• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6C
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• pp.444-449
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• 2008

Selected mapping is well-known scheme for peak to average power ratio(PAPR) reduction in orthogonal frequency multiplexing(OFDM) systems. In this paper, we proposed a new scheme for generating a set of candidate transmission sequences. In conventional SLM, candidate sequences were generated by rotating the phases of the frequency domain OFDM M-ary symbols but in proposed scheme, candidate sequences are generated by multiplying the m-sequences with data in bit format of OFDM signals. Computer simulation results show that, as compared to the conventional SLM scheme, the proposed approach has better PAPR reduction performance and especially in case of OFDM systems which has small number of subcarriers has better performance than large ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.223-231
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• 2011

It has been shown that the performance of multiple-input multiple-output (MIMO) spatial multiplexing systems is significantly degraded when spatial correlation exists between transmit and receive antenna pairs. In this paper, we investigate designs of a new statistical precoder for spatial multiplexing systems with maximum likelihood (ML) receiver which requires only correlation statistics at the transmitter. Two kinds of closed-form solution precoders based on rotation and power allocation are proposed by means of maximizing the minimum E tlidean distance of joint symbol constellations. In addition, we extend our results to linear receivers for correlated channels. We provide a method which yields the same profits from the proposed precoders based on a simple zero-forcing (ZF) receiver. The simulation shows that 2dB and 8dB gains are achieved for ML and ZF systems with two transmit antennas, respectively, compared to the conventional systems.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.917-922
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• 2018

In the conventional interchannel interference self-cancellation (ICI-SC) schemes, the length of sampling window is the same as the symbol length of orthogonal frequency division multiplexing (OFDM). Thus, the number of complex operations to compute the interference coefficient of each subchannel is significantly increased. To solve this problem, we present an approximated mathematical model for the coefficients of ICI-SC schemes. Based on the proposed approximation, we analyze mean squared error (MSE) and computational complexity of the ICI-SC schemes with the length of sampling window. As a result, the presented approximation has an error of less than 0.01% on the MSE compared to the original equation. When the number of subchannels is 1024, the number of complex computations for the interference coefficients is reduced by 98% or more. Since the computational complexity can be remarkably reduced without sacrificing the self-cancellation capability, it is considered that the proposed approximation is very useful to develop an algorithm for the ICI-SC scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.468-475
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• 2009

In OFDM-based Full Duplex Relays (FDR) with Decode and Forward (DF) scheme, an interference cancellation technique in the frequency domain is more efficient than the one in the time domain. However, an Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) may occur due to the timing mismatch between the feedback interference signal and the desired signal from Base Station (BS) when the feedback interference cancellation and demodulation are performed in the frequency domain. In this paper, the effects of timing mismatch on the synchronous type and asynchronous type of OFDM-based FDR are analyzed for uplink and downlink cases. Then, synchronization procedure and methods for reducing ISI and ICI in OFDM-based FDR with frequency-domain feedback interference canceller are proposed and verified by computer simulation.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.18-25
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• 2008

In this paper, new lossless coding method of spectral coefficients for audio codec is proposed. Conventional lossless coder uses Huffman coding utilizing the statistical characteristics of spectral coefficients, but does not provide the high coding efficiency due to its simple structure. To solve this limitation, new lossless coding scheme with better performance is proposed that consists of bit-plane transform and run-length coding. In the proposed scheme, the spectral coefficients are first transformed by bit-plane into 1-D bit-stream with better correlative properties, which is then coded intorun-length and is finally Huffman coded. In addition, the coding performance is further increased by applying the proposed bit-plane coding selectively to each group, after the entire frequency is divided into 3 groups. The performance of proposed coding scheme is measured in terms of theoretical number of bits based on the entropy, and shows at most 6% enhancement compared to that of conventional lossless coder used in AAC audio codec.

