• Journal of Information Processing Systems
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• 제13권3호
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• pp.630-642
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• 2017

In this paper, we propose the opportunistic non-orthogonal multiple access (NOMA)-based cooperative relaying system (CRS) with channel state information (CSI) available at the source, where CSI for the source-to-destination and source-to-relay links is used for opportunistic transmission. Using the CSI, for opportunistic transmission, the source instantaneously chooses between the direct transmission and the cooperative NOMA transmission. We provide an asymptotic expression for the average achievable rate of the opportunistic NOMA-based CRS under Rayleigh fading channels. We verify the asymptotic analysis through Monte Carlo simulations, and compare the average achievable rates of the opportunistic NOMA-based CRS and the conventional one for various channel powers and power allocation coefficients used for NOMA.

• 한국인터넷방송통신학회논문지
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• 제8권4호
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• pp.25-33
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• 2008

레일레이 페이딩 채널에서 전력제한을 받는 기회전송 유무에 따른 협동 다중 릴레이 시스템의 성능을 연구하였다. 전제 네트워크의 전력이 제한되었을 때 3가지의 전력 할당방법을 검토하였고, 그 결과 기회전송 전력 할당방식이 다른 전력할당방식에 비해서 가장 좋은 성능을 나타내었다. 전체 네트워크의 전력이 증가할 경우 기회전송 릴레이가 증가하였고, 기회 협동 다이버시티의 차수를 증가시키게 되며, 결국 종단간 성능이 개선됨을 알 수 있었다.

• 한국통신학회논문지
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• 제31권9A호
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• pp.856-867
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• 2006

This paper proposes a new algorithm for opportunistic scheduling that take advantage of both multiuser diversity and power control. Motivated by the multicast RTS and priority-based CTS mechanism of OSMA protocol, we propose an opportunistic packet scheduling with power control scheme based on IEEE 802.11 MAC protocol. The scheduling scheme chooses the best candidate receiver for transmission by considering the SINR at the nodes. This mechanism ensures that the transmission would be successful. The power control algorithm on the other hand, helps reduce interference between links and could maximize spatial reuse of the bandwidth. We then formulate a convex optimization problem for minimizing power consumption and maximizing net utility of the system. We showed that if a transmission power vector satisfying the maximum transmission power and SINR constraints of all nodes exist, then there exists an optimal solution that minimizes overall transmission power and maximizes utility of the system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2029-2046
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• 2016

Energy consumption is an important index in mobile ad hoc networks. Data packet transmission increases among nodes, particularly in big data communication. However, nodes may be unable to transmit data packets because of energy over-consumption. Consequently, information may be lost and network communication may block. While opportunistic network is a kind of mobile ad hoc networks, researchers do not focus on energy consumption in opportunistic network communication. This study proposed an effective sensor energy supply scheme that can be applied in opportunistic networks. This scheme considers nodes sensor requests and communication model. In this scheme, nodes do not only accomplish energy supply in communication, but also extend communication time in opportunistic networks. Compared with the Spray and Wait algorithm and the Binary Spray and Wait algorithm in simulations, the proposed scheme extends communication time, increases data packet transmission, and accomplishes energy supply among nodes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권5호
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• pp.1992-2008
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• 2018

Mobile opportunistic network is a kind of ad hoc networks, which implements the multi-hop routing communication with the help of contact opportunity brought about by the mobility of the nodes. It always uses opportunistic data transmission mode based on store-carry-forward to solve intermittent connect problem of link. Although many routing schemes have been proposed, most of them adopt the greedy transmission mode to pursue a higher delivery efficient, which result in unfairness extremely among nodes. While, this issue has not been paid enough attention up to now. In this paper, we analyzed the main factors that reflect fairness among nodes, modeled routing selection as a multiple attribute decision making problem, and proposed our Fairness-aware Routing Strategy, named FARS. To evaluate the performance of our FARS, extensive simulations and analysis have been done based on a real-life dataset and a synthetic dataset, respectively. The results show that, compared with other existing protocols, our FARS can greatly improve the fairness of the nodes when ensuring the overall delivery performance of the network.

