• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.22-34
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• 1997

In LEO system, the signal degradation is mainly due to fading and Doppler shift, so that the analysis of the signal degradation and compensation techniques are very important. As the Doppler shift compensator, the block demodulator has been known to be useful in compensating for the time-varing Doppler shift, but its compensating ability is about several hundreds Hz in 32 ksymbols / s QAM (QPSK) signal transmission. Therefore, in this paper, to compensate for severe fading and Doppler shift more than several kHz, we use a conventional pilot symbol-aided fading compensator, and propose the Doppler shift compensator. It is shown that the proposed compensator is able to compensate for Doppler shift more than several kHz. And a pilot symbol-aided fading compensator is shown to be a suitable scheme for severe Rician fading ($K{\leq}10 dB$) as well as Rayleigh fading. Also, it is shown that the equal gain combiner improves greatly the QAM performance even if the fading or Doppler shift becomes deeper or larger.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.1
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• pp.1-6
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• 2021

In this paper, in order to mitigate ISI(inter-symbol interference) in a diffusion-based molecular communication channel, an ISI Hamming code is proposed in which ISI characteristics are applied to a channel decoding algorithm. In order to prove the bit error rate performance of the proposed channel code, the bit error rate performance of the major channel codes applied to the molecular communication channel with ISI was compared and analyzed through simulation. From the simulation results, it can be seen that the bit error rate performance of the ISI Hamming code is the best when the number of radiated molecules is less than or equal to 1100. In addition, when the number of transmitted molecules is M=1000, the decoding method of the ISI Hamming code proposed in this paper has improved the bit error rate of approximately 5.9×10-5 compared to the Hamming code using only soft values. Compared with the ISI-mitigating channel code, which is effective for removing ISI in the molecular communication channel, the ISI Hamming code proposed in this paper is the most advantageous in a channel environment where the number of transmitted molecules is not big (M<1100). And we can see that the ISI-mitigating channel code is more advantageous when the number of transmitted molecules is large(M>1100).

• ETRI Journal
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• v.42 no.4
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• pp.562-574
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• 2020

Quadrature spatial modulation (QSM) utilizes the in-phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.8
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• pp.3550-3566
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• 2020

As a widely used way to exfiltrate information, wireless covert channel (WCC) brings a serious threat to communication security, which enables the wireless communication process to bypass the authorized access control mechanism to disclose information. Unlike the covert channel on the network layer, wireless covert channels on the physical layer (WCC-P) is a new covert communication mode to implement and improve covert wireless communication. Existing WCC-P scheme modulates the secret message bits into the Gaussian noise, which is also called covert digital communication system based on the joint normal distribution (CJND). Finding the existence of this type of covert channel remains a challenging work due to its high undetectability. In this paper, we exploit the square autocorrelation coefficient (SAC) characteristic of the CJND signal to distinguish the covert communication from legitimate communication. We study the sharp increase of the SAC value when the offset is equal to the symbol length, which is caused by embedding secret information. Then, the SAC value of the measured sample is compared with the threshold value to determine whether the measured sample is CJND sample. When the signal-to-noise ratio reaches 20db, the detection accuracy can reach more than 90%.

• Journal of architectural history
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• v.14 no.1 s.41
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• pp.7-19
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• 2005

The purpose of this paper is the study on the piazza plan of basilica S. Pietro. The results of study are as follows: 1. The piazza of the basilica S. Pietro was planned in relation to building-piazza-symbol of interior piazza-street as city planning characteristic of Baroque and architectural characteristic of elliptical piazza form. 2. The function of piazza of basilica S. Pietro was planned for religious meeting of a grand scale than a piazza for the common run of people. 3. In general, the disposition, ground, elevation and section plan of the piazza of basilica S. Pietro was planned by principle of spatial and formal composition, according to axis, symmetry, proportion, division and contrast. 4. The location, scale, shape of piazza for disposition and ground plan of the piazza of basilica S. Pietro was basically decided by not only elements of Basilica building, Vatican Palace, Street and Walls of surroundings with axis of the Basilica building, but Fountain and Obelisk as existing constituent elements. 5. The elevation of the piazza of basilica S. Pietro was composed of boundary that was enclosed from wall of trapezoid piazza and gallery of elliptical piazza with equal height as symmetry. And the section plan was planned to approach into the Basilica through slope and stairs of gentle angle, utilizing of existing land form.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.57-62
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• 2005

In this paper, we propose a channel estimation method by impulse signal train in OFDM. In order to estimate the channel response, 4 impulse signals are generated and transmitted during one OFDM (Orthogonal Frequency Division Multiplexing) symbol. The intervals between the impulse signals are all equal in time domain. At the receiver, the impulse response signals are summed and averaged. And then, the averaged impulse response signal is zero padded and fast Fourier transformed to obtain the channel estimation. The BER performance of the proposed method is compared with those of conventional estimation method using the long training sequence in fast fading environments. The simulation results show that the proposed method improves by 3 dB in terms of Eb/No, compared with the conventional method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2859-2872
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• 2019

