Browsing Elektrik-Elektronik Mühendisliği / Electrical - Electronics Engineering by Publisher "IEEE-INST Electrical Electronics Engineers Inc"
Now showing items 1-20 of 22
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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 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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An Improved Adaptive Subspace Tracking Algorithm Based on Approximated Power Iteration
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2018)A subspace tracking technique has drawn a lot of attentions due to its wide applications. The main objective of this approach is to estimate signal or noise subspace basis for the sample covariance matrix. In this paper we focus on providing a fast stable and adaptive subspace tracking algorithm that is implemented with low computational complexity. An alternative realization of the fast approximate power iteration (FAPI) method termed modified FAPI (MFAPI) is also presented. Rather than solving ...
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Broadband Decoupling and Matching of a Superdirective Two-Port Antenna Array
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2008)Decoupling and matching networks may be used to improve the performance of compact antenna arrays where mutual radiator coupling has caused a degradation of the diversity capabilities. A popular network consists of a 180 degrees rat-race directional coupler which decouples the antenna ports followed by impedance matching networks at each port. Researchers however usually neglect the presence of losses both within the antenna array and the decoupling and matching network. For this reason we have ...
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Code shift keying impulse modulation for UWB communications
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2008)In this paper the system performance of M-ary code shift keying (MCSK) impulse modulation is studied in detail and compared to M-ary pulse position modulation (MPPM) under single- and multi-user scenarios. For that bounds on the semi-analytic symbol-error rate (SER) expressions are derived and simulation studies are conducted. When practical implementations of MCSK and MPPM are considered it is shown that MCSK can provide about 2 dB performance gain over MPPM as it reduces the effects of multipath ...
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Conditional Power and Rate Adaptation for MQAM/OFDM Systems Under CFO With Perfect and Imperfect Channel Estimation Errors
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2015)In this paper a new conditional power and rate adaptation scheme for orthogonal frequency-division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO) with perfect and imperfect channel state information (CSI). The conventional adaptive scheme is shown to be a special case of the conditionally adaptive scheme technique that enables the resulting nonconvex optimization problem which is solved in a feasible way. It leads to a solution for optimal power adaptation ...
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Construction of Lossless Ladder Networks With Simple Lumped Elements Connected Via Commensurate Transmission Lines
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2009)In this work an algorithm to design lossless ladder networks with simple lumped elements connected via commensurate transmission lines is proposed. After giving the algorithm a lumped-element low-pass Chebyshev filter was transformed to its mixed-element counterpart to illustrate the utilization of the algorithm. The filter designed for a frequency band around 1 GHz was fabricated and experimentally characterized. We find very good agreement between measured and simulated transducer power gain ...
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Design of Practical Broadband Matching Networks With Mixed Lumped and Distributed Elements
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2014)Computer-aided design (CAD) tools are always preferred for designing broadband matching networks. However these tools give excellent results when the suitable matching network topology and initial element values are provided. Therefore in this brief a new initialization algorithm is proposed to get suitable network topology and element values for CAD tools. Then the power transfer capability of the matching network can be improved by using any CAD tool. It is clear from the example studied that ...
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Fault-tolerant training of neural networks in the presence of MOS transistor mismatches
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2001)Analog techniques are desirable for hardware implementation of neural networks due to their numerous advantages such as small size low power and high speed. However these advantages are often offset by the difficulty in the training of analog neural network circuitry. In particular training of the circuitry by software based on hardware models is impaired by statistical variations in the integrated circuit production process resulting in performance degradation. In this paper a new paradigm of ...
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Joint Channel Estimation Equalization and Data Detection for OFDM Systems in the Presence of Very High Mobility
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2010)This paper is concerned with the challenging and timely problem of joint channel estimation equalization and data detection for uplink orthogonal frequency division multiplexing (OFDM) systems in the presence of frequency selective and very rapidly time varying channels. The resulting algorithm is based on the space alternating generalized expectation maximization (SAGE) technique which is particularly well suited to multicarrier signal formats leading to a receiver structure that also incorporates ...
