• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.925-928
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• 2013

In this paper, we propose a relay-based wireless power transmission scheme in order to solve the problems of an existing wired power transmission for energy harvesting system. The proposed scheme can be transferred electromagnetic induction-based wireless power transmission by placing a 4-way coils in the energy block. We confirm the reliability of the electricity transmission through the relay control algorithm. Consequently, the proposed scheme can extend the transmit receive paths of transmission power.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.6
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• pp.1-8
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• 2009

Though the wireless ad-hoc network which is recently highly focused is power limited network, one of the main research topic is power saving. We propose a optimal power allocation strategy and derive the optimal power of the opportunistic transmission relays for minimum outage probability of the power limited network. It is shown that the proposed optimal power allocation has always better performance than that of the equal power allocation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.2
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• pp.175-177
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• 2016

This letter considers wireless energy and information transfer for an amplify-and-forward two-way relay network. When the relay harvests the energy and transfers the information signal through power splitting, the optimal power splitting minimizing the outage probability is derived explicitly and its gain is confirmed by simulations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.65-71
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• 2016

Cooperative relaying systems have been studied actively to improve the system performance effectively in wireless fading channels. Most of the cooperative relay studies are assumed fixed relay, recently the performance analysis of the cooperative relaying systems with spatially random relays considering the practical mobile environment are introduced. However the comparative studies for relay selection methods of incremental cooperative relay systems, the performance of which is influenced by the selection methods, have not been studied. Therefore we derive the performance of the system which has MRC(Maximal-ratio combining) with Max SNR(signal-to-noise ratio) selection or Max-min SNR selection, respectively. And the outage performances of the system with Max or Max-min selection method are compared for different transmit power allocation to the source and to the relays. The analytical results serve as useful tools for relay selection and power allocation to transmit nodes for opportunistic incremental relaying systems.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.598-603
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• 2008

Relay system is a promising technique for the high downlink throughput or coverage extension in the next generation wireless systems. In this paper, the transmit scheme for orthogonal frequency division multiplexing (OFDM) based relay system with hierarchical modulation is designed. Without using much power from the base station, the proposed scheme can guarantee the cell edge users to get high data rates as the inner cell users. In the simulation, the performance of proposed scheme was compared with the conventional one in which there is no hierarchical modulation. Numerical results show that the proposed scheme can save much power whether the unicast case or multicast case.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.6
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• pp.638-644
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• 2018

Relay systems have recently gained attentions because of its capability of cell coverage extension and the power gain as the one of key technologies for 5G. Relays can be exploited for small-cell base stations and the autonomous network, where communication devices communicate with each other cooperatively. Therefore, the relay technology is expected to enable the low power and large capacity communication. In order to maximize the benefits of using a limited number of relays, the efficient relay selection method is required. Especially, when two nodes exchange their data with each other via relay, the relay selection can maximize the average data rate by the spatial location of the relay. For this purpose, the average data rate is analyzed first according to the relay selection. In this paper, we analyzed the average data rate when two nodes exchange their data via dual-hop decode and forward relaying considering the interference by the concurrent transmission under Nakagami-m fading channel. The correctness of the analysis is verified by the Monte Carlo simulation. The results show that the concurrent transmission is superior to the non-concurrent transmission in the high required data rate region rather than in the low required data rate region.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.215-220
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• 2012

Recently, one of the research topics is wireless Ad-Hoc network minimizing power consumption because of limited power. We propose optimal power allocation scheme of each transmit node and derive performance analysis of system that recently designed Double opportunistic relay system which fixed branch receiver to use more than efficient power consumption. Optimal power location scheme is shown that outage probability has always better performance than equal power allocation. Furthermore, we are known that outage probability is minimized by increasing average transmit relays to obtain the diversity gain when average channel power gain is less.

• The Journal of the Korea Contents Association
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• v.13 no.5
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• pp.19-27
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• 2013

This paper implements the standby power control system composed of a master device and slave devices. The standby power is managed by cutting power supply after controlling the relay of a slave device based on the authentication of master device's RFID card. RFID interface and wireless communication module are embedded in a master device, and one master device is linked with many slave devices in wireless. Each slave device executes the operation needed in power control independently. We implements the function of manual power on/off system in a slave device, and the function of user ID enrollment by switch manipulation in a master device. Also this system can communicate bidirectionally in wireless and runs on TinyOS. The result of experiment shows that the user authentication is executed in a master device and this authenticated information is transmitted to a slave device in wireless, and standby power is cutted by controlling the relay of a slave device. Installing this system in a building or an office, we can expect energy saving.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.580-581
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• 2018

In order to reduce end-to-end delay in EH-WSN (energy harvestin wireless sensor netowk), medium access control protocols using multi-hop routing technique have been studied. In a real environment, there are many situations where it is difficult to harvest enough energy than the energy consumed. Therefore, it is required to design a MAC protocol that allows nodes to reliably relay data without exhausting power in multi-hop transmission. In this paper, we propose a power-efficient MAC protocol that can select the relay node according to the residual power and the energy collection rate to increase network lifetime.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.17-22
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol over Rayleigh fading channels. In the proposed protocol, the multi-hop cooperative transmission is used to improve the system performance. Due to broadcast nature, we do not limit the receiving node to be only the next node, but the destination and all the nodes between the transmitting node and the destination. The proposed protocol can hence save the average transmit power, compared with multi-hop direct transmission protocol due to the skipped transmissions from some intermediate nodes or chosen relays. The proposed scheme is implemented and evaluated in mobile ad-hoc wireless networks.