• Journal of Astronomy and Space Sciences
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• v.38 no.4
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• pp.217-227
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• 2021

In this study, we describe an analytical process for designing a low Earth orbit constellation for discontinuous regional coverage, to be used for a surveillance and reconnaissance space mission. The objective of this study was to configure a satellite constellation that targeted multiple areas near the Korean Peninsula. The constellation design forms part of a discontinuous regional coverage problem with a minimum revisit time. We first introduced an optimal inclination search algorithm to calculate the orbital inclination that maximizes the geometrical coverage of single or multiple ground targets. The common ground track (CGT) constellation pattern with a repeating period of one nodal day was then used to construct the rest of the orbital elements of the constellation. Combining these results, we present an analytical design process that users can directly apply to their own situation. For Seoul, for example, 39.0° was determined as the optimal orbital inclination, and the maximum and average revisit times were 58.1 min and 27.9 min for a 20-satellite constellation, and 42.5 min and 19.7 min for a 30-satellite CGT constellation, respectively. This study also compares the revisit times of the proposed method with those of a traditional Walker-Delta constellation under three inclination conditions: optimal inclination, restricted inclination by launch trajectories from the Korean Peninsula, and inclination for the sun-synchronous orbit. A comparison showed that the CGT constellation had the shortest revisit times with a non-optimal inclination condition. The results of this analysis can serve as a reference for determining the appropriate constellation pattern for a given inclination condition.

• Publications of The Korean Astronomical Society
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• v.31 no.3
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• pp.65-76
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• 2016

We study a manuscript that includes 28 oriental constellations in the flags of barracks in Gangjin. According to the Joseon Chronicles, the constellation flags in the manuscript are thought to have originated from Seon-Pil Kim (金善弼) who first made 28 constellation flags for the barracks in 1878 during the Joseon Dynasty. Seon-Pil Kim was a commander and he used the 28 constellation flags for communications in a military camp. The flags also contain 28 animals and letter-like symbols with constellation maps. We examine the constellation maps in flags in terms of shapes and number of stars, and compare them with those of constellations in the Korean and Chinese star charts such as CheonSangYeolChaBunYaJiDo (天象列次分野之圖), Joseon-Butienge (朝鮮步天歌), Suzhou (蘇州) Star Chart, and Tang-Butiange (唐步天歌). Finally, we found that the shape of constellations in the flags might be similar to those in the Chinese Tang-Butienge. We also found several errors such as the shape, connecting pattern, and number of constellations drawn in the flags. It seems that the constellation flags were unofficially used in military camps in the late Joseon dynasty. Meanwhile, the 28 constellations are divided into four groups and each group has its own color and direction. We suppose that the constellation flags might represent the positions of military camps and each group of flags has their own color based on their cardinal points.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.297-300
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• 2003

In this paper, fingerprint minutiae mosaicking algorithm using minutiae of fingerprint is proposed. First, minutiae map is generated from minutiae of fingerprint and minutiae constellation is generated from fingerprint minutiae map. Minutiae constellation is constellation-shaped structure generated from Voronoi Diagram and Delaunay Triangulation using information of minutiae. Secondly, common region is detected by similarity of minutiae constellation of fingerprint minutiae map and minutiae map of individual fingerprint image is composed. Consequently composite minutiae map by mosaicking of fingerprint minutiae improve the performance of the fingerprint matching system.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.2
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• pp.125-138
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• 2020

One of the most important steps to consider in utilizing micro-satellites for surveillance or reconnaissance operations is the design of the satellite constellation. The Walker-Delta constellation which is commonly used in designing satellite constellations is not ideal for this operation in which military satellites are required to monitor specific regions continuously in a stable manner. This study aims to discuss the methodology for designing a satellite constellation that is capable of monitoring the fixed region at the fixed time each day by using the Sun synchronous Orbit. The BB(Beach Ball) constellation that we propose outperforms the Walker-Delta constellation in terms of robustness and it holds the merit of being simple in its design, thereby making future expansions more convenient. We expect the BB constellation will have a high applicability as the operational concept of military surveillance satellites is established in the near future.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.12-21
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• 1996

The trellis shaping is the method of selecting a minimum weight sequence from an equivalent class of possible transmitted sequences. It is perforemed by searching through the trellis diagram of a shaping convolutional code Cs. A shaping gain of the order of 1dB may be obtained with a simple 4-state shaping code. But when the rellis shaping is applied to multi-dimensional constellation, the shaping gain is decreased and the transmission delay is increased, which make it difficult to apply the trellis shaping to multi-dimensional constellation. In this paper, in order to solve these problems, the shell mapping algorithm is used for the mapper in the proposed trellis shaping. The simulatio result shows that the proposed trellis shaping is better than coventional trellis shaping to multi-dimensional constellation. In this paper, in order to solve these problems, the shell mapping on multi-dimensional costellation with respect to shaping gain and transmission delay. And the constellation expansion ratio (CER) and the capacity of transmitted injformation are identical to those of conventional trellis shaping on multi-dimensional constellation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.121-127
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• 2010

