• Journal of Communications and Networks
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• 제12권4호
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• pp.366-374
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• 2010

Coded cooperation is a promising user cooperation scheme. In this paper, we first propose a novel network-coding-based coded cooperation scheme. When a user decodes its partner's information correctly in the first frame, it transmits the combination of the partner's parity bits and its own parity bits through network coding in the second frame. This is distinct from the classical scheme, where the user only transmits the partner's parity bits during cooperation. We analyze the outage probability of the proposed scheme, and show that it achieves a full diversity order. Numerical evaluations reveal that the proposed scheme outperforms the classical scheme when the inter-user channel is poor, yet is worse when the inter-user channel is strong. Also, the results show that the proposed scheme always outperforms that of no cooperation in various channel conditions while the performance of classical scheme is worse than that of no cooperation with the poor inter-user channels. This means that the performance of the proposed scheme is more stable than the classical scheme and the proposed scheme is more tolerant to the poor inter-user channels. To combine the advantages of the proposed scheme and the classical scheme under different inter-user channel conditions, we propose an adaptive solution. This adaptive scheme enhances the system performance considerably in all channel conditions in spite of the inter-user channel quality, at the expense of only one acknowledgement or non-acknowledgement bit.

• 한국인터넷방송통신학회논문지
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• 제15권5호
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• pp.91-103
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• 2015

본 논문은 제주 정낭 채널 code I, II에 이은 "수신기 협력을 이용한 간섭 디코딩 기반 3-user NOR 스위칭 채널"을 다루고 있다. 제주 정낭 코드 (Jeju Jong Nang code) 는 스위칭 회로를 "1" 또는 "0" 의 이진 심볼로 해석하는 인류 최초의 HBCC (human binary coded communication)로 여겨진다. 본 논문에서는 3-user 정낭 NOR 스위칭 채널 기반 수신기 협력 간섭 디코딩의 실제적인 예를 소개한다. 제안한 시스템 모델은 TUJN (three user Jong Nang) NOR 스위칭 on-off 로직과 3-user 결정적 (deterministic) NOR 스위칭 채널 및 수신기 협력 GIC (Gaussian interference channel)로 구성되어 있다. 따라서 이 모델은 Shannon의 이진 시스템과 erasure 채널 용량에도 잘 맞는다. 또한 자유도를 증가시키기 위해 각 협력 수신기가 이웃 수신기들을 도울 수 있다는 의미의 결정적 채널을 얻기 위한 3-user Gaussian 간섭 디코딩의 응용 예를 제시하고, 이웃 수신기 협력을 통한 최적 간섭 완화 sum rate이 7 bits에 달한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1279-1300
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• 2017

In the interweave cognitive networks, the interference from the primary user degrades the performance of the cognitive user transmissions. In this paper, we propose an adaptive cooperation scheme in the interweave cognitive networks to improve the performance of the cognitive user transmissions. In the proposed scheme for the bidirectional communication of two end-source cognitive users, the bidirectional communication is completed through the non-relay direct transmission, the one-way relaying cooperation transmission, and the two-way relaying cooperation transmission depending on the limited feedback from the end-sources. For the performance analysis of the proposed scheme, we derive the outage probability and the finite-SNR diversity multiplexing tradeoff (f-DMT) in a closed form, considering the imperfect spectrum sensing, the interference from the primary user, and the power allocation between the relay and the end-sources. The results show that compared with the direct transmissions (DT), the pure one-way relaying transmissions (POWRT), and the pure two-way relaying transmissions (PTWRT), the proposed scheme has better outage performance. In terms of the f-DMT, the proposed scheme outperforms the full cooperation transmissions of the POWRT and PTWRT.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3037-3054
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• 2013

Interference between primary user (PU) and secondary user (SU) transceivers should be mitigated in order to implement underlay spectrum sharing in cognitive radio networks (CRN). Considering this scenario, an improved joint subcarrier and bit allocation scheme for cognitive user with primary users' cooperation (PU Coop) in CRN is proposed. In this scheme, the optimization problem is formulated to minimize the average interference power level at the PU receiver via PU Coop, which guarantees a higher primary signal to interference plus noise ratio (SINR) while maintaining the secondary user total rate constraint. The joint optimal scheme is separated into subcarrier allocation and bit assignment in each subcarrier via arith-metric geo-metric (AM-GM) inequality with asymptotical optimization solution. Moreover, the joint subcarrier and bit optimization scheme, which is evaluated by the available SU subcarriers and the allocated bits, is analyzed in the proposed PU Coop model. The performance of cognitive spectral efficiency and the average interference power level are investigated. Numerical analysis indicates that the SU's spectral efficiency increases significantly compared with the PU non-cooperation scenario. Moreover, the interference power level decreases dramatically for the proposed scheme compared with the traditional Hughes-Hartogs bit allocation scheme.

