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    A Comparative Performance Analysis of Blind Equalization Algorithms in Single Carrier Visible Light Communications
    (Institute of Electrical and Electronics Engineers Inc., 2020) Yasar, Sabiha; Sinop, Hayriye; Tek, Yusuf İslam; Tuna, Elif Büşra; Karaerik, Kudret; Avci, Busra; Aykiri, Gazihan
    It is very important to estimate and equalize the multipath optical channel blindly in visible light communication (VLC) systems. It is recommended that it is used Constant Modulus Algorithm (CMA), modified CMA (M-CMA) and normalized CMA (N-CMA) algorithms, which are among the most commonly used blind equalization algorithms to eliminate inter-symbol interference (ISI) caused by a multipath optical channel in a closed environment in this paper. Computer simulations and comparative performance analysis of the algorithms mentioned above are performed over the Mean Square Error (MSE) and ISI performance metrics in stationary and non-stationary environment. It is observed that the best performances are obtained with M-CMA algorithm in MSE comparisons and the best performances are obtained with NCMA algorithm in ISI comparisons from the computer simulation results. © 2020 IEEE.
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    A Novel ACO-OFDM System Based on Fast Walsh Hadamard Transform
    (Institute of Electrical and Electronics Engineers Inc., 2020) Avci, Busra; Aykiri, Gazihan; Karaerik, Kudret; Tuna, Elif Büşra; Yasar, Sabiha; Sinop, Hayriye; Tek, Yusuf İslam
    Visible Light Communication (VLC), an alternative to radio frequency (RF), was born as a promising technology. In VLC systems, orthogonal frequency division multiplexing (OFDM) has received much attention due to its high data rate, simple equalization and robustness against inter symbol interference (ISI). However, high peak to average power ratio (PAPR) and LED non-linearity have remarkable effects on the performance of indoor VLC-OFDM systems. Asymmetrically clipped optical OFDM (ACO-OFDM) is a technique that sacrifices spectral efficiency to transmit a unipolar frequency division multiplexed signal over a unipolar channel. In this study, fast Walsh Hadamard transform based ACO-OFDM (FWHT-ACO-OFDM) method is proposed to improve the performance of ACO-OFDM system by recovering this spectral efficiency. The performance of the proposed method is verified by computer simulation studies for bit error rate (BER) and PAPR performance criteria. From the simulation consequence, it is seen that the proposed method is better for both performance criteria than ACO-OFDM methods. © 2020 IEEE.
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    A Novel Double Tree Complex Wavelet Transform OFDM Based on Fast Walsh Hadamard Transform
    (Institute of Electrical and Electronics Engineers Inc., 2020) Karaerik, Kudret; Tuna, Elif Büşra; Tek, Yusuf İslam; Sinop, Hayriye; Yasar, Sabiha; Avci, Busra; Aykiri, Gazihan
    In this paper, combining with the fast Walsh Hadamard transform (FWHT) to improve the performance of the double-tree complex wavelet transform (DTCWT) based OFDM technique developed to eliminate the disadvantages of the orthogonal frequency division multiplexing (OFDM) system is suggested. In order to test the achievement of the proposed DTCWT FWHT OFDM method, computer simulation studies are performed in AWGN and flat Rayleigh fading channel environments. In addition, peak to average power ratio (PAPR) simulations, which are one of the major disadvantages of the classical OFDM system, are also realized. From the achieved simulation results, it is seen that the suggested method has better performance than classical OFDM, Discrete Wavelet Transform (DWT) based OFDM and DTCWT OFDM techniques for both performance metrics. © 2020 IEEE.
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    A Novel PAPR Improvement Approach for the Next Generation Waveforms
    (Institute of Electrical and Electronics Engineers Inc., 2020) Tek, Yusuf İslam; Tuna, Elif Büşra; Karaerik, Kudret; Sinop, Hayriye; Yasar, Sabiha; Avci, Busra; Aykiri, Gazihan
    Today, the research for a new waveform for 5G and beyond wireless communication systems continues, with high spectral efficiency, high energy efficiency, low cost and less drawbacks of multi-carrier technologies. A novel peak to average power ratio (PAPR) improvement approach based on selected mapping (SLM) technique has been suggested in this paper. In this research, SLM technique is examined to improve the PAPR performance on alternative waveforms suggested in the literature for 5G and beyond. The examined method consists of a combination of alternative waveforms and selected mapping technique. This method has been tried on new generation waveforms for the PAPR reduction for the first time. In this study, the proposed method is applied to the zero-tail discrete Fourier transform spread OFDM (ZT DFT-S OFDM) and Unique Word OFDM (UW-OFDM) of alternative waveforms. Computer simulation works are executed to confirm and compare the proposed method on AWGN and flat Rayleigh fading channels. From the acquired simulation outcomes, it is seen that PAPR performance is improved. © 2020 IEEE.
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    Comparison of Single Carrier and Multi Carrier Communication Systems over Large Intelligent Reflecting Surfaces
    (Institute of Electrical and Electronics Engineers Inc., 2020) Sinop, Hayriye; Yasar, Sabiha; Tuna, Elif Büşra; Tek, Yusuf İslam; Karaerik, Kudret; Özen, Ali
    Large intelligent reflective surfaces are considered a promising technology for future wireless communication systems, as they can intelligently change the wireless environment to improve communication performance. In this study, the performance of single carrier and multi-carrier communication systems over large intelligent reflective surfaces is examined. In order to compare multi-carrier communication systems and single-carrier communication systems on large smart reflective surfaces, computer simulation studies are performed in a flat fading Rayleigh channel environment. Simulation results show that single-carrier communication systems are better than multicarrier communication systems. © 2020 IEEE.
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    Investigation of the Performance of Single Carrier Visible Light Communication Systems in Multi-Path Fading Optical Channels
    (IEEE, 2020) Yasar, Sabiha; Sinop, Hayriye; Tek, Yusuf İslam; Tuna, Elif Büşra; Karaerik, Kudret; Özen, Ali
    In this paper, the performances of single carrier visible light communication systems are analyzed in multi-path fading optical channels. Distortions in the data sent due to the multipath optical channel are corrected by linear and nonlinear channel equalizers. Computer simulations are performed to compare the equalizers with each other and to obtain the uncoded and encoded bit error rate performances. As a result of the simulation results, it was observed that the Convolutional coded and Turbo coded system eliminates the error floor at each iteration.
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    PAPR Reduction Method for Next Generation Waveforms
    (IEEE, 2020) Tek, Yusuf İslam; Yasar, Sabiha; Sinop, Hayriye; Karaerik, Kudret; Tuna, Elif Büşra; Özen, Ali
    Today, the search for a new waveform for 5G and beyond wireless communication systems continues, with high spectral efficiency, low cost and less disadvantages of multi carrier systems. In this paper, amplitude clipping method is examined to improve the peak to average power ratio (PAPR) performance on alternative waveforms proposed in the literature for 5G and beyond. The examined method consists of a combination of alternative waveforms and amplitude clipping technique. This method has been tried on new generation waveforms for the first time. In this study, the proposed method is applied to the zero-tail discrete Fourier transform spread OFDM (ZT DFT-S OFDM) and Unique Word OFDM (UW OFDM) of alternative waveforms. Computer simulation studies are performed to test and compare the proposed method on AWGN and flat Rayleigh fading channels. From the obtained simulation results, it is observed that PAPR performance is improved without changing the BER performance of alternative waveforms in small rate clipping by the proposed method.