• 동력기계공학회지
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• 제4권4호
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• pp.78-83
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• 2000

It is often necessary to observe the working environment of a robot to control it efficiently in the remote location. The remote sensing data and control commands are transmitted via various media such as radio, microwave, and computer network. The World Wide Web can be used as the infrastructure for teleoperation of mobile robots. In this paper we propose an advanced technique of the remote control of mobile robots on the web. For the real-time control, the image separation algorithm is proposed to transmit the current positions of mobile robots instead of transmitting the full frame image. It is shown by experiments that the proposed algorithm is effective.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.729-732
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• 2001

Digital signal processors(DSP) are widely used in modern power conversion devices, ac motor drives. However, generating pulse-width modulation(PWM) gating signals requires so high sampling rates that most computation resources of the DSP must be devoted to generating them. This paper presents an ASIC realization of 2 channel space-vector PWM(SVPWM). The developed DSP(ECLDSP) board can transmit gating signals to 2 converter/inverter and control them. ECLDSP board is used for control the various kinds of power-quality improvement systems.

• 대한기계학회논문집A
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• 제30권6호
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• pp.684-690
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• 2006

This study proposes and validates a new column type electric power steering system (EPS-TT). It is driven by a uni-directional motor and two electro-magnetic clutches. The assist motor produces assist torque in only one direction and two clutches transmit the torque to the column of steering system in either left or right direction with respect to the steering input. A full order and a reduced order models are developed to evaluate the EPS-TT. Models are also used to investigate the vehicle responses. A PID control logic is designed to control the torque of the assist motor. A driver model is applied to the system and the resulting performances are analyzed. The results show that the performances of the full order model are similar to those of reduced order model. The results also prove that the performances achieved by the EPS-TT are improved compared to those of a conventional EPS-TT across the frequency domain.

• 한국통신학회논문지
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• 제32권10A호
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• pp.1023-1033
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• 2007

This study considers a joint congestion control, routing and power control for energy-constrained wireless networks. A mathematical model is introduced which includes maximization of network utility, maximization of network lifetime, and trade-off between network utility and network lifetime. The framework would maximize the overall throughput of the network where the overall throughput depends on the data flow rates which in turn is dependent on the link capacities. The link capacity on the other hand is a function of transmit power levels and link Signal-to-Interference-plus-Noise-Ratio (SINR) which makes the power allocation problem inherently difficult to solve. Using dual decomposition techniques, subgradient method, and logarithmic transformations, a joint algorithm for rate and power allocation problems was formulated. Numerical examples for each optimization problem were also provided.

• 한국정보과학회논문지:정보통신
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• 제37권3호
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• pp.228-233
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• 2010

최근 데이터 서비스에 대한 수요가 폭발적으로 증가하는데 반해, 사용가능한 자원은 한정되어 있기 때문에 효율적인 자원 관리가 네트워크 성능을 증가시키기 위한 중요한 요소가 되고 있다. 특히 무선 네트워크에 있어서 제한된 자원의 효율적 활용을 통해 더 많은 수요를 수용함으로써 소비자의 만족도를 증대시킬 수 있다. 본 논문에서는 진화게임을 이용한 적응적 전력제어를 통한 효율적인 자원 할당 기법을 제안한다. 제안된 기법은 네트워크의 채널 상황에 따라 적응적 분산방식으로 전송전력 수준을 조정하여 현재 네트워크 상황에 유연하게 대응함으로서 효율적인 네트워크 관리를 수행한다. 컴퓨터 시뮬레이션을 통하여 기존에 제안된 전력제어 기법에 비해 본 논문에서 제안한 방법이 다양한 네트워크 환경 하에서 우수한 성능을 가지는 것을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.611-627
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• 2017

For enhancing the coverage of wireless networks and increasing the spectrum efficiency, small cell networks (SCNs) are considered to be one of the most prospective schemes. Most of the existing literature on resource allocation among non-cooperative small cell base stations (SBSs) has widely drawn close attention and there are only a small number of the cooperative ideas in SCNs. Based on the motivation, we further investigate the cooperative approach, which is formulated as a coalition formation game with power control algorithm (CFG-PC). First, we formulate the downlink sub-channel resource allocation problem in an SCN as a coalition formation game. Pareto order and utilitarian order are applied to form coalitions respectively. Second, to achieve more availability and efficiency power assignment, we expand and solve the power control using particle swarm optimization (PSO). Finally, with our proposed algorithm, each SBS can cooperatively work and eventually converge to a stable SBS partition. As far as the transmit rate of per SBS and the system rate are concerned respectively, simulation results indicate that our proposed CFG-PC has a significant advantage, relative to a classical coalition formation algorithm and the non-cooperative case.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4957-4976
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• 2016

