• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.12
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• pp.2826-2834
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• 2013

In mobile ad hoc networks (MANET), power-saving technology of mobile nodes is divided into transmit power control (TPC), power-saving mode (PSM), and routing. TPC and PSM are operated in physical layer but the routing is managed in network layer, so the design of a joint algorithm is needed to provide better performance. Therefore, in this paper, we propose a joint power-saving and routing algorithm for maximizing the network lifetime while satisfying the end-to-end data rate in ad hoc networks. The proposed algorithm first applies the TPC or PSM to reduce the power consumption of mobile nodes and then performs the routing by considering the decided node lifetime in order to maximize the path lifetime. Simulation results show that the proposed algorithm maximize the lifetime while satisfying the required rate according to the number of mobile nodes and the level of interference.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.316-323
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• 2009

Power allocation of soft frequency reuse(SFR) to increase cell edge user throughput by reducing inter-cell interference is proposed for coordinated cellular systems. SFR is the effective technique to increase cell edge user throughput, however, it costs the degradation of total system throughput. The cost increases when SFR operated in distributed resource controlled systems fails to be fast adaptive in the change of user distribution. The proposed scheme enables coordinated cells to control transmit power adaptively depending on user distribution so that it minimizes the loss of system throughput introduced from SFR while it guarantees enhancement of cell edge user throughput. Through system level simulation considering neighboring two cells, evaluation result for adaptive power allocation is shown compared with static power allocation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.138-143
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• 2005

This paper aims to optimize an access probe algorithm for the CDMA 2000 system. The incremental value of PWR_STEP increases as NUM_STEP as 1dBm±0.2 for access probe of the area with good receiving sensitivity when the mobile station transmits via access channel and does not receive any ACK message. However, for the area with weak receiving sensitivity, according to the algorithm of open-loop power control, the transmitting power amplifier becomes saturated and PWR_STEP incremental value keeps performing access probe to 0dBm±0.2. Therefore interference and battery consumption increases according to the transmission of the mobile station. We have optimized the access probe algorithm according to the receiving sensitivity. We transmit the incremental value of access probe power, with delaying as much RT slot value as indicated by IS-95C standard in case of good receiving sensitivity and with delaying RT+l slot value in case of weak receiving sensitivity. Simulation results showed that the proposed algorithm contributes to decrease of the interference and battery consumption according to the transmitting power of the mobile station and improves the call duration.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.185-186
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• 2012

본 논문에서는 HVDC C&P(High Voltage Direct Current Control and Protection) 시스템의 네트워크 이중화 방법을 제안한다. 본 논문에서 제안하는 HVDC C&P 시스템 네트워크 이중화 방법은 2개의 이더넷 라인을 제어기에 직접 연결하고, 연결된 라인으로 동시에 정보를 송신하여, 제어기에서 정보를 필터링하여 사용하는 방법을 사용한다. 또한 네트워크 라인의 효과적인 결선 체크를 위해 제어기간 송수신을 통해 네트워크 라인의 결선을 체크하는 방법을 사용한다. 위와 같은 방법은 HVDC C&P 시스템의 네트워크 안정성을 향상시키는 효과를 기대할 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.649-651
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• 2018

Since the ubiquitous sensor network is not connected to external power source and operated by its own battery, it is required to maximize the network life using the efficient energy utilization. In a conventional hop count based routing protocol, most sensor nodes are designed with a constant transmission power. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes by controlling the transmit power according to the residual power of the nodes, and compared the performance of the proposed routing protocol through computer simulations.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.254-255
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• 2017

공진형 컨버터에서 일반적으로 소프트 스위칭과 같은 조건을 만족시키기 위해 주파수 제어를 많이 사용한다. 그러나 전계결합형 무선전력전송 시스템 특성상 이격 거리나 정렬 오차 정도 따라 송 수신부를 연결하는 링크 캐패시턴스 값이 민감하게 변한다. 이런 시스템에서는 공진 주파수 추종과 동시에 시비율 제어가 필요하다. 송신부 앞 또는 부하단에 dc/dc컨버터를 추가하는 2단 구성은 시스템 효율이 1단 구성에 비해 낮다는 단점이 있다. 따라서 본 논문에서는 무선전력전송 시스템에 비대칭 하프 브릿지를 사용하여 시비율 제어와 주파수 추종제어를 할 수 있는 구조를 제안한다. 이는 시뮬레이션을 이용하여 검증한다.

• Journal of Digital Contents Society
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• v.18 no.2
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• pp.365-371
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• 2017

IEEE 802.11 Wireless Local Area Network (WLAN) adopts Power Saving Mode(PSM) to save the power. Unlike existing PSM, this paper proposes a new scheme for the power saving of the Mobile Host(MH) when a MH performs the data transmission after the competition-based DCF(Distributed Coordination Function) and competition free-based PCF(Point Coordination Function). In this paper, The proposed scheme estimates the distance between the MH with the authority of data transmission and the Access Point(AP) and then adaptively controls the power of the MH considering the distance. Through the simulation result, we find that the proposed scheme consumes the smaller transmission power and has the similar success rate of packet transmission when it is compared to the existing scheme which uses the same power without the consideration of the distance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.125-132
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• 2017

Vehicular safety service reduces traffic accidents and traffic congestion by informing drivers in advance of threats that may occur while driving using vehicle-to-vehicle (V2V) communications in a wireless environment. For vehicle safety services, every vehicle must broadcasts a Basic Safety Message(BSM) periodically. In congested traffic areas, however, network congestion can easily happen, reduce the message delivery ratio, increase end-to-end delay and destabilize vehicular safety service system. In this paper, to solve the network congestion problem in vehicle safety communications, we approximate the relationship between channel busy ratio and the number of vehicles and use it to estimate the total network congestion. We propose a new context-aware transmit power control algorithm which controls the transmission power based on total network congestion. The performance of the proposed algorithm is evaluated using Qualnet, a network simulator. As a result, the estimation of total network congestion is accurately approximated except in specific scenarios, and the packet error rate in vehicle safety communication is reduced through transmit power control.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.214-220
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• 2006

In this paper, we propose the transmit power controlled adaptive modulated OFDM with frequency symbol spreading and equalization(TPC-AMS/FSS-OFDM) system. In the transmitter of the TPC-AMS/FSS-OFDM, each SP transformed signal is spread by orthogonal spreading codes and combined, so the detected signals obtain the same SINR(signal interference to noise ration) for each frequency symbol spreading block. In this case, we can assign the same modulation level and transmit power for each frequency symbol spreading block. Thus, the proposed system provides the increased throughput performance with reducing the total transmit power, FBI and MLI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.535-544
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• 2013

This paper considers an uplink power control scheme for a virtual multi-input multi-output (MIMO) multi-cell system where multiple mobile stations with single transmit antenna form a virtual MIMO link. Unlike the conventional approach of the game theoretic formulation to add a power penalty term to improve the performance, a constraint on the total effective interference power is introduced to the maximization of the utility function of the transmission rate with linear receive beamforming. Introducing inertia, we show that the proposed power control is guaranteed to converge. The simulation results verify that the proposed power allocation can significantly improve the performance in an interference limited multi-cell system.