• 한국안전학회지
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• 제21권3호
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• pp.137-142
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• 2006

Quantification of error possibility, in an HRA process, should be performed so that the result of the qualitative analysis can be utilized in other areas in conjunction with overall safety estimation results. And also, the quantification is an essential process to analyze the error possibility in detail and to obtain countermeasures for the errors through screening procedures. In previous studies for the quantification of error possibility, nominal values were assigned by the experts' judgements and utilized as corresponding probabilities. The values assigned by experts' experiences and judgements, however, require verifications on their reliability. In this study, the validity of new error possibility values in new MCR design was verified by using the Onisawa's model which utilizes fuzzy linguistic values to estimate human error probabilities. With the model of error probabilities are represented as analyst's estimations and natural language expression instead of numerical values. As results, the experts' estimation values about error probabilities are well agreed to the existing error probability estimation model. Thus, it was concluded that the occurrence probabilities of errors derived from the human error analysis process can be assessed by nominal values suggested in the previous studies. It is also expected that our analysis method can supplement the conventional HRA method because the nominal values are based on the consideration of various influencing factors such as PSFs.

• 한국정보통신학회논문지
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• 제14권5호
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• pp.1155-1163
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• 2010

기존의 웨이브릿 편이 변조 시스템은 스케일링 함수(scaling function)를 1로, 웨이브릿(wavelet)을 0으로 하는 1비트 변조방법이 있고, 스케일링 함수와 웨이브릿 그리고 이 두 신호를 반전시켜서 생성된 4개의 반송파를 사용하는 2비트 변조방법이 있다. 본 논문에서는 2비트 변조방법인 4-ary 스케일링 웨이브릿 편이변조(4-ary SWSK : 4-ary scaling wavelet shift keying) 시스템을 정의하고, QPSK 시스템으로부터 정의된 시스템의 비트 에러 확률과 부호 에러 확률을 유도한다. 제안한 4-ary SWSK 성능을 분석하기 위하여, 기존의 QPSK(quadrature phase shift keying), MFSK(M-ary frequency shift keying), 그리고 제안한 방법의 비트 에러 확률 및 부호 에러 확률을 구한다. 실험결과 제안한 방법의 비트 에러 확률과 부호 에러 확률이 좋은 성능을 보였다.

• 한국음향학회지
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• 제12권1호
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• pp.47-54
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• 1993

Performance analysis is very important to transmit the high quality information and to construct the optimal system for the minimze the noise from the channel of spread spectrum system. In this paper the error rate performance is analyzed with computer simulation in noncoherent frequency hopping M-qry frequency shift keying(FH/MFSk) systems with regard to thermal noise under the partial band jamming environments. AS a result, in case the thermal noise is disregarded, bit error probability of system in jamming fraction ρ and Eb/Nj(bit energy to jamming power density) is reduced with the increase of K and in worst case 32FSK system is better than 2FSK system by 3.23dB with the variatio of Eb/Nj. In case thermal noise is considered, bit error probability of system by 3.23dB with the variation of Eb/Nj. In case thermal noise is considered, bit error probability of system are reduced with the increase of K and Eb/No(bit energy to thermal noise density). Bit error probability in connection with worst case ρ is not largely influenced form over the 14dB to K=1 and 8dB to K=5 accordingly thermal noise disregarding. These results may be useful for avoiding the common vulnerabilities when the spread spectrum system is designed.

• 한국통신학회논문지
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• 제31권6C호
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• pp.575-581
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• 2006

본 논문에서는 Alamouti, Tarokh, Su와 Xia 등에 의해 도입된 직교 시공간 부호를 포함한 임의의 선형 직교 시공간 블록 부호에 대해, 준정지 레일리 페이딩 채널에서의 정확한 비트 오율 성능을 분석한다. 먼저 1차원 심볼 오류 함순(one-dimensional symbol error function, ODSEF)를 정의한다. 이것은 직교 시공간 블록 부호의 정확한 쌍 오류 확률(pairwise error probability)에 의하여 얻어진다. ODSEF와 Cho 와 Yoon의 QAM에 대한 비트 오율 표현을 이용하여, 직교 시공간 블록 부호에 대한 일반적인 표현을 구하고, 이를 이용하여, 선형 직교 시공간 블록 부호의 정확한 폐형의 비트 오율을 구한다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1991년도 춘계학술대회
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• pp.65-70
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• 1991

A hybrid model which uses a probabilistic model and a MLP(multi layer perceptron) model for pattern recognition of EMG(electromyogram) signals is proposed in this paper. MLP model has problems which do not guarantee global minima of error due to learning method and have different approximation grade to bayesian probabilities due to different amounts and quality of training data, the number of hidden layers and hidden nodes, etc. Especially in the case of new test data which exclude design samples, the latter problem produces quite different results. The error probability of probabilistic model is closely related to the estimation error of the parameters used in the model and fidelity of assumtion. Generally, it is impossible to introduce the bayesian classifier to the probabilistic model of EMG signals because of unknown priori probabilities and is estimated by MLE(maximum likelihood estimate). In this paper we propose the method which get the MAP(maximum a posteriori probability) in the probabilistic model by estimating the priori probability distribution which minimize the error probability using the MLP. This method minimize the error probability of the probabilistic model as long as the realization of the MLP is optimal and approximate the minimum of error probability of each class of both models selectively. Alocating the reference coordinate of EMG signal to the outside of the body make it easy to suit to the applications which it is difficult to define and seperate using internal body coordinate. Simulation results show the benefit of the proposed model compared to use the MLP and the probabilistic model seperately.

