고속 시변 채널 OFDM을 위한 저복잡도 양방향 탐색 순차적 간섭 제거

임동민,Lim, Dongmin 대한전자공학회 2013 전자공학회논문지 Vol.50 No.9

In this paper, we propose a low complexity bilateral search SIC for OFDM in fast time-varying channels. Due to the possibility of error propagation in SIC, symbol detection ordering within the block of symbols has a significant effect on the overall performance. In this paper, the first symbol to be detected is determined based on CSEP values, and then the next symbol to be detected is selected according to the updated CSEP while bilaterally searching from the boundary of the detected symbol group. Through computer simulations, we show that the proposed method has performance improvements with almost the same computation complexity over the conventional methods in the high SNR region. It has a performance approaching the MFB, known as the performance upper bound, within 2dB at the BER of $10^{-5}$. 본 논문에서는 고속 시변 채널 OFDM을 위한 저복잡도 양방향 탐색 순차적 간섭 제거(Successive Interference Cancellation: SIC) 방식을 제안한다. SIC에서는 오류 전파에 의한 성능 저하 가능성으로 인하여 심볼 블록 내에서의 심볼 검출 순서가 전체적인 성능에 큰 영향을 미친다. 본 논문에서는 조건 심볼오류확률(Conditional Symbol Error Probability: CSEP)을 기준으로 최초로 검출되는 심볼을 결정하고, 그 다음 검출될 심볼은 기검출된 심볼군의 경계에서 양방향으로 탐색하여 CSEP를 갱신한 후 결정하는 방식을 이용한다. 컴퓨터 모의실험 결과 제안된 방식은 기존 방식과 비교하여 높은 SNR 영역에서 거의 동일한 계산량으로 보다 우수한 성능을 나타낸다. 제안된 방식은 비트에러율 = $10^{-5}$에서 성능 상한치인 정합필터 한계(Matched Filter Bound: MFB)에 2dB 이내로 접근하는 성능을 가진다.

고속 시변 채널 OFDM을 위한 파일럿 심볼을 이용한 저복잡도 LS 채널 예측

임동민(Dongmin Lim) 大韓電子工學會 2011 전자공학회논문지TC (Telecommunications) Vol.48 No.11

본 논문에서는 고속 시변 채널 OFDM을 위한 파일럿 심볼을 이용하는 저복잡도 LS(Least Square) 채널 예측 방식을 제안한다. 제안된 방식은 기존의 BEM(Basis Expansion Model) 채널 모델 LS 예측 방식과 비교하여 동일한 성능에서 저장공간 및 계산량이 줄어드는 저복잡도 특성을 나타낸다. In this paper, we propose a pilot symbol assisted low complexity LS channel estimation method for OFDM in fast time varying channels. The proposed method shows low complexity characteristics in terms of memory space and processing time compared with conventional BEM channel model LS estimation methods.

고속 시변 채널 OFDM을 위한 안정화된 LS 신호검출

임동민(Dongmin Lim) 한국통신학회 2016 한국통신학회논문지 Vol.41 No.1

Advanced Technology of the Fourth Industrial Revolution and Korean Ancient History - Study on the use of artificial intelligence to decipher Wooden Tablets and the restoration of ancient historical remains using virtual reality and augmented reality -

Dongmin Lim(임동민) 고려대학교 한국사연구소 2019 International Journal of Korean History Vol.24 No.2

승용차 센터필러 조인트 부분의 구조강성재 적용에 따른 동특성 해석

임동민(Dongmin Lim),김찬묵(Chanmook Kim) 한국소음진동공학회 2009 한국소음진동공학회 학술대회논문집 Vol.2009 No.4

The Native Origins of the Paekche Refugee Ye (禰) Family and the Background of Their Activities in the Tang Dynasty

Dongmin Lim(임동민) 고려대학교 한국사연구소 2017 International Journal of Korean History Vol.22 No.2

고속 시변 채널 OFDM을 위한 저복잡도 양방향 탐색 순차적 간섭 제거

임동민(Dongmin Lim) 대한전자공학회 2013 전자공학회논문지 Vol.50 No.1

해방 이전 한국 고대 해양사 연구 동향

임동민 ( Dongmin Lim ) 해군사관학교 해양연구소 2019 해양역사문화 Vol.6 No.0

The research trend of Korean ancient maritime history before the liberation of Korea divided into the ‘historical geography’ at the late Choson dynasty and the ‘modern history’ at the Colonial period. Tonggukchir(東國地理誌) at the 17th century, one of the historical geography at the late Choson dynasty, cited several ancient records on maritime history. Yojigo(輿地考) at the 18th century, set up chapters such as ‘Sea Route’ to describe ancient routes. In the 19th century, (海東歴史) deduced ancient sea routes through various record in East Asia. These studies have made the foundation for the perception of maritime history at present, but it is aifncult to say modern history. The nationalism history at the Colonial period was initiated by Choi Namseon(崔南善), Shin Chaeho(申采浩), and embodied by Jung Inbo(鄭寅普). In the nationalism history, the sea was largely used as a symbol of the nation-states lost territory, but it did not fundamentally overcome colonialism. The colonialism history of Japan studied ancient Korean maritime history for the justification of colonial rule. Unlike studies in the 1910s and 1920s, Imanishi Ryu(今西龍) and others agreed with Korea’s role in the ancient maritime history of East Asia. However, they maintained the colonialism history in a large framework. After the liberation of Korea, Korean modern history has used nation(民族)’ for overcoming colonialism history. However, recent studies try to consider the concept of ‘modern’ in the nationalism and colonialism history. Therefore, we need to think beyond the ’modern’ and ‘nation(民族)’ concept in the maritime history.

