Ali ÖZEN

Makale/Derleme | 2012 | Radioengineering Journal

A novel variable step size constant modulus algorithm (VSS-CMA) based on autocorrelation of error signal has been proposed to improve the weakness of previous VSSCMAs for application to blind equalization in this paper. Computer simulations have been performed to illustrate the performance of the proposed method in frequency selective Rayleigh fading channels. The obtained simulation results using WiMAX (IEEE 802.16-2004) radio standard have demonstrated that the proposed VSS-CMA algorithm has considerably better performance than conventional CMA, normalized CMA (NCMA) and the other VSS-CMA algorithms.

Ali ÖZEN

Bildiri | 2019 | IEEE 42th International Conference on Telecommunications and Signal Processing, TSP 2019 , pp.647 - 650

In this paper, color shift keying (CSK) modulation, which is selected as one of the modulation methods in visible light communication systems, is integrated with orthogonal frequency division multiplexing (OFDM) to increase the spectrum yield. However, the conventional fast Fourier transform (FFT) based OFDM needs that the CSK symbols be Hermitian symmetric, resulting in wasted bandwidth. In this study, it is proposed a real Fourier field based CSK OFDM technique using discrete Cosine transform (DCT), which can transform the real-value signal into a real-value signal and eliminate the need for Hermitian symmetry. Thus, the use of sp . . .ectra has been doubled due to the removal of Hermitian symmetry in classical FFT-based OFDM systems. In order to test the achievement of the recommended CSK-modulated DCT-based OFDM (DCT-OFDM) and compare with the classical FFT-based OFDM and discrete sine transform (DST) based OFDM systems computer simulation studies are carried out in additive white Gaussian noise (AWGN) channel environment and a single path channel in indoor environment, where the transmitter and the receiver see each other (Line of sight, LOS). From the computer simulation outcomes, it is observed that approximately 17 dB of SNR gain is obtained with the proposed method for the 1E-3 BER value. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2019 | IEEE 27th Signal Processing and Communications Applications SIU 2019 , pp.1 - 4

Bu bildiride, gelecek nesil kablosuz haberleşme sistemleri için Walsh Hadamard Dönüşümü (Walsh Hadamard Transform, WHT) yayılmalı evrensel filtreli çoklu taşıyıcı (Universal Filtered Multi Carrier, UFMC) dalga formu (WHTUFMC) önerilmektedir. Önerilen yöntemle 5. Nesil (5th Generation, 5G) dalga biçimi adaylarından UFMC dalga formunun başarımının arttırılması hedeflenmektedir. Önerilen dalga formunun başarımını sınamak ve klasik OFDM ve UFMC ile AWGN ve düz Rayleigh sönümlemeli kanallarda karşılaştırmak için bilgisayar benzetim çalışmaları yapılmaktadır. Elde edilen benzetim sonuçlarından önerilen dalga formunun en iyi başarımlara sa . . .hip olduğu görülmektedir. In this paper, the Walsh Hadamard Transform (WHT) spread universal filter multi carrier (UFMC) waveform (WHT-UFMC) is recommended for the next generation wireless communication systems. The proposed method aims to increase the performance of the UFMC waveform, which is from the 5th Generation (5G) waveform candidates. Computer simulation studies are performed to test the performance of the proposed waveform and to compare with the classical OFDM and UFMC in AWGN and flat Rayleigh fading channels. It is seen that the proposed waveform has the best performances from the obtained simulation results. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2019 | IEEE 27th Signal Processing and Communications Applications SIU 2019 , pp.1 - 4

Bu bildiride, görünür ışık haberleşme sistemlerinde modülasyon yöntemlerinden biri olarak seçilen renk kaydırmalı anahtarlama (Color Shift Keying, CSK) modülasyonunun AWGN ve renkli gürültü ortamlarında bit hata oranı (Bit Error Rate, BER) başarımları analiz edilmektedir. Renkli gürültü olarak kırmızı, mavi, pembe ve mor gürültü kullanılmaktadır. Ayrıca, bina içi kapalı ortamlarda verici ile alıcının bir birini gördüğü (Line of sight, LOS) tek yollu kanal kullanılarak görünür ışık haberleşme sistemlerinin başarımları incelenmektedir. 4-CSK, 8-CSK ve 16-CSK modülasyonları için bilgisayar benzetim çalışmaları yapılmaktadır. Bilgisayar . . . benzetim sonuçlarından en iyi başarımların AWGN’den sonra kırmızı gürültülü ortamlarda elde edildiği görülmektedir. In this paper, bit error rate (BER) performances of the color shift keying (CSK) modulation which is selected as one of the modulation methods in visible light communication systems, are analyzed in AWGN and color noise environments. Red, blue, pink and violet noises are used as colored noise. In addition, the performance of visible light communication systems is investigated by using a single-path channel in indoor environments where the transmitter and the receiver see each other (Line of sight, LOS). Computer simulation studies are performed for 4-CSK, 8-CSK and 16-CSK modulation. It is seen that the best performances of computer simulation results are obtained in red noisy environments after AWGN. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2019 | IEEE 27th Signal Processing and Communications Applications SIU 2019 , pp.1 - 4