This paper relates with the improved CMA blind adaptive equalization algorithm which uses the constellation matching method that improve the inverse modelling efficiency of a communication channel compared to the present CMA blind adaptive equalizer. The amplitude distortion can be compensated in the present CMA blind adaptive equalizer which is used for the reduction of intersymbol interference by distortion that generate such as a band limited wireless mobile channel, but in the improved adaptive alogorithm operates with the minimize the amplitude phase distortion in the output of equalizer by applying the cost function that is composition of additional signal constellation matching error terms. In order to evaluation of the inverse modeling efficiency of improved algorithm, the residual intersymbol interference and recovered signal constellation were compared by computer simulation. As a result of comparion of computer simulation, the improved algorithm has a good stability in the residual intersymbol interference in the steady state, but it has a slow convergence rate in the adaptation state in initial state.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.105-110
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• 2015

This paper relates with the eualization performance of Constellation Matching-MMA (CM-MMA) in order to the consists of optimum receiver for the minimization of intersymbol interference and additive noise effects that is occurs in the nonlinear communication channel. The error signal were obtained that combines the Constellation Matching technique that inserts the zero point between the signal point of equalizer for improving the residual isi and convergence speed compared to the currently used MMA algorithm. In the initial state of adaptive equalization, it depends on the MMA characteristics mainly. And in the steady state, it depends on the CM characteristics mainly. In order to analyzing the equalization performance, the output signal constellation, residual isi, maximum distortion, MSE and SER were applied, then it were compared with the present MMA algorithm. As a result of computer simulation, the CM-MMA has more better performance in the every performance index, and it was also confirmed that the constellation matching effect can be obtained in the greater than 20dB signal to noise ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1339-1345
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• 2007

An important drawback in Lattice Reduction (LR) aided detectors has been investigated. For the solution, an improved LR aided detection with ignorable complexity overhead is proposed for MIMO system, where the additional correction operation is performed for the case of unreliable symbol decision. We found that LR aided detection errors mainly occur when the lattice points after the inverse lattice transform in the final step fall outside the constellation point set. In the proposed scheme, we check whether or not the lattice point obtained through LR detection is out of constellation. Only for the case of out of constellation, we additionally perform ML search with reduced search region restricted to the neighboring points near to the obtained lattice points. Using this approach, we can effectively and significantly improve the detection performance with just a slight complexity overhead which is negligible compared to full searched ML scheme. Simulation results show that the proposed scheme achieves the detection performance near to that of the ML detection with a lower computational complexity.

• The Journal of Information Technology
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• v.1 no.2
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• pp.39-53
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• 1998

The CMA and MCMA adaptive blind equalization algorithm has an inevitable error caused by mismatching between the original constellation at the steady state after the equalization and the unique constellation. This problem is due to considering the new type constellation(constant modulus, reduced constellation) as desired constellation. In this paper, we propose a new adaptive blind equalization algorithm which can reach to the steady state with rapid convergence speed and achive the improvement of error value in the steady state. The Proposed algorithm has a new error function using the decided original constellation instead of the reduced constellation. By computer simulation, it is comfirmed that the proposed algorithm has the performance superiority in terms of residual ISI and convergence speed compared with the adaptive blind equalization algorithm of CMA family, Constant Modulus Algorithm with Carrier Phase Recovery and Modified CMA(MCMA).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.103-109
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• 2014

This paper related with the CR-MMA which is possible to improving the equalization performance by applying the concept of constellation reduction in the MMA adaptive equalization alogorithm in order to reduce the intersymbol interference that is occurred in the nonlinear communication channel. In the updating process of MMA adaptive equalizer, the error signal is being obtained by using the equalizer output, and the performance will be degraded by the increase the error signal in the high order QAM constellation. But by using the constellation reduction, the high order QAM signal will be changed to the 4-QAM signal constellation and then the error signal will be obtained. By doing so, the error signal will be minimized and it is possible to improve the equalization performance in the high order QAM transmitted signal. The Computer simulation was performed in order to compare the performance of the proposed CR-MMA algorithm and original MMA algorithm in the same communication channel and noise environment. For this, the recoverd signal constellation which is the output of equalizer, residual isi and MD (Maximum Distortion) learning curve which is represents the convergence performance and SER which is represents the roburstness of noise were used. As a result of simulation, the CR-MMA has more superior to the MMA. And it was confirmed that the CR-MMA has roburstness to the noise in the SER performance.