• 융합신호처리학회논문지
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• 제22권2호
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• pp.64-70
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• 2021

최근 무선 네트워크 기반 실시간 원격제어에 대한 관심이 크게 증가하고 있다. 무선 네트워크를 통하여 실시간 원격 제어를 구현하는데 있어서, 중요한 요소들 중 하나가 실시간 제어메시지의 지연시간 성능이다. 특히, 주기적으로 송신되는 실시간 제어메시지의 안정적인 수신을 위해 지연시간 지터를 줄이는 기술이 필요하다. 본 논문에서는 실시간 제어메시지를 무선 네트워크에서 운용 하는데 있어서 지연시간 지터를 감소시키는 동기화 전송을 제안한다. 제안된 동기화 전송은 송신노드와 무선통신기 간의 동기화를 바탕으로 적절한 전송시점을 제어하여 실시간 제어메시지가 항상 정해진 시간에 무선 네트워크를 통하여 전송 되도록 한다. 군용무인차량 시스템을 이용한 실험 결과에 따르면, 제안된 동기화 전송은 지연시간 지터를 일반 전송 방식의 지연시간 지터의 32% 수준으로 감소시켰다.

• Journal of Power Electronics
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• 제19권1호
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• pp.211-219
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• 2019

In magnetically coupled resonant (MCR) wireless power transfer (WPT) systems, the introduction of additional intermediate coils is an effective means of improving transmission characteristics, including output power and transmission efficiency, when the transmission distance is increased. However, the position of intermediate coils in practice influences system performance significantly. In this research, a three-coil MCR WPT system is adopted as an exemplification for determining how the spatial position of coils affects transmission characteristics. With use of the fundamental harmonic analysis method, an equivalent circuit model of the system is built to reveal the relationship between the output power, the transmission efficiency, and the spatial scales, including the axial, lateral, and angular misalignments of the intermediate and receiving coils. Three cases of transmission characteristics versus different spatial scales are evaluated. Results indicate that the system can achieve relatively stable transmission characteristics with deliberate adjustments in the position of the intermediate and receiving coils. A prototype of the three-coil MCR WPT system is built and analyzed, and the experimental results are consistent with those of the theoretical analysis.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2007년도 추계 종합학술대회 논문집
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• pp.126-129
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• 2007

최근 유무선 혼합망의 사용이 증가됨에 따라 무선망의 핸드오프, 경로 손실, 페이딩, 등과 같은 전송 오류의 원인을 개선하기 위한 연구가 전개되고 있다. 유선의 신뢰성을 보장하는 표준 TCP, SCTP를 무선망에 적용하는 것은 혼잡제어, 흐름제어의 메커니즘을 적용함으로써 데이터 전송의 효율을 저하시킨다. 본 연구는 무선망에서 SCTP를 적용하기 위해서 SCTP와 SNOOP을 혼합하는 것으로, 무선망에서 전송오류가 발생했을 때 BS의 동작과정을 개선한 것이다. BS(Basic Station : 기지국)는 전송오류 시 ZWP(Zero Window Probe)를 MN(Mobile Node:이동노드)에게 보내어 경로와 상태를 확인하고 RWND를 갱신하여 에러상태를 확인한다. 그리고 새로운 경로를 선택하고, FH(Fixed Host : 고정호스트)에게는 ZWA(Zero Window Advertisement)를 보내어 혼잡제어나, 흐름제어 메커니즘을 호출하는 것을 방지하고 대기상태로 기다리게 한다. 무선망의 연결이 안정된 후에 데이터 전송을 함으로써 데이터의 전송 효율을 약 10% 향상한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.131-132
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• 2007

In this paper, we designed and implemented bio-signals transmission and storage system using wireless sensor network based on ZigBee. Wireless sensor network is organized with routing protocol based on tree structure. The data is transmitted to monitoring system based on SIP. ZigBee will be used as various combinations with other wireless network technologies for application purposes.

