The Experts below are selected from a list of 45783 Experts worldwide ranked by ideXlab platform
Chang-hee Lee - One of the best experts on this subject based on the ideXlab platform.
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Decision Threshold Control Method for the Optical Receiver of a WDM-PON
Journal of Optical Communications and Networking, 2010Co-Authors: Hoon-keun Lee, Jung-hyung Moon, Sil-gu Mun, Ki-man Choi, Chang-hee LeeAbstract:We demonstrate an improvement of optical receiver performance for an optical signal with beat noises. The Decision Threshold level is adjusted automatically according to the detected average optical power. This simple method improves optical receiver performance under a wide range of input signal conditions, e.g., beat noise level and extinction ratio. Thus this proposed method is useful to optical receivers for WDM-PONs. By employing this control circuit, we successfully demonstrate a WDM-PON based on a wavelength-locked Fabry–Perot laser diode at 1.25 Gb/s per channel with 100 GHz spacing.
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An automatic Decision Threshold control circuit for WDM-PON based on the wavelength-locked F-P LDs
OECC ACOFT 2008 - Joint Conference of the Opto-Electronics and Communications Conference and the Australian Conference on Optical Fibre Technology, 2008Co-Authors: Hoon-keun Lee, Jung-hyung Moon, Sil-gu Mun, Ki-man Choi, Chang-hee LeeAbstract:We propose and demonstrate a simple Decision Threshold control circuit. By employing this method, we demonstrate a feasibility of WDM-PON at 1.25 Gb/s per channel with 100 GHz spacing based on the wavelength-locked F-P LDs.
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An optimization method for the Decision Threshold level in optical receivers for WDM-PONs
Network Architectures Management and Applications IV, 2006Co-Authors: Sil-gu Mun, Chang-hee LeeAbstract:We demonstrate an optimization method of the Decision Threshold level in optical receivers for WDM-PONs based on wavelength locked Fabry-Perot laser diodes. The Decision Threshold level is controlled by the average optical power. For the WDM-PON with 100 GHz channel spacing, we reduced required injection power for color-free operation by 6 dB using the proposed method.
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Reduction of the Power Penalty Induced by Low-Frequency Tone Using Variable Decision Threshold Technique
Journal of the Optical Society of Korea, 2002Co-Authors: Chang-hee Lee, Sung-man Kim, Jin-serk Baik, Kun-youl ParkAbstract:We propose 'variable Decision Threshold technique' to decrease the power penalty induced by low-frequency tones. The proposed scheme uses a simple low-speed receiver to change the Decision Threshold of the optical receiver according to the low-frequency tones. We demonstrate the proposed method at 2.5 Gb/s.
Ayse Bener - One of the best experts on this subject based on the ideXlab platform.
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reducing false alarms in software defect prediction by Decision Threshold optimization
Empirical Software Engineering and Measurement, 2009Co-Authors: Ayse Tosun, Ayse BenerAbstract:Software defect data has an imbalanced and highly skewed class distribution. The misclassification costs of two classes are not equal nor are known. It is critical to find the optimum bound, i.e. Threshold, which would best separate defective and defect-free classes in software data. We have applied Decision Threshold optimization on Naive Bayes classifier in order to find the optimum Threshold for software defect data. ROC analyses show that Decision Threshold optimization significantly decreases false alarms (on the average by 11%) without changing probability of detection rates.
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ESEM - Reducing false alarms in software defect prediction by Decision Threshold optimization
2009 3rd International Symposium on Empirical Software Engineering and Measurement, 2009Co-Authors: Ayse Tosun, Ayse BenerAbstract:Software defect data has an imbalanced and highly skewed class distribution. The misclassification costs of two classes are not equal nor are known. It is critical to find the optimum bound, i.e. Threshold, which would best separate defective and defect-free classes in software data. We have applied Decision Threshold optimization on Naive Bayes classifier in order to find the optimum Threshold for software defect data. ROC analyses show that Decision Threshold optimization significantly decreases false alarms (on the average by 11%) without changing probability of detection rates.
