Elektrik-Elektronik Mühendisliği / Electrical - Electronics Engineering
Recent Submissions
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Frustrated Potts model: Multiplicity eliminates chaos via reentrance
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Publisher and Date:(Amer Physical Soc, 2020)The frustrated q-state Potts model is solved exactly on a hierarchical lattice, yielding chaos under rescaling, namely, the signature of a spin-glass phase, as previously seen for the Ising (q = 2) model. However, the ground-state entropy introduced by the (q > 2)-state antiferromagnetic Potts bond induces an escape from chaos as multiplicity q increases. The frustration versus multiplicity phase diagram has a reentrant (as a function of frustration) chaotic phase.
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A hybrid deep learning framework for unsupervised anomaly detection in multivariate spatio-temporal data
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Publisher and Date:(MDPI AG, 2020)Multivariate time-series data with a contextual spatial attribute have extensive use for finding anomalous patterns in a wide variety of application domains such as earth science, hurricane tracking, fraud, and disease outbreak detection. In most settings, spatial context is often expressed in terms of ZIP code or region coordinates such as latitude and longitude. However, traditional anomaly detection techniques cannot handle more than one contextual attribute in a unified way. In this paper, a ...
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Minimum Length Scheduling for Discrete Rate Based Full Duplex Wireless Powered Communication Networks
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Publisher and Date:(Springer, 2019)In this study, we consider a wireless powered communication network where multiple users with radio frequency energy harvesting capabilities communicate to a hybrid energy and information access point in full duplex mode. We characterize an optimization framework for minimum length scheduling to determine the optimal rate adaptation and transmission scheduling subject to energy causality and traffic demand constraints of the users considering discrete-rate transmission model. We first formulate ...
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Energy Efficient SCMA Supported Downlink Cloud-RANs for 5G Networks
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Publisher and Date:(IEEE, 2020)Cloud-radio access networks (C-RANs) are regarded as a promising solution to provide low cost services among users through the centralized coordination of baseband units for 5G wireless networks. The coordinated multi-point access, visualization and cloud computing technologies enable C-RANs to provide higher capacity and wider coverage, as well as manage the interference and mobility in a centralized coordinated way. However, C-RANs face many challenges due to massive connectivity and spectrum ...
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Optical spatial modulation design
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Publisher and Date:(Royal Soc, 2020)Visible light communication (VLC) systems are inherently signal-to-noise ratio (SNR) limited due to link budget constraints. One favourable method to overcome this limitation is to focus on the pre-log factors of the channel capacity. Multiple-input multiple-output (MIMO) techniques are therefore a promising avenue of research. However, inter-channel interference in MIMO limits the achievable capacity. Spatial modulation (SM) avoids this limitation. Furthermore, the performance of MIMO systems in ...
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New channel estimation techniques for cooperative underwater acoustic OFDM systems
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Publisher and Date:Cooperative underwater acoustic communication systems come into prominence in recent years. Since underwater channels are sparse and additive noise entering the system is colored Gaussian noise it is very difficult to estimate the underwater channels and theoretically makes it interesting. in the first part of the thesis the transmission from source to the target recipient is realized by means of a relay system. Orthogonal frequency division multiplexing (OFDM)-based channel estimation problem is ...
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Pilot assisted channel estimation for asymmetrically clipped optical OFDM over visible light channels
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2017)The Visible Light Communication(VLC) has drawn significant attention recently for wireless communication in addressing the performance limitations of wireless systems due to the scarcity of bandwidth. In VLC system the visible lights is used not only for illuminating rooms but also for an optical data transmission. Asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) has been proposed for VLC systems to provide optically power efficient solution in the optical domain. ...
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Busy tone based power control for coordination of IEEE 802.11af and 802.22 system [IEEE 802.11af ve 802.22 Sistemlerinin Uyumlu Çalışmaları için Meşgul Ton Tabanlı Güç Kontrolü]
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2017)In this paper a new power control algorithm based on busy tone approach has been proposed for the coordination of IEEE 802.22 and IEEE 802.11af systems in TV white space. Different from the earlier studies in addition to both 802.11af access point and clients listening to the busy tone they also adjust their communication power according to the location information and use hopping for communication if needed. Acccordingly interference caused to 802.22 systems has been reduced while the 802.11af ...
