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Yayın Eurasip journal on wireless commuication and networking: Editorial(Springer International Publishing, 2005-04-15) Panayırcı, Erdal; Georghiades, Costas N.; Wang, Xinheng; Çırpan, Hakan Ali[No abstract available]Yayın New criteria for the existence of stable equilibrium points in nonsymmetric cellular neural networks(2003) Özcan, Neyir; Arık, Sabri; Tavşanoğlu, Ahmet VedatThis paper presents new criteria for the existence of stable equilibrium points in the total saturation region for cellular neural networks (CNNs). It is shown that the results obtained can be used to derive some complete stability conditions for some special classes of CNNs such as positive cell-linking CNNs, opposite-sign CNNs and dominant-template CNNs. Our results are also compared with the previous results derived in the literature for the existence of stable equilibrium points for CNNs.Yayın Maximum likelihood blind channel estimation for space-time coding systems(Hindawi Publishing Corporation, 2002-05) Çırpan, Hakan Ali; Panayırcı, Erdal; Çekli, ErdinçSophisticated signal processing techniques have to be developed for capacity enhancement of future wireless communication systems, In recent years, space-time coding is proposed to provide significant capacity gains over the traditional communication systems in fading wireless channels. Space-time codes are obtained by combining channel coding, modulation, transmit diversity, and optional receive diversity in order to provide diversity at the receiver and coding gain without sacrificing the bandwidth. In this paper, we consider the problem of blind estimation of space-time coded signals along with the channel parameters. Both conditional and unconditional maximum likelihood approaches are developed and iterative solutions are proposed. The conditional maximum likelihood algorithm is based on iterative least squares with projection whereas the unconditional maximum likelihood approach is developed by means of finite state Markov process modelling. The performance analysis issues of the proposed methods are studied. Finally, some simulation results are presented.Yayın An analysis of stability of a class of neutral-type neural networks with discrete time delays(Hindawi Publishing Corporation, 2013) Orman, Zeynep; Arik, SabriThe problem of existence, uniqueness, and global asymptotic stability is considered for the class of neutral-type neural network model with discrete time delays. By employing a suitable Lyapunov functional and using the homeomorphism mapping theorem, we derive some new delay-independent sufficient conditions for the existence, uniqueness, and global asymptotic stability of the equilibrium point for this class of neutral-type systems. The obtained conditions basically establish some norm and matrix inequalities involving the network parameters of the neural system. The main advantage of the proposed results is that they can be expressed in terms of network parameters only. Some comparative examples are also given to compare our results with the previous corresponding results and demonstrate the effectiveness of the results presented.Yayın Analysis of Nonlinear Dynamics of Neural Networks(Hindawi Publishing Corporation, 2013) Arik, Sabri; Park, Juhyun; Huang, Tingwen; Oliveira, José J[No abstract available]Yayın Real-time frame buffer implementation based on external memory using FPGA(Elsevier B.V., 2018) Davutoğlu, Doğancan; Yıldız, Nerhun; Ayten, Umut Engin; Tavşanoğlu, Ahmet VedatIn this paper, design of a real-time video frame buffer with an external memory interface is proposed. In addition, simulation and implementation processes of the design is described. The mentioned system is able to buffer video signals up to 1920×1080 full-HD resolution at 60 Hz frame rate. The memory interface is designed based on an external SDRAM memory and supports burst read/write operations. Input video resolution, video buffer size on memory and burst size of the memory interface are user defined and can be configured.Yayın A low-complexity KL expansion-based channel estimator for OFDM systems(Springer International Publishing, 2005-04-05) Şenol, Habib; Çırpan, Hakan Ali; Panayırcı, ErdalThis paper first proposes a computationally efficient, pilot-aided linear minimum mean square error (MMSE) batch channel estimation algorithm for OFDM systems in unknown wireless fading channels. The proposed approach employs a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve (KL) orthogonal expansion and finds MMSE estimates of the uncorrelated KL series expansion coefficients. Based on such an expansion, no matrix inversion is required in the proposed MMSE estimator. Moreover, optimal rank reduction is achieved by exploiting the optimal truncation property of the KL expansion resulting in a smaller computational load on the estimation algorithm. The performance of the proposed approach is studied through analytical and experimental results. We then consider the stochastic Cramér-Rao bound and derive the closed-form expression for the random KL coefficients and consequently exploit the performance of the MMSE channel estimator based on the evaluation of minimum Bayesian MSE. We also analyze the effect of a modelling mismatch on the estimator performance. To further reduce the complexity, we extend the batch linear MMSE to the sequential linear MMSE estimator. With the fast convergence property and the simple structure, the sequential linear MMSE estimator provides an attractive alternative to the implementation of channel estimator.
