Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Conference Object Citation - Scopus: 1Kod Bölüşümlü Çoklu Erişim (cdma) İletişiminde Gauss Olmayan Sönümlü Kanal Kestirimi için Pearson Sistemi'ne Dayalı Gözü Kapalı Kaynak Ayrıştırma Yöntemi(Institute of Electrical and Electronics Engineers Inc., 2004) Kalkan, Olcay; Altınkaya, Mustafa AzizIn this work, a Pearson System based-blind source separation method is used for detecting the signal coming to a mobile user which is subject to multiple access interference in a CDMA downlink communication. Considering some fading channel measurements showing that the fading channel coefficients may have an impulsive nature, these coefficients are modeled with an a-stable distribution whose shape parameter a takes values between 1.8 and 1.9. These a values show that the distribution resembles a Gaussian distribution but has a more impulsive nature. Simulation studies show that the conventional MMSE receiver fails in this impulsive fading scenario. Both the independent component analysis (ICA) method using the conventional hyperbolic tangent score function and the Pearson System-based ICA are successful in estimating the channel coefficients and the proposed Pearson System-based ICA method performs faster.Conference Object Citation - Scopus: 1Özilinti Matrisinin Oluşturulma Yönteminin Modele Dayalı Sinüzoidal Parametre Kestirimindeki Etkileri(Institute of Electrical and Electronics Engineers Inc., 2004) Altınkaya, Mustafa AzizAlthough the maximum likelihood method gives the optimum solutions for the parameter estimation problem of the sinusoids embedded in noise, it is computationally difficult since it generally requires to solve nonlinear optimization problems. So some model-based parameter estimators with high frequency resolution property are preferred quite often. In order to find these estimates the first step is usually forming the autocorrelation (AC) matrix. In this work the effects of the method utilized in the generation of the AC matrix on the performances of sinusoidal parameter estimators are investigated. One way of forming the AC matrix is to use a Toeplitz structure with either the biased or the unbiased AC lag estimates as the matrix elements. Another way is to use the socalled "covariance method" in the AC matrix generation. In this method the matrix formed is no longer Toeplitz; but it is still symmetric. We can think of that the Toeplitz AC matrix is a perturbed version of the non-Toeplitz AC matrix. The differences in the performances of the MUSIC spectral estimator with Toeplitz; and non-Toeplitz AC matrix usage is related to the perturbation in the AC matrix estimate. For this purpose the 3 x 3 AC matrix is is utilized in the estimation of the frequency of a single sinusoid using the MUSIC frequency estimator. The accuracy of the perturbation analysis is checked with the simulation results. Additionally, the fact that the performance of an estimator with data windowing and Toeplitz AC matrix generation becomes near to the performance of the same estimator with non-Toeplitz AC matrix is shown with simulation studies.Conference Object Citation - Scopus: 1Asimetrik Alfa-kararlı Kaynakların Enküçük Saçılım Kriteri Kullalınarak Ayrıştırılması(Institute of Electrical and Electronics Engineers Inc., 2006) Altınkaya, Mustafa AzizIn this work, we extend the method which separates symmetric alpha-stable sources using minimum dispersion criterion to the case of skewed alpha-stable mixtures. Thus, a more robust method based on fractional lower order statistics is developed which is capable of separating general alpha-stable sources.Conference Object Kırpılmış ortalamalı gürbüz konum kestiriminde yeni sonuçlar(IEEE, 2014) Altınkaya, Mustafa AzizWhen there are more than necessary distance measurements in localization by distance measurements with closed form estimators, forming smaller subgroups of measurements and averaging the location estimates obtained with these subgroups of measurements makes it possible to eliminate outlier measurements if they are present. In order to eliminate these outlier results, the nearest estimate to the geometric median of estimates is proposed as a reference in this work. Conducted simulation studies show that significant gains can be obtained using geometric median in place of arithmetic average in robust averaging methods.Conference Object Citation - WoS: 2Citation - Scopus: 3Long Term Wind Speed Prediction With Polynomial Autoregressive Model(Institute of Electrical and Electronics Engineers Inc., 2015) Karakuş, Oktay; Kuruoğlu, Ercan E.; Altınkaya, Mustafa AzizWind energy is one of the preferred energy generation methods because wind is an important renewable energy source. Prediction of wind speed in a time period, is important due to the one-to-one relationship between wind speed and wind power. Due to the nonlinear character of the wind speed data, nonlinear methods are known to produce better results compared to linear time series methods like Autoregressive (AR), Autoregressive Moving Average (ARMA) in predicting in a period longer than 12 hours. A method is proposed to apply a 48-hour ahead wind speed prediction by using the past wind speed measurements of the (Cesme Peninsula. We proposed to model wind speed data with a Polynomial AR (PAR) model. Coefficients of the models are estimated via linear Least Squares (LS) method and up to 48 hours ahead wind speed prediction is calculated for different models. In conclusion, a better performance is observed for higher than 12-hour ahead wind speed predictions of wind speed data which is modelled with PAR model, than AR and ARMA models.Conference Object Enzimatik Reaksiyonların Kimyasal Langevin-levy Denklemiyle Modellenmesi(IEEE, 2012) Altınkaya, Mustafa Aziz; Kuruoğlu, Ercan EnginChemical Langevin Equation (CLE) describes a useful approximation in stochastic modeling of chemical reactions. CLE-based ?-leaping algoritm updates the quantities of every molecule in a reaction system with a period of ?, firing every reaction in the system so many times that the concentration of each molecule can be assumed to remain in the current concentration state. Substituting the Brownian motion in the CLE with a Levy flight, one might expect the CLE to converge more rapidly. This work shows that alpha (Levy)-stable increments can be used in ?-leaping, demonstrating it with the example of a detailed kinetic model describing the enzymatic transgalactosylation reaction during lactulose hydrolysis. © 2012 IEEE.Conference Object Citation - Scopus: 2Performance Analysis of Lattice Reduction Aided Mimo Detectors(Institute of Electrical and Electronics Engineers, 2012) Kılıçaslan, Kağan; Altınkaya, Mustafa AzizLattice reduction is a powerful method used in detection and precoding of wireless multiple input-multiple output (MIMO) systems. The basic idea is to consider the channel transfer matrix as a basis for the transmitted symbols. The channel transfer matrix is reduced to a more orthogonal matrix using lattice reduction algorithms. This in turn, improves the performance of conventional MIMO receivers. In this study, it is shown that this performance improvement depends on the modulation order. © 2012 IEEE.