• Journal of Korean Historical Folklife
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• no.27
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• pp.267-361
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• 2008

This article traces how the modern Chinese "nation" was constructed as an "imagined community" around Huang-ti (the Yellow Emperor) in late Qing. Huang-ti was a legendary figure in ancient China and the imperial courts monopolized the worship of him. Many late Qing intellectuals appropriated this symbolic figure and, through a set of discursive strategies of "framing, voice and narrative structure," transformed him into a privileged symbol for modern Chinese national identity. What Huang-ti could offer was, however, no more than a "public face" for the imagined new national community, or in other words, a formal structure without substantial contents. No consensus appeared on whom the Chinese nation should include and where the Chinese nation should draw its boundaries. The anti-Manchu revolutionaries emphasized the primordial attachment of blood and considered modern China an exclusive community of Huang-ti's descent. The constitutional reformers sought to stretch the boundaries to include the ethnic groups other than the Han. Some minority intellectuals, particularly the Manchu ones, re-constructed the historic memory of their ethnic origin around Huang-ti. The quarrels among intellectuals of different political persuasion testify how Huang-ti as the most powerful cultural symbol became a site for contests and negotiations in the late Qing process of national construction.

• Archives of design research
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• v.19 no.1 s.63
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• pp.89-98
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• 2006

As the concept of city changes city is viewed in the perspective of business to make profits, not in the perspective of physical space. In the case of Korea urbanization processed over the level of 80% and the formation of identity is suggested for the way to improve city competitiveness as of globalization and liberalization. Seoulentered the level of developed countries in the perspective of functions and facilities, but its image is evaluated poor because of the lack of cultural competitiveness, tourismattractiveness and service system. Dependency of public transportation which is public facilities representing city indirectly is very high, but in information service and visual systems of pubic transportation operations and management are not enough and differentiated image and loyalty are hard to find. In 2004 government of city of Seoul suggested modifications, but compared to London, Paris and Tokyo consistent system, the lack of control and management of use environment of design, excessive visual information and destruction of connection are pointed out. Therefore to solve these problems the introduction of design system is needed to develop identity after applying characteristics and regulations for using to disordered visual stuff. These procedurescan be explained as City Identity Program (CIP) and this study tries to embody city image through public transportation design system. As the study method for this the status of public transportation design system of London, Paris and Tokyo were searched and compared to that of Seoul. Based on this systematization of symbol marks per public transportation being used right now, the development of design guidelines to form identity, relation of design and the strategy of systematization per method and media were proposed.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.3 s.303
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• pp.81-90
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• 2005

When we transmit signals, which are quantized by the vector quantizer (VQ), through noisy channels, the overall performance of the coding system is very dependent on the employed quantization scheme and the channel error effect. In order to design an optimal coding system, the source and channel coding scheme should be jointly optimized as in the channel-optimized VQ. As a suboptimal approach, we may consider the robust VQ (RVQ). In RVQ, we consider developing an index assignment function for mapping the output of quantizers to channel symbols so that the effect of the channel errors is minimized. Recently, a VQ, which can reduce the encoding complexity and is called the sample-adaptive product quantizer (SAPQ), has been proposed. SAPQ has very similar quantizer structure as to the product quantizer (PQ). However, the quantization performance can be better than PQ. Further, the encoding complexity and the memory requirement for the codebooks are lower than the regular full-search VQ case. In this paper, SAPQ is employed in order to design an RVQ to channel errors by reducing the vector dimension. Discussions on the codebook structure of SAPQ and experiments are introduced in an aspect of robustness to noisy channels.

• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.198-206
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• 2009

Recently, there has been a trend designing a consistent and uniform regional identity in South Korean provinces as demonstrated by efforts in Chungcheongnam buk-Do. The motivating goals have been to establish an identity for local residents, provide voluntary services, achieve higher value-added business, introduce new management strategies, and establish a local brand through the exportation of local specialties. The by-products of these goals when accomplished include: maintaining a consistent policy, securing governmental economic efficiency of the province, characterizing local culture and improving quality of life. In this study, I tried to find out whether a local logo which is associated with a city plays a core role in the city's identity by comparing each symbol's shape, color and other components which are ways of expressing its meaning. In this respect, I analyzed the type of the Chungcheongnam buk-Do's symbol marks (30) and tried to suggest the desirable direction in developing symbol marks.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.249-255
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• 2014

In this paper, we proposed to reduce the interference in the visible light Communication with multi-LEDs for improving the performance of BER and satisfied the QoS. LED is not only lighting device, but also transmitting device in the VLC. Our proposed system is aim to decrease the interference in the multi-LEDs. In addition, it occurred the ISI and CCI by transmitter to receiver different distance. To solve this problem, we proposed the multi-LEDs system using walsh code to reduce ISI and CCI. In addition, our proposed system is able to improve the performance of BER and satisfied the Qos to desire users.