• 융합신호처리학회논문지
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• 제12권3호
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• pp.188-193
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• 2011

본 논문에서는 OADF(Opportunistic Adaptive Decode-and-Forward) 릴레이 시스템에 대한 새로운 성능분석 기법을 레일리 페이딩 채널에 대하여 제안하였다. 제안된 분석 기법에서는 릴레이들의 복호 오류 사건(error-event)을 기반으로 수신된 순시 신호대 잡음비(Signal-to-Noise Ratio: SNR)를 표현한다. 또한 SNR의 확률 밀도 함수(Probability Density Function: PDF)를 기존의 분석 기법보다 일반적인 (PDF 표현에서 합 기호의 개수 및 그 영역이 구체화된)형태로 제시한다. 그리고 이를 이용하여 정확한 평균 오류율((Average Error Rate), 누락 확률(Outage Probability) 및 평균 채널용량(Average Channel Capacity)을 일반적인 형태로 유도한다. 제안된 성능분석 기법의 정확성은 모의실험을 통하여 검증한다. OADF 기법을 다른 기법들과 비교하여 평균 오류 확률, 누락 확률 및 채널 용량 측면에서 성능 향상 정도가 우수함을 확인하였다.

• 대한수학회논문집
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• 제37권3호
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• pp.765-800
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• 2022

Quantization for probability distributions concerns the best approximation of a d-dimensional probability distribution P by a discrete probability with a given number n of supporting points. In this paper, we have considered a probability measure generated by an infinite iterated function system associated with a probability vector on ℝ. For such a probability measure P, an induction formula to determine the optimal sets of n-means and the nth quantization error for every natural number n is given. In addition, using the induction formula we give some results and observations about the optimal sets of n-means for all n ≥ 2.

• 한국안전학회지
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• 제22권1호
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• pp.61-66
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• 2007

Car crashes are the leading cause of death for persons of every age. Specially, human-related factor has been known to be the primary causal factor of such crashes than vehicle-and environmental-related factors. There are various studies to analyze driver's behavior and characteristics in driving for reducing the car crashes in many areas of car engineering, psychology, human factor, etc. However, there are almost no studies which analyze mainly the human errors in driving and estimate their probabilities in terms of human reliability analysis. This study estimates the probability of human error in driving, i.e. driver error probability. First, fifty driver errors are investigated through DBQ (Driver Behavior Questionnaire) revision and the error likelihoods in driving are collected which are judged by skillful drivers using revised DBQ. Next, these likelihoods are converted into driver error probabilities using the results that verbal probabilistic expressions are changed into quantitative probabilities. Using these probabilities we can improve the warning effects on drivers by indicating their driving error likelihoods quantitatively. We can also expect the reduction effects of car accident through controlling especially dangerous error groups which have higher probabilities. Like these, the results of this study can be used as the primary materials of safety education on drivers.

• ETRI Journal
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• 제17권4호
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• pp.25-35
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• 1996

This paper derives the symbol error probability for quadrature amplitude modulation(QAM) with L-fold space diversity in Rayleigh fading channels. Two combining techniques, maximal ratio combining(MRC) and selection combining(SC), are considered. The formula for MRC space diversity is obtained by averaging the symbol error probability of M-ary QAM in an additive white Gaussian noise(AWGN) channel over a chi-square distribution with 2L degrees of freedom. The obtained formula overcomes the limitations of the earlier work, which has been limited only to deriving the symbol error rate(SER) of QAM with two branch MRC space diversity. The formula for SC space diversity is obtained by averaging the symbol error probability of M-ary QAM in an AWGN channel over the distribution of the maximum signal-to noise ratio among all of the diversity channels for SC space diversity has been reported yet. Analytical results show that the probability of error decreases with the order of diversity gain per additional branch decreases as the number of branches becomes larger. On the other hand, the performance of 16 QAM with MRC becomes much better than that of SC as the number of branches becomes larger. By giving the order of diversity, L, and the number of signal points, M, we have been able to obtain the SER performance of QAM with general space diversity. These results can be used to determine the order of diversity to achieve the desired SER in land mobile communication system employing QAM modulation.

• 한국인터넷방송통신학회논문지
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• 제19권2호
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• pp.67-71
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• 2019

본 논문은 이동형 위성단말이 운용되는 환경에서 기준이 되는 오류확률 성능을 도출한다. 위성단말이 이동을 하면 주변 장애물에 의해 shadwoingd 발생하고, BER성능을 저하시킨다. 분석을 위해 이동형 위성단말이 운용되는 환경을 모의한 Lutz모델을 활용한다. Lutz모델은 Rician분포와 Suzuki모델을 결합한 형태이다. 오류확률은 두 분포함수를 수식적 분석을 이용하여 도출한다. 한반도 수풀지역에서 측정 결과로 시뮬레이션한 결과는 Lutz모델을 이용해 근서화한 BER결과와 유사했다. 직관적으로 측정결과와 근사화한 결과는 유사하고, 수치적으로 SNR이 30dB에서 BER오차는 약 3e-4이하이다.