• Information and Communications Magazine
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• v.13 no.11
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• pp.192-210
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• 1996

본 고에서는 일반 가정 및 소규모 업무용 가입자들을 대상으로 광대역 멀티미디어 서비스를 경제적으로 제공할 수 있는 ATM 기반의 디지털 Hybrid Fiber-Coax 망에 대한 표준화 동향을 분석하고, 양방향 통신 서비스를 수용하기 위한 기술적 사항에 대해 고찰한 내용을 기술한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.5
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• pp.1129-1140
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• 2017

Unidirectional data transmission system, which allows physical one way transmission, removes the backward link physically to prevent the intrusion from the outside through the network. However, the system is difficult to apply to the environment requiring either backward transmissions or bi-directional communications. In this paper, we proposed Limited Two-way communications system, called as LimTway, which only allows outbound TCP two-way communications. LimTway uses two one-way links(forward, backward). While the forward one-way link is staying to be activated so that an allowed outbound UDP traffic could be transmitted one-way always, the backward one-way link is activated while allowed outbound TCP sessions are established. In order to prevent the intrusion from the outside during the period, the software of LimTway is designed to allow only the transmissions of both outbound TCP two-way communication traffics and outbound UDP traffics.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.941-943
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• 2013

A standardized communication protocol is required to exchange the data of electric charge and current-using electric power through the two-way communications between the smart meter and electric power supplier. In this paper, a two-way communications technologies is designed for control technologies and de/registration services of electric equipment, and the international communication protocols is applied to the communications technologies.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.506-513
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• 2009

In this paper, we propose a bi-directional communication method applying time reversal technique in underwater acoustic channel in order to exchange data between sensor nodes with an available relay node. The proposed method reduces the conventional 4-step relaying procedure to 2-step and improves the system capacity. Moreover, it increases transmission range efficiently while the relay node can be implemented with low complexity. Simulation results demonstrate that the proposed scheme achieves 3.2 bps/Hz higher capacity than that of the conventional method at SNR 20 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.815-822
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• 2010

Two-way relaying scheme based on relay selection can not only achieve higher rate but also get the selection diversity gain according to the number of relays. However the scheme can not achieve combining gain because it does not consider the direct link between users. In this paper, we propose, with multiple relays, opportunistic cooperative two-way relaying scheme and incremental cooperative two-way relaying scheme which can achieve both selection diversity gain and combining gain. Simulation results show that proposed scheme outperform the conventional scheme by achieving both combining gain and selection diversity gain according to the number of relays.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.65-72
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• 2016

In this paper, we developed a bidirectional LDC(Low DC-DC converter) for vehicle which is composed of a full bridge converter and a current doubler at the second side. The LDC is a converter that converts DC input from one side to DC output on the other side, and the converter which was developed in this thesis is capable of transferring power in both directions. It has been verified that the developed LDC has 90% efficiency at 1400W and approximately 85% efficiency at 2KW.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.25-28
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• 2003

본 논문은 Ka 밴드(26.5GHz-40GHz)를 사용한 양방향 멀티미디어 시스템의 설계에 대해서 다루고 있다. 우선 무궁화 3호 위성을 이용한 시범사업의 구성 및 운영과정에 대해서 개괄하고, 시범운영에서 발견된 문제점을 소개한다. Ka 밴드 양방향 위성 시스템은 MF-TDMA(Multi-Frequency Time Division Multiple Access) 방식을 사용하여 최대 전송속도 2Mbps 이상이고, QOS(Quality of Service) 제공 등 다양한 기능을 갖추고 있으나 Ka 주파수 특성상 그 안정성에 있어서 어려움을 갖고 있다. 강우감쇄 및 전송 지연 등의 현상들을 소개하고 향후 위성 양방향 시스템의 구성과 응용 서비스를 구현할 때 고려해야 할 사항들에 대해 고찰해 보고, 해결방안을 제시하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.163-168
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• 2010

In this paper, we propose novel two-way relaying scheme in which number of two users transmit the signal to number of two destination. The scheme is difference with conventional multi-hop two-way relay scheme in which number of two users exchange the each signal. In the conventional scheme, each user have to perform back-propagating self-interference method to remove the own signal from received signal. It occurred to increase the complexity for signal processing at the user. To overcome the problem, we apply the Pre-cancellation which can reduce the process of back-propagating self-interference to our proposal network Simulation result show that proposal scheme outperform the convention multi-hop two-way relay scheme. Also we analysis the trad-off between performance and complexity accordance with using Pre-cancellation method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.31-37
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• 2009

In the two-way relay channel, the relay employ Amplify-and-Forward (AF) or Decode-and-Forward (DF) protocol, and broadcast the network-coded signal to both user. In the system, DF protocol provides maximum throughput at low signal to noise ratio(SNR). On the other hand, at high SNR, AF protocol provides maximum throughput. The paper propose active transmission scheme which employ Amplify-and-Forward or Decode-and-Forward protocol based on received SNR at the relay over Two-way relay channel. The optimal threshold is investigated numerically for switching the protocol. Through numerical results, we confirm that the proposed scheme outperforms conventional schemes over two-way relay channel.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.31-34
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• 2008

양방향 중계 채널(two-way relay channel)은 2명의 사용자가 중계기(relay)의 도움을 받아 서로 정보를 주고받는 통신 채널이다. 중계기에서는 각각의 사용자로부터 독립적으로 수신한 두 데이터 패킷에 네트워크 코딩 기법을 적용하고, 이를 통해 만든 패킷을 두 사용자에게 동시에 전송한다. 따라서 양방향 중계 채널에서는 기존의 협력 통신에 비해 보다 효율적인 자원의 사용이 가능하다. 한편, 다중 중계기 환경에서의 중계기 선택 기반 전송 방식은 시스템의 전력 제한(power constraint), 전송 패킷의 동기화(synchronization) 문제 등을 고려할 때 다중 중계기 기반 전송 방식보다 우수한 성능을 얻을 수 있다. 본 논문에서는 양방향 다중 중계기 채널에서 중계기 선택 기법을 제안한다. 양방향 중계 채널에서는 수신한 두 신호의 결합을 위해 중계기에서 네트워크 코딩 기법을 적용함으로써 중계기의 부담이 보다 증가하는 특징이 있다. 또한, 중계기는 신호 전송 시 두 사용자 모두에게 전송하게 되고 이로 인해 두 수신지와의 채널 조건을 모두 고려하여야 한다. 따라서 중계기 선택은 데이터 패킷의 전송이 시작되기 전에 분산된 방식(distributed method)으로 이루어지며, 각각의 사용자와 중계기 간 일시적(instantaneous) 채널 이득을 바탕으로 사용자-사용자 간(end-to-end) 경로 조건의 최대값을 계산하는 메트릭(metric)을 중계기 선택 기준으로 사용한다. 모의실험을 통해 제안된 중계기 선택 기법이 중계기의 개수에 해당하는 다이버시티 이득을 얻을수 있음을 보여준다.