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  • Title/Summary/Keyword: Optimal modulation control

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Improvement of Received Optical Power Sensitivity in Asymmetric 2.5Gbps/1.2Gbps Passive Optical Network with Inverse Return to Zero(RZ) coded Downstream and NRZ upstream re-modulation (역 RZ 부호로 코딩된 하향신호의 재변조를 이용한 비대칭 2.5Gbps/622Mbps 수동 광가입자 망에서의 수신 감도의 개선)

  • Park, Sang-Jo
    • Journal of the Korea Society of Computer and Information
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    • v.15 no.3
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    • pp.65-72
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    • 2010
  • We propose the asymmetric 2.5Gbps/622Mbps PON(Passive Optical Network) in order to reduce the bandwith of filter at receiver with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation. I theoretically analyze BER(Bit Error Rate) performance and the power sensitivity with the optimal threshold level by performing simulation with MATLAB according to the types of downstream data. The results have shown that the optimal threshold level at the optical receiver could be saturated at 0.33 as the optical received power increase more than -26dBm to keep 1012 of BER to a minimum. Also the power sensitivity is more improved by about 3dB by fixing the threshold level at 0.33 than the conventional receiver. The proposed system can be a useful technology for optical access networks with asymmetric upstream and downstream data rates because the optical receiver can be used without controlling threshold levels and that does not require a light source in optical network unit (ONU) and its control circuits in the optical line termination (OLT).

Modelling a Stand-Alone Inverter and Comparing the Power Quality of the National Grid with Off-Grid System

  • Algaddafi, Ali;Brown, Neil;Rupert, Gammon;Al-Shahrani, Jubran
    • IEIE Transactions on Smart Processing and Computing
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    • v.5 no.1
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    • pp.35-42
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    • 2016
  • Developments in power electronics have enabled the widespread application of Pulse Width Modulation (PWM) inverters, notably for connecting renewable systems to the grid. This study demonstrates that a high-quality power can be achieved using a stand-alone inverter, whereby the comparison between the power quality of the stand-alone inverter with battery storage (off-grid) and the power quality of the utility network is presented. Multi-loop control techniques for a single phase stand-alone inverter are used. A capacitor current control is used to give active damping and enhance the transient and steady state inverter performance. A capacitor current control is cheaper than the inductor current control, where a small current sensing resistor is used. The output voltage control is used to improve the system performance and also control the output voltage. The inner control loop uses a proportional gain current controller and the outer loop is implemented using internal model control proportional-integral-derivative to ensure stability. The optimal controls are achieved by using the Sisotool tool in MATLAB/Simulink. The outcome of the control scheme of the numerical model of the stand-alone inverter has a smooth and good dynamic performance, but also a strong robustness to load variations. The numerical model of the stand-alone inverter and its power quality are presented, and the power quality is shown to meet the IEEE 519-2014. Furthermore, the power quality of the off-grid system is measured experimentally and compared with the grid power, showing power quality of off-grid system to be better than that of the utility network.

A Mock Running And Transient State Test of Propulsion VVVF Inverter for Electric Locomotive using A Inertia Load (관성부하를 이용한 전동차 추진용 VVVF 인버터의 모의주행 및 과도상태시험)

  • 정만규;서광덕
    • The Transactions of the Korean Institute of Power Electronics
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    • v.4 no.6
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    • pp.491-499
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    • 1999
  • This paper is on the high perfonnance propulsion IGBT VVVF inverter adopted new technique for railways. To prove the high performance and stabilit~r of traction, running tests are carried out under the simulated condition alike real field. The tests are perfonned on not only a steady states but also a transient states such a as input voltage variation using inertia load equivalent to 160tons train. The vector control technique is a adopted to improve traction for 4 motors. The low switching synchronous PW1\l method based on a space v voltage vector modulation is pro\XlSed as the optimal method for propulsion system railway. The output voltage l is controlled continuously to six step by prolxlsed ovennodu]ation technique without sudden torque variation.

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Feasibility on Statistical Process Control Analysis of Delivery Quality Assurance in Helical Tomotherapy (토모테라피에서 선량품질보증 분석을 위한 통계적공정관리의 타당성)

  • Kyung Hwan, Chang
    • Journal of radiological science and technology
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    • v.45 no.6
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    • pp.491-502
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    • 2022
  • The purpose of this study was to retrospectively investigate the upper and lower control limits of treatment planning parameters using EBT film based delivery quality assurance (DQA) results and to analyze the results of statistical process control (SPC) in helical tomotherapy (HT). A total of 152 patients who passed or failed DQA results were retrospectively included in this study. Prostate (n = 66), rectal (n = 51), and large-field cancer patients, including lymph nodes (n = 35), were randomly selected. The absolute point dose difference (DD) and global gamma passing rate (GPR) were analyzed for all patients. Control charts were used to evaluate the upper and lower control limits (UCL and LCL) for all the assessed treatment planning parameters. Treatment planning parameters such as gantry period, leaf open time (LOT), pitch, field width, actual and planning modulation factor, treatment time, couch speed, and couch travel were analyzed to provide the optimal range using the DQA results. The classification and regression tree (CART) was used to predict the relative importance of variables in the DQA results from various treatment planning parameters. We confirmed that the proportion of patients with an LOT below 100 ms in the failure group was relatively higher than that in the passing group. SPC can detect QA failure prior to over dosimetric QA tolerance levels. The acceptable tolerance range of each planning parameter may assist in the prediction of DQA failures using the SPC tool in the future.