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Adjusting Decision Threshold in Naive Bayes based IVF embryo selection
2009 14th National Biomedical Engineering Meeting, 2009Co-Authors: Asli Uyar, Ayse Bener, H. Nadir Ciray, Mustafa BahceciAbstract:In this study, IVF embryo selection has been considered as a binary classification problem and predictibality of implantation outcome of individual embryos has been tested using Naive Bayes method. First, in order to perform classification experiments, an embryo based dataset has been constructed from database of Bahceci IVF Centre. Since the class distribution of dataset is highly imbalanced (11% Pozitive and 89% Negative implantation outcomes) the Decision Threshold of Naive Bayes classifier has been optimized using the features of ROC analysis. Experimental results show that classification with optimized Threshold performs better than classification with default Threshold.
S.g. Glisic - One of the best experts on this subject based on the ideXlab platform.
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Automatic Decision Threshold level control in direct-sequence spread-spectrum systems
IEEE Transactions on Communications, 1991Co-Authors: S.g. GlisicAbstract:An algorithm for automatic Decision Threshold-level control in direct-sequence spread-spectrum systems is presented and analyzed. Using this algorithm, instantaneous setting of the Threshold is possible. An additional loop called a Threshold loop is used to improve the system performance. This loop is based on a constant false alarm rate (CFAR) criterion. The purpose of the algorithm is to set a Decision Threshold in the system which will provide a small probability of false alarm (P/sub 3/ to 0) and a large probability of signal detection (P/sub d/ to 1) at the same time. The analysis has shown that the Threshold probability distribution function (PDF) is narrower (equaling better performance) in the case of the CFAR algorithm, but this comes at the cost of a considerably larger integration time for the system (the system time response is slower). As a compromise, the instantaneous algorithm is modified so that k successive samples of the signal are used to determine the value of the Threshold. This permits better control of the shape and position of the Threshold PDF with respect to the P/sub 3/ and P/sub d/ curves. At the same time, the time response of the system is good and can be easily controlled.
Mathini Sellathurai - One of the best experts on this subject based on the ideXlab platform.
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optimal Decision Threshold for eigenvalue based spectrum sensing techniques
International Conference on Acoustics Speech and Signal Processing, 2014Co-Authors: Tharmalingam Ratnarajah, Jiang Xue, Ebtihal H G Yousif, Mathini SellathuraiAbstract:This paper investigates optimization of the sensing Threshold that minimizes the total error rate (i.e., the sum of the probabilities of false alarm and missed detection) of eigenvalue-based spectrum sensing techniques for multiple-antenna cognitive radio networks. Four techniques are investigated, which are maximum eigenvalue detection (MED), maximum minimum eigenvalue (MME) detection, energy with minimum eigenvalue (EME) detection, and the generalized likelihood ratio test (GLRT) detection. The contribution of this paper is of four parts. Firstly, we present the derivative of the matrix-variate confluent hypergeometric function, which is required for the MED case. Secondly, we derive the probabilities of false alarm for both cases MME and EME detection. Thirdly, we derive the probability of missed detection for the GLRT detector. Finally, we provide the exact expressions required to obtain the optimal sensing Thresholds for all cases. The simulation results reveal that for all the investigated cases the chosen optimal sensing Thresholds achieve the minimum total error rate.
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distribution of the ratio of the largest eigenvalue to the trace of complex wishart matrices
IEEE Transactions on Signal Processing, 2012Co-Authors: Ayse Kortun, Tharmalingam Ratnarajah, Mathini Sellathurai, Caijun ZhongAbstract:This correspondence investigates the statistical properties of the ratio T = λ1/Σi=1mλi , where are λ1 ≥ λ2 ≥ ··· ≥ λm the m eigenvalues of an m × m complex central Wishart matrix W with n degrees of freedom. We derive new exact analytical expressions for the probability density function (PDF) and cumulative distribution function (CDF) of T for complex central Wishart matrices with arbitrary dimensions. We also formulate simplified statistics of T for the special case of dual uncorrelated and dual correlated complex central Wishart matrices (m = 2) . The investigated ratio T is the most important ratio in blind spectrum sensing, since it represents a sufficient statistics for the generalized likelihood ratio test (GLRT). Thus, the derived analytical results are used to find the exact Decision Threshold for the desired probability of false alarm for Blind-GLRT (B-GLRT) detector. It is shown that the exact Decision Threshold based B-GLRT detector gives superior performance over the asymptotic Decision Threshold schemes proposed in the literature, which leads to efficient spectrum usage in cognitive radio.
