• Title, Summary, Keyword: CW 동기화

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Optimal CW Synchronization Scheme in IEEE 802.11 WLANs (IEEE 802.11 WLAN 환경에서 최적의 CW 공유 방안)

  • Lee, Jin-Lee;Lee, Su-Bin;Kyung, Yeunwoong
    • Journal of The Korea Internet of Things Society
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    • v.6 no.4
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    • pp.15-19
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    • 2020
  • In this paper, we propose a optimal CW(Conention Window) synchronization scheme in IEEE 802.11 WLANs. IEEE 802.11 WLANs support DCF(Distributed Coordination Function) mode for the MAC(Medium Access Control) operation. In DCF, the CW increases exponentially according to the collisions and becomes minimum CW according to the success of data transmissions. However, since the base minimum CW value is hardware or standard specific, the number of active stations and network status are not considered to determine the CW value. Even though the researches on optimal CW have beend conducted, they do not consider the optimal CW synchronization among mobile stations which occur network performance degradation. Therefore, this paper calculates the optimal CW value and shares it with mobile stations in the network.

A Study on the Synthetic Aperture Radar Processor using AOD/CCD (AOD/CCD를 이용한 합성개구면 레이다 처리기에 관한 연구)

  • 박기환;이영훈;이영국;은재정;박한규
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.19 no.10
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    • pp.1957-1964
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    • 1994
  • In this thesis, a Synthetic Aperture Rarar Processor that is possible real-time handling is implemented using CW(Continuose Wave) laser as a light source, CCD(charge Coupled Device) as a time integrator, and AOD(Acousto-Optic Device) as the space integrator. One of the advantages of the proposed system is that it does not require driving circuits of the light source. To implement the system, the linear frequency modulation(chirp) technique has been used for radar signal. The received data for the unit target was processed using 7.80 board and accompanying electronic circuits. In order to reduce the smear effect of the focused chirp signal which occurs Bragg diffrection angle of the AOD has been utilized to make sharp pulses of the laser source, and the pulse made synchronized with the chirp signal. Experiment and analysis results of the data and images detected from CCD of the proposed SAR system demonstrated that detection effect is degrated as the unit target distance increases, and the resolving power is improved as the bandwidth of the chirp signal increases. Also, as the pulse width of the light source decreases, the smear effect has been reduced. The experimental results assured that the proposed system in this papre can be used as a real time SAR processor.

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Novel 10 GHz Bio-Radar System Based on Frequency Multiplier and Phase-Locked Loop (주파수 체배기와 PLL을 이용한 10 GHz 생체 신호 레이더 시스템)

  • Myoung, Seong-Sik;An, Yong-Jun;Moon, Jun-Ho;Jang, Byung-Jun;Yook, Jong-Gwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.2
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    • pp.208-217
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    • 2010
  • This paper presents a novel 10 GHz bio-radar system based on a frequency multiplier and phase-locked loop(PLL) for non-contact measurement of heartbeat and respiration rates. In this paper, a 2.5 GHz voltage controlled oscillator (VCO) with PLL is employed to as a frequency synthesizer, and 10 GHz continuous wave(CW) signal is generated by using frequency multiplier from 2.5 GHz signal. This paper also presents the noise characteristic of the proposed system. As a result, a better performance and economical frequency synthesizer can be achieved with the proposed bio-radar system. The experimental results shows excellent bio-signal measurement up to 100 cm without any additional digital signal processing(DSP), and the proposed system is validated.