• Journal of Communications and Networks
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• 제12권5호
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• pp.442-448
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• 2010

Cooperative relaying methods have attracted a lot of interest in the past few years. A conventional cooperative relaying scheme has a source, a destination, and a single relay. This cooperative scheme can support one symbol transmission per time slot, and is caned full rate transmission. However, existing fun rate cooperative relay approaches provide asymmetrical gain for different transmitted symbols. In this paper, we propose a cooperative relaying scheme that is assisted with dual relays and provides full transmission rate with the same macro-diversity to each symbol. We also address equalization for the dual relay transmission system in addition to addressing the issues concerning the improvement of system performance in terms of optimal power allocations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.147-162
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• 2009

In this paper, we propose a Cooperative Transmission Strategy using Entropy-based Relay Selection in Mobile Ad-hoc Wireless Sensor Networks(MAWSN) with Rayleigh Fading Environments. The main features and contributions of the proposed cooperative transmission strategy are as follows. First, entropy-based relay selection is used to improve data transmission reliability from a source node to a destination node. Second, we present a theoretical analysis model for the proposed cooperative transmission strategy with the outage probability of the end-to-end performance. The performance of our protocol is evaluated using analysis and simulation.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.1046-1048
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• 2009

협업통신은 다중경로페이딩의 문제를 해결하고 전송전력소모를 감소시키기위한 효과적인 기술이다. 릴레이선택과 전력할당은 협업통신의 성능을 결정하는 중요한 요소이다. 본 논문에서는 센서네트워크에서 네트워크수명 극대화를 위해 새로운 형태의 다중 릴레이선택 방법과 전력할당 알고리즘을 제안한다. 제안하는 릴레이 선택 알고리즘은 채널상태 뿐아니라 각 노드의 잔여전력을 함께 고려함으로써 전송전력을 극소화하고 네트워크의 수명을 증가시킨다. 시뮬레이션결과는 제안된 알고리즘이 기존의 방식에비해 더 긴 네트워크 수명을 갖을 수 있음을 보여준다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권6호
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• pp.1996-2013
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• 2015

This paper considers a scenario that more D2D users exist in the cell, they compete for cellular resources to increase their own data rates, which may cause transmission interference to cellular users (CU) and the unfairness of resource allocation. We design a resource allocation scheme for selfish D2D users assisted by cooperative relay technique which is used to further enhance the users' transmission rates, meanwhile guarantee the QoS requirement of the CUs. Two transmission modes are considered for D2D users: direct transmission mode and cooperative relay transmission mode, both of which reuses the cellular uplink frequency resources. To ensure the fairness of resource distribution, Nash bargaining theory is used to determine the transmission mode and solve the bandwidth allocation problem for D2D users choosing cooperative relay transmission mode, and coalition formation game theory is used to solve the uplink frequency sharing problem between D2D users and CUs through a new defined "Selfish order". Through theoretical analysis, we obtain the closed Nash bargaining solution under CUs' rate constraints, and prove the stability of the formatted coalition. Simulation results show that the proposed resource allocation approach achieves better performance on resource allocation fairness, with only little sacrifice on the system sum rates.

• 한국통신학회논문지
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• 제35권3C호
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• pp.255-263
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• 2010

본 논문에서는 60GHz WPAN (Wireless Personal Area Network) 시스템에서 릴레이를 이용한 협력 통신 기법을 제안하였다. 60GHz 대역은 LOS (Line-Of Sight)가 보장되어 있지 않은 경우 통신이 불가능하고 거리에 따른 신호 감쇄가 심하기 때문에 릴레이를 이용한 협력 통신 기법이 효과적이다. LOS가 존재하는 환경에서도 수신단이 송신단으로부터 받은 데이터뿐만 아니라 릴레이를 통해 데이터를 수신한다면 수신된 정보의 신뢰성을 높일 수 있다. 하지만 이 경우에 송신단이 데이터를 전송하는 시간뿐만 아니라 릴레이가 데이터를 전송하는 시간이 필요하기 때문에 정보의 전송률이 저하된다. 본 논문에서는 이러한 문제점을 해결하기 위하여 협력 통신 시스템에 적합한 Reed-Solomon(RS) code와 convolutional code(CC)의 직렬 연접 부호 구조를 이용하여 이러한 단점을 최소화 한다. 제안하는 협력 통신 기법은 릴레이에서 systematic RS code의 parity만을 convolutional code로 인코딩하여 전송하므로, 릴레이가 전송해야 하는 데이터의 양이 매우 적어 시스템의 전송 효율을 향상시킨다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.956-958
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• 2010

The paper considers MIMO two-way scheme to optimize the end to end capacity in local wireless mesh network. The basic idea is to perform data transmission via intermediate cooperative nodes and cooperative relay therefore higher throughput can be achieved. Each node is equipped with multiple antennas, and has two time slots one for transmission (Tx) and the other is reception (Rx), which are arranged alternatively in the network. In the conventional SISO network, it takes at least four time slots to accomplish the function of two-way relay. Moreover, cooperative technique is used in order to enhance multiplexing of forward and backward streams.

