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Bulunan: 14 Adet 0.002 sn
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Erişime Açık

A novel ACO-OFDM system based on fast walsh hadamard transform

Ali ÖZEN | Büşra AVCI | Gazihan AYKIRI | Kudret KARAERİK | Elif Büşra TUNA | Sabiha YAŞAR | Hayriye SİNOP | Yusuf İslam TEK

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 multiplexe ...Daha fazlası

Erişime Açık

A novel double tree complex wavelet transform OFDM based on fast walsh hadamard transform

Ali ÖZEN | Kudret KARAERİK | Elif Büşra TUNA | Yusuf İslam TEK | Hayriye SİNOP | Sabiha YAŞAR | Büşra AVCI | Gazihan AYKIRI

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 als ...Daha fazlası

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A novel concatenated lwt and wht based ufmc waveform design forthe next generation wireless communication systems

Ali ÖZEN | Asuman SAVAŞÇIHABEŞ

A novel concatenated Lifting Wavelet Transform (LWT) and Walsh Hadamard Transform (WHT) with Universal Filtered MultiCarrier (UFMC) waveform is suggested as an alternative to Orthogonal Frequency Division Multiplexing (OFDM) waveformfor the next generation wireless telecommunication systems in this paper. The suggested waveform is composed of LWT andWHT with UFMC waveform. Both the elimination the disadvantages of OFDM and the improvement the achievement of UFMCwaveform, from the fifth generation waveform candidates, has been aimed with the suggested waveform. In order to verify theperformance ...Daha fazlası

Erişime Açık

A novel gfdm waveform design based on cascaded wht-lwt transform for the beyond 5g wireless communications

Asuman SAVAŞÇIHABEŞ | Ali ÖZEN

In this paper, a new WHT-LWT-GFDM waveform obtained by combining Walsh–Hadamard Transform (WHT), Lifting Wavelet Transform (LWT), and Generalized Frequency Division Multiplexing (GFDM) is presented for use in next-generation wireless communication systems. The proposed approach meets the requirement of 5th-generation (5G) and beyond communication schemes in terms of low latency, low peak-to-average-power ratio (PAPR), and low bit-error rate (BER). To verify the performance of the presented waveform, PAPR and BER simulation results were obtained in additive white Gaussian noise (AWGN) and flat ...Daha fazlası

Erişime Açık

Lifting wavelet transform based multicarrier modulation scheme for coherent optical communication systems

Ali ÖZEN

In this paper, it was proposed a new multicarrier modulation scheme, based on lifting wavelet transform for coherent optical communication systems. This new wave scheme used the energy compaction property of lifting wavelet transform that provides low leakage in subcarriers. The new wave scheme based system was allowed improved performance in terms of bit error rate and reduction in the peak to average power ratio compared to conventional cyclic prefix based OFDM. It was found that the use of the new wave scheme was possible to extend the transmission distance by 100 km and 150 km compared to ...Daha fazlası

Erişime Açık

Seismic performance of shallow depth tuned liquid damper

Ali BOZER

Tuned Liquid Dampers (TLD) consist of a container that is generally partially filled with water. When the sloshing frequency of the water mass is tuned to the fundamental mode of the primary structure a significant amount of sloshing and wave breaking can be achieved which are the primary sources of energy dissipation. Although TLDs are easy to install, operate and maintain; it is generally challenging to model the nonlinear nature of sloshing water. Equivalent mechanical models provide a simplified solution in which sloshing liquid mass, liquid damping, and sloshing frequency are represented ...Daha fazlası

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A novel papr reduction technique combining the pts and clipping method

Ali ÖZEN | Asuman SAVAŞÇIHABEŞ

In this paper, it is recommended to combine the partial transmit sequence (PTS) and amplitude clipping (AC) methods as a solution to the peak to average power ratio (PAPR) problem of multi-carrier (MC) communication systems. The suggested technique is verified on zero tail discrete cosine transform spread OFDM (ZT-DCT-s OFDM), ZT discrete Fourier transform spread OFDM (ZT-DFT-s OFDM) and ZT discrete sine transform spread OFDM (ZT-DST-s OFDM) waveforms, from the next generation waveform alternative to OFDM, with classical OFDM waveform. Computer simulation studies are performed to verify the su ...Daha fazlası

Erişime Açık

Enhancing The Performance Of Flip-Ofdm Systems With Channel Coding Techniques For Visible Light Communications

Ali ÖZEN

This paper suggests employing channel encoders techniques to develop the attainment of the Flip-OFDM system. Reed Solomon (RS) and convolutional coders (CC) are used as channel coding techniques. Simulation works are carried out in AWGN channel and flat fading optical LOS channel surroundings to compare the performance of Non-Encoded VLC-OFDM, NonEncoded Flip-OFDM, RS-Coded Flip-OFDM and 1/2 rate CC Coded Flip-OFDM systems on bit error rate (BER) achievement benchmark. From the acquired numerical outcomes, it is observed that especially the 1/2 CC Coded Flip-OFDM method is better than other me ...Daha fazlası

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A comparative study of coded and uncoded optical frequency domain channel equalizer in visible light communications

Ali ÖZEN

This article recommends using channel encoders to develop the achievement of optical single carrier frequency domain equalizers (OSC-FDE) in multi-path optical channel environment, which is an alternative to OFDM waveform for visible light communication (VLC) systems. Reed Solomon (RS) and convolutional coding (CC) are used as channel encoders. Computer simulations are made to compare the encoded OSCFDE method with the non-encoded OSC-FDE and VLC-OFDM methods over the bit error rate (BER) achievement criteria. From the acquired outcomes, it is perceived that 18 dB SNR development is achieved, ...Daha fazlası

Erişime Açık

Determination of monthly wind speed of Kayseri region with gray estimation method

Alper AYDEMİR

Wind has been used to facilitate human life throughout history, but besides being a beneficial renewable energy resource it could transform into a hazardous disaster which could result high loss of life and property. The wind energy was first used for purposes such as produce cereals, transport sailing ships in the sea. Nowadays, wind energy is used in electricity production. The temporal spatial variability and difficulties faced during measurement process of wind speed increased the importance of studies related with wind speed forecast. In this study, Gray estimation method was applied to m ...Daha fazlası

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An implicit unconditionally stable integration method for nonlinear structural dynamics and earthquake engineering problems

Kamuran ARI

A novel time integration procedure is designed in order to solve the differential equation of motion of dynamics and earthquake engineering problems. The procedure is constituted on the principle of impulse-momentum, leading to a lesser number of assumed fields. The algorithmic properties of the procedure are determined by stability and accuracy analyses. Overshooting tendency, which is not related to stability and accuracy characteristic of a method, and order of accuracy are also examined. It is displayed that the new method is unconditionally stable and non-dissipative. Also, the numerical ...Daha fazlası

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