Browsing Elektrik-Elektronik Mühendisliği / Electrical - Electronics Engineering by Title
Now showing items 207-226 of 330
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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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Partial Power and Rate Adaptation for MQAM/OFDM Systems under CFO
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Publisher and Date:(IEEE, 2014)In this paper a new partial power and rate adaptation scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO). The conventional adaptive scheme is shown to be a special case of the partially adaptive scheme technique which enables the resulting non-convex optimization problem solved in a feasible way. It leads to a solution for optimal power adaptation that maximizes the spectral efficiency of an OFDM system using M-ary ...
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Partial power and rate adaptation for MQAM/OFDM systems under CFO
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Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2014)In this paper a new partial power and rate adaptation scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO). The conventional adaptive scheme is shown to be a special case of the partially adaptive scheme technique which enables the resulting non-convex optimization problem solved in a feasible way. It leads to a solution for optimal power adaptation that maximizes the spectral efficiency of an OFDM system using M-ary ...
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Performance Analysis of Maximal Ratio Transmission with Relay Selection in Two-way Relay Networks Over Nakagami-m Fading Channels
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Publisher and Date:(Springer, 2016)In this paper we investigate the performance of an amplify-and-forward multi-input multi-output two way relay network where two sources are equipped with multiple antennas employing maximal ratio transmission and the communication is carried through the selected relay resulting in the largest received power. Assuming the fading channel coefficients are Nakagami-m distributed we derive the sum symbol error rate (SSER) outage probabilities for each user and the overall system. In addition diversity ...
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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 Investigation of IEEE 802.11af Systems Under Realistic Channel Conditions
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Publisher and Date:(IEEE, 2015)As the analog TV broadcasting channels have become less frequently used in the last decade there has been a great interest in these frequency bands for the deployment of metropolitan local and personal area networks. Among them the local area network standard IEEE 802.11af defines PHY and MAC layer implementation of such networks in these unused frequency bands also named television white space (TVWS). According to the standard the systems may use contiguous or non-contiguous channels during their ...
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Performance of IEEE 802.15.4a systems in the presence of narrowband interference
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Publisher and Date:(2011)The regulatory agencies in Europe and Japan require the implementation of avoidance techniques in some bands to reduce interference to licensed systems. Accordingly ultra-wideband impulse radio (UWB-IR) based Wireless Personal Area Network (WPAN) standard IEEE 802.15.4a has suggested using linear combination of pulses to reduce interference to coexisting primary systems. In this paper we consider the implementation of linear combination of pulses for a peaceful coexistence and assess the UWB-IR ...
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Performance of IEEE 802.15.4a Systems in the Presence of Narrowband Interference
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Publisher and Date:(IEEE, 2011)The regulatory agencies in Europe and Japan require the implementation of avoidance techniques in some bands to reduce interference to licensed systems. Accordingly ultra-wideband impulse radio (UWB-IR) based Wireless Personal Area Network (WPAN) standard IEEE 802.15.4a has suggested using linear combination of pulses to reduce interference to coexisting primary systems. In this paper we consider the implementation of linear combination of pulses for a peaceful coexistence and assess the UWB-IR ...
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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
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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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Performance of space time codes with transmit antenna selection over frequency selective fading channels in the presence of channel estimation errors
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Publisher and Date:(2008)This paper presents a performance analysis of space-time coded systems with transmit antenna selection over frequency selective fading channels when the erroneously estimated fading coefficients are available only at the receiver. An upper bound on the pairwise error probability is derived and numerical examples are presented. The analysis does not assume any specific coding or channel estimation algorithm. With imperfect channel state information (CSI) used both at the antenna selection and the ...
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Performance of space-time coded systems with transmit antenna selection
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Publisher and Date:(IEEE, 2007)We deal with transmit antenna selection for space-time coded (STC) systems over multiple input multiple output (MIMO) channels. Using pairwise error probability analysis and simulation results we show that transmit antenna selection based on received power levels does not reduce the achievable diversity order for full rank STCs. Initially we prove the results for Rayleigh flat fading channels and then we state our expectations for the case of frequency selective (FS) fading. In addition to the ...
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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 Stack Equalizer over Frequency Selective Fading Channels
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Publisher and Date:(IEEE, 2008)In this paper the performance of the low complexity modified stack equalizer over frequency-selective fading channels is inspected. With the help of simulation results it is illustrated that by sacrificing the computational complexity insignificantly the performance of the modified equalizer can be made closer to optimum. This equalizer can be used at the receiver of uncoded systems or bit interleaved coded systems with iterative receivers.
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Performance of stack equalizer over frequency selective fading channels [Frekansa baǧlı sönümlemeli kanallarda yiǧit denkleştiricinin başarımı]
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Publisher and Date:(2008)In this paper the performance of the low complexity modified stack equalizer over frequency-selective fading channels is inspected. With the help of simulation results it is illustrated that by sacrificing the computational complexity insignificantly the performance of the modified equalizer can be made closer to optimum. This equalizer can be used at the receiver of uncoded systems or bit interleaved coded systems with iterative receivers. ©2008 IEEE.
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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:(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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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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Phase transitions between different spin-glass phases and between different chaoses in quenched random chiral systems
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Publisher and Date:(Amer Physical Soc., 2017)The left-right chiral and ferromagnetic-antiferromagnetic double-spin-glass clock model with the crucially even number of states q = 4 and in three dimensions d = 3 has been studied by renormalization-group theory. We find for the first time to our knowledge four spin-glass phases including conventional chiral and quadrupolar spin-glass phases and phase transitions between spin-glass phases. The chaoses in the different spin-glass phases and in the phase transitions of the spin-glass phases with ...
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Physical-Layer Security in Visible Light Communications
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Publisher and Date:(IEEE, 2020)Optical wireless communications (OWC) and its potential to solve physical layer security (PLS) issues are becoming important research areas in 6G communications systems. In this paper, an overview of PLS in visible light communications (VLC), is presented. Then, two new PLS techniques based on generalized space shift keying (GSSK) modulation with spatial constellation design (SCD) and non-orthogonal multiple access (NOMA) cooperative relaying are introduced. In the first technique, the PLS of the ...