Yazar "Çögen, Fatih" seçeneğine göre listele

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    Code-index modulation aided quadrature spatial modulation for high-rate MIMO systems
    (Ieee-Inst Electrical Electronics Engineers Inc, 2019) Aydın, Erdoğan; Çögen, Fatih; Başar, Ertuğrul
    In this correspondence paper, a novel code-index modulation (CIM) aided quadrature spatial modulation (QSM) scheme, called CIM-QSM, is proposed for highly spectrum and energy efficient multiple-input multiple-output (MIMO) systems. The CIM-QSM scheme transmits information over three different transmit entities: modulated symbols, activated antenna indices, and spreading code indices. Hence, a higher efficiency in terms spectrum and energy use, and better error performance compared to the conventional direct sequence spread spectrum, spatial modulation (SM), QSM, and CIM aided SS (CIM-SS) schemes are obtained by the CIM-QSM technique for MIMO communication systems. Analytical expressions for the average bit error rate, energy efficiency, and throughput of the CIM-QSM system are performed and the theoretical results are validated with Monte Carlo simulation results.
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    Cooperative quadrature spatial modulation with Euclidean distance and capacity optimized antenna selection
    (Wiley, 2021) Çögen, Fatih; Aydın, Erdoğan
    In this study, new cooperative-quadrature spatial modulation techniques based on Euclidean distance and capacity optimized antenna selection techniques (EDAS-CQSM and COAS-CQSM) are proposed for cooperative communication systems. The considered cooperative system consists of three terminals that are the source terminal (ST), relay terminal (RT), and destination terminal (DT). The decode-and-forward (DF) cooperative technique is considered to retransmit the signal at the RT. In order to improve the performance of the conventional QSM demodulator in the RT and DT, both antenna selection techniques have been used in both the ST and RT to reduce performance degradation due to error propagation of the DF scheme. Therefore, the overall performance of the considered CQSM system has been increased. Furthermore, computer simulations have shown that the proposed EDAS/COAS-CQSM systems have better the performances than the cooperative spatial modulation (CSM), CQSM, EDAS-CSM, COAS-CSM, and traditional DF-based cooperative system with the same bit rate.
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    Differential chaos shift keying assisted media-based modulation
    (İstanbul Üniversitesi, 2021) Önal, Beyza; Aydın, Erdoğan; Çögen, Fatih
    This study proposes a new energy-efficient and high data-rated communication technique by combining media-based modulation (MBM) and differential chaos shift keying technique (DCSK), called DCSK–MBM. The MBM technique, which forms the infrastructure of this proposed system, is one of the newest members of the index modulation family, while DCSK offers considerable performance improvements for fading channels. Communication comprises two stages in the DCSK system. In the first stage, only the reference symbol is transmitted to the receiver side, whereas in the second stage, information is carried along with the reference symbol. The negative aspect of this method is that it reduces both transmission data rate and spectral efficiency. The MBM technique provides a significant increase in both spectral efficiency and data rate because it performs index modulation with reconfigurable antennas and transmits extra information bits. To minimize the disadvantages of the DCSK technique and create a more energy-efficient and high data-rated technique, the MBM technique is combined with the DCSK technique. Thus, considerable progress is made. All performance analyses are performed over Rayleigh fading channels for M-ary phase shift keying/quadrature amplitude modulation.
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    Generalized code index modulation and spatial modulation for high rate and energy-efficient MIMO systems on rayleigh block-fading channel
    (IEEE, 2021) Çögen, Fatih; Aydın, Erdoğan; Kabaoğlu, Nihat; Başar, Ertuğrul; İlhan, Hacı
    In this article, a high data rate and energy-efficient multiple-input multiple-output transmission scheme is considered by combining two popular and rational modulation techniques: spatial modulation (SM) and code index modulation-spread spectrum (CIM-SS). Since in the considered system, called generalized CIM-SM (GCIM-SM), incoming information bits determine modulated symbols, activated transmit antenna indices as well as their corresponding spreading code indices, data bits are conveyed not only by modulated symbols but also by the indices of the active antenna and spreading codes. Hence, a GCIM-SM scheme accommodates faster data rates while spending less transmission power and possessing better error performance compared to the conventional direct sequence spread spectrum (DS-SS), SM, quadrature SM (QSM), and CIM-SS systems. The mathematical expressions of the GCIM-SM system for bit error rate, throughput, energy efficiency, and the system complexity are derived to analyze the overall system performance. Besides, it has been shown via computer simulations that the GCIM-SM system has lower transmission energy, faster data transmission rate, and better error performance than DS-SS, SM, QSM, and CIM-SS systems. Performance analysis of the considered
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    Hexagonal quadrature amplitude modulation aided spatial modulation
    (Ieee, 2019) Çögen, Fatih; Aydın, Erdoğan
    In this study, a new multiple-input multiple-output (MIMO) transmission scheme with energy-efficiency is proposed by combining spatial modulation (SM) and energy-efficient hexagonal quadrature amplitude modulation (HQAM) constellation scheme, briefly called HQAM-SM. HQAM optimizes the assignment of code words to points in the form of a hexagonal constellation to minimize the average Hamming distance. This arrangement always uses energy more effectively than conventional quadrature amplitude modulation (QAM) and performs almost the same performance as QAM at higher SNRs. Besides, as it is known, SM is a promising MIMO technique for next-generation communication techniques, which carry data both with antenna and conventionally modulated symbols. In this study, a more energy-efficient system is proposed compared to the conventional SM, in which SM will carry data with HQAM instead of carrying data with conventional modulated symbols in addition to antenna index. The performance analysis of the proposed HQAM-SM system was performed on Rayleigh fading channels.