Bu bildiride, gelecek nesil telsiz haberleşme sistemlerinin dalga formu adaylarından genelleştirilmiş frekans bölmeli çoğullama (Generalized Frequency Division Multiplexing, GFDM) dalga biçiminin başarımını arttırmak için lifting dalgacık dönüşümü (Lifting Wavelet Transform, LWT) ile GFDM yapısının birleştirilmesi (LWT-GFDM) önerilmektedir. Önerilen yöntem 5. Nesil (5th Generation, 5G) haberleşme sistemlerinin düşük gecikme süresi, düşük PAPR (Tepe Ortalama Güç Oranı) ve düşük OOBE (Bant Dışı Yayılım) gibi istekleri için uygundur. Önerilen yöntemin başarımını test etmek ve klasik OFDM, GFDM ve Ayrık Dalgacık Dönüşümü (Discrete Wavel . . .et Transform, DWT) kullanan GFDM (DWT-GFDM) ile karşılaştırmak için AWGN ve düz Rayleigh sönümlemeli kanallarda bilgisayar benzetim çalışmaları yapılmaktadır. Elde edilen benzetim sonuçlarından önerilen yöntemin en iyi başarımlara sahip olduğu gözlenmektedir. In this paper, it is recommended that the combination of generalized frequency division multiplexing (GFDM) structure with lifting wavelet transform (LWT) to increase the performance of GFDM waveform from waveform candidates of the next generation wireless communication systems. The proposed LWT-GFDM method is suitable for the requirements of the 5th Generation (5G) communication systems such as low latency, low PAPR (Peak to Average Power Ratio) and low OOBE (Out of Band Emission). In order to test the performance of the proposed method and compare it with classical OFDM, GFDM and GFDM using discrete wavelet transform (DWT-GFDM), computer simulation studies are performed in AWGN and flat Rayleigh fading channels. It is observed that the proposed method has the best performances from the obtained simulation results. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2019 | IEEE 27th Signal Processing and Communications Applications SIU 2019 , pp.1 - 4

Bu bildiride, kaotik haberleşme sistemleri için bulanık mantık üzerine kurulan yeni bir kör kanal denkleştirici önerilmektedir. Klasik haberleşme sistemleri için ters süzgeçleme kriterleri (Inverse Filtering Criteria, IFC) tabanlı algoritma, süper üstel algoritma (Super Exponential Algorithm, SEA) ve sabit genlik algoritması (Constant Modulus Algorithm, CMA) en popüler üç kör kanal denkleştirme algoritmasıdır. Ancak bu algoritmalar, kaotik haberleşme sistemleri için istenen başarım değerlerinde yeterli olmamakta ve geliştirilmeleri gerekmektedir. Bu çalışmada, kaotik haberleşme sistemleri için bulanık mantık üzerine kurulan normaliz . . .e edimiş CMA (Fuzzy Logic Normalized CMA, F-N-CMA) algoritması önerilmektedir. Önerilen yöntemin doğruluğunu sınamak ve klasik CMA, değiştirilmiş CMA (Modified CMA, M-CMA) ve normalize edilmiş CMA (Normalized CMA, N-CMA) algoritmaları ile karşılaştırmak için bilgisayar benzetim çalışmaları yapılmaktadır. Benzetim sonuçlarından önerilen yöntemle en iyi MSE-Adım Sayısı, MSE-SNR, ISI-Adım Sayısı ve ISI-SNR başarımlarının elde edildiği gözlenmektedir. In this paper, a new blind channel equalizer based on fuzzy logic is proposed for chaotic communication systems. Inverse filtering criteria (IFC) based algorithm, super exponential algorithm (SEA) and constant modulus algorithm (CMA) are the most popular three-blind channel equalization algorithm for classical communication systems. However, these algorithms are not sufficient for the desired performance values for chaotic communication systems and need to be developed. In this study, the normalized CMA algorithm based on fuzzy logic (Fuzzy Logic Normalized CMA, F-N-CMA) is proposed for chaotic communication systems. Computer simulation studies are performed to test the accuracy of the proposed method and to compare with the classical CMA, modified CMA (Modified CMA, M-CMA) and normalized CMA (Normalized CMA, NCMA) algorithms. It is observed that the best MSE-Iteration Number, MSE-SNR, ISI-Iteration Number and ISI-SNR achievements are obtained with the proposed method from the simulation results. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2019 | 3rd International Symposium on Innovative Approaches in Scientific Studies, ISAS 2019 , pp.1 - 4

Bildiri

Ali ÖZEN

Bildiri | 2019 | 3. International Scientific and Vocational Studies Congress , pp.1 - 6

