Browsing by Author "Uysal, Murat"
Now showing items 1-18 of 18
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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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Channel estimation in underwater cooperative OFDM system with amplify-and-forward relaying
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Publisher and Date:(IEEE, 2012)This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm due to the reduced number of taps to be estimated. The resulting novel algorithm initially estimates ...
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Channel Modeling for Visible Light Communications
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Publisher and Date:(Springer-Verlag Berlin, 2016)In this chapter, we present a novel and realistic channel modeling approach for visible light communications that overcomes the limitations of previous works. In our work, we consider wavelength dependency, effect of realistic light sources as well as different types of reflections such as specular and mixed cases of diffuse and specular. We use nonsequential ray tracing algorithms to calculate the detected power and path lengths from source to detector for each ray. These are then processed to ...
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Generalized LED Index Modulation Optical OFDM for MIMO Visible Light Communications Systems
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Publisher and Date:(IEEE, 2016)In this paper we propose a generalized light emitting diode (LED) index modulation scheme for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) visible light communications (VLC) systems. The proposed scheme generalizes the LED index modulation concept by using the spatial multiplexing principle to transmit complex OFDM signals through VLC channels by separating these signals into their real-imaginary and positive-negative parts. The maximum a posteriori (MAP) ...
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IEEE 802.15.7r1 Reference Channel Models for Visible Light Communications
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Publisher and Date:(IEEE-Inst Electrical Electronics Engineers Inc, 2017)The IEEE has established the standardization group 802.15.7r1 "Short Range Optical Wireless Communications", which is currently in the process of developing a standard for visible light communication (VLC). As with any other communication system, realistic channel models are of critical importance for VLC system design, performance evaluation, and testing. This article presents the reference channel models that were endorsed by the IEEE 802.15.7r1 Task Group for evaluation of VLC system proposals. ...
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Information Theoretical Performance Analysis and Optimisation of Cooperative Underwater Acoustic Communication Systems
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Publisher and Date:(Inst Engineering Technology-IET, 2016)In this study the authors investigate the information theoretical limits on the performance of single-carrier cooperative underwater acoustic communication systems in the presence of intersymbol interference. The authors assume decode-and-forward relaying and consider orthogonal half-duplex cooperation. Under the assumptions of sparse and frequency-selective Rician fading channel and non-white correlated Gaussian ambient noise the authors derive expressions for bounds on the individual and achievable ...
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Information theoretical performance limits of single-carrier underwater acoustic systems
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Publisher and Date:(Inst Engineering Technology-IET, 2014)In this study the authors investigate the information theoretical limits on the performance of point-to-point single-carrier acoustic systems over frequency-selective underwater channels with intersymbol interference. Under the assumptions of sparse and frequency-selective Rician fading channel and non-white correlated Gaussian ambient noise the authors derive an expression for channel capacity and demonstrate the dependency on channel parameters such as the number location and power delay profile ...
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Modeling of Visible Light Channels and Performance Analysis of ACO-OFDM
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Publisher and Date:(IEEE, 2015)Spectrum scarcity of traditional radio communication has led communication engineers to find new alternatives. Indoor visible light communication is one alternative to solve this problem since its spectrum is not regulated and it has much wider bandwidth then traditional communication systems. This increased the research done in the field of visible light communications. However a proper indoor channel model is lacking and all previous studies assumes that only additive white Gaussian noise (AWGN) ...
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MP-SAGE Based Channel Estimation for Underwater Cooperative OFDM Systems
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Publisher and Date:(IEEE, 2013)In this paper an efficient channel estimation algorithm is proposed for amplify-and-forward (AF) cooperative relay based orthogonal frequency division multiplexing (OFDM) system in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise The algorithm is based on the combinations of the matching pursuit (MP) and the space-alternating generalized expectation-maximization (SAGE) technique to improve the estimates of the channel taps and their location as well as ...
