Browsing Elektrik-Elektronik Mühendisliği / Electrical - Electronics Engineering by Title
Now showing items 1-20 of 319
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A broadband microwave amplifier design by means of immittance based data modelling tool
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Publisher and Date:(IEEE, 2002)In this paper a practical broadband microwave amplifier design algorithm is introduced utilizing the immittance data-modelling tool. In the course of design first the optimum input and output terminations for the active device are produced employing the real frequency technique. Then these terminations are modelled utilizing the new immittance-modelling tool to synthesize the front-end and back-end matching networks. An example is included to exhibit the implementation of the proposed design ...
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A low-complexity KL expansion-based channel estimator for OFDM systems
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Publisher and Date:(2005)This 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 ...
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A low-complexity time-domain MMSE channel estimator for space-time/frequency block-coded OFDM systems
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Publisher and Date:(Hindawi Publishing Corporation, 2006)Focusing on transmit diversity orthogonal frequency-division multiplexing (OFDM) transmission through frequency-selective channels this paper pursues a channel estimation approach in time domain for both space-frequency OFDM (SF-OFDM) and space-time OFDM (ST-OFDM) systems based on AR channel modelling. The paper proposes a computationally efficient pilot-aided linear minimum mean-square-error (MMSE) time-domain channel estimation algorithm for OFDM systems with transmitter diversity in unknown ...
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A Mobile Channel Model for VLC and Application to Adaptive System Design
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2017)In this letter we propose a realistic channel model for visible light communication (VLC) assuming a mobile user. Based on non-sequential ray tracing we first obtain channel impulse responses for each point over the user movement trajectories and then express path loss and delay spread as a function of distance through curve fitting. Our results demonstrate large variations in received power. In system design this necessitates the use of adaptive schemes where transmission parameters can be selected ...
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A Monte Carlo implementation of the SAGE algorithm for joint soft-multiuser decoding channel parameter estimation and code acquisition
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Publisher and Date:(2010)This paper presents an iterative scheme for joint timing acquisition multi-channel parameter estimation and multiuser soft-data decoding. As an example an asynchronous convolutionally coded direct-sequence code-division multiple-access system is considered. The proposed receiver is derived within the space-alternating generalized expectation-maximization framework implying that convergence in likelihood is guaranteed under appropriate conditions in contrast to many other iterative receiver ...
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A new approach for coexistence of IEEE 802.11af and IEEE 802.22 systems
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2018)In this paper various algorithms are proposed to help IEEE 802.11af and IEEE 802.22 wireless systems to coexist in TV white space by considering multiple techniques. By using busy tone power control and multihop communication techniques improvements have been made compared to prior approaches. With this approach while IEEE 802.22 systems are protected from intra-network interference IEEE 802.11af systems are still able to continue transmitting packets. Considering the communication parameters and ...
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A New Technique for OFDM: OFDM-Index Modulation
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Publisher and Date:(IEEE, 2013)In this study a novel scheme called orthogonal frequency division multiplexing with index modulation (OFDMIM) is proposed for frequency selective channels. In this scheme the information is conveyed not only by only M -ary signal constellations as in classical OFDM but also by the indices of the active subcarriers which are determined according to the information bits. Different transceiver structures have been investigated for the proposed scheme and it has been shown via computer simulations ...
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A Novel Indoor Channel Model for TVWS Communications based on Measurements
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Publisher and Date:(IEEE, 2018)In this paper we present an indoor measurement campaign for TV white space bands inside a university building. The measurement results are compared with different indoor propagation models in the literature. We observed large estimation errors for the total path loss value from all existing models. Consequently we are proposing a new indoor propagation model for TVWS frequencies which concatenates the effects of frequency dependent path loss with penetration losses due to walls and windows. ...
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A numerical method for frequency determination in the astable cellular neural networks with opposite-sign templates
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Publisher and Date:(IEEE, 2006)In this study a numerical method is proposed to determine the oscillation frequencies in the astable cellular neural networks with opposite-sign templates [1]. This method depends on the training of a multilayer perceptron that uses various template coefficients and the correspondant frequency values as inputs and outputs. First of all a frequency surface is obtained from templates and then training samples are picked from this surface in order to apply to multilayer perceptron. The effects of the ...
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A Reliable Successive Relaying Protocol
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2014)Successive relaying has recently emerged as an effective technique for cooperative networks and provides significant improvements in bandwidth efficiency over traditional relaying techniques ;however to achieve full-diversity the available successive relaying protocols generally assume noise-free sourcerelay and interference-free inter-relay channels. In this paper a novel successive relaying protocol is proposed for N-relay wireless networks by removing these optimistic assumptions. The proposed ...
