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수중음향통신 시스템의 비트 오류 성능 향상을 위한 등화 모드 선택 방법
김현수,서종필,김재영,김성일,정재학,Kim, Hyeon-Su,Seo, Jong-Pil,Kim, Jae-Young,Kim, Seong-Il,Chung, Jae-Hak 한국음향학회 2012 韓國音響學會誌 Vol.31 No.1
수중음향채널에서 시변 다중경로 전달특성에 의해 발생하는 시변 인접심볼간 간섭을 완화할 수 있는 방법으로 선형 등화와 결정궤환 등화 기법을 사용할 수 있다. 그러나 선형 등화 기법은 간섭성분을 완벽하게 제거하지 못하는 단점이 있고, 결정궤환 등화기는 검출 오류 발생 시 오류 전파가 발생하는 문제를 가지고 있다. 본 논문에서는 이러한 문제점을 개선하기 위해 훈련 시퀀스를 이용하여 등화 모드를 선택하는 기법을 제안한다. 제안된 기법은 훈련시퀀스로부터 산출된 신호 대 잡음비에 따라 등화기법을 선택하여 동작시키는 방법으로 낮은 SNR일 때에는 선형 등화 기법이 적용하여 오류전파를 줄이고, 높은 SNR일 때에는 결정궤환 등화 기법을 적용하여 간섭성분을 제거함으로써 하나의 등화기법을 사용하는 경우보다 오류 성능을 향상시킬 수 있다. 해상실험을 통해 얻은 채널 응답을 이용하여 전산모의실험을 수행한 결과 제안된 기법이 효과적으로 오류 성능이 개선됨을 보였다. The linear and decision-feedback equalization can mitigate time-varying intersymbol interference (ISI) caused by time-varying multipath propagation for underwater acoustic channels. The perfect elimination of interference components, however, is difficult using the linear equalization and the decision feedback equalizer has an error propagation problem. To overcome these shortcomings, this paper proposes an equalizer mode selection method using training sequences. The proposed method selects an equalization mode corresponding to the signal-to-noise ratio (SNR). If the SNR is low, the proposed system operates the linear equalizer for preventing the error propagation and if the SNR is high, the decision feedback equalizer for eliminating the residual ISI. Therefore, the proposed method can improve the error performance compared to the conventional equalizers. The computer simulation shows the proposed method improves the bit error performance using practical underwater channels responses acquired from the sea experiment.
김현수(Kim Hyeon-su) 한국시학회 2011 한국시학연구 Vol.- No.31
Yun, Dong-ju’s 「The First Poem」 is producing a variety of meanings by omitting its meanings and expressing it indirectly. This paper is to understand the meaning of the work, not the intention of the poet, based on the fact that literature is content to exist by itself. The meaning of a work is the real meaning which the work represents through linguistic combination and structure. This poem is divided into two stanzas. The first stanza of 1~8 lines is expressing the poet’s feelings, and the second stanza of 9 lines shows the imaginary scenes of nature. The first stanza is divided into 1~4 lines containing mental distress and 5~8 lines representing love and practice will. The scenes of the second stanza are symbolically representing the heart of the poet who has overcome conflicts and troubles. 「The First Poem」 is a work which has encapsulated the pure heart seeking beautiful and peaceful world with concise and implicative words. In terms of space, this poem is divided into Heaven and Earth, and in terms of conflicts, it shows the process of division and combination of the realistic ego which is tormented in the real world and the essential ego which wishes for the beautiful and peaceful heavenly world. Though the realistic ego is ambivalent and worried about the gap between reality and ideals, it recovers its essential ego through aiming for the heavenly world and pursues the peaceful and pure world which it always longs for inwardly.