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on the performance of eigenvalue based cooperative spectrum sensing for cognitive radio
IEEE Journal of Selected Topics in Signal Processing, 2011Co-Authors: Ayse Kortun, Tharmalingam Ratnarajah, Mathini Sellathurai, Caijun Zhong, Constantinos B PapadiasAbstract:In this paper, the distribution of the ratio of extreme eigenvalues of a complex Wishart matrix is studied in order to calculate the exact Decision Threshold as a function of the desired probability of false alarm for the maximum-minimum eigenvalue (MME) detector. In contrast to the asymptotic analysis reported in the literature, we consider a finite number of cooperative receivers and a finite number of samples and derive the exact Decision Threshold for the probability of false alarm. The proposed exact formulation is further reduced to the case of two receiver-based cooperative spectrum sensing. In addition, an approximate closed-form formula of the exact Threshold is derived in terms of a desired probability of false alarm for a special case having equal number of receive antennas and signal samples. Finally, the derived analytical exact Decision Thresholds are verified with Monte-Carlo simulations. We show that the probability of detection performance using the proposed exact Decision Thresholds achieves significant performance gains compared to the performance of the asymptotic Decision Threshold.
Zixiong Wang - One of the best experts on this subject based on the ideXlab platform.
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Performance Improvement of OOK Free-Space Optical Communication Systems by Coherent Detection and Dynamic Decision Threshold in Atmospheric Turbulence Conditions
IEEE Photonics Technology Letters, 2012Co-Authors: Zixiong Wang, Wen-de Zhong, Changyuan YuAbstract:In this letter, we analyze the performance improvement of on-off-keying free-space optical communication systems in atmospheric turbulence conditions due to coherent detection and the dynamic Decision Threshold (DDT) scheme. Our analytical results show that the DDT scheme provides a 5.7-dB power reduction for achieving a bit error rate of 10-3 compared with the conventional fixed Decision Threshold scheme. In addition, the improvement achieved by the DDT scheme is related to the strength of amplitude and phase fluctuations, not to the power of the local oscillator.
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ICICS - Dynamic Decision Threshold and adaptive coherent detection in FSO communication system
2011 8th International Conference on Information Communications & Signal Processing, 2011Co-Authors: Zixiong Wang, Wen-de ZhongAbstract:In this paper, we first compare the bit error rate (BER) performance of OOK FSO transmission systems under noncoherent and coherent detections. With coherent detection, BER of 10−9 can be achieved under different atmospheric turbulence scenarios from weak to strong. In addition, we propose a dynamic Decision Threshold scheme to further improve the performance of coherent detection, where the Decision Threshold is varied in every sub-millisecond time slot. It is found that when the power of local oscillator is 8dBm, dynamic Decision Threshold scheme provides a 4.0dB power reduction in achieving BER of 10−9 towards traditional fixed Decision Threshold scheme. In addition, we propose an adaptive coherent detection in FSO system, where a high power-local oscillator (LO) is used to mitigate the deep fading while a low power-LO is to mitigate the rest fading scenarios. Result shows that the outage probability is reduced completely and the average power is only 10% of the high power-LO
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Performance evaluation of OOK free-space optical transmission system with dynamic Decision Threshold and coherent detection
2010 Photonics Global Conference, 2010Co-Authors: Zixiong Wang, Wen-de Zhong, Shaoliang Zhang, Changyuan Yu, Yicheng DingAbstract:Transmission performance of free-space optical (FSO) communication is severely degraded by scintillation effect, which is a slow fading process. In this paper, we propose a dynamic Decision Threshold scheme to efficiently detect the bit stream. The Decision Threshold is varied in every sub-millisecond time slot. In addition, it is shown that coherent detection with 10dBm-local oscillator (LO) can make the BER performance better than 10-3 under different atmospheric turbulence scenarios from weak to strong.
