• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.692-710
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• 2013

Conventional interference alignment (IA) for a MIMO interference channel (IFC) requires global and perfect channel state information at transmitter (CSIT) to achieve the optimal degrees of freedom (DoF), which prohibits practical implementation. In order to alleviate the global CSIT requirement caused by the coupled relation among all of IA equations, we propose an IA scheme with a single feedback link of each receiver in a limited feedback environment for a three-user MIMO IFC. The main feature of the proposed scheme is that one of users takes out a fraction of its maximum number of data streams to decouple IA equations for three-user MIMO IFC, which results in a single link feedback structure at each receiver. While for the conventional IA each receiver has to feed back to all transmitters for transmitting the maximum number of data streams. With the assumption of a random codebook, we analyze the upper bound of the average throughput loss caused by quantized channel knowledge as a function of feedback bits. Analytic results show that the proposed scheme outperforms the conventional IA scheme in term of the feedback overhead and the sum rate as well.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.59-64
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• 2003

The parameter modification of the initial FEM model to match it with the experimental results needs the modal information and the modal sensitivity matrix to the parameter change. There are two cases this methodology is ill-equip to deal with; the deficiency of the necessary modal information and the ill-conditioning of the sensitivity matrix. In this research, a novel concept of the feedback exciter that uses the summation of the white noise and the signals from the measurement sensors multiplied with feedback gains as the reference signal is proposed. There are 2 advantages using this external feedback excitation. First, we can use the change of the system response such as modal data by the active energy Path from the sensor to the exciter. This change of the system response can be additional clues to the system dynamics that we want to know. Secondly, the external energy Path alternates the offset of the Parameter change to the system response. That means the modal sensitivity of the parameters becomes different from the original sensitivities by the feedback excitation. Through the feedback loop, we can change the similar modal sensitivities of some updating parameters and consequently discriminate the parameters using the closed-loop modal data. To demonstrate the discrimination performance, the parameter estimation of an indeterminate structure by use of the feedback method is introduced.

• 방송공학회논문지
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• 제10권4호통권29호
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• pp.540-547
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• 2005

ATSC DTV 수신기의 결정 궤환 등화기는 양자화기나 지연시간이 없는 트렐리스 복호기에서 에러가 발생하면, 발생된 에러는 후방 필터의 입력으로 사용되어 에러 전파 현상을 야기한다. 에러 전파 현상은 잔류 에러의 증가와 수렴 속도 저하라는 등화기의 성능 열화를 가져온다. 따라서 본 논문에서는 에러 전파 현상을 해결하기 위하여 이중 후방 필터 구조의 결정 궤환 등화기를 제안한다. 제안된 등화기의 후방 필터는 지연 시간이 없는 트렐리스 복호기의 출력을 입력으로 사용하는 결정 후방 필터와 등화기의 출력을 입력으로 사용하는 비결정 후방 필터로 구성되어 있다. 부가적으로 사용된 비결정 후방 필터는 에러 전파 현상이 발생하지 않고, 또한 결정 후방 필터에서 발생되는 에러 전파 현상을 보상한다. 따라서 제안된 등화기는 기존의 등화기에 비해서 수렴 속도는 빨라지고 잔류에러는 감소한다. 전산 모의 실험을 통하여 제안된 이중 후방필터 구조의 등화기의 성능 향상을 분석하였다.

• 한국정보전자통신기술학회논문지
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• 제13권1호
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• pp.42-47
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• 2020

OFDM 기반 초고속 통신시스템을 위한 IFFT/FFT 프로세서는 저면적 저전력이면서 데이터 처리량이 높고 프로세싱 지연이 적어야 한다. 따라서, 파이프라인과 병렬처리를 적용한 radix-2k 알고리즘 기반 MDF(multipath delay feedback) 구조가 적합하다. 기존의 MDF 구조에서 입력신호의 워드길이에 비례하여 커지는 피드백 메모리는 면적과 전력소모가 크다. 본 논문에서는 OFDM 응용을 위한 radix-22 MDF IFFT 프로세서의 피드백 메모리 크기 감소 방법을 제안한다. MDF 구조에서 첫 두 스테이지의 피드백 메모리의 크기는 전체 피드백 메모리의 75%를 차지하므로 첫 두 스테이지의 피드백 메모리 크기 감소에 초점을 맞춘다. OFDM 전송에서 IFFT 입력신호는 변조데이터와 파일럿과 널 신호로 구성된다는 특징을 이용하여 변조데이터와 파일럿/널 신호를 각각 부호있는 정수로 매핑하여 입력신호의 워드길이를 감소시키는 방법을 제안한다. 시뮬레이션을 통해 제안한 방법이 기존 방법보다 피드백 메모리의 크기를 약 39%까지 감소시킬 수 있음을 보인다.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.179-185
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• 2010

본 논문에서는 특징 되먹임 알고리즘의 성능을 평가하기위해 특징되먹임 알고리즘의 성능에 가장 큰 영향을 주는 특징마스크를 검증한다. 특징 되먹임 기반 패턴 인식 방법은 PCALDA로 추출된 특징을 원 영역으로 역사상하여 인식에 중요한 부분을 추출하는 기법이다. 추출된 특징은 특징마스크의 형태로 원 영역으로 역사상 되므로, 특징마스크의 특징성능 검증에 대한 연구가 필수적이다. 본 논문에서는 Yale data 기반의 얼굴 인식에서 특징마스크를 검출하여 특징마스크에 따른 인식률 변화를 고찰하고 검출된 특징마스크의 성능을 검증한다.

