• Journal of Communications and Networks
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• 제8권3호
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• pp.267-274
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• 2006

Self-spreading (SSP) is a spread spectrum technique where the spreading sequence is generated from data bits. Although SSP allows communications with low probability of interception by unintended receivers, despreading by the intended receiver is prone to error propagation. In this paper, we propose both a new transmitter and a new receiver based on SSP with the aim to a) reduce error propagation and b) increase the concealment of the transmission. We first describe a new technique for the generation of SSP spreading sequence, which generalizes SSPs of existing literature. We include also coding at the transmitter, in order to further reduce the effects of error propagation at the receiver. For the receiver, we propose a turbo architecture based on the exchange of information between a soft despreader and a soft-input soft-output decoder. We design the despreader in order to fully exploit the information provided by the decoder. Lastly, we propose a chip decoder that extracts the information on data bits contained in the spreading sequence from the received signal. The performance of the proposed scheme is evaluated and compared with existing spread-spectrum systems.

• 한국구조물진단유지관리공학회 논문집
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• 제10권6호
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• pp.213-223
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• 2006

본 연구에서는 화강풍화토 지반에 시공된 PHC 매입말뚝의 지지력의 평가를 위해 인공신경망을 적용하였다. 오류역전파 인공신경망의 적용성을 증명하기 위해 168개의 PHC 매입말뚝의 현장시험 데이터가 사용되었다. 연구결과 오류역전파 인공신경망의 말뚝지지력 평가가 동재하시험결과와 잘 일치함을 보여주었으며, 이러한 결과는 인공신경망을 이용한 PHC 매입말뚝의 지지력 평가가 신뢰성이 있음을 보여준다.

• 대한의용생체공학회:의공학회지
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• 제10권3호
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• pp.343-350
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• 1989

A new algorithm classifying ECG Arrhythmia signals using Back-propagation network is proposed. The base-line of ECG signal is detected by high pass filter and probability density function then input data are normalized for learning and classifying. In addition, ECG data are scanned to classify Arrhythmia signal which is hard to find R-wave. A two-layer perceptron with one hidden layer along with error back-propagation learning rule is utilized as an artificial neural network. The proposed algorithm shows outstanding performance under circumstances of amplitude variation, baseline wander and noise contamination.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.281-282
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• 2008

Turbo equalizers which use MAP (maximum a posteriori probability) equalizer or MMSE (minimum mean square error) equalizer have shown high performance and adoptability [1], [2]. In this paper, we show that the BP (belief propagation) algorithm can also be applied in equalizer and when it is connected with channel code, it can replace the MAP equalizer with similar complexity and performance.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.45-51
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• 2015

In this paper, we discuss the belief propagation decoding algorithm for polar codes. The performance of Polar codes for shorter lengths is not satisfactory. Motivated by this, we propose a novel technique to improve its performance at short lengths. We showed that the probability of messages passed along the factor graph of polar codes, can be increased by multiplying the current message of nodes with their previous message. This is like a feedback path in which the present signal is updated by multiplying with its previous signal. Thus the experimental results show that performance of belief propagation polar decoder can be improved using this proposed technique. Simulation results in binary-input additive white Gaussian noise channel (BI-AWGNC) show that the proposed belief propagation polar decoder can provide significant gain of 2 dB over the original belief propagation polar decoder with code rate 0.5 and code length 128 at the bit error rate (BER) of $10^{-4}$.

• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.760-766
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• 2008

This paper proposes an efficient location technique to find an indoor location under the IEEE 802.11 wireless local area networks. The proposed method is based on the range measurements obtained from a simple radio frequency propagation model. Thus, unlike the radio frequency fingerprint correlation method, it does not suffer from the computational burden during the real-time location service period and can quickly reply the location requests of many users at the same time. To increase the location accuracy in spite of the frequent non-line-of-sight error occurrences, the proposed method calibrates the distortion of the non-line-of-sight error by a simple measurement surveying procedure that does not require the surveyor's manual interaction. Experimental results show the capability of the proposed method.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.559-564
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• 2013

In this paper a new hybrid forecast method composed of wavelet transform and neural network is proposed to forecast the wind speed more accurately. In the field of wind energy research, accurate forecast of wind speed is a challenging task. This will influence the power system scheduling and the dynamic control of wind turbine. The wind data used here is measured at 15 minute time intervals. The performance is evaluated based on the metrics, namely, mean square error, mean absolute error, sum squared error of the proposed model and compared with the back propagation model. Simulation studies are carried out and it is reported that the proposed model outperforms the compared model based on the metrics used and conclusions were drawn appropriately.

• 한국통신학회논문지
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• 제36권3C호
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• pp.170-174
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• 2011

본 논문은 양방향 중계 채널(Two-Way Relay Channel) 에서 기존에 연구되었던 협력 통신(Cooperative Communication) 에서 네트워크 부호화(Network Coding)에 대해 간단히 소개한다. 협력 통신 시스템에서의 직교성을 이용한 새로운 네트워크 부호화 기법을 제안한다. 제안된 직교 사상 네트워크 부호화 기법은 기존에 널리 사용되고 있는 DF(Decode-and-Forward) 모듈러 합 기법의 전송률을 유지하면서 DF 기법의 단점인 오류 전파(Error Propagation) 현상을 제거하여 향상된 BER(Bit Error Rate) 성능을 보인다.

• 소음진동
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• 제9권2호
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• pp.377-386
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• 1999

This paper is a study on model method for estimating system inputs from vibration responses, which is one of indirect input identification methods in frequency domain. The method has advantages over direct inverse method especially when points of operational inputs are inaccessible so that artificial excitation forces cannot be applied to obtain frequency response functions of the complete system. Procedures of extended modal model method are proposed and checked by numerical experiment. Mechanisms of error propagation, i.e., how errors in modal parameters such as poles nad mode shape vectors affect estimation of the input forces, are illustrated. Then, in order to counteract the error propagation, discrete modal filter approach is taken in this paper to compute the inversion of modal matrix in which the most serious errors seem to be generated. Further, a Reduced form of Modified Reciprocal Modal Vector(RMRMV) is proposed for estimating multiple inputs. It is shown to have smaller orthogonality error than MRMV.

• 정보처리학회논문지C
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• 제14C권2호
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• pp.163-170
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• 2007

차세대 네트워크는 다양한 특성을 가진 무선 액세스 네트워크들로 구성되는 오버레이 네트워크 형태로 구성된다. 이와 같은 네트워크 환경에서 이동 사용자에게 멀티미디어 서비스를 고품질로 제공하기 위해서는 핸드오버 횟수를 최소화하고 오류전파문제를 해결해야 한다. 이에 본 논문에서는 mSCTP (mobile Stream Control Transmission Protocol)을 기반으로 오류전파문제를 개선함으로써 오버레이 네트워크 환경에서 종단 간 수직 핸드오버 시 이동 사용자에게 고품질의 멀티미디어 서비스를 제공하는 방안을 제안한다. 제안하는 방안은 다음 4가지 기능을 이용한다. (1) 멀티미디어 프레임의 전송 경로를 프레임 유형별로 분리, (2) 멀티미디어 프레임 손실률을 최소화하는 재전송 정책, (3) 바이캐스팅 (bicasting)을 통한 Forced 수직 핸드오버 수행, (4) 핑퐁 현상이 성능에 미치는 영향을 줄이기 위한 안정기간 사용, 시뮬레이션을 통해 제안하는 방안은 오류복원력을 달성함으로써 이동 사용자에게 고품질의 멀티미디어 서비스를 제공함을 알 수 있었다.