This paper investigates the error performance of the amplify-and-forward (AF) relaying systems in the context of full-duplex (FD) communication. In addition to the inherent self-interference (SI) due to simultaneous transmission and reception, coexistent FD terminals may cause crosstalk. In this paper, we utilize the information exchange via the crosstalk channel to construct a particular distributed space-time code (DSTC). The residual SI is also considered. Closed-form pairwise error probability (PEP) is first derived. Then we obtain the upper bound of PEP in high transmit power region to provide more insights of diversity and coding gain. The proposed DSTC scheme can attain full cooperative diversity if the variance of SI is not a function of the transmit power. The coding gain can be improved by lengthening the frame and proper power control. Feasibility and efficiency of the proposed DSTC are verified in numerical simulations.

• 디지털콘텐츠학회 논문지
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• 제18권2호
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• pp.365-371
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• 2017

IEEE 802.11 무선랜에서는 전력 절약을 위하여 Power Saving Mode(PSM)를 채택하고 있다. 본 논문에서는 기존의 PSM과는 다르게 경쟁기반인 DCF(Distributed Coordination Function)와 무경쟁기반인 PCF(Point Coordination Function) 수행 후에 이동 단말이 정보 전송을 할 때 이동 호스트의 전력 절약을 위한 새로운 방식을 제안한다. 본 논문에서 제안하는 방식은 정보 전송의 권한을 가진 이동 호스트가 액세스 포인트(Access point)와의 거리를 추정하고 그 거리를 고려하면서 이동 호스트의 송신 출력을 능동적으로 제어한다. 모의실험을 통하여 우리는 제안한 방법이 거리와 상관없이 동일한 전송 전력을 사용하는 기존의 방법과 비교할 때 더 작은 전송 전력을 소모하면서도 비슷한 패킷 전송의 성공률을 가짐을 알 수 있다.

• Journal of electromagnetic engineering and science
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• 제16권4호
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• pp.199-205
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• 2016

We present a novel schematic using a 3-dB coupler to transmit radiofrequency (RF) power to two receivers selectively. Whereas previous multiple receiver supporting schemes used hardware-switched methods, our scheme uses a soft power-allocating method, which has the advantage of variable power allocation in real time to each receiver. Using our scheme, we can split the charging area and focus the RF power on the targeted areas. We present our soft power-allocating method in three main points. First, we propose a new power distribution hardware structure using a FPGA (field-programmable gate array) and a 3-dB coupler. It can reconfigure the transmitting power to two receivers selectively using accurate FPGA-controlled signals with the aid of software. Second, we propose a power control method in our platform. We can variably control the total power of transmitter using the DC bias of the drain input of the amplifier. Third, we provide the possibility of expansion in multiple systems by extending these two wireless power transfer systems. We believe that this method is a new approach to controlling power amplifier output softly to support multiple receivers.

• 한국전자파학회논문지
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• 제18권9호
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• pp.1077-1082
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• 2007

본 논문에서는 3${\sim}$10 GHz대 통신용 초광대역 시스템이 3.5 GHz대 고정(fixed) WiMAX(Worldwide Interoperability for Microwave Access)에 미치는 간섭 영향에 대해 고찰하였고, WiMAX에 미치는 잠정적인 간섭을 줄이기 위해 초광대역 시스템의 송신 전력을 제어하는 방법을 제안하였으며, 몬테카를로 시스템 레벨 시뮬레이션을 통해 간섭 저감 효과를 분석하였다. 간섭 영향은 단위 면적 1$km^2$내에 존재하는 다수의 초광대역 시스템과 단일 WiMAX 수신기를 가정하였을 때, 초광대역 시스템의 간섭에 의한 WiMAX의 outage 확률로 평가하였으며, 결과의 일례로써 초광대역 시스템의 밀도가 20$devices/km^2$이고 송신 전력 제어 동적 출력 범위가 30 dB일 때, 송신 전력 제어 방법을 적용한 경우 간섭 저감 방법을 적용하지 않는 경우보다 초광대역 시스템의 간섭에 의한 WiMAX의 outage 확률이 42 % 감소되는 효과를 보였다. 결론적으로 제안된 송신 전력 제어 방법은 초광대역 시스템이 WiMAX에 미치는 간섭 영향을 저감시린 수 있음을 보였다.