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Joint Detection of Primary Systems Using UWB Impulse Radios
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2011)Regulation in Europe and Japan requires the implementation of detect-and-avoid (DAA) techniques in some bands for the coexistence of licensed primary systems and secondary ultra wideband (UWB) systems. In a typical coexistence scenario a primary system may have potentially interdependent uplink-downlink communication channels (e. g. simultaneous uplink-downlink communications in a frequency division duplex system) overlapping with the frequency band of a UWB system. If such interdependencies of ...
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Joint Optimization of Wireless Network Energy Consumption and Control System Performance in Wireless Networked Control Systems
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2017)Communication system design for wireless networked control systems requires satisfying the high reliability and strict delay constraints of control systems for guaranteed stability with the limited battery resources of sensor nodes despite the wireless networking induced non-idealities. These include non-zero packet error probability caused by the unreliability of wireless transmissions and non-zero delay resulting from packet transmission and shared wireless medium. In this paper we study the ...
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Low-Complexity MAP-Based Successive Data Detection for Coded OFDM Systems Over Highly Mobile Wireless Channels
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2011)This paper is concerned with the challenging and timely problem of data detection for coded orthogonal frequency-division multiplexing (OFDM) systems in the presence of frequency-selective and very rapidly time varying channels. New low-complexity maximum a posteriori probability (MAP) data detection algorithms are proposed based on sequential detection with optimal ordering (SDOO) and sequential detection with successive cancellation (SDSC). The received signal vector is optimally decomposed into ...
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New Trellis Code Design for Spatial Modulation
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2011)Spatial modulation (SM) in which multiple antennas are used to convey information besides the conventional M-ary signal constellations is a new multiple-input multiple-output (MIMO) transmission technique which has recently been proposed as an alternative to V-BLAST (vertical Bell Labs layered space-time). In this paper a novel MIMO transmission scheme called spatial modulation with trellis coding (SM-TC) is proposed. Similar to the conventional trellis coded modulation (TCM) in this scheme a ...
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Nondata-aided joint channel estimation and equalization for OFDM systems in very rapidly varying mobile channels
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2012)This paper is concerned with the challenging and timely problem of joint channel estimation and equalization for orthogonal frequency division multiplexing (OFDM) systems in the presence of frequency selective and very rapidly time varying channels. The resulting algorithm is based on the space alternating generalized expectation maximization-maximum a posteriori probability (SAGE-MAP) technique which is particularly well suited to multicarrier signal formats. The algorithm is implemented in the ...
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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 analysis of transmit and receive antenna selection over flat fading channels
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2008)The paper considers two different antenna selection schemes for space-time coded systems over flat fading channels. First we explore antenna selection at the transmitter side based on the received signal to noise ratios. We then study the joint selection of receive and transmit antennas. Both schemes assume a slowly fading channel (i.e. quasi-static fading) and require some limited feedback from the receiver to the transmitter. By computing upper bounds on the pairwise error probabilities and ...
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Performance of spatial modulation in the presence of channel estimation errors
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2012)This work investigates the negative effects of channel estimation errors on the performance of spatial modulation (SM) when operating over flat Rayleigh fading channels. The pairwise error probability of the SM scheme is derived in the presence of channel estimation errors and an upper bound on the average bit error probability is evaluated for M-PSK and M-QAM signalling. It is shown via computer simulations that the derived upper bound becomes very tight with increasing signal-to-noise ratio (SNR) ...
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Performance of transmit and receive antenna selection in the presence of channel estimation errors
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2008)This letter considers the effect of channel estimation errors on the performance of space-time coded (STC) systems with transmit and receive antenna selection over quasi-static flat fading channels. By performing pairwise error probability analysis and presenting numerical examples we show that the diversity order achieved with perfect channel state information (CSI) is still achievable with imperfect CSI used both at the antenna selection and the space-time decoding processes. We note that our ...
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Power and Rate Adaptation Based on CSI and Velocity Variation for OFDM Systems Under Doubly Selective Fading Channels
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Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2016)In this paper a novel joint continuous power and rate adaptation scheme is proposed fordoubly selective fading channels in orthogonal frequency division multiplexing (OFDM) systems based on terminal velocity and perfect or imperfect channel state information (CSI). The analysis and simulation results show that the continuous power and rate adaptation scheme is very effective and improve the performance of OFDM systems substantially under time-varying fading channels as compared with the traditional ...