• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1566-1573
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• 2021

Rendezvous is a process that assists nodes in a Cognitive Radio Networks (CRNs) to discover each other. In CRNs where a common control channel is unknown and a number of channels are given, it is important how two nodes find each other in a known search region. In this paper, I have proposed and analyzed a channel hopping sequence using Sidel'nikov sequence by which each node visits an available number of channels. I analyze the expected time to-rendezvous (TTR) mathematically. I also verify the Rendezvous performance of proposed sequence in the view of TTR under 2 user environment compared with JS algorithm and GOS algorithm. The Rendezvous performance of proposed sequence is much better than GOS algorithm and similar with JS algorithm. But when M is much smaller than p, the performance of proposed sequence is better than JS algorithm.

• Journal of Korea Multimedia Society
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• v.13 no.9
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• pp.1357-1364
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• 2010

With the emergence of digital TV broadcasting, various TV channels are provided to a TV audience. But it is getting hard for the audience to find his or her preferred TV programs due to the huge number of TV channels. In order to mitigate the difficulty, channel navigation schemes have been proposed. The schemes predict preferred TV channel from viewer's previous watching histories, and provide the predicted channels when the viewer wants to change TV channel. As channel navigation schemes, there are Most Recently Selected (MRS) scheme providing the most recently watched channel, and Most Frequently Selected (MFS) scheme providing the most frequently selected channel. However, MFS and MRS scheme could be inappropriate to current TV system broadcasting various TV programs in a channel because they are based on the viewer's patterns of watching TV channels. Therefore, this paper proposes an efficient channel navigation scheme, Program Most Frequently Selected (PMFS), based on patterns of watching TV programs instead of TV channels. Simulation results show that the proposed scheme PMFS reduces the seek distance compared to the previous channel navigation schemes, MFS and MRS.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.299-302
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• 2011

분산비디오압축(DVC, Distributed Video Coding) 기술은 부호화기의 복잡한 과정을 복호화기로 이동시킴으로써 경량화 비디오 부호화를 위한 새로운 방법으로 주목 받고 있다. 하지만 복호화기에서 채널 복호 과정과 움직임 추정/보상 과정이 수행됨으로써 복호화기의 복잡도가 상당히 증가하게 되며, 이에 복호화기 채널 복호 과정을 고속화하기 위한 방법이 지속적으로 제안되고 있다. 그러나 채널 복호 과정이 고속화될수록 움직임 추정/보상에 소요되는 계산량이 상대적으로 증가하게 되어, 이에 대한 연구가 필요하다. 따라서 본 논문에서는 상대적으로 증가하는 움직임 추정/보상 과정에 적응적 탐색 영역 방법을 적용하여 DVC 복호화기를 고속화하는 알고리즘을 제안한다. 제안 방법은 고정된 탐색 영역을 사용한 보조 정보 생성 방법과 비교하여 평균 76%의 시간절감이 가능하며, 성능저하는 BDBR이 약 0.31% 증가하는 정도로 크지 않다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1891-1897
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• 2009

This paper describes the optimization of the spectrum sensing in terms of the throughput of the cognitive radio (CR)system. The conventional rapers do not describe the optimization problem of the spectrum sensing by considering the channel search and channel move of the CR system to be caused by the appearance of the incumbent user. However this paper evaluates the throughput of the CR user by considering the situations such as the channel search and channel move additionally. Also, this paper suggests the sensing structure being separated the data receiver from sensing receiver, and compares the sensing performance for the same receiver structure of sensing and communication with that for the separated sensing receiver in terms of the throughput of the CR user. The numerical result demonstrates that the performance of the throughput efficiency is improved by the proposed sensing receiver to be separated from the data communication path.

• Journal of Digital Convergence
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• v.18 no.6
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• pp.255-269
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• 2020

This paper aims to analyze the factors influencing consumer's choice of smartphone purchase channel in multichannel environments. Recently, smartphone purchase channels are becoming more complex and diverse. A smartphone with a short purchase cycle is a product applying advanced technology, the research of this topic would be significant. The major findings of this study are as follows. First, depending on the consumer's shopping orientation, the consumer group was classified into three groups of preference 1. Active shopping, 2. Convenient shopping, and 3. Rational shopping. Second, it was analyzed that the consumer's shopping orientation influenced the decisions of the information search channel and the purchase channel. Third, there was a significant difference between the search and purchase channels in the three groups. Finally, in the channel experience, there was a significant difference in price satisfaction by group. The results of these studies are expected to provide practical implications for establishing a customized multi-channel strategy. This study provides a desirable model for research on smartphone purchase channels.