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Extending the lifetime of WSNs with Maximum Energy Selection Algorithm (MESA)
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2017)The limited battery supply of a sensor node is one of the most important factors that limit the lifetime of the WSNs. As a consequence increasing the lifetime of WSNs through energy efficient mechanisms has become a challenging research area. Previous studies have shown that instead of implementing direct transmission or multi-hop routing clustering can significantly improve the total energy dissipation and lifetime of a WSN. The traditional LEACH and LEACH based algorithms have evolved from this ...
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Sparse Channel Estimation for Space-Time Block Coded OFDM-Based Underwater Acoustic Channels
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2018)Communication over acoustic signals underwater results in multi-scale multi-lag channels due to multipath propagation. Hence a robust channel estimation technique has to be present at the receiver. In this paper assuming underwater channels undergoing Rayleigh fading a path-based channel model that characterizes each path of the time-varying sparse channel by a delay a Doppler scale and an attenuation factor is considered. Alamouti's space-time block transmit diversity scheme is used in the form ...
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VLSI implementation of GRBF (Gaussian Radial Basis Function) networks
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Publisher and Date:(IEEE, 2000)A GRBF network is designed for VLSI implementation. Building blocks of the network consist mainly of analog circuits: op-amp multiplier multiplying DAC (digital to analog converter) floating resistor summer and exponentiator. Parameters of the network (center width of the Gaussian function and output layer weights) are represented digitally for convenient interfacing. It is shown that individual GRBF units allow independent tuning of center width and amplitude. Several network structures are ...
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Parameter quantization effects in Gaussian potential function neural networks
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Publisher and Date:(World Scientific and Engineering Academy and Society, 2001)In hardware implementations of Gaussian Potential Function Neural Networks (GPFNN) deviation from ideal network parameters is inevitable because of the techniques used for parameter storage and implementation of the functions electronically resulting in loss of accuracy. This loss in accuracy can be represented by quantization of the network parameters. In order to predict this effect theoretical approaches are proposed. One-input one-output GPFNN with one hidden layer have been trained as function ...
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Edge detection using steerable filters and CNN
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Publisher and Date:(European Signal Processing Conference EUSIPCO, 2002)This paper proposes a new approach for edge detection using steerable filters and cellular neural networks (CNNs) where the former yields the local direction of dominant orientation and the latter provides iterative filtering. For this purpose steerable filter coefficients are used in CNN as a B template. The results are compared to the results where only CNN or steerable filters are used. As a result of this study the performance of the system can be improved since iterative filtering property ...
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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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Sliding mode controller solution for the shallow submerged operation ok a submarine
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Publisher and Date:(IFAC Secretariat, 2003)In this paper a submarine controller is presented which can accommodate the sea wave effects on a submarine a(shallow water operation. Sliding mode method is implemented in a way that the robustness of the controller increased with respect to disturbance distribution vector in order to perform the depth control of a shallow submerged submarine under sea wave disturbances. Designed controller kept the submarine performance within acceptable limits. Copyright © 2003 IFAC.
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Real frequency design of Pi and T matching networks with complex terminations
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2018)In this paper real frequency design of Pi and T matching networks with complex terminations is studied. Generally the generator and load termination impedances are given as measurement values. So they can be regarded as a resistor and a reactive element connected in series. To be able to design a Pi network this series impedance models must be transformed to parallel models. But for T network designs the assumed series models can be utilized there is no need a transformation process. Then Pi or T ...
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Pilot-aided bayesian MMSE channel estimation for OFDM systems: Algorithm and performance analysis
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Publisher and Date:(2004)This paper proposes a computationally efficient pilot-aided minimum mean square error (MMSE) channel estimation algorithm for OFDM systems. The proposed approach employs a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve (KL) orthogonal expansion and estimates uncorrelated series expansion coefficients. Moreover optimal rank reduction is achieved in the proposed approach by exploiting the optimal truncation property of the KL expansion resulting in a ...
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An open software architecture of neural networks: Neurosoft
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Publisher and Date:(2004)Software architecture of generic distributed neural networks and its relevant information model have been developed. Principles of on-line architecture building training controlling (managing) and topological optimization guidelines are provided and extensively discussed.
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Power control and resource allocation in TDD-OFDM based femtocell networks with interference
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2018)Femtocell technology is a promising solution for different dilemmas in cellular networks. In femtocell power control the interference experienced by the network is divided into two main tiers according to the type of network whose signal is interfering with another network. In utilizing the functionality of a two-tier network where femtocell technology is deployed a major challenge is in sharing the frequency resource of a macrocell. This paper proposes an enhanced dynamic algorithm bounded by two ...
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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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