• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.12
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• pp.2812-2817
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• 2013

In this paper, an outage probability for the best relay selection in decode-and-forward relaying systems in the presence of interference is analyzed over Rayleigh fading channels. Based on the outage performance results, we propose a method to determine effective relay candidates for the best relay selection, where the effective relay candidates represent the relays except for relays that make no contribution to improving the performance. in all possible relays given in the system. By determining the effective relay candidates, the feedback overhead of channel state information and the energy consumption of relays can be significantly reduced while minimizing the performance degradation. In this paper, we provide important parameters that affect the determination of the effective relay candidates.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.40-47
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• 2012

In dual-hop relaying systems, the conventional partial relay selection is based on the channel information only for the first hop. On the other hand, the efficient partial relay selection is based on the channel information for the hop with the minimum of the average channel powers for the first and second hops at each end-to-end link since the correlation coefficient between the end-to-end link quality and the link quality of the hop with the minimum of the average channel powers for the first and second hops is larger than that between the end-to-end link quality and the link quality of the other hop. In this paper, the outage probability of the conventional partial relay selection and the efficient partial relay selection in dual-hop decode-and-forward relaying systems is analyzed for non-identically distributed Rayleigh fading channels. Through numerical investigation, the outage performance of the efficient partial relay selection is compared with the outage performances of the conventional partial relay selection and the best relay selection based on all the channel information for the first and second hops.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.520-526
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• 2018

In this paper, considering the superposition transmission-based wireless cooperative multicast communication system (ST-CMS) with multiple relays and destinations, we propose a relay selection scheme to improve the data rate of multicast communication. In addition, we adopt the optimal power allocation coefficient for the superposition transmission to maximize the data rate of the proposed relay selection scheme. To propose the relay selection scheme, we derive an approximate expression for the data rate of the ST-CMS, and present the relay selection scheme using only partial channel state information based on the approximate expression. Moreover, we derive an approximate average data rate of the proposed relay selection scheme. Through numerical investigation, comparing the average data rates of the proposed relay selection scheme and the optimal relay selection scheme using full channel state information, we show that the proposed scheme provides extremely similar performance to the optimal scheme in the high signal-to-noise power ratio region.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.108-110
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• 2015

In this paper, we proposed the relay node selection scheme using property of node such as velocity, direction in Delay Tolerant Networks. the existing selection scheme is caused the problem increasing the transmission delay and packet loss, if select the relay node for different mobile with destination. To overcome this problem, we proposed the relay node selection scheme using the property of mobile node. the proposed scheme represents and shares the property of mobile node. The proposed algorithm assumed the sketchy position of node from mobile node delivering property of destination. In addition, the propose algorithm recognizes and analyzes the context of mobile node to provide the relay node transferring the data efficiently. The simulation result provides the better result in terms of transmission delay and packet delivery ratio by selecting transmission by relay node according property of node.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.117-118
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• 2015

본 논문은 Delay Tolerant Networks(DTNs)에서 이동노드의 이동 속성 정보를 효율적으로 관리하여 목적노드를 지향하여 이동하는 중계노드를 선정하는 기법을 제안한다. 목적노드와 상이한 이동성을 가진 중계노드를 통해 전송 지연시간 및 패킷 손실이 발생할 가능성이 높아지게 된다. 따라서 본 논문에서는 부정확한 이동 속성 정보로 인하여 발생할 수 있는 전송 지연시간 및 패킷 손실이 증가하는 문제를 해소하기 위해, 이동노드 간 이동 속성 정보를 관리하고 연결성을 분석함으로써 중계노드를 선정하는 기법을 제안한다. 제안하는 알고리즘에서 이동노드는 주기적으로 자신의 속도와 방향을 상황인식 매트릭스에 저장하며, 다른 이동노드와 통신이 확립되면 저장된 이동 속성 정보를 교환하게 된다. 또한 교환된 이동 속성 정보를 연결성으로 분석함으로써 목적노드를 지향하여 이동하는 중계노드를 선정한다. 주어진 모의실험 결과, 최신의 이동 속성 정보를 활용하여 중계노드를 선정함으로써 패킷전송률 측면에서 더 향상된 결과를 보여주었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.42-49
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• 2014

The conventional best relay selection based on all the channel information for the first and second hops in dual-hop systems has a large consumption of resources for channel feedback. In this paper, we analyze the average bit error rate for partial relay selection based on the channel information only for the first hop in dual-hop decode-and-forward relaying systems, where we assume independent Rayleigh fading channels. In particular, we provide an exact and closed-form expression for the average bit error rate of M-ary QAM. Also, through numerical investigation, the performance of the partial relay selection is compared with the performance of the best relay selection, and the performance is evaluated for different numbers of relays and various average channel power ratios for the first and second hops.

• Journal of Korea Multimedia Society
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• v.11 no.7
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• pp.986-996
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• 2008

The home network environment based on the power line communication has some unexpected events. The noise source from the home appliances makes the network impedance increased, and the transmission packets distorted. Therefore the packet transmission from the source node may not be delivered to the destination node directly. In this paper we propose a new self-healing mechanism which relays the packet to the directly unreachable destination automatically with the help of intermediate nodes. In order to choose the minimum required intermediate nodes our mechanism makes a spanning tree with both the directly reachable nodes and indirectly reachable nodes via the intermedia nodes. We developed the network simulator in order to compare its performance to the Echelon's repeater selecting mechanism. Though it required more packet relations than Echelon's but the reachable probability to the destination was highly increased about two times.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.70-80
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• 2012

In this paper, we consider the amplify-and-forward relaying systems with the relay selection (AF-RS) using full channel information (FCI) and using partial channel information (PCI), respectively, in which the direct communication link between a source and a destination is available. And, the outage probabilities for the AF-RS using FCI and using PCI are investigated in Rayleigh fading channels, respectively. We provide exact outage probabilities, tight outage probability lower bounds, and asymptotic outage probabilities, respectively. And also, we present coding gains achievable by the AF-RS using FCI and using PCI. Through numerical investigation, all the analytic expressions are verified, and the coding gains are respectively evaluated with different average channel powers for the first and the second hop as well as different numbers of relays.

• Information and Communications Magazine
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• v.33 no.4
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• pp.92-98
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• 2016

본고에서는 5세대 이동통신 시스템의 유망기술 중 하나인 차세대 버퍼도움 (buffer-aided) 중계전송 기법의 핵심개념과 최신연구 동향에 대해서 알아본다. 먼저, 3개 노드로 구성되는 기본 중계기 네트워크에서 버퍼도움 중계전송의 원리와 관련 연구결과들을 살펴본다. 다음으로 다수 노드로 구성되는 다중 중계기 네트워크에서 기존 중계기 선택전송 기법 및 최신 버퍼도움 중계기 선택전송 기법에 대해서 비교하여 살펴본다. 마지막으로 차세대 버퍼도움 중계전송 기법응 다양한 환경에 적용한 응용 연구에 대해 살펴보고 본고를 마친다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.431-433
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• 2016

In this paper, we propose an algorithm that analyzes characteristic nodes to select efficient relay nodes using message distribution. Existing delay-tolerant network (DTN) routing algorithms have problems with large latency and overhead on account of the deficiency of network information in an unsteady network. We must solve this problem, predict future networks using node state information, and apply a weight factor that changes according to the message distribution. Simulation results show that the proposed algorithm provides enhanced performance compared to existing DTN routing algorithms.