• Journal of the Korea Computer Graphics Society
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• v.14 no.3
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• pp.11-17
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• 2008

Many methods which represent complex surfaces using height map without a number of vertex have been researched. However, a single layer height map cannot present more complex objects because it has only one height value on each position. In this paper, we introduce the new approach to render more complex objects, which are not generated by single layer height map, using multi layer height map. We store height values of the scene to each texture channel by the ascending order. A pair of ordered height values composes a geometry block and we use this property. For accurate ray search, we store the highest value in odd channels and the lowest value in even channels to generate quad tree height map. Our ray search algorithm shows accurate intersections between viewing ray and height values using quad tree height map. We solve aliasing problems on grazing angles occurred in previous methods and render the result scene on real-time.

• Proceedings of the Korean Society for Information Management Conference
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• 2006.08a
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• pp.17-22
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• 2006

본 연구에서는 질문지법을 이용하여 과학기술분야 연구자들의 정보요구를 파악하고 이를 바탕으로 정보요구별 탐색행태를 분석하였다. 분석결과, 특정 정보요구에 대해 비공식 커뮤니케이션 채널이 정보탐색에 중요한 영향을 미치는 것으로 나타났으며, 탐색과정에서 이용자가 느끼는 정보부족의 원인에 대해서는 정보요구별로 어느 정도 차이가 있는 것이 확인되었다. 반면, 정보탐색환경에서 연구자들이 중요하게 생각하는 요소는 정보요구별로 큰 차이가 없는 것으로 나타났다. 정보요구를 바탕으로 과학기술분야 연구자의 탐색행태 분석결과를 적용함으로써 이용자 특성에 따라 개별화된 과학기술 정보 서비스를 기대할 수 있다.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.50-54
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• 2010

A Container Security Device (CSD) which is different existing RFID Tag strengthens the physical security as mounted inside the container and the information security as encrypts doubly a data. CSD must use the resources efficiently in order to operate with the battery. Therefore, it needs low-power mechanism which repeats the sleep period and channel scan period. However, by adjusting these periods, the trade-off occurs between energy efficiency and network connectivity. In this paper, we implement low-power CSD and resolve this problem by adjusting beacon period and channel scan time. As a result, We guarantee the network connectivity 95% or more and maximum life up to 16 days using common AA batteries.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8B
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• pp.809-818
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• 2002

In this paper, we propose a fast cell search algorithm keeping compatible with the standard cell search algorithm of the WCDMA system. The proposed algorithm can acquire the synchronization of slot and frame times, and the code group identification using only one synchronization channel while the standard algorithm employs two synchronization channels called P-SCH and S-SCH. The proposed synchronization channel structure is the same as the P-SCH structure of the WCDMA system. However, the P-SCH is modulated with a specific polarization code, which is one element of new code group codes. The proposed algorithm can reduce both the BS' transmission power and the complexity of receiver as compared with the conventional one since only on synchronization channel is used. It is shown through the computer simulation that the proposed algorithm yields a significant improvement in terms of cell search time compared with the standard especially in low SNR environments.

• The Transactions of the Korea Information Processing Society
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• v.5 no.1
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• pp.215-222
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• 1998

프랙탈을 기반으로 한 칼라 영상 부호화는 영상을 RGB,YIQ나 CMYK와 같은 기본적인 채널로 분리한 후, 각각의 채널을 독립적으로 프랙탈 이진 영상 부호화 기법에 적용함으로써 쉽게 부호화할 수 있다. 그러나 이 방법은 각각의 채널에 대해 부호화를 반복해야 하기 때문에 많은 계산 시간이 필요하다는 단점이 있다. 본 논문에서는 이러한 단점을 개선하기 위하여 국부적 지역 탐색법을 사용하였으며, 압축률 향상을 위해 각 채널마다 사람의 눈에 느껴지는 민감성의 정도가 다른 YIQ 모델을 사용하여 I나 Q 채널보다 Y채널에 더 많은 비트를 할당하였다. 각각의 치역 블록에 대하여 Y채널에 가장 잘 매칭이 되는 정의역 블록을 찾았으며, I와 Q 채널을 위해서는 잘 매칭이 되는 대응 블록을 이용하였다. 따라서 각각의 YIQ채널을 위한 최적의 변환식을 계산하는 과정에서 단지 하나의 기하학적인 변환식(변환과 선택된 정의역 블록의 주소)만이 필요할 뿐이다. 이러한 접근 방법은 기존의 부호화 방법들과 비교해 볼 때 부호화 시간의 단축과 압축률 향상을 동시에 얻을 수 있다.