In this study, zero tail inverse Lifting wavelet transform spread fast Walsh Hadamard transformed OFDM (ZT-ILWTs FWHT OFDM) is recommended as an alternative to the OFDM waveform for the new generation of wireless transmission systems. The recommended waveform is composed of a combination of inverse Lifting wavelet transform (ILWT) and fast Walsh Hadamard transform (FWHT) with OFDM waveform. The proposed waveform is tested with computer simulation studies for bit error rate (BER), peak to average power ratio (PAPR) and out of band emission (OOBE) performance criteria. From the attained results, it is observed that the recommended wav . . .eform is better than classical OFDM and zero-tail discrete Fourier transform spread OFDM (ZT-DFT-S OFDM) waveforms for all three performance criteria Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2018 | IEEE 41th International Conference on Telecommunications and Signal Processing, TSP 2018 , pp.5 - 8

n this paper, it is proposed a new unique word (UW) OFDM waveform based on zero-tail discrete Sine transform spread OFDM (ZT UW DST-S OFDM). The proposed waveform improves the ZT DST-S-OFDM and UW OFDM methods by removing the influence of the data symbols on the tail of the transmitted signal. In this study, the effects of different UW sequences such as Zadoff-Chu, CAZAC, 15 bit PN, 8 bit complementary code keying (CCK), 0-word, 1-word and -1-word on the bit error rate (BER) and channel tracking (Doppler) performance of the proposed ZT UW DST-S OFDM systems are investigated. In order to test the performance of the proposed method, c . . .omputer simulation studies are performed on time invariant and time variant frequency selective Rayleigh fading channels. The obtained results confirm that the proposed waveform has better BER and channel tracking (Doppler) performance than the conventional OFDM and ZT DFT-S OFDM systems. In particular, it is observed that the ZT UW DST-S OFDM using Zadoff-Chu sequence has the best BER and channel tracking performance. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2018 | IEEE 41th International Conference on Telecommunications and Signal Processing, TSP 2018 , pp.9 - 12

In this paper, zero-tail discrete cosine transform spread OFDM (ZT DCT-S OFDM) waveform is proposed as an alternative to 5th generation (5G) waveform enhancement studies. In order to verify the performance of the proposed method and compare with the conventional OFDM and zero-tail discrete Fourier transform spread OFDM (ZT DFT-S OFDM) systems, computer simulations are performed on time invariant and time variant frequency selective Rayleigh fading channels. The obtained simulation results show that the proposed ZT DCTS OFDM method has better bit error rate (BER) and channel tracking (carrier frequency offset, CFO) performance than c . . .onventional OFDM and ZT DFT-S OFDM systems Daha fazlası Daha az

Ali ÖZEN | Büşra CENİKLİOĞLU

Bildiri | 2018 | IEEE 41th International Conference on Telecommunications and Signal Processing, TSP 2018 , pp.13 - 16

In this study, a novel zero tail discrete wavelet transform spread orthogonal wavelet division multiplexing (ZT DWT-S OWDM) waveform design has been proposed as a solution to the problem of poor peak to average power ratio (PAPR) performance of conventional orthogonal frequency division multiplexing (OFDM) systems. The effects of different waveletfamilies such as Haar, Daubechies, Symlets, Coiflets and Bi-Orthogonal on PAPR performance of ZT DWT-S OWDM systems are investigated. Computer simulation studies are carried out to compare the ZT DWT-S OWDM waveform with the conventional OFDM and zero-tail discrete Fourier transform spread . . .OFDM (ZT DFT-S OFDM) waveforms. The results show that the ZT DWT-S OWDM waveform has better PAPR performance than the conventional OFDM and ZT DFT-S OFDM waveforms. In particular, it is observed that ZT DWT-S OWDM using Bi-Orthogonal wavelet family has the best PAPR performance. Daha fazlası Daha az

Ali ÖZEN

Bildiri | 2018 | IEEE 41th International Conference on Telecommunications and Signal Processing, TSP 2018 , pp.565 - 568

In optical communication, which is an important part of the Radio over Fiber (RoF) systems, coherent optical OFDM (CO-OFDM) systems allow the use of amplitude and phase belong to the light at the same time for data transmission. However, the data transmission speed and distance of the COOFDM system are limited by optical channel impairment effects. One of the major disadvantages of CO-OFDM systems is its sensitivity to fiber nonlinearity effects. For this reason, in order to be used the new signal processing techniques efficiently in the receiver, the optical channel information must be estimated and the received signal must be equa . . .lized. In this work, different equalizer constructions are investigated and a frequency domain channel equalizer used in the novel DWT-based CO-OFDM system has been proposed. With the simulation studies made, the equalizers were compared and the results were given with different changes. From the obtained simulation results, it is seen that the proposed method provides about 5.5 OSNR gain for 1E-4 BER value. Daha fazlası Daha az