• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.321-327
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• 2012

This paper presents a comparative analysis on three different types of performance indices of obstacle detection for an overlapped ultrasonic sensor ring. Due to beam overlap, the entire sensing zone of each ultrasonic sensor can be divided into three smaller sensing subzones, which leads to significant reduction of positional uncertainty in obstacle detection. First, the positional uncertainty in obstacle detection is expressed in terms of the area of a sensing subzone, and type 1 performance index is then defined as the area ratio of side and center sensing subzones. Second, based on the area of a sensing subzone, type 2 performance index is defined taking into account the size of the entire range of obstacle detection as well as the degree of the positional uncertainty in obstacle detection. Third, the positional uncertainty in obstacle detection is now expressed in terms of the length of the uncertainty arc spanning a sensing subzone, and type 3 performance index is then defined as the average value of the uncertainty arc lengths over the entire range of obstacle detection. Fourth, using a commercial low directivity ultrasonic sensor, the changes of three different performance indices depending on the parameter of an overlapped ultrasonic sensor ring are examined and compared.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.20-33
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• 2015

Spectrum sensing is a key component of cognitive radio. The prediction of the primary user status in a low signal-to-noise ratio is an important factor in spectrum sensing. However, because of noise uncertainty, secondary users have difficulty distinguishing between the primary signal and an unauthorized signal when an unauthorized user exists in a cognitive radio network. To resolve the sensitivity to the noise uncertainty problem, we propose an entropy-based spectrum sensing scheme to detect the primary signal accurately in the presence of an unauthorized signal. The proposed spectrum sensing uses the conditional entropy between the primary signal and the unauthorized signal. The ability to detect the primary signal is thus robust against noise uncertainty, which leads to superior sensing performance in a low signal-to-noise ratio. Simulation results show that the proposed spectrum sensing scheme outperforms the conventional entropy-based spectrum sensing schemes in terms of the primary user detection probability.

• ETRI Journal
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• 제41권2호
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• pp.176-183
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• 2019

Spectrum sensing plays an important role in spectrum sharing. Energy detection is generally used because it does not require a priori knowledge of primary user (PU) signals; however, it is sensitive to noise uncertainty. An order statistics (OS) detector provides inherent protection against nonhomogeneous background signals. However, no analysis has been conducted yet to apply OS detection to spectrum sensing in a wireless channel to solve noise uncertainty. In this paper, we propose a robust spectrum sensing scheme based on generalized order statistics (GOS) and analyze the exact false alarm and detection probabilities under noise uncertainty. From the equation of the exact false alarm probability, the threshold value is calculated to maintain a constant false alarm rate. The detection probability is obtained from the calculated threshold under noise uncertainty. As a fusion rule for cooperative spectrum sensing, we adopt an OR rule, that is, a 1-out-of-N rule, and we call the proposed scheme GOS-OR. The analytical results show that the GOS-OR scheme can achieve optimum performance and maintain the desired false alarm rates if the coefficients of the GOS-OR detector can be correctly selected.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.225-228
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• 2007

This paper presents a geostatistical methodology to model local uncertainty in spatial estimation of sediment grain size with high-resolution remote sensing imagery. Within a multi-Gaussian framework, the IKONOS imagery is used as local means both to estimate the grain size values and to model local uncertainty at unsample locations. A conditional cumulative distribution function (ccdf) at any locations is defined by mean and variance values which can be estimated by multi-Gaussian kriging with local means. Two ccdf statistics including condition variance and interquartile range are used here as measures of local uncertainty and are compared through a cross validation analysis. In addition to local uncertainty measures, the probabilities of not exceeding or exceeding any grain size value at any locations are retrieved and mapped from the local ccdf models. A case study of Baramarae beach, Korea is carried out to illustrate the potential of geostatistical uncertainty modeling.

• 로봇학회논문지
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• 제5권1호
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• pp.23-31
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• 2010

This paper suggests a multiple robot simulator which considers the uncertainties in robot motion and sensing. A mobile robot moves with errors due to some kinds of uncertainties from actuators, wheels, electrical components, environments. In addition, sensors attached to a mobile robot can't make accurate output information because of uncertainties of the sensor itself and environment. Uncertainties in robot motion and sensing leads researchers find difficulty in building mobile robot navigation algorithms. Generally, a robot algorithm without considering unexpected uncertainties fails to control its action in a real working environment and it leads to some troubles and damages. Thus, the authors propose a simulator model which includes robot motion and sensing uncertainties to help making robust algorithms. Sensor uncertainties are applied in range sensors which are widely used in mobile robot localization, obstacle detection, and map building. The paper shows performances of the proposed simulator by comparing it with a simulator without any uncertainty.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권5호
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• pp.1131-1145
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• 2013