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    Performance analysis of Hexagonal QAM constellations on quadrature spatial modulation with perfect and imperfect channel estimation
    (Elsevier, 2021) Çögen, Fatih; Aydın, Erdoğan
    In this study, the quadrature spatial modulation (QSM) technique, which is a rational multiple-input multiple-output (MIMO) transmission technique and frequently encountered in recent studies in the literature, and the hexagonal quadrature amplitude modulation (HQAM) constellation technique, which combines symbols in an "optimum" way are combined. This new MIMO scheme has been named by the authors as HQAM-QSM. Also, the impact of imperfect channel knowledge on the performance of the proposed scheme is examined. The HQAM constellation technique is a technique that provides better results under the same power assumption than the conventional QAM constellation in terms of symbol separation and is more often encountered when it comes to energy-efficiency. Due to the nature of HQAM symbols, error-floor occurs when the QSM system is applied. Hence, the optimum angle is obtained by rotating the HQAM symbols. With this optimum angle, it has been seen that the error-floor disappeared and the performance of the system is improved. Besides, the HQAM technique performs similar bit error rates (BER) to QAM at high signal-to-noise ratio (SNR) values. From this point forth, in our study, the rational HQAM-QSM technique, which uses energy-efficient HQAM symbols instead of traditional modulated QAM symbols and also carries information effectively on two active antennas, is proposed. Performance analysis of the HQAM-QSM technique is performed on Rayleigh fading channels. (C) 2021 Elsevier B.V. All rights reserved.
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    Performance analysis of HQAM based spatial modulation over Nakagami-m Fading Channels
    (Institute of Electrical and Electronics Engineers, 2020) Çögen, Fatih; Aydın, Erdoğan
    In this study, the performance analysis of the recently proposed Hexagonal Square Amplitude Modulation Spatial Modulation (HQAM-SM) system on Nakagami-m fading channels is presented. Performance analysis was performed considering the most general state of the Nakagami-m channel distribution phase for the phase without uniform-distribution. HQAM optimizes the assignment of code words to points in the form of a hexagonal constellation to minimize the average Hamming distance. This arrangement always uses energy more effectively than conventional quadrature amplitude modulation (QAM) and performs almost the same performance as QAM at higher SNRs. In this study, a more energy-efficient system was proposed for Nakagami-m fading channels compared to conventional SM, where SM will carry data with HQAM instead of carrying data with conventional modulated symbols in addition to the antenna index. Performance analysis of the proposed system was carried out in Nakagami-m fading channels.
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    Transmit Antenna Selection for Spatial Modulation Based on Hexagonal Quadrature Amplitude Modulation
    (2021) Çögen, Fatih; Aydın, Erdoğan
    There is a tremendous demand from various industries for next-generation 5G networks, which has dramatically increased the need for high data rates and energy efficiency. It is an indisputable fact that next-generation networks should be not only energy-efficient but also resource-efficient. Given the fact that 10% of the current energy consumption in the world is caused by Information and Communication Technology, it is evident that energy-efficiency has become the most crucial performance criteria in the next-generation communication techniques. Based on these needs, we previously suggested the hexagonal quadrature amplitude modulation (HQAM) aided spatial modulation (SM) technique (HQAM-SM) to the literature. In this study, we found it appropriate to do this research to further increase the performance of the HQAM-SM scheme through the antenna selection technique and to investigate the effects of antenna selection technique on HQAM-SM. Moving from this point, in this article, rational capacity-optimized antenna selection (COAS), SM, and energy-efficient HQAM techniques are combined, and a new system called COAS-HSM is presented. Hexagonal constellations are to optimize the constellation points to form a hexagonal constellation to minimize the Hamming distance between the constellation points. This layout not only offers better energy efficiency than traditional QAM constellations but also performs almost the same BER performance as QAM at high signal-to-noise ratio (SNR) values. On the other hand, antenna selection algorithms are one of the transmission schemes that have been frequently encountered in the literature in recent years, and that considerably increases the performance of various multiple-input multiple-output (MIMO) communication structures. In particular, the COAS transmission scheme is an intelligent method of selecting transmission antennas over the highest channel amplitudes. Performance analysis of the proposed COAS-HSM technique is carried out in Rayleigh fading channels.
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    Two-way code index modulation
    (Institute of Electrical and Electronics Engineers Inc., 2019) Aydın, Erdoğan; Çögen, Fatih
    In this study, a new code index modulation (CIM) aided two-way network coded (TW-CIM) scheme with high energy-efficiency, high data speed and good error performance is proposed. In the proposed system model, unlike conventional decode-and-forward (DF) cooperative network coded communication techniques that perform three time-interval communications, only two time-intervals are used for communication since the spreading codes used are orthogonal to each other. In the proposed system structure, as well as the transmitted modulated symbol data, the spreading code indices carry data. In the TWCIM system, two different users communicate via a half-duplex relay based on the CIM technique. The considered TW-CIM system has been compared with the cooperative TW-DF system at different data rates. The theoretical error analysis of the proposed system is performed and the average bit error probability is achieved. Performance analyzes have been performed on Rayleigh fading channels for BPSK modulation. © 2019 IEEE.