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A Simple Iterative Equalizer for Space Time Coded Multiple Antenna Systems
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Publisher and Date:(IEEE, 2009)In this paperg a simple low complexity iterative receiver for spacetime coded zSTCg transmission is proposed and the pen formance over frequencyyselective fast and quasistatic fading channels is investigatedF Simulation results show that the pery formance of the proposed structure improves with each iteraytionF Considering the practically prohibitive complexity of opytimal equalizersg the proposed iterative receiver can be more desirable in wireless systems with large number of antennasg big ...
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A systems software architecture for training neural fuzzy neural and genetic computational intelligent networks
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Publisher and Date:(IEEE, 2006)A systems software architecture for training distributed neural fuzzy neural and genetic networks and their relevant information models have been developed. Principles of on-line architecture building training managing and optimization guidelines are provided and extensively discussed. Qualitative comparisons of neural training strategies have been provided.
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Abstraction in FPGA implementation of neural networks
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Publisher and Date:(World Scientific and Engineering Academy and Society, 2008)A model for FPGA implementation of multilayer perceptron neural networks is presented. The model tries to incorporate object oriented design principles in the analysis training and design of components using hardware description languages. The synthesis will be based on the tools supplied by the FPGA vendors. The results indicate that the method can be utilized and it can be further improved to create a general methodology that bridges the gap between hardware and software in embedded system design.
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Achievable Performance of Bayesian Compressive Sensing Based Spectrum Sensing
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Publisher and Date:(IEEE, 2014)In wideband spectrum sensing compressive sensing approaches have been used at the receiver side to decrease the sampling rate if the wideband signal can be represented as sparse in a given domain. While most studies consider the reconstruction of primary user's signal accurately it is indeed more important to analyze the presence or absence of the signal correctly. Furthermore these studies do not consider the achievable lower bounds of reconstruction error and how well the selected method performs ...
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Across dimensions: Two- and three-dimensional phase transitions from the iterative renormalization-group theory of chains
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Publisher and Date:(2020)Sharp two- and three-dimensional phase transitional magnetization curves are obtained by an iterative renormalization-group coupling of Ising chains, which are solved exactly. The chains by themselves do not have a phase transition or nonzero magnetization, but the method reflects crossover from temperaturelike to fieldlike renormalization-group flows as the mechanism for the higher-dimensional phase transitions. The magnetization of each chain acts, via the interaction constant, as a magnetic ...
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Advanced signal processing algorithms for wireless communications
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Publisher and Date:(Springer-Verlag Berlin, 2006)Traditional wireless technologies are not well suited to meet the extremely demanding requirements of providing the very high data rates with the ubiquity mobility and portability characteristic of cellular systems. Some fundamental barriers related to the nature of the radio channel as well as the limited bandwidth availability at the frequencies of interest stand in the way. Unique sets of efficient advanced signal processing algorithms and techniques is the one of the primary enablers that will ...
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Alternative Transducer Power Gain Expression in Broadband Matching Network Designs
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Publisher and Date:(IEEE, 2016)In this paper a reflection coefficient based transducer power gain expression has been derived which is an alternative to the impedance based expression exists in the literature. A broadband double matching problem is solved by using the derived gain expression and the obtained performance has been compared with the performance obtained via the existing expression.
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Amplitude and Frequency Modulations with Cellular Neural Networks
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Publisher and Date:(Springer, 2015)Amplitude and frequency modulations are still the most popular modulation techniques in data transmission at telecommunication systems such as radio and television broadcasting gsm etc. However the architectures of these individual systems are totally different. In this paper it is shown that a cellular neural network with an opposite-sign template can behave either as an amplitude or a frequency modulator. Firstly a brief information about these networks is given and then the amplitude and frequency ...
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An Alternative Approach To Design Lumped Element Delay Equalizers
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Publisher and Date:(Istanbul Univ Fac Engineering, 2015)In this paper an algorithm has been proposed to design lumped element delay equalizers which is considered as a single block as opposed to the existing methods in literature. Then after obtaining the desired delay performance the designed delay equalizer is divided and realized as cascaded first-order and/or second-order all-pass circuits. An example is given to illustrate the utilization of the proposed algorithm.
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An efficient joint channel estimation and decoding algorithm for turbo-coded space-time orthogonal frequency division multiplexing receivers
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Publisher and Date:(Inst Engineering Technology-IET, 2008)The challenging problem in the design of digital receivers of today's and future high-speed high data-rate wireless communication systems is to implement the optimal decoding and channel estimation processes jointly in a computationally feasible way. Without realising such a critical function perfectly at receiver the whole system will not work properly within the desired performance limits. Unfortunately direct implementation of such optimal algorithms is not possible mainly due to their ...