Energy detection is a widely used method for spectrum sensing in cognitive radios due to its simplicity and accuracy. However, it is severely affected by the noise uncertainty. To solve this problem, a blind multiband spectrum sensing scheme which is robust to noise uncertainty is proposed in this paper. The proposed scheme performs spectrum sensing over the total frequency channels simultaneously rather than a single channel each time. To improve the detection performance, the proposal jointly utilizes the likelihood function combined with Gerschgorin radii of unitary transformed covariance matrix. Unlike the conventional sensing methods, our scheme does not need any prior knowledge of noise power or PU signals, and thus is suitable for blind spectrum sensing. In addition, no subjective decision threshold setting is required in our scheme, making it robust to noise uncertainty. Finally, numerical results based on the probability of detection and false alarm versus SNR or the number of samples are presented to validate the performance of the proposed scheme.

• 한국전자파학회논문지
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• 제23권12호
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• pp.1406-1411
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• 2012

에너지 검파 기반 스펙트럼 감지 방식은 잡음 전력에 대한 불확실성에 취약한 것으로 알려져 있다. 이러한 문제점을 해결하기 방안 중의 하나로 협력 스펙트럼 감지 기술을 함께 사용하는 방안이 제안된 바 있다. 그러나 아직까지 페이딩 채널 환경에서 이 방식에 대한 성능 분석이 발표된 바가 없다. 본 논문에서는 에너지 검파 기반 스펙트럼 감지 방식에 대한 이전 연구 결과를 토대로 에너지 검파 기반 협력 스펙트럼 감지 방식에 대한 수학적 분석 결과를 제시하고자 한다. 분석 결과에 따르면 잡음 전력에 대한 불확실성이 존재할 때는 스펙트럼 감지 시간이 늘어나거나 OR 융합 방식의 협력 스펙트럼 감지에 참여하는 2차 사용자가 많아질수록 오경보 확률과 검파 확률이 높아진다는 것을 확인할 수 있었다.

• 전자공학회논문지
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• 제50권1호
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• pp.15-20
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• 2013

일반적으로 에너지 검파 기반 스펙트럼 감지 방식은 잡음 전력에 대한 불확실성에 취약한 것으로 알려져 있다. 이러한 문제점을 해결하기 방안 중의 하나로 이중 임계값을 사용하는 에너지 검파 기반 협력 스펙트럼 감지 방식이 제안된 바 있다. 그러나 아직까지 페이딩 채널 환경에서 이 방식에 대한 성능 분석이 수행된 바 없다. 본 논문에서는 에너지 검파 기반 스펙트럼감지 방식에 대한 이전 연구 결과를 활용하여 에너지 검파 기반 협력 스펙트럼 감지 방식에 대한 닫힌 형태의 수학적 분석 결과를 제시하고자 한다.

• 대한원격탐사학회지
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• 제20권6호
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• pp.383-396
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• 2004

이 논문은 원격탐사 화상 분류에서 공간적 불확실성 분포를 얻기 위해 공간 통계를 적용하였다. 분류 항목 할당과 참조 자료와 연계된 각각의 불확실성 표현을 위해 2가지 정량적 방법을 제안하였다. 우선 분류 항목 할당에 따른 불확실성 표현을 위해 3가지 정량적 지수를 제안하였다. 그리고 참조 자료와 분류 결과를 결합하고 이와 연계된 불확실성 혹은 정확성 분포를 얼기 위해 지구통계학적 시뮬레이션 기법을 적용하였다. 다중 센서 원격탐사 화상을 이용한 감독 토지 피복 분류 실험을 수행하여 제안 방법을 예시하고, 적용시 제안점을 논의하였다. 실험 결과, 이 논문에서 제시한 방법론을 통해 분류 결과의 해석과 평가를 위한 부가적인 정보추출이 가능하였으며, 제시 방법론의 검증을 위한 다양한 자료에의 적용이 필요한 것으로 판단된다.

• 한국통신학회논문지
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• 제42권5호
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• pp.982-984
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• 2017

시간 영역에서 펄스 레이다 신호는 송신 펄스가 존재하는 구간과 표적으로부터 반사된 수신 신호가 존재하는 구간으로 구분할 수 있으며, 수신 신호 성분은 송신 펄스에 비해 크기가 매우 작고, 표적으로 부터 반사된 성분을 제외하고는 잡음으로 구성되어 있다. 본 논문에서는 이러한 성질을 이용하여 잡음 전력에 대한 불확실성이 존재하는 환경에서 에너지 검파를 이용하여 레이다 신호를 검출하는 방안을 제시하고자 한다.