• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.1
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• pp.71-76
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• 2023

This paper studied a method of attenuating nonlinear noise using a Wiener filter of a neural network structure in an acoustic noise attenuator. This system improves nonlinear noise attenuation performance with a deep learning algorithm using a neural network Wiener filter instead of using a conventional adaptive filter. A voice is estimated from a single input voice signal containing nonlinear noise using a 128-neuron, 8-neuron hidden layer and an error back propagation algorithm. In this study, a simulation program using the Keras library was written and a simulation was performed to verify the attenuation performance for nonlinear noise. As a result of the simulation, it can be seen that the noise attenuation performance of this system is significantly improved when the FNN filter is used instead of the Wiener filter even when nonlinear noise is included. This is because the complex structure of the FNN filter expresses any type of nonlinear characteristics well.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.1
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• pp.48-56
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• 2023

This paper implements many-to-many communication between users and develops a multi-functional smart helmet for worker protection and environmental safety in the shipbuilding and shipping industry. First, the communication situation is recorded in the field to perform signal processing for noise that interferes with communication. Then, it deals with the contents of developing smart helmets, data acquisition, algorithms, and simulations. The simulation results analyzed by applying the adaptive algorithm are shown, and their usefulness is confirmed. In conclusion, looking at the optimization process for the convergence factor of the Least Mean Square and Filtered-x Least Mean Square Adaptation Algorithm was possible. It is thought that it has laid the foundation for implementing many-to-many communication, the function of smart helmets that reduces or removes various noises at the shipyard in the future.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1983.10a
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• pp.39-43
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• 1983

The exess noise factor of APD defired in different manner has been studied. And the Signal to noise ratio, error probabilities of the COK optical receiver have been presented in terms of avalanche gein.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.8
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• pp.3589-3605
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• 2018

In this paper, we investigate an individual channel estimation problem for multiple-input multiple-output (MIMO) two-way amplify-and-forward (AF) relay networks. To avoid self-interference during the estimation of the individual MIMO channels, a novel blind interference cancellation (BIC) approach is proposed based on an orthogonal preceding framework, where a pair of orthogonal precoding matrices is utilized at the source nodes. By designing an optimal decoding scheme, we propose to decompose the bidirectional transmission into a pair of unidirectional transmissions. Unlike most existing approaches, we make the practical assumption that the nonreciprocal MIMO channel and the mutual interference of multiple antennas are both taken into consideration. Under the precoding framework, we employ an orthogonal superimposed training strategy to obtain the individual MIMO channels. However, the AF strategy causes the noise at the terminal to be the sum of the local noise and the relay-propagated noise. To remove the relay-propagated noise during the estimation of the second-hop channel, a partial noise-nulling method is designed. We also derive a closed-form expression for the total mean square error (MSE) of the MIMO channel from which we compute the optimal power allocation. The simulation results demonstrate that the analytical and simulated curves match fully.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.809-815
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• 2003

It is very important to get very high switching speed as well as low phase noise of frequency synthesizer in the OFDM/FH communication system. In this paper we compare the phase noises and switching speeds of the conventional PLL and digital hybrid PLL(DH-PLL) frequency synthesizer, also, we investigate the effect of phase noise on the performance of OFDM/FH communication system. DH-PLL has high switching speed property at the cost of circuit complexity and more power consumption. Unlike the conventional PLL in which the phase noise and switching speed have the trade off relationship in respect of loop filter bandwidth, DH-PLL frequency synthesizer can perform fast switching speed and low phase noise simultaneously. Under the condition of same hopping speed requirement, DH-PLL can achieve faster switching speed and lower SNR penalty compared with conventional PLL in the OFDM/FH communication system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.164-171
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• 2008

Adaptive equalizers are inevitable schemes in digital communication systems for compensating the transmission channel distortion. Additionally, to obtain the required BER(Bit Error Rate), the adaptive algorithms appropriate to the mobile communication channels are required. In this paper, we propose the NPDFE (Noise-Predictive Decision Feedback Equalizer) for communication systems performance improvement in mobile communication channels. The performance of the proposed NPDFE with QPSK (Quadrature Phase Shift Keying) is simulated under AWGN (Additive White Gaussian Noise), Ricean fading, ETSI (European Telecommunications Standards Institute) fading, and Rayleigh fading channels. The equalizers used in simulations are a LE (Linear Equalizer), a DFE (Decision Feedback Equalizer), and a NPDFE. Moreover, the equalizer performance criterion of the QPSK is the BER.

