple access relay channel (MARC) where multiple users communicate with a common destination via a relay, is an innovative approach and one of the most important network coding applications in wireless cooperative communications in recent years. In this paper, noncoherent differential binary phase shift keying (DPSK) technique which eliminates the need for channel estimation cost is applied to the MARC system model that uses maximum likelihood detection approach at the common destination. Noncoherent DPSK modulation of the MARC system model provides full diversity gain that has been observed at the resulting Monte-Carlo simulation. © 2015 IEEE.Öğe Error performance analysis of decode and forward based cooperative systems with relay selection [Çöz ve ilet tabanli röle seçimli isbirlikli sistemlerin hata performans analizi](2013) Ipek Akin A.; Ilhan H.; Özdemir Ö.In this paper, error performance analysis of a cooperative system with relay selection that utilizes decode and forward (DF) method is considered. The source-relay, relay-destination and source-destination links are modeled as Nakagami-m distributed random variables. The effects of the cooperative maximal ratio combining (C-MRC) used to decrease performance degradation due to error propagation in DF based wireless cooperative networks and classical maximal ratio combining (MRC) methods on error performance of the system are investigated with computer simulations. It has been shown that C-MRC technique provides significant performance improvement with respect to the MRC method. © 2013 IEEE.Öğe Link adaptive relaying with virtual noise based detection in cooperative wireless networks [Isbirlikli telsiz aglarda sanal gürültüye dayali sezim ile link uyarlamali iletim](2013) Bozdag A.; Ilhan H.; Özdemir Ö.Cooperative communication is an approach that provides diversity gain in wireless communications systems by eliminating the requirement of locating physical antenna arrays at terminals. In this study, a scheme that combines link adaptive relaying (LAR) and virtual noise modeling based detection techniques which have been introduced in the literature to prevent performance degradation in decode and forward based cooperative wireless networks due to error propagation is proposed and its error performance is investigated for Nakagami-m channels. It has been shown by simulation results that the proposed system provides significant performance improvement in various situations with respect to the classcial LAR structures in which maximal ratio combining is employed at the destination. © 2013 IEEE.Öğe Network coded noncoherent cooperative communications [A? kodlamali evre uyumsuz işbirlikli iletişim](IEEE Computer Society, 2014) Karabulut M.A.; Ilhan H.; Ozdemir O.In recent years, network coding has received significant attention as an innovative approach that improves the spectral efficiency of wireless communication systems. The Multiple Access Relay Channel (MARC) where multiple users communicate with a common destination via a relay, is one of the important network coding applications in wireless cooperative communications. In this paper, error performance of MARC system non-coherent BFSK technique is studied. This technique, which employs training sequences, is a prominent approach for decreasing the system complexity and cost by eliminating the need for channel estimation. The numerical results for Rayleigh fading channels have shown that proposed approach provides full diversity gain. © 2014 IEEE.Öğe Relaying selection based multiple access relay channel [Röle Seçimli Çoklu Erişim Röle Kanali](Institute of Electrical and Electronics Engineers Inc., 2016) Karabulut M.A.; Özdemir O.; Ilhan H.Relay selection in case of fast cascade Rayleigh fading channels has been examined in multiple access relay channel structure which is one of the high spectral efficiency network coding applications. Error performance analysis of MARC system has been made for noncoherent binary frequency shift keying (BFSK) and it has been shown that the proposed approach provides full diversity gain. © 2016 IEEE.Öğe SNR-based antenna selection with threshold value in wireless channels [Telsiz kanallarda esik degerlikli SNR-tabanli anten seçimi](2013) Aydin E.; Ilhan H.; Özdemir O.In this study, in order to reduce the end-to-end bit error rate (BER) at the destination, two different antenna selection models based on signal to noise ratio (SNR) have been proposed. Relay node contains multiple antennas and BPSK modulation is used. In these models under consideration, different optimal decision rule is determined theoretically. To generate each threshold decision rule, either instantaneous and average SNR or both together in S?D, S?R and R?D links are used. Proposed antenna selection algorithm with the optimal threshold value can reduce significantly the end-to-end BER according to the simple relaying technique. © 2013 IEEE.Öğe Virtual noise based detection in cooperative systems with co-channel interference [Ortak Kanal Girişimi Bulunan Işbirlikli Sistemlerde Sanal Gürültüye Dayali Sezim](Institute of Electrical and Electronics Engineers Inc., 2016) Aslan H.; Ilhan H.; Özdemir O.In this paper, we have investigated the effect of cochannel interference on Decode-and-forward based cooperative communication system by providing the analytical results and computer simulations over Rayleigh fading channels. Virtual noise technique is used with co-channel interference at relay and destination terminals. It can be clearly observed that virtual noise techniques provides full diversity gain for proposed system. The accuracy of the analytical results shown by computer simulations. © 2016 IEEE.