• 한국멀티미디어학회논문지
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• 제17권6호
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• pp.687-696
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• 2014

An integrated ship area network has functionality of remote control and autonomous management of various sensors and instruments embedded or boarded in a ship. For such environment, an wireless bridge is essential to transmit control and/or managing information to sensors or instruments from a central integrated ship area network station. In this paper, one of reliable schemes of WiMedia based wireless bridge using relay cooperative transmission using WiMedia distributed MAC protocol is proposed to increase a communication reliability between cluster headers, irrespective of channel variation. Simulation results show that the proposed wireless bridge using relay cooperative transmission scheme increases communication reliability.

• 전기학회논문지
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• 제58권6호
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• pp.1238-1240
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• 2009

In the wireless sensor network, cooperative transmission is an effective technique to combat multi-path fading and reduce transmitted power. Relay selection and power allocation are important technical issues to determine the performance of cooperative transmission. In this paper, we proposed a new multi-relay selection and power allocation algorithm to increase network lifetime. The proposed relay selection scheme minimizes the transmitted power and increase the network lifetime by considering residual power as well as channel conditions. Simulation results show that proposed algorithm obtains much longer network lifetime than the conventional algorithm.

• 대한전자공학회논문지TC
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• 제48권3호
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• pp.28-35
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• 2011

고용량의 멀티미디어 데이터 전송이 비약적으로 늘어나는 차세대 이동통신 시스템에서 cooperative ARQ 기법은 단말의 QoS를 만족시키기 위한 효과적인 방법이다. 그러나 기존의 cooperative ARQ 기법은 수신노드의 feedback을 받아서 재전송을 하기 때문에 채널 변화가 극심한 MANET 환경에서는 실시간 전송을 보장하기 어렵다는 단점이 있다. 본 논문에서는 ad-hoc OFDMA 통신 네트워크에서 cognitive relay를 이용한 협력통신 기반 cooperative ARQ 재전송 기법을 제안한다. 제안된 기법에서는 송신노드가 전송한 신호의 SINR을 relay가 사전에 sensing함으로써, 수신노드가 feedback 신호를 전송하기 전에 협력 통신을 능동적으로 제안한다. 이를 통하여, 무선 채널의 변화에 따른 지연 분산 특성을 극소화함으로써 실시간 통신을 원활하게 한다. 또한, relay에서 협력 통신을 제안할 때, 잘못된 제안을 최소화하기 위하여 최적의 sensing threshold를 유지할 수 있도록 하는 적응적 sensing threshold 최적화 알고리듬을 제안한다. 모의실험을 통하여, 실시간 멀티미디어 데이터 전송 시스템에서 제안된 cooperative ARQ 재전송 기법이 기존의 알고리듬에 비하여 프레임 전달시간 및 프레임 손실률 측면에서 우수한 성능을 가짐을 확인하였다.

• Journal of Communications and Networks
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• 제13권4호
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• pp.377-384
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• 2011

Cooperative beamforming has previously been proven to be an efficient way to improve the cooperative diversity. This method generally requires all relay nodes to participate in beamforming, which can be seen as "all participate" cooperative beamforming. However, not all relay nodes have constructive impacts on the end-to-end bit error rate (BER) performance. Based on this observation, we propose a new cooperative scheme which only selects those "appropriate" relay nodes to perform cooperative beamforming. Such relay nodes can be simply determined with mean channel gains. Therefore, the selection complexity is significantly reduced as global instantaneous channel state information is not required. This scheme guarantees that energy is only allocated to the "appropriate" relay nodes, and hence provides superior diversity. We also prove that power allocation among source and selected relay nodes is a convex problem, and can be resolved with lower computational complexity. Simulation results demonstrate that our scheme achieves an essential improvement in terms of BER performance for both optimal and limited feedback scenarios, as well as high energy-efficiency for the energy-constrained networks.