• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1802_1803
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• 2009

위치추정은 현재 이동로봇 분야에서 매우 중요하게 다루어지는 문제이다. RFID 위치추정 시스템은 저렴하고, 오차누적의 위험이 없고, map과 같은 사전정보의 제약이 없기에 범용적으로 사용될 수 있다. 하지만 RFID 위치추정에 있어, tag들의 서로 다른 인식거리 차이는 위치추정의 오차를 증폭시키는 역할을 한다. 따라서 이 논문에서는 이를 극복하기 위해 tag들의 인식거리 정보를 활용하여 위치추정을 수행한다. 또한 보다 정확한 위치추정을 위해, 송신신호 전력조절을 통하여, 인식거리를 조절하는 방법을 사용한다. 이들의 성능은 simulation을 통해서 확인하였다.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.114-115
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• 2019

이 논문은 무선 전력 전송을 이용하는 마우스의 급전 패드와 리시버 설계 방법을 제안한다. 마우스의 급전 패드는 코일의 턴간 간격을 불균등하게 조절하여 균일한 자기장을 급전 패드 상에서 얻게 하며, 집전코일은 급전코일과 비교해 크기가 작기 때문에 낮은 결합계수와 품질계수를 가져 원하는 전압을 얻기 어려운데 이를 위해 PCB 코일을 멀티레이어로 제작하고 PCB 패턴의 폭을 조절하여 높은 인덕턴스를 갖게 설계한 후 유한요소해석을 통해 설계한 시스템을 시험했다.

• Convergence Security Journal
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• v.12 no.3
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• pp.27-34
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• 2012

In this paper, using a new low-power consumption method for ZigBee device, which consume low-power using an output power control algorithm through RSSI monitoring as interlocking wireless network using ZigBee which has advantages of a low-power consumption, a low-cost, a compatibility and a draft international standardization enacted by IEEE and ZigBee Alliance, with wired network using built coaxial cable to overcome the disadvantage of the existing wireless sensor network, is proposed. Effectiveness of the output power control algorithm through RSSI monitoring has been verified by experimentation for more optimized low-power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3B
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• pp.247-254
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• 2009

Over the last decade multiple-input and multiple-output (MIMO) systems have been actively researched and started to be deployed in wireless communications owing to the significant increase in channel capacity. In this paper, we propose a energy saving MAC protocol in systems by focusing on energy efficiency instead of capacity maximization. We considers the energy consumption together with the tradeoff between reliability (i.e., diversity) and throughput (i.e., multiplexing gain), and dynamically chooses an appropriate number of antennas for transmission. In computing the total energy consumption, we counts circuit energy as well as transmission energy. Naturally the circuit energy consumption is directly proportional to the number of active antennas. Through numerical analysis, we confirm that our power saving MAC scheme for MIMO considerably saves energy consumption compared to conventional capacity maximization schemes that use a fixed number of MIMO channels, for a given outage constraint. Our finding is that the capacity maximizing communication which possibly can be regarded best in terms of energy efficiency gives a different solution from the energy minimizing communication.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.39-44
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• 2010

In LTE-Advanced systems, every sector uses the entire range of the frequency resource, and when the UEs are located at a cell edge, user throughputs degrade due to the interferences from the adjacent cells. In this paper, we propose a combined scheme for inter-cell interference avoidance and power control. In the proposed algorithm, the sectors consist of the right edge, the left edge and the center for resource allocation and we control the transmission power to improve the user throughputs at the edge of each cell. Using a system level simulation, we analyze low 5th percentile and average user throughputs of the UEs who are located the cell, center and edge when the inter-cell interference avoidance and the power control are combined.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.11
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• pp.393-402
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• 2014

We have experienced an explosive increase of the IoT(Internet of Things) technology based devices including smart phones and the wireless communications. Also the growing power consumption in IEEE 802.11 WLANs(Wireless LANs) driven by these dramatic increases in not only mobile users and but also wireless APs(Access Points). To reduce the power consumption, this paper proposes a wireless AP power saving algorithm, which minimizes the transmission power without decrease the transmission and carrier sense ranges. A wireless AP which is use in our algorithm checks its own original coverage periodically for whether there is a new STA(Station) or not when its transmission power is decreased. Moreover, if there are no signaling message to connect the wireless AP, it changes its operation mode Wake-up to sleep. A Result shows that the proposed AP algorithm can reduce the total power consumption of the wireless AP approximated 18% and 35% compared to the conventional wireless AP with and without the existing power saving algorithm, respectively.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1081-1085
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• 2010

In the wireless sensor networks, power consumption and interference among the nodes can be reduced by using the transmission power control. Because link quality is changed by spatial and temporal effect, link failures are frequently occurred. In order to adapt to link quality variation, existing transmission power control schemes broadcast beacon messages periodically to neighbor nodes and control the transmission power dynamically. However, it can effect on the time and energy overhead according to period of transmission power control. In this paper, the dynamic method of transmission power control by the link quality variation and variable period are proposed. When a link quality is unstable, the control duty cycle is reduced and the link quality is agilely maintained. In contrast, when link quality is stable, the control period is increased and control overhead is decreased.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.363-368
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• 2003

In this paper, the characteristics of the horn antenna for the high power transfertation system is stuided and several kinds of a horn antenna are compared and finally a conical hem antenna using multi-mode is proposed. In the high power system, the efficiency of power transfer is very important. Therefore the feeding hem of a reflector must have a circular symmetric radiation pattern. And the side lobe must be suppressed to reduce a spillover power loss and interference. By using multi-mode in a circular hem antenna, the whole length can be shorter and the radiation pattern can be adjusted according to the shape and direction of a reflector. This is confirmed by the experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.47-52
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• 2011

Nano-scale power splitter based on Si plasmonic waveguides are designed by utilizing the multimode interference (MMI) coupler. Effective dielectric method and longitudinal modal transmission-line theory are used for simulating the light propagation and optimizing the structural parameters at 3-D guiding geometry. The designed $1{\times}2$ 50:50 MMI power splitter has a nano-scale size of only $800nm{\times}850nm$. In order to achieve a variable power splitting ratio, a $2{\times}2$ MMI coupler is designed and the corresponding power splitting ratio can be tuned in the range of 78.5%:15.5%~5.5%:86.6%. Also, it is shown that it has a large bandwidth of $1.5{\mu}m{\sim}1.7{\mu}m$. In this range, the transmission is over 0.8.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1647-1655
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• 2006

본 연구는 무선 및 사용자요구사항 등 환경의 변화에 따라 부반송파(subcarrier) 할당, 변조방식 및 전력량을 조절하는 적응형 다중사용자 OFDM 시스템을 다룬다. 먼저 사용자별 전송요구 비트수 및 전체 사용가능한 전력량에 대한 제약 조건하에서 총 데이터 전송량(Throughput)을 최대화하는 최적화 문제를 모형화한다. 이 문제는 대부분의 기존 연구들을 포함할 수 있을 정도로 포괄적이지만 미분이 불가능한 비선형 최적화 문제이면서도 빠른 계산시간을 요구한다. 본 연구는 쌍대간격(Duality Gap)이 0이라는 제안 문제의 특성을 바탕으로 하여 Subgradient 쌍대최적화(Dual Optimization) 기법을 적용한다. 또한 이러한 접근법은 사용자 또는 무선환경의 변화에 적극적으로 적응하는 무선자원 할당 메커니즘을 제시한다.