Interference alignment (IA) has been a powerful approach to achieve the maximum degree of freedom (DoF) for K users multiple-input-multiple-output (MIMO) interference channels. However, due to the feasibility constraint, aligning all the interference signals at each receiver is impractical for large K without symbol extension. In this paper, we propose two best-effort interference alignment (BEIA) schemes that the network selects the maximum number of interfering transmitters to align their signals given the feasibility conditions when each transmitter-receiver pair has a constant number of data streams. Besides, in case of not all interfering signals aligned at each receiver, an upper bound of the average throughput is derived. Simulation results show that the proposed schemes have superiority over the traditional methods, such as time division multiple access (TDMA) and cluster IA(CIA), in low and moderate signal-to-noise ratio (SNR) region in terms of average user throughput. In addition, the proposed max-min relative interference distance alignment scheme outperforms the proposed scheme of equal interfering transmitters number alignment in terms of both average user throughput and minimum user throughput.

• International Journal of Computer Science & Network Security
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• v.22 no.12
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• pp.51-56
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• 2022

In space based constellation network, users are allowed to enter or leave the network arbitrarily. Hence, the number, identities and transmitted data of active users vary with time and have considerable impacts on the receiver's performance. The so-called problem of multiuser detection means identifying the identity of each active user and detecting the data transmitted by each active user. Traditional methods assume that the number of active users is equal to the maximum number of users that the network can hold. The model of traditional methods are simple and the performance are suboptimal. In this paper a Maximum A Posteriori Probability (MAP) based multiuser detection method is proposed. The proposed method models the activity state of users as Markov chain and transforms multiuser detection into searching optimal path in grid map with BCJR algorithm. Simulation results indicate that the proposed method obtains 2.6dB and 1dB E_b/N₀ gains respectively when activity detection error rate and symbol error rate reach 10^-3, comparing with reference methods.

• Korean Journal of Heritage: History & Science
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• v.39
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• pp.191-217
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• 2006

The chief mourners do their best to carry the dead and various things related to him in the departure of a funeral procession. "Sejongsillok" and "Gukjooryeui" had already written the national funeral supplies for carriage in detail in the early of Joseon period. But they were the standard book of national ceremony. The Ilbang of Gukjangdogam made the national funeral supplies for carriage in the late of Joseon; Daeyeo, Gyeonyeo, Yoyeo, Chaeyeo, Gaja etc. "Gukjangdogamuigye" explained these in detail; size, materials, made-place etc. I used "Gukjangdogamuigye" published in the late of Joseon to explain the national funeral supplies for carriage. Because Kingdom's ceremony in Joseon was representative to the country, it couldn't depend on an individual taste. King was the symbol of a nation and the star tin point of the political power at that time. So its ceremony was to show people the representative example as a national ceremony. The national funeral supplies for carriage carried the dead of King and various things related to him. Gukjangdogam managed them carefully. People thought that the mean of these things was equal to King's authority at that time. So these weren't the mere national funeral supplies for carriage, the symbolic instruments equal to King.

• Journal of Families and Better Life
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• v.23 no.5 s.77
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• pp.63-77
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• 2005

The purpose of this study was to examine the changes and the characteristics of the attitudes toward children and spaces provided for them. by analyzing people's daily lives in housing spaces and architects' floor plans between the 1920s and the 1960s. Different kinds of data were obtained from a variety of early literature, research reports, newspaper articles, historical documents, and magazines from the period. Findings of this study are as follows: 1. Before modernization in Korea, children had been regarded as immature persons. Confucian ideas of children viewed them as 'small adults' or 'immature adults.' Thus spaces for children's daily lives were neither differentiated from those of the adults' nor deemed important. However, since the Western invasions and colonization by Japan, a remarkable change in the attitudes toward children took place. Children began to be considered a hope for the future as well as members of modem families. In addition, the introduction of the new word, 'eorini (children),' by Mr. Bang Jeonghwan, brought about a significant change in social consciousness of children. 2. The appearance of 'adongshil (children's room)' on architects' floor plans, which was a result of the social critique against androcentrism during the l930s and 1940s, was highly meaningful. The new floor plans not only emphasized rationalization of the space but also upgraded the children's status in the family. 3. Since the liberation (1945), children's space was differentiated from parental spare by the introduction of private rooms and shared spaces. The privacy of each generation was expressed by the division, and the generations were considered equal in this space distribution. In conclusion, the appearance of children's rooms required conflict-laden changes of social ideals and of the family system. It also was a symbol of modernization.