의회제도 개헌론에 대한 헌법 원리적 검토: 국회 헌법 개정 자문위원회의 활동결과보고서를 중심으로

임동민 ( Dongmin Lim ) 연세대학교 법학연구원 공공거버넌스와 법센터 2015 연세 공공거버넌스와 법 Vol.6 No.2

Constitutional amendment can secure its legitimacy when contributing to the realization of constitutionalism and a variety of constitutional principles that constitute the constitutionalism pursued by the Republic of Korea. In particular, looking back on the past constitutional history of the Republic of Korea when the constitution was degraded to the means of ruling of imperial president or means of securing legitimacy of unjust regime, the key premises of constitutional amendment discussion should be the realization of the constitutional principles such as sovereignty of people, division of powers, legalism. This study, which was started from this critical mind, reviewed the parliamentary system constitutional amendment proposal of the report of National Assembly Constitutional Amendment Advisory Committee that will be a key criterion of constitutional amendment discussion that will be carried out in the future from the point of view of the constitutional principle and reached the following conclusions: First, the organization and construction plan of the National Assembly around the bicameral system will contribute to representative democracy in terms of reflecting the political opinions of local minorities easily likely to be degraded to permanent minorities in national decision-making through construction of regional representative councilors. Also, the bicameral system will contribute to division of powers in that the sole lead of the unicameral floor majority can be checked through another National Assembly and the power fusion phenomenon of the government and unicameral system can be checked by another National Assembly. In addition, the bicameral system will contribute to constitutionalism in terms of carefully deciding national ideas and encouraging laws to comply with constitutional ideology by preventing snatch legislation institutionally. But, electing more than 1/2 of members of the House of Representatives functioning as political members as proportional representatives leaves room for undermining representative democracy when considering the political reality of the Republic of Korea. Second, a plan of weakening the privilege of freedom from arrest stipulates ‘punishment of more than imprisonment over long-term 5 years’as the exceptional reason of privilege of freedom from arrest, containing a number of bribery charges, Public Official Election Act penalties in the special law. This undermines sovereignty of people and representative democracy in terms of making it difficult for members of the National Assembly working for the interests of the whole nation as representatives of the people to perform their duties. Also, it undermines the principle of division of powers in terms of not being able to protect members of the National Assembly from illegal·unjust power action of the government for the members of the National Assembly. In addition, this plan is contrary to the principle of excess prohibition because the means for achieving the goal for preventing the abuse of parliamentary privilege of freedom from arrest is excessively broad so there is no minimality of the infringement and the balance of the legal interest is lacking in that the loss of public interest is greater than profits gained through this. Third, a plan of weakening the privilege of exemption from liability stipulates ‘defamation, insulting remarks, comments violating the democratic basic order’as the exceptional reason of privilege of freedom from arrest. This undermines division of powers in terms of excessively weakening the government control function of the National Assembly. Also, it constricts freedom of political expression by making it difficult to raise critical doubts for candidates to run in an election for public office and this ultimately undermines sovereignty of people and representative democracy. In addition, given the precedent of the Constitutional Court, comments violating the democratic basic order set up North following as official remarks and limits of voting of a member of the National Assembly and this causes the limitation of freedom of political expression and damage of sovereignty of people and representative democracy. Fourth, a plan of abolishing and strengthening inspections of government offices undermines the public``s right to know, the condition of the realization of sovereignty of people due to the abolition of inspections of government offices. Also, given the political culture of the Republic of Korea, it is difficult to consider that inspections of government offices will act as an effective national control function and this weakening of the National Assembly’s government control function seems not appropriate for today’s division of powers requiring more powerful government control means due to the trends of administrative nation.

주파수 선택적 시변 채널 OFDM 시스템에서의 파일럿 심볼을 이용한 채널 예측 및 등화

임동민(Dongmin Lim) 한국전자파학회 2007 한국전자파학회논문지 Vol.18 No.12

본 논문에서는 주파수 선택적 시변 채널 OFDM 시스템에서 파일럿 심볼을 이용하는 채널 예측 및 등화 방식의 성능을 분석하고 문제점 및 개선 방안을 제시한다. 주파수 영역 채널 행렬의 대역폭을 제한하기 위하여 시간 영역 윈도우를 도입하며, 채널 예측에 LS(Least Square) 및 선형 MMSE(Minimum Mean Square Error) 예측 방식을 이용한다. 채널 등화에는 채널 예측에 이용되는 파일럿 심볼의 존재가 고려된 선형 MMSE 및 결정 귀환 등화방식을 이용한다. 계산량을 감소시키기 위하여 채널 등화 알고리즘에 요구되는 선형 연립 방정식의 풀이에 band LU 행렬 분해 알고리즘을 도입하며, 컴퓨터 시뮬레이션을 통하여 기존 방식과의 성능을 비교한다. 결정 귀환등화 방식에 시간 영역 윈도우를 적용하는 경우, 결정 귀환 관련 행렬의 대역폭이 제한되지 않아 성능이 저하되는 문제점을 분석하였다. In this paper, we analyze the performance of pilot symbol assisted channel estimation and equalization schemes for OFDM systems over frequency-selective time-varying channels and propose methods to improve the system performance. In the least square(LS) and linear minimum mean square error(MMSE) channel estimation, time domain windowing is introduced for banding the frequency domain channel matrix. The linear MMSE and decision feedback equalization schemes are employed with the pilot symbols for channel estimation taken into account in the equalization process. To reduce computational complexity, the band LU matrix factorization algorithm is introduced in solving the linear systems involved in the equalization, and the performances are compared with the known previous results by computer simulations. When time domain windowing is employed in the decision feedback equalization, the matrix related with the decision feedback process is shown to be unbanded and the resultant performance degradation is analyzed.