• Journal of information and communication convergence engineering
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• 제9권6호
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• pp.676-682
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• 2011

Sybil attack can disrupt proper operations of wireless sensor network by forging its sensor node to multiple identities. To protect the sensor network from such an attack, a number of countermeasure methods based on RSSI (Received Signal Strength Indicator) and LQI (Link Quality Indicator) have been proposed. However, previous works on the Sybil attack detection do not consider the fact that Sybil nodes can change their RSSI and LQI strength for their malicious purposes. In this paper, we present a Sybil attack detection method based on a transmission power range. Our proposed method initially measures range of RSSI and LQI from sensor nodes, and then set the minimum, maximum and average RSSI and LQI strength value. After initialization, monitoring nodes request that each sensor node transmits data with different transmission power strengths. If the value measured by monitoring node is out of the range in transmission power strengths, the node is considered as a malicious node.

• 산업기술연구
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• 제28권A호
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• pp.113-117
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• 2008

Wireless carrier sense multiple access (CSMA) systems are widely used but show extremely different transmission efficiency according to the operation environment. Simulation or prototype deployment is needed to see the transmission efficiency of a wireless CSMA system with the partial packet retransmission scheme. The lower bound for the transmission efficiency of such a system is found mathematically in this work. This shows how much the partial packet retransmission scheme improves the transmission efficiency quantitatively. It also shows that the maximum throughput is obtained at higher offered load compared to the conventional CSMA system without the partial packet transmission. The result of this work can be applied to IEEE 802.11 networks or wireless mesh networks.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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• pp.27-30
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• 2003

Wireless power transmission system is one of the very interesting field not only in a technical and economical point of view but also that people are still trying to realize lossless power transmission. This paper has a purpose on the efficient power transmission at the passive type ICcard by using wireless power transmission system. The most difficult but important part of the passive type RF-ID system is building the system that supplies power from Reader-antenna to IDcard-antenna. To check what is the most efficient way to deliver power depending on what kind of specifications of the power-amp in reader, antenna and antenna in IDcard is for operating IDcard circuit efficiently receiving the power from reader-antenna. For this, we used 125kHz sinewave for RF signal as a basic specification, power-amp : OP-Amp for amplifying signal and AB Class push-pull power-amp for amplifying power, loop type antenna.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2281-2301
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• 2014

In wireless ad hoc networks the nodes focus on achieving the maximum SINR for efficient data transmission. In order to achieve maximum SINR the nodes culminate in exhausting the battery power for successful transmissions. This in turn affects the successful transmission of the other nodes as the maximum transmission power opted by each node serves as a source of interference for the other nodes in the network. This paper models the choice of power for each node as a non cooperative game where the throughput of the network with respect to the consumption of power is formulated as a utility function. We propose an adaptive pricing scheme that encourages the nodes to use minimum transmission power to achieve target SINR at the Nash equilibrium and improve their net utility in multiuser scenario.

• 조명전기설비학회논문지
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• 제26권1호
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• pp.75-81
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• 2012

In this paper, the wireless power transfer system using the magnetic resonance was designed, analyzed by circuit analysis methode and the calculated transfer function was compared with the measured one. The self-resonant coil was made up of the commonly used capacitor which had the lumped capacitance and it enabled the stable magnetic resonance not to be affected by the circumstance. The transmission efficiency of this system was 70[%] at the 15[cm] between the transmission and receiving coil and the measured transfer function was similar to the calculated one, which means the circuit analysis methode is valid in this system. When the intermediate coils were added between the transmission and receiving coil, the transmission efficiency was increased, which produced the increase of transfer distance. In the case of the five intermediate coils adding, the 35[%] transmission efficiency was achived at the 90[cm] distance.

• 반도체디스플레이기술학회지
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• 제14권4호
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• pp.88-91
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• 2015

In this paper, we have designed and fabricated a BPF (Band Pass Filter) for 5.8GHz Microwave Wireless Power Transmission. We $used{\lambda}g/2$ open-circuited stubs in addition to T-shaped transmission lines for the BPF. This BPF removes harmonics caused by diodes of RF-DC converter, and thus the RF-DC converter converts more RF power to the DC. The performance of the BPF was measured and shown through direct comparison of voltages converted by the doubler as a RF-DC Converter with and without the BPF.