• 한국통신학회논문지
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• 제35권3A호
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• pp.245-253
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• 2010

본 논문에서는 협력통신을 위한 coded cooperation 시스템의 성능 분석을 기술한다. Coded cooperation은 user cooperation과 채널 부호의 결합된 프로토콜로서 기존의 coded cooperation의 연구는 주로 이동통신 환경을 고려한 Rayleigh fading 채널에서 이루어 졌다. 최근에 초고속 근거리 무선전송을 위한 60GHz 대역의 반송파를 이용한 연구가 활발해 지면서 Rician fading 채널 기반의 협력통신 분석에 대한 필요성이 제기되었다. 본 논문에서는 coded cooperation 시스템의 outage probability 성능과 bit error probability의 성능을 Rician fading 채널에서 분석하고 Rayleigh fading 채널에서와 같이 다이버시티 오더 값이 2로 유지됨을 보인다.

• 정보처리학회논문지C
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• 제13C권3호
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• pp.317-322
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• 2006

본 논문에서는 LEACH (Low-Energy Adaptive Hierarchy)를 사용한 무선센서네트워크에서 순환 부호를 사용하여 효율적인 사용자 협력 프로토콜을 제안한다. 제안한 시스템에서는 송수신단 간에 채널 상태 정보가 필요하지 않기 때문에 순환 부호를 부호화하는 것과 복호하는 것은 단순해지고 센서 노드의 처리 복잡도가 크게 줄어들 수 있다. 모의실험 결과를 통해서 순환 부호를 적용한 센서 네트워크는 단일 홉 전송의 비트오율 $10^{-4}$에서 네트워크 수명이 10dB까지 절약되는 것을 알 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.2972-2991
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• 2016

WLAN is the best choice in the place where complex network is hard to set up. Intelligent terminals are more and more assembled in some areas now. However, according to IEEE 802.11n/802.11ac, the access-point (AP) can only serve one user at a single frequency channel. The spectrum efficiency urgently needs to be improved. In theory, AP with multi-antenna can serve multiple users if these users do not interfere with each other. In this paper, we propose a user clustering scheme that could achieve multi-user selection through the mutual cooperation among users. We focus on two points, one is to achieve multi-user communication with multiple antennas technique at a single frequency channel, and the other one is to use a way of distributed users' collaboration to determine the multi-user selection for user clustering. Firstly, we use the CSMA/CA protocol to select the first user, and then we set this user as a source node using users' cooperation to search other proper users. With the help of the users' broadcast cooperation, we can search and select other appropriate user (while the number of access users is limited by the number of antennas in AP) to access AP with the first user simultaneously. In the network node searching, we propose a maximum degree energy routing searching algorithm, which uses the shortest time and traverses as many users as possible. We carried out the necessary analysis and simulation to prove the feasibility of the scheme. We hope this work may provide a new idea for the solution of the multiple access problem.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.379-384
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• 2006

본 논문은 컴포넌트 검색 성능을 향상시키기 위해 사용자 피드백을 효율적으로 수행하는 방법을 제안하고자 한다. 기존의 퍼지 기법이 적용된 피드백의 단점을 극복하기 위하여 검색된 컴포넌트의 선택여부에 따라 동일한 함수이지만 학습률을 달리할 수 있는 가우시안 함수를 이용한 상호작용 함수를 제안한다. 또한 피드백 함수에 사용자 프로필을 적용하여 사용자 등급에 따라 사용자 의견이 시스템에 반영되는 정도를 다르게 해주었다. 본 연구의 사용자 검색 피드백은 가우시안 함수를 적용한 피드백 함수와 사용자 프로필을 이용하여 시스템을 장기간에 걸쳐 서서히 변화시킬 수 있는 적응형 검색 방법이다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.674-677
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• 2006

Orthogonal frequency division multiple access (OFDMA) has emerged as one of the core multiple access schemes in 4G to mitigate the problems of frequency selectivity and inter-symbol interferences. In OFDMA, cooperative transmission can be adopted in transmission between each user and base station. Cooperative transmission can provide better channel environments and additional transmitter diversity. In this paper, we formulate a user and subcarrier assignment problem in OFDMA system with user cooperation and propose an efficient scheme to solve it.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2005년도 춘계학술대회 논문집
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• pp.100-105
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• 2005

Development of complex discrete event simulators requires cooperation between domain experts and modeling experts who involve the development. With the cooperation the domain experts derive user requirement and modeling experts transform the requirement to a simulation model. This paper proposes a method for consistency verification of simulation model in DEVS formalism against the user requirement in UML diagrams. It also presents an automated tool, called VeriDEVS, which implements the proposed method. Inputs of VeriDEVS are three UML diagrams, namely use case, class and sequence diagrams, and DEVS Graph, all in Visio; outputs of a verification result is represented in PowerPoint files.