• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.335-338
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• 2002

For high data rate transmission over wireless fading channels, space-time trellis ceding techniques can be employed to increase the Information capacity of the communication system dramatically. In this paper, we consider the concatenated space time LDPC (Low Density Parity Check) codes. Extra ceding gains In addition to the diversity advantage is shown to be achieved for certain space-time trellis codes transmitted over quasi-static lading channels.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.558-560
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• 2000

The role of power line is not limited to providing electrical power. Power line fumed out to be an candidate to cope with the existing communication channels. It is need to be measured the properties of power line as communication channels, before successful communication system is possible. This paper presents the characteristics of power line noise and attenuation measurements in the frequency range of $0{\sim}10$ MHz, and then suggests applicable communication techniques in brief. Power line channel is configured in our laboratory and the length of it is 250 meters.

• 적정기술학회지
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• 제7권2호
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• pp.172-187
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• 2021

In remote villages without access to modern IT technology, simple devices such as smartcards can be used to carry out business transactions. These devices typically store multiple business applications from multiple vendors. Although devices must prevent malicious or accidental security breaches among the applications, a secure communication channel between two applications from different vendors is often required. In this paper, first, we propose a method of establishing secure communication channels between applications in embedded operating systems that run on multi-applet smart cards. Second, we enforce the high assurance using an intransitive noninterference security policy. Thirdly, we formalize the method through the Z language and create the formal specification of the proposed secure system. Finally, we verify its correctness using Rushby's unwinding theorem.

• 한국IT서비스학회지
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• 제9권2호
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• pp.163-177
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• 2010

In this paper, we consider a channel ordering problem that seeks to maximize the service quality in mobile radio communication systems. If a base station receives a connection request from a mobile user, one of the empty channels belonging to the base station is assigned to the mobile user. In case multiple empty channels are available, we can choose one that incurs least interference with other channels assigned to adjacent base stations. However, note that a pair of channels that are not separated enough generates interference only if both channels are assigned to mobile users. That is, interference between channels may vary depending on the channel assignment sequence for each base station and on the distribution of mobile users. To find a channel assignment sequence that seems to generate minimum interference, we develop an optimization model considering various scenarios of mobile user distribution. Simulation results show that channel assignment sequence determined by the scenario based optimization model significantly reduces the interference provided that scenarios and interference cost are properly generated.

• 한국인터넷방송통신학회논문지
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• 제16권4호
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• pp.7-14
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• 2016

본 연구는 인터넷 방송 중 게임을 전문적으로 하는 미국의 Twitch TV(트위치 TV)에서 나타나는 인기 채널을 분석한다. 현재 한국에서 인터넷 방송은 아프리카가 실질적 독점을 하고 있으나, Twitch TV는 전 세계적으로 인기가 높으며 현재 한국에서 영향력을 확대하기 위해 노력 중에 있다. 구체적으로 본 연구는 1월부터 6월까지 매주 금요일 9시에 Twitch TV에서 나타나는 국내(한국)와 해외의 인기 채널을 총 20회 조사한 뒤, 채널에서 나타나는 (1) 시청자(접속자) 수 (2) 게임의 출연수 (3) 게임의 장르 (4) 게임의 개발 국가의 차이점을 입체적으로 조사하였다. 인터넷 방송은 지상파 TV와 달리 시청률의 개념은 없지만, 채널에 연결 된 접속자 수를 기반으로 인기 채널이 구별 될 수 있다. 이를 통해, Twitch TV의 특징을 연구하고, 더 나아가 인터넷 방송의 미래에 대해서도 토론한다.

• 한국인터넷방송통신학회논문지
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• 제9권6호
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• pp.29-35
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• 2009

본 논문에서는 무선인지네트워크를 위한 효율적인 채널 선택 알고리즘을 제안하고 그 성능을 비교분석한다. 제안된 알고리즘에서는 다중의 가용한 채널들 중 최적 채널 선택을 위해 히스토리 윈도우 범위에서 각 채널의 기(primary) 사용자에 의한 채널 사용률 및 성능, 현 채널 품질 그리고 기 사용자의 통계적 트래픽 활동 특성을 고려한다. 시뮬레이션을 통해 무선인지(secondary)사용자들이 제안된 알고리즘을 통하여 다중의 채널들중 데이터 전송을 위한 최적의 채널을 선택할 수 있음을 보였다.

• ETRI Journal
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• 제38권3호
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• pp.435-443
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• 2016

In this paper, an efficient beam tracking algorithm for a regularized zero-forcing (RZF) approach in slowly fading multiple-input and single-output (MISO) broadcast channels is considered. By modifying an RZF equation, an RZF beam tracking algorithm is proposed using matrix perturbation theory. The proposed algorithm utilizes both beams from the previous time step and channel difference (between the previous and current time steps) to calculate the RZF beams. The tracking performance of the proposed algorithm is analyzed in terms of the mean square error (MSE) between a tracking approach and an exact recomputing approach, and in terms of the additional MSE caused by the beam tracking error at the receiver. Numerical results show that the proposed algorithm has almost the same performance as the exact recomputing approach in terms of the sum rate.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권3호
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• pp.1131-1143
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• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• 한국전자통신학회논문지
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• 제5권2호
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• pp.133-137
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• 2010

본 연구에서는 128채널 3차원 심장전기도 시스템의 영상화를 PC 기P반에서 구현하였다. 데이터를 받는 시간을 제외하더라도 실제적으로 구간을 설정하고 분석하는 시간은 1분도 걸리지 않아 짧은 시간 내에 분석해야 하는 심장 수술시 매우 유용함을 알 수 있었다. 특히 PC 기반으로 구현되었기 때문에 이동은 물론 데이터 보관이 용이하다. 또한 수술후에도 언제든지 데이터를 불러내어 분석 할 수 있으며 원하는 결과를 쉽게 확인할 수 있다.

• Journal of information and communication convergence engineering
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• 제5권3호
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• pp.273-280
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• 2007

The numerical methods for finding the optimal parameters in 640 Gbps (16 channels $\times$ 40 Gbps) WDM system with optical phase conjugator (OPC) are proposed, which effectively compensate the distorted overall WDM channels. The considered optimal parameters are the OPC position and the dispersion coefficient of fibers. The numerical approaches are accomplished through two different procedures. One of these procedures is that the optimal OPC position is previously searched and then the optimal dispersion coefficient is searched at the obtained optimal OPC position. The other is the reverse of the above procedure. From the numerical results, it is confirmed that two optimal parameters depend on each other, but less related with the searching procedure. The methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which is a serious problem of applying the OPC into multi-channels WDM system.