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Novel Channel Models For Visible Light Communications
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Publisher and Date:(Spie-Int Soc Optical Engineering, 2015)In this paper we investigate channel modeling for visible light communications (VLC) using non-sequential ray tracing simulation tools. We create three dimensional realistic simulation environments to depict indoor scenarios specifying the geometry of the environment the objects inside the reflection characteristics of the surface materials as well as the characteristics of the transmitter and receivers i.e. LED sources and photodioes. Through ray tracing simulations we compute the received optical ...
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Optical MIMO-OFDM With Generalized LED Index Modulation
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2017)Visible light communications (VLC) is a promising and uncharted new technology for the next generation of wireless communication systems. This paper proposes a novel generalized light emitting diode (LED) index modulation method for multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM)-based VLC systems. The proposed scheme avoids the typical spectrum efficiency losses incurred by time- and frequency-domain shaping in OFDM signals. This is achieved by exploiting ...
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Performance of MIMO Enhanced Unipolar OFDM With Realistic Indoor Visible Light Channel Models
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2016)Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems realistic indoor optical channel modeling becomes an important issue to be handled. In this paper first we obtain new realistic indoor VL channel characterizations and models in a multiple-input multiple-output (MIMO) transmission scenario using non-sequential ray tracing approach for the channel impulse responses (CIRs). Practical ...
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Performance of MIMO Enhanced Unipolar OFDM With Realistic Indoor Visible Light Channel Models
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2016)Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems realistic indoor optical channel modeling becomes an important issue to be handled. In this paper first we obtain new realistic indoor VL channel characterizations and models in a multiple-input multiple-output (MIMO) transmission scenario using non-sequential ray tracing approach for the channel impulse responses (CIRs). Practical ...
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Performance of MIMO Enhanced Unipolar OFDM with Realistic Indoor Visible Light Channel Models
Authors:
Publisher and Date:(IEEE, 2016)Visible light communication (VLC) involves the dual use of illumination infrastructure for high speed wireless access. Designing such optical based communication systems realistic indoor optical channel modeling becomes an important issue to be handled. In this paper first we obtain new realistic indoor VL channel characterizations and models in a multiple-input multiple-output (MIMO) transmission scenario using non-sequential ray tracing approach for the channel impulse responses (CIRs). Practical ...
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Sparse Channel Estimation and Equalization for OFDM-Based Underwater Cooperative Systemsw with Amplify-and-Forward Relaying
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2016)This paper is concerned with a challenging problem of channel estimation and equalization for amplify-and-forward cooperative relay based orthogonal frequency division multi-plexing (OFDM) systems in sparse underwater acoustic (UWA) channels. The sparseness of the channel impulse response and prior information for the non-Gaussian channel gains modeled by an exact continuous Gaussian mixture (CGM) are exploited to improve the performance of the channel estimation algorithm. The resulting novel ...
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Sparse Channel Estimation for OFDM-Based Underwater Acoustic Systems in Rician Fading With a New OMP-MAP Algorithm
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Publisher and Date:(IEEE, 2019)In this paper a new channel estimation algorithm is proposed that exploits channel sparsity in the time domain for an orthogonal frequency division multiplexing (OFDM)-based underwater acoustical (UWA) communications systems in the presence of Rician fading. A path-based channel model is used in which the channel is described by a limited number of paths each characterized by a delay Doppler scale and attenuation factor. The resulting algorithm initially estimates the overall sparse channel tap ...
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Sparse channel estimation for OFDM-based underwater cooperative systems with amplify-and-forward relaying
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Publisher and Date:(IEEE Computer Society, 2014)This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm due to the reduced number of taps to be estimated. The resulting novel algorithm initially estimates ...
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Sparse underwater acoustic channel estimation in colored Gaussian noise [Renkli̇ Gauss gürültülü seyrek sualtı akusti̇k kanalların kestirimi]
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Publisher and Date:(IEEE, 2012)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. Therefore it is very difficult to estimate the underwater channels and theoretically makes it interesting. In this study 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 solved ...