• 전자공학회논문지S
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• 제35S권3호
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• pp.29-38
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• 1998

This ppaer suggests a congestion control scheme for CL(ConnectionLess) overlay network using the feedback loops getween CL werver, between CL servers, and the header translation table of CL server. The CL overlay network for CBDS(Connectionless Broadband Data Service) defined by ITU0T(International Telecommunication Union-Telecommunication) consists of CL servers which route frames and links which connect between CL user and CL server or between CL servers. In this CL overlay network, two kinds of congestions, link congestion and CL server congestion, may occur. We suggest a scheme that can solve the congestion using ABR(Available Bit Rate) feedback control loop, the traffic control mechanism. This scheme is the link-by-link method suing the ABR feedback control loops between CL user and CL server or between CL servers, and the header translation table of CL server. As CL servers are always endpoints of ABR connections, the congestion staturs of the CL server can be informed to the traffic sources using RM(Resource Management) cell of the ABR feedback loops. Also CL server knows the trafffic sources making congestion by inspecting the source address field of CLNAP-PDUs(ConnectionLess Network Access Protocol - Protocol Data Units). Therefore this scheme can be implemeted easily using only both ABR feedback control loop of ATM layer and the congestion state table using the header translation table of CL server because it does not require separate feedback links for congestion control of CL servers.

• International Journal of Control, Automation, and Systems
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• 제3권1호
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• pp.56-69
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• 2005

In this paper, it is clearly shown that the two well-known necessary and sufficient conditions mp n as generic static output feedback pole-assignment and mp + d(m+p) n+d as generic minimum d-th order dynamic output feedback pole-assignment on complex field, unbelievably, do not match up each other in strictly proper linear systems. For the analysis, a diagram analysis is newly created (which is defined by the analysis of 'convoluted rectangular/dot diagrams' constructed via node-branch conversion of the signal flow graphs of output feedback gain loops). Under this diagram analysis, it is proved that the minimum d-th order dynamic output feedback compensator for pole-assignment in m-input, p-output, n-th order systems is quantitatively decomposed into static output feedback compensator and its associated d number of arbitrary 1st order dynamic elements in augmented (m+d)-input, (p+d)-output, (n+d)-th order systems. Total configuration of the mismatched data is presented in a Table.

• 한국어교육
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• 제28권1호
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• pp.141-171
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• 2017

This study investigates Korean language teachers' perception/beliefs and practices in written feedback. Two types of data were collected: (1) teachers' feedback on three compositions by elementary-level learners, and (2) a survey questionnaire. The result showed that teachers perceived written feedback to be important even though they had not enough opportunities to receive appropriate training. Lack of training brought about limited feedback in terms of both quantity and quality, and inconsistency between their beliefs and practice. This study closes with the needs for teacher training and further studies on teachers' feedback practices.

• 한국정보시스템학회지:정보시스템연구
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• 제23권2호
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• pp.91-107
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• 2014

In computer-mediated idea generation where contributions can be anonymous, the ability to accurately monitor performances is limited, inducing social loafing. Prior research has suggested that social loafing is likely an important factor in reducing task performance. Researchers have theorized that loafing could be minimized if clear performance feedback is provided. Our prior study evidences a substantial performance gain by the provision of real time performance information about who is contributing and who is not. However, our prior study incorporated the quantity feedback only to create a larger pool of ideas based on the long-standing assumption (i.e., quantity breeds quality), not considering the quality feedback. As a result, taking advantage of anonymity in the form of pseudonymity, individuals in almost all groups exhibited a tendency of self-presentation by capitalizing on ideas of which quality was low and even frivolous (i.e., junk comments) toward the later stages of the session. Thus, we have learned that the quantity performance feedback alone does not have enough restrictiveness to consistently control the performance behavior throughout the session. Since a process chart allows participants to monitor process variation by comparing new performance data to past performance data, we incorporated real-time visual process performance feedback to reveal performance histories by connecting the sequence of idea quality scores in a time-series format. Using this environment, a laboratory experiment was conducted with five-member groups that examined the influence of both identifiability (i.e., anonymity versus pseudonymity) and process performance feedback (i.e., yes or no) in a $2{\times}2$ factorial design. The result showed that groups in the process performance feedback treatment outperformed groups in the no feedback treatment. Additionally, process performance feedback and identifiability interacted such that groups in the process performance feedback/pseudonymity treatment had the highest performance. The implications of these findings for future research, as well as the implications for the design of group idea generation procedures are discussed.

• 영어어문교육
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• 제16권1호
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• pp.19-40
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• 2009

Teacher written feedback on student compositions has received tremendous attention in second language (L2) writing research. Notwithstanding the importance of understanding both teachers' and students' perspectives on the feedback process, much of the feedback research has only looked into one-side of the story - adopting either the teacher's or the student's perspective. The current study is an attempt to look into both sides of the story by examining the types of written feedback that students prefer, the extent to which students' preferences and teachers' actual feedback practice overlap, and the extent to which student perceptions of teacher feedback coordinate teacher self-reflections on their feedback practice. Three English composition classes (3 teachers and 46 students) at a university participated in this study. It analyzed student and teacher data from questionnaires and teacher written feedback on student compositions. The results showed that students' preference for feedback on global and local issues varied across the three composition classes. This is partly a consequence of how students perceived the type of feedback that their teachers practiced. Teacher self-reflection on and student perception of teacher written-feedback generally coordinated. These findings are discussed in light of how contextual factors affect learner perception of teacher written feedback and underscore the need for examining students' reactions to feedback and teacher self-reflection.