• Journal of Digital Contents Society
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• v.5 no.2
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• pp.143-150
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• 2004

In this paper, we propose and analyze a new scheme which uses the same scramble codes to each group after symbol grouping to reduce the PAPR (peak-to-avenge power ratio) problem in OFDM system. The conventional SLM scheme randomizes OFDM symbols entered into IFFT block by several scramble codes and then transmits the lowest one among PAPRs. Therefore, the SLM scheme can reduce the additional information as many as the number of grouped OFDM symbols by using same scramble codes after M grouping of sub-carriers. It can also improve PAPR performance more than conventional SLM scheme when we use scramble codes as same as those numbers of SLM scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.640-648
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• 2011

We propose relay selection schemes using STBC (Space Time Block Coding) technique in OFDM (Orthogonal Frequency Division Multiplexing)-based wireless systems. The proposed schemes select the optimum relay having the maximum instantaneous equivalent channel gain among multiple candidate relays. Also, in order to reduce the system overhead, a symbol grouping method which groups some amount of symbols before selecting the optimum relay is proposed. The simulation results show that the proposed relay selection schemes can obtain more selection diversity gain as the number of selectable relay candidates increases. Furthermore, the proposed scheme with the symbol grouping can reduce system overhead without any degradation of the performance in fading channels with low frequency selectivity.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.516-519
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• 2003

본 논문은 OFDM 시스템에서 PAPR (peak-to-average power ratio) 저감을 위해 심볼 그룹핑 후 그룹별로 같은 스크램블 코드를 이용하였다. 기존의 SLM 기법은 IFFT단에 들어가는 부반송파 벡터를 여러개의 스크램블 코드에 의해 랜덤화 시켜 PAPR중 작은 값을 선택하여 전송한다. 그러므로 SLM 기법은 스크램블의 코드 갯수만큼 부가 정보를 전송함으로 대역의 손실이 발생한다. 본 논문에서는 부반송파들을 M개로 그룹화 하여 동일한 스크램블 코드를 사용함으로써 그룹화한 OFDM 심볼의 갯수만큼 정보 데이터를 줄일 수 있다. 또한 SLM 기법에서 사용한 숫자만큼 스크램블 코드를 사용한다면 기존의 SLM 기법보다 PAPR 성능을 개선할 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1481-1484
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• 2005

In this paper, we propose a novel OFDM-based system structure to reduce PAPR (Peak-to-Average Power Ratio) and improve BER for OFDM system in which BER enhancement is obtainable based on WH (Walsh-Hadamard) transform to transmit concurrently each data symbol on all subcarriers so as to take advantage of frequency diversity and remedy the effect of channel's frequency-selectivity. By doing so, we also attain a low PAPR. Moreover, DGT (Data Grouping Technique) that is independent on the side information is also applied to further reduce PAPR. The simulation programs have been also performed to verify the validity of the proposed system.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.41-44
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• 2001

In the wide variety of radio propagation channel models, frequency selective fading which from multipath waves and diversity noises, electric and electronic devices ...etc in our environment, change characteristics of the sub channels in the wide bandwidth. so orthogonality among the OFDM subcarriers would be distorted and ICI(Inter Channel Interference), ISI(Inter Symbol Interference) be generated. This paper investigate BER characteristics of the OFDM System using Subband Grouping Method which adopted different channel modulation for each subband.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1406-1409
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• 2016

In this paper, we propose the heuristic signal grouping algorithm to estimate channel state value over full blind communication situation which means that there is no information about the modulation scheme and the channel state information between the transmitter and the receiver. Hereafter, using the constellation rotation method and the probability density function(pdf) the modulation scheme is determined to perform automatic modulation classification(AMC). Furthermore, the modulation type and a channel state value estimation capability is evaluated by comparing the proposed scheme with other conventional techniques from the simulation results in terms of the symbol error rate(SER) and the root mean square error (RMSE).

• Archives of design research
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• v.20
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• pp.199-208
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• 1997

The emphasis of simplicity in design is because of the desire to deliver much content with a simplest way. Since in general, a simple form is outstanding in its symbolical nature and the relief of plastic beauty is easy by it, it is usually applied to a form of a symbol mark. However, in the meantime, if any local autonomous group or enterprise which has not tried to give efforts to its advertisement than they might expect and might be disadvantageous in competition. For consumers, when they experienced several, forms of simple, symbol mark, would not remember the special features of each mark. Rather, for the psychology of perception, they might remember only the formative, common features, there by grouping the marks by their common features. In this study, some symbol marks in Dobong-gu Ward Office and Wonju city were inspected, reviewed, and analized. And its is a finding that the subjects of this study could not distinguish or identify any of marks from another mark having a similar image of it: the reason is that the simplicity of a symbol mark made or allowed them to recognize it identical with the other imaged: it proves that the mistakes, defects of memory, and accumulated errors are oriented to the identical image. After all, the appearented image and perceived image are differnt. Any of symbolmarks which takes a simple form does not mean the perceived image is also simple. As a final conclusion, designers, in order to produce any of competitive symbolmarks, need to thoroughly understand psychology of gestalt.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1131-1137
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• 2009

In this paper, a resource management technique for digital duplexing (DD) systems using orthogonal frequency division multiple access (OFDMA) is proposed. The proposed technique can reduce the dynamic range of the signal received at the subscriber station (SS) and minimize the effects of inter-symbol interference (ISI) and inter-carrier interference (ICI) due to the time difference of arrival (TDoA) without using a cyclic suffix. It is shown by computer simulation that the proposed technique can reduce the number of bits for an analog-to-digital converter (ADC) and increase the signal-to-interference and noise ratio (SINR) significantly.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.4 s.316
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• pp.117-122
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• 2007

For multiple antenna systems, we consider the hybrid iterative detection of the maximum a posteriori probability(MAP) detection and the linear detection such as the minimum-mean-square-error(MMSE) filtering with soft cancelation. We devise methods to obtain both the lower complexity of the linear detection and the superior performance of the MAP detection. Using the a prior probability of the coded bit which is extrinsic of the outer decoder, we compute the threshold of grouping and determine the detection scheme symbol by symbol. Through the simulation results, it is shown that the proposed receiver obtains the superior performance to the MMSE detector and the lower complexity than the MAP detector.

• Journal of IKEEE
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• v.13 no.2
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• pp.167-174
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• 2009

Music evokes human emotions or creates music moods through various low-level musical features. Typical music clip consists of one or more moods and this can be used as an important criteria for determining the similarity between music clips. In this paper, we propose a new music retrieval scheme based on the mood change patterns of music clips. For this, we first divide music clips into segments based on low level musical features. Then, we apply K-means clustering algorithm for grouping them into clusters with similar features. By assigning a unique mood symbol for each cluster, we can represent each music clip by a sequence of mood symbols. Finally, to estimate the similarity of music clips, we measure the similarity of their musical mood sequence using the Longest Common Subsequence (LCS) algorithm. To evaluate the performance of our scheme, we carried out various experiments and measured the user evaluation. We report some of the results.