• Journal of Advanced Navigation Technology
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• v.25 no.5
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• pp.357-362
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• 2021

UWB(ultra wide band) communication systems employ short pulses to transmit information which spreads the signal energy over a very wide frequency spectrum. Received signal-to-noise power ratio of UWB signals is an important factor in determining the accuracy of a positioning system. As the signal to noise power ratio gets higher, positioning errors decrease since noise becomes less effective. Calculation of signal to noise power ratio as a function of communication distance provides important guidelines for the system design. And the performance of a positioning system also depends heavily on the channel model. As a result of the analysis, it was found that the performance of the received signal to noise power ratio according to the communication distance was better in the LOS channel environment than in the Non LOS(line of sight) channel environment. And as the symbol interval of the preamble signal increases at a specific communication distance, the channel capacity of the UWB system increases.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1805-1810
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• 2014

The phase noise spectrum distribution for remote controller using the BPSK mode and low data rate of 50 kbps was designed and proposed in this paper. In case of applying the BPSK that transmission performance is superior to FSK method, the performance degradations due to phase noise are generated. To minimize the phase noise effect, it is important to dispatch the digital signal in channel environment with required phase noise characteristics. To provide the terminal design technique and the proper channel environment with required phase noise characteristics, the phase noise spectrum distribution was designed for required phase noise characteristics. By analyzing the phase noise effects for damping factor and noise bandwidth of the carrier recovery circuit, the phase noise spectrum design that consider the damping factor and noise bandwidth was performed. Based on the IESS-308 standards, also, the phase noise effects was analyzed. The phase noise spectrum design techniques and phase noise spectrum that is suitable to remote controller were proposed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.6
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• pp.563-573
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• 2013

The ship radiated noise level fluctuates by the interference between direct and reflected paths. The effect of sea surface reflection path on interference depends strongly on sea surface roughness. This paper describes error characteristics of ship acoustic signature estimation by sea surface scattering effect. The coherent reflection coefficient which explains a magnitude of sea surface scattering and its resultant interference acoustic field is analyzed quantitatively as a function of a grazing angle, effective surface height, frequency, source-receiver range and depths of source and receiver. Theoretical interference acoustic field is compared with experimental result for two different sea surfaces and five different frequencies by changing source-receiver range. It is found that both matches well each other and a magnitude of interference acoustic field is decreasing by increasing a grazing angle, effective surface height, frequency, and depths of source and receiver and decreasing source-receiver range. For given experimental conditions, the transmission anomaly which is a bias error of ship acoustic signature estimation, is about a range of 1~3 dB. The bias error of an existing ship radiated noise measurement system is also analyzed considering wind speed, source depth and frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.10
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• pp.868-878
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• 1990

Upon introducing satellite communication system to Korea, one of the important problems to cope with is the effect from the probable intentional interference I.e. jamming. In this paper we have investigated how much the performance of ordinary PSK signal and Directed Sequence Spread Spectrum PSK signal degrade by the effect of jamming in the satellite communication system. In analysis we have consider the M ary PSK signal and the liniter type nonlinear satellite transponder in an environment of uplink tone or noise jamming plus Gaussian noise and downlink Gaussian noise. Using the derived error rate equation we have evaluated the error performance of BPSK and QPSK systems and compared this with that of DS BPSK system. Form the results, we know that the nonlinear satellite system is degraded more severely by the effect of noise jamming than tone jamming and the effect of tone jamming on the error rate performance can be reduced more remarkably by increasing the process gain in DS BPSK system rather than increasing carrier to jamming noise power ratio in conventional BPSK system.