• Journal of Communications and Networks
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• 제18권5호
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• pp.806-817
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• 2016

Opportunistic routing (OR) has been proposed as a viable approach to improve the performance of wireless multihop networks with lossy links. However, the exponential growth of the bandwidth-sensitive mobile traffic (e.g., mobile video streaming and online gaming) poses a great challenge to the performance of OR in term of bandwidth guarantee. To solve this problem, a novel mechanism is proposed to opportunistically forwarding data packets and provide bandwidth guarantee for the bandwidth-sensitive traffic. The proposal exploits the broadcast characteristic of wireless transmission and reduces the negative effect of wireless lossy links. First, the expected available bandwidth (EAB) and the expected transmission cost (ETC) under OR are estimated based on the local available bandwidth, link delivery probability, forwarding candidates, and prioritization policy. Then, the policies for determining and prioritizing the forwarding candidates is devised by considering the bandwidth and transmission cost. Finally, bandwidth-aware routing algorithm is proposed to opportunistically delivery data packets; meanwhile, admission control is applied to admit or reject traffic flows for bandwidth guarantee. Extensive simulation results show that our proposal consistently outperforms other existing opportunistic routing schemes in providing performance guarantee.

• 한국정보통신학회논문지
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• 제23권10호
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• pp.1254-1260
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• 2019

최근 5세대 이동통신 시스템은 4차 산업혁명의 핵심 요소로 큰 주목을 받고 있다. 본 논문에서는, 이동통신 시스템에서 사물인터넷 시나리오를 지원하기 위해 파일럿 지원 기회적 전송 기반의 새로운 임의 접속 기법을 제안한다. 제안하는 기법은 임의 접속 절차 3단계에서 데이터 패킷을 전송할 때 다수 개의 상향링크 자원 중 하나의 자원을 임의로 선택하여 기회적 전송을 하는 동시에 데이터 복호를 위해 각 데이터 패킷에 다중화하는 상향링크 파일럿 신호 또한 임의로 선택하게 함으로써 패킷 충돌 확률을 획기적으로 낮추는 것을 주요 특징으로 한다. 확률 모델을 이용하여 패킷 충돌 확률 및 상향링크 자원 효율 관점에서 제안한 기법을 수학적으로 분석 하고, 모의실험을 통해 분석의 유효성을 확인하고 제안 기법의 우수성을 입증한다.

• 대한임베디드공학회논문지
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• 제14권4호
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• pp.177-186
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• 2019

In wireless sensor networks, the transmission success ratio would be decreased when the scale of the WSNs increased. To defeat this problem, we propose a multipath routing based on opportunistic routing for improving end-to-end reliability in large-scale wireless sensor networks. The proposed scheme exploits the advantages of existing opportunistic routing and achieves high end-to-end success ratio by branching like a multipath routing through local decision without information of the whole network. As a result of the simulation result, the proposed scheme shows a similar or higher end-to-end transmission success ratio and less energy consumption rather than the existing scheme.

• 한국인터넷방송통신학회논문지
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• 제9권6호
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• pp.1-8
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• 2009

최근에 많은 연구가 진행되고 있는 무선 ad-hoc 네트워크는 전력 제한 시스템이기 때문에 전력 절약은 ad-hoc 네트워크의 매우 중요한 연구 주제 중 하나이다. 그러므로 본 논문에서는 무선 ad-hoc 네트워크에 기회전송 릴레이(Opportunistic transmission relay) 시스템을 적용하였을 때, 전체 시스템의 오수신율이 최소가 되도록 제한된 전력을 각 송신 노드에 최적으로 할당하는 방법에 관하여 제안하고 각 값들을 수식적으로 유도하였다. 유도한 결과는 각 노드들에 통일한 전력을 할당할 때보다 시스템의 오수신 특성이 항상 우수하였다.

• Journal of information and communication convergence engineering
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• 제8권1호
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• pp.40-44
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• 2010

opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, with bring new research challenges in MAC design. We propose a cognitive MAC protocol using statistical channel information and selecting appropriate idle channel for transmission. The protocol based on the CSMA/CA, exploits statistics of spectrum usage for decision making on channel access. Idle channel availability, spectrum hole sufficiency and available channel condition will be included in algorithm statistical information. The model include the control channel and data channel, the transmitter negotiates with receiver on transmission parameters through control channel, statistical decision results (successful rate of transmission) from exchanged transmission parameters of control channel should pass the threshold and decide the data transmission with spectrum hole on data channel. A dynamical sensing range as a important parameter introduced to maintain the our protocol performance. The proposed protocol's simulation will show that proposed protocol does improve the throughput performance via traditional opportunistic spectrum access MAC protocol.