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Item Cooperative spectrum sensing method for MC-CDMA systems in cognitive radio networks(Ieee, 2018) Yilmazel, Rustem; Seyman, Muhammet NuriThe development of wireless communication networks has made spectrum management more compulsory. Different systems such as Multi-carrier code division multiple access (MC-CDMA) have to be adapted for cognitive radio technology to solve this problem. In this article, cooperative spectrum sensing technique, which is one of the spectrum sensing techniques, is adapted to MC-CDMA technology. This method can be used to decrease the mathematical density of the obtained spectral characteristics or to get better the probability of detection. Cognitive radio has made it possible to make spectrum perception more effective and reduce the possibility of false perception. The aim is to increase the likelihood that an unauthorized user will be able to identify the presence of a licensed user by cooperating with each other. The theoretical value and the simulated result are compared and then the results are interpreted according to the changing signal-to-noise ratios (SNRs).Item The Slab Albedo Problem for Pure-Triplet Anisotropic Scattering by Singular Eigenfunction Method(Amer Inst Physics, 2017) Tureci, D.; Tureci, R. G.One-speed, time independent and homogenous medium neutron transport equation can be solved by using pure-triplet anisotropic scattering. This solution bases on finding the Case's eigenfunctions and the orthogonality relations of these eigenfunctions. The infinite medium Green function can be written by using the jump condition after finding Case's eigenfunctions. The slab albedo problem can be investigated as numerical by using suggested solutions over surfaces with the singular eigentimetion method which bases on the infinite medium Green function. The selected numerical results can be tabulated.Item Back Propagation Neural Network Approach for Channel Estimation in OFDM System(Ieee, 2010) Taspinar, Necmi; Seyman, M. NuriIn high data rate communication systems which use orthogonal frequency division multiplexing as a modulation scheme, at receiver channel impulse responses must be estimated for coherent demodulation. In this paper, multilayered perceptrons (MLP) neural network with backpropagation (BP) learning algorithm is proposed as a channel estimator for OFDM systems. Our proposed MLP neural channel estimator is compared to least square (LS) algorithm, minimum mean square error (MMSE) algorithm and radial basis function neural network (RBF) in respect to bit error rate (BER) and mean square error (MSE) criteria in order to evaluate the performances. MLP neural network has better performance than LS algorithm and RBF neural network and its performance is close to MMSE algorithm and the perfect channel impulse responses. Moreover, there is unnecessary of channel statistics, matrix computation and noise information when our proposed neural network is used for channel estimation.
