Yazar "Ilhan, Haci" seçeneğine göre listele

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    Antenna Selection for Decode and Forward Based MIMO Cooperative Networks
    (IEEE, 2014) Aydin, Erdogan; Ilhan, Haci; Ozdemir, Ozgur
    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.
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    Differential Modulation Based Network Coded Cooperative Communications
    (IEEE, 2015) Karabulut, Muhammet Ali; Ilhan, Haci; Ozdemir, Ozgur
    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.
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    The Effect of Co-channel Interference in DF Based MARC System with Relay Selection
    (IEEE, 2017) Karabulut, Muhammet Ali; Aslan, Hayri; Ozdemir, Ozgur; Ilhan, Haci
    Network coding has recently received significant attention as an innovative approach to improve the throughput of wireless communication systems. The multiple access relay channel (MARC), in which multiple users communicate with a common destination via relays, is one of the important network coding applications for wireless cooperative communications. In this paper, the effect of co-channel interference in decode-and forward (DF) based MARC model with relay selection is investigated by obtaining the average bit error rate (BER) results of the proposed system for cascaded Rayleigh fading channels. The simulation results obtained by using binary phase shift keying (BPSK) modulation have shown that the proposed system overcome diversity gain reduction due to error propagation, and detrimental effects of the co-channel interference.
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    Link Adaptive Relaying with Noncoherent BFSK and DPSK Modulations in Multiple Access Relay Channels
    (IEEE, 2015) Karabulut, Muhammet Ali; Ozdemir, Ozgur; Ilhan, Haci
    Network coding has recently received significant attention as an innovative approach to improve the throughput of wireless communication systems. The multiple access relay channel (MARC), in which multiple users communicate with a common destination via a relay, is one of the important network coding applications for wireless cooperative communications. In this paper, link adaptive relaying (LAR) approach which combats performance degradation due to error propagation in digital relaying based wireless networks has been applied to the MARC model with noncoherent binary frequency shift keying (BFSK) and differential binary phase shift keying (DPSK) signalings which are among the prominent techniques for eliminating the need for channel estimation by training sequences. Simulation results for Nakagami-m fading channels have shown that the proposed MARC model with LAR scheme outperforms the noncooperative system that involves direct transmissions and overcome the diversity gain reduction due to error propagation.
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    Link Adaptive Relaying with Virtual Noise Based Detection in Cooperative Wireless Networks
    (IEEE, 2013) Bozdag, Ahmet; Ilhan, Haci; Ozdemir, Ozgur
    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.
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    Mitigating Error Propagation in Cooperative Intervehicular Communications
    (IEEE, 2014) Ozdemir, Ozgur; Ilhan, Haci
    Cooperative wireless communication has attracted intense interest as an alternative way to multiple-antenna systems to obtain spatial diversity. In this paper, we investigate the performance of a vehicle-to-vehicle cooperative scheme where another vehicle in the vicinity of the source vehicle acts as a relay. The underlying source-to-relay, relay-to-destination, and source-to-destination links are modeled as cascaded Nakagami-m fading which provides a realistic description of an intervehicular channel. Unlike the most studies on cooperative intervehicular communications in the literature which are based on analog relaying, we employ digital relaying approach and investigate the performance of the techniques developed for mitigating error propagation in decode and forward based wireless relay systems such as maximum likelihood, cooperative maximal ratio combining, link adaptive relaying, virtual noise based detection and soft information relaying. Simulation results show that detection schemes with these techniques outperform the noncooperative system that involves direct transmission between the source and destination terminals and overcome the diversity gain reduction due to error propagation.
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    Network Coded Noncoherent Cooperative Communications
    (IEEE, 2014) Karabulut, Muhammet Ali; Ilhan, Haci; Ozdemir, Ozgur
    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.
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    Performance Analysis of C-MRC Technique in DF Based Cooperative System with Co-Channel Interference
    (IEEE, 2015) Aslan, Hayri; Ilhan, Haci; Ozdemir, Ozgur
    We have investigated the performance analysis of DF (Decode-And-Forward) based cooperative system using cooperative MRC (C-MRC) at the destination with co-channel interference in Rayleigh fading channels. The performance of C-MRC is compared with maximal-ratio combining (MRC) using the effective Signal to Interference plus Noise Ratio (SINR) of the system. It is seen that performance of C-MRC technique is much better than that of MRC. The Monte Carlo simulations are provided to illustrate the effect of interference on the performance where interference channels are independent and identically distributed.
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    Relaying Selection Based Multiple Access Relay Channel
    (IEEE, 2016) Karabulut, Muhammet Ali; Ozdemir, Ozgur; Ilhan, Haci
    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.
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    SNR-based Antenna Selection Schemes for Cooperative Relay Networks in Wireless Channels
    (IEEE, 2014) Aydin, Erdogan; Ilhan, Haci; Ozdemir, Ozgur
    In this paper, two different antenna selection models based on signal-to-noise ratio (SNR) have been proposed in order to reduce the end-to-end bit error rate (BER) of decode and forward (DF) relaying cooperative system where source and destination terminals contain single antenna while relay terminal has multiple antennas. Specifically, by using instantaneous and average SNR of source-to-destination, source-to-relay and relay to-destination links, optimal decision rules are derived theoretically for antenna selection at the relay terminal. Later, BER expressions of considered system have been derived for two antenna selection models over Rayleigh fading channels. Theoretical and simulation results show the validity of proposed mathematical analysis and point out the confirmation of theoretical results.
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    SNR-Based Antenna Selection with Threshold Value in Wireless Channels
    (IEEE, 2013) Aydin, Erdogan; Ilhan, Haci; Ozdemir, Ozgur
    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.
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    Virtual Noise Based Detection in Cooperative Systems with Co-Channel Interference
    (IEEE, 2016) Aslan, Hayri; Ilhan, Haci; Ozdemir, Ozgur
    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.