• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2411-2418
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• 2011

The most typically utilized positioning method in the existing indoor WPS that is a positioning method utilizing distributed wireless network is the finger print. Its positioning is carried out by calculating the difference between the AP information map and WiFi AP signal collected. However, there are problems like low accuracy and high cost when the existing method and the radio map formation are applied to outdoors. In this paper, the characteristics of the existing WPS are surveyed and their problems are examined. In addition, we propose a new WPS using weak signal and a method to construct radio map in order to solve the above problems. And then, the results of experimental test will be analyzed.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.1
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• pp.61-67
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• 2011

The GPS new civil signal is modulated on the L2 carrier at a frequency of 1227.6MHz. The L2C signal is composed of two multiplexed code signals, which include CM code with a 10,230 chip sequency repeating every 20ms, and CL code which has a 767,250 chip sequency repeating every 1.5 seconds. Thus, the new civil signal have much improved cross correlation properties so that the position fixing can be possible even with very weak signals. However, it requires very long acquisition time because of its long code length. This paper presents an efficient signal acquisition method for L2C AGPS receiver. Snapshot mode and coarse time assistance are assumed and total integration time is given by 1.5 sec. By SNR worksheet and computer simulation, it is proven that L2C signal can be acquired with very weak power less than -150dBm. Considering the acquisition time and the sensitivity, it is recommended that the highest power signal is acquired with CM code first to reduce TTFF. By the timing synchronization, at this time, search space of the code phase for other signals can be greatly reduced so that CL code can be used in signal acquisition to maximize sensitivity with small computation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2745-2752
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• 2014

In recent years, Transport Demand Management has been conducted for the efficient management of transport. In ITS applications in particular, the prerequisite is accurate and reliable positioning. However, the major problems are satellite signal outage, and multipath. This paper proposes that outage and multipath measurement can be detected and estimated using elevation angle and signal to noise ratio data association relation in stand-alone GPS. In order to verify the performance of the proposed method, it is then evaluated by the car test. the evaluation test environment has low accuracy and unreliable positioning because of signal outage or multipath such as steep hill and high buildings. In the evaluation test result, 918times abnormal signal occurred and it was confirmed that the proposed method showed more improved 9.48m(RMS) horizontal positioning error than without proposed method.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1299-1301
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• 1999

This paper describes a initial screening methods for weak line selection using sensitivity matrix. The elements of sensitivity matrix for line suceptance have 1 or -1, 0. From this property of sensitivity matrix, the eigen-sensitivity for line suceptance can be computed very simply and selected weak line for small signal stability or transient stability. The proposed algorithm is applied to small signal stability of New England 39-bus system and also applied to voltage stability of New England 30-bus system too.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.49-53
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• 2005

We are often faced with the task of having to estimate the amplitude of a source signal in the presence of a background. In the simplest case, the background can be taken as being flat, and of unknown magnitude B, and the source signal of interest assumed to be the amplitude A of a peak of known shape and position. We present a robust method to find the most probable values of A and B by applying the one-dimensional Newton-Raphson method. In the derivation of the formula, we adopted the Bayesian statistics and assmumed Poisson distribution so that the results could be applied to the analysis of very weak signals, as observed in FIMS (Far-ultraviolet IMaging Spectrogaph).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2C
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• pp.150-159
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• 2007

In Part 1 of this paper, the test statistics are obtained for detecting weak known signals in observations corrupted by multiplicative and first-order Markov additive noise. In this second part, the asymptotic and finite sample-size performance of several detectors are obtained and compared based on the test statistics. From the performance comparisons, it is confirmed that the dependence among interference components need to be taken into account to maintain the detection performance.

• Electronics and Telecommunications Trends
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• v.39 no.2
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• pp.93-102
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• 2024

As the scale of research and development (R&D) increases, countries and companies are consistently establishing R&D directions to meet strategic goals and market demands as well as roadmaps to increase efficiency through concentration and selection. However, establishing an effective roadmap and discovering promising technologies are challenging under the current numerous technological possibilities and uncertainties. The importance of discovering promising technologies to secure future technological competitiveness is recognized worldwide, and Europe, the United States, and Japan are establishing processes to identify promising future technologies and support related R&D. Methods for discovering promising future technologies can be classified into future social needs analysis, forecasting, surveys, use of expert opinions, and data analysis. We describe the types and limitations of technology roadmaps and investigate the status of domestic and foreign organizations using weak signal search through quantitative data analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.8
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• pp.742-747
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• 2004

Outdoors we can easily acquire our accurate location by GPS. However, the GPS signal can't be acquired indoors because of its weak signal power level. Adequate positioning method is demanded for many indoor positioning applications. At present, wireless local area network (WLAN) is widely installed in various areas such as airport, campus, and park. This paper proposes a positioning algorithm using WLAN signal strength to provide the position of the WLAN user indoors. There are two methods for WLAN based positioning, the signal propagation method uses signal strength model over space and the empirical method uses RF power propagation database. The proposed method uses the probability distribution of the power propagation and the maximum likelihood estimation (MLE) algorithm based on power strength DB. Test results show that the proposed method can provide reasonably accurate position information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.523-531
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• 2005

We derive decision regions of the maximum likelihood(ML) and suboptimum ML(S-ML) detectors in the first order moving average(FOMA) of an impulsive process. The ML and S-ML detectors are compared in terms of the bit-error-rate in the antipodal signaling system. Numerical results show that the S-ML detector, despite its reduced complexity and simpler structure, exhibits practically the same performance as the optimum ML detector. It is also shown that the performance gap between detectors for FOMA and independent and identically distributed noise becomes larger as the degree of noise impulsiveness increases.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.167-174
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• 1995

The anomlous signal, anomaly, recorded by a sub-bottem profiler is analized for exploration of buried objects in the ocean, This anomaly is known as a signal diffracted from the edge of the buried object. Signals obtained from model that and numerical simulation are analized for investigating characteristics of the diffracted signal. From this study a diffracted signal and a non-diffracted signal can be identified, and the location of the object can be obtained. In order to identify an object in the seafloor the dimension of the object should be greater than the wave length used for exploration, and the acoustic impedance should be much greater than that of sediments. A 2-trace stacking of the signals can enhance the feature of strongly diffracted signals whereas it can diminish weak signals.