Novel Gain Control Scheme for VLC systems (VLC 시스템의 새로운 이득 제어)

  • Lee, Sun Yui;Jung, Kuk Hyun;Hwang, Yu Min;Lee, Sung Hun;Kim, Jin Young
    • Journal of Satellite, Information and Communications
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    • v.9 no.3
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    • pp.41-46
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    • 2014
  • In this paper, a transceiver of VLC (Visible Light Communication) using LED white lighting has been implemented. We analyzed differences between conventional wireless communication and VLC with high-speed data transmission in a variety of environments, and confirmed symbols which passed through a channel using QAM. In order to get a high data rate, we found some variables that should be considered essentially though experiments. In addition, we set a bandwidth and found an optimal gain according to the distance between transmitter and receiver. We analyzed proposed system model through Labview and finally showed a system performance. The performance showed a 2Mbps QAM data rate in real visible light indoor channels.

Novel Gain Control Scheme of Efficient Signal Detection Technique for Multiple Access VLC Systems (다중 접속 가시광 통신을 위한 신호 검출 기법의 게인 조절)

  • Lee, Sun Yui;Kim, Jin Young
    • Journal of Satellite, Information and Communications
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    • v.11 no.1
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    • pp.32-36
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    • 2016
  • In this paper, a transceiver of VLC (Visible Light Communication) using LED white lighting has been implemented. We analyzed differences between conventional wireless communication and VLC with high-speed data transmission in a variety of environments, and confirmed symbols which passed through a channel using QAM. In order to get a high data rate, we found some variables that should be considered essentially though experiments. In addition, we set a bandwidth and found an optimal gain according to the distance between transmitter and receiver. We analyzed proposed system model through Labview and finally showed a system performance and to efficient data transmission and detection for VLC, we apply the orthogonal sequences to VLC system.

Design of a Digital Burst MODEM for High-Speed ATM Satellite Communications Part I : Analysis of Synchronization Techniques (고속 ATM 위성통신을 위한 TDMA 버스트 모뎀 설계 1부 : 수신기 동기기술 분석)

  • Hwang, Sung-Hyun;Kim, Ki-Yun;Choi, Hyung-Jin
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.35S no.10
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    • pp.34-41
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    • 1998
  • In this paper, we evaluate synchronization techniques suitable for high-speed ATM satellite communications with a transmission rate of 155Mbit/s, and propose optimal algorithms that improve the tracking performance, where QPSK is selected for a modulation scheme, and the receiver is operated in burst mode. Based on these asumptions, we proposed modified algorithms and architectures for automatic frequency control(AFC), carrier recovery(CR), and symbol timing recovery(STR) for burst acquisition. Analysis is performed under AWGN environments with respect to the number of required symbol, steady-state stability, and hardware implementation for the proposed algorithms.

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Selection of Cross-layered Retransmission Schemes based on Service Characteristics (서비스 특성을 고려한 다 계층 재전송 방식 선택)

  • Go, Kwang-Chun;Kim, Jae-Hyun
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.5
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    • pp.3-9
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    • 2015
  • The wireless communication system adopts an appropriate retransmission scheme on each system protocol layer to improve reliability of data transmission. In each system protocol layer, the retransmission scheme operates in independently other layers and operates based on the parameters without reference to end-to-end performance of wireless communication system. For this reason, it is difficult to design the optimal system parameters that satisfy the QoS requirements for each service class. Thus, the performance analysis of wireless communication system is needed to design the optimal system parameters according to the end-to-end QoS requirements for each service class. In this paper, we derive the mathematical model to formulate the end-to-end performance of wireless communication system. We also evaluate the performance at the MAC and transport layers in terms of average spectral efficiency and average transmission delay. Based on the results of performance evaluations, we design the optimal system parameters according to the QoS requirements of service classes. From the results, the HARQ combined with AMC is appropriate for the delay-sensitive service and the ARQ combined with AMC is appropriate for a service that is insensitive to transmission delay. Also, the TCP can be applied for the delay-insensitive service only.

Comparison of Retinal Ganglion Cell Responses to Different Voltage Stimulation Parameters in Normal and rd1 Mouse Retina (정상망막과 변성망막에서 전압자극 파라미터 변화에 따른 망막신경절세포의 반응 비교)

  • Ye, Jang-Hee;Ryu, Sang-Baek;Kim, Kyung-Hwan;Goo, Yong-Sook
    • Progress in Medical Physics
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    • v.21 no.2
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    • pp.209-217
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    • 2010
  • Retinal prostheses are being developed to restore vision for the blind with retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Since retinal prostheses depend upon electrical stimulation to control neural activity, optimal stimulation parameters for successful encoding of visual information are one of the most important requirements to enable visual perception. Therefore, in this paper, we focused on retinal ganglion cell (RGC) responses to different voltage stimulation parameters and compared threshold charge densities in normal and rd1 mice. For this purpose, we used in vitro preparation for the retina of normal and rd1 mice on micro-electrode arrays. When the neural network of rd1 mouse retinas is stimulated with voltage-controlled pulses, RGCs in degenerated retina also respond to voltage amplitude or voltage duration modulation as well in wild-type RGCs. But the temporal pattern of RGCs response is very different; in wild-type RGCs, single peak within 100 ms appears while in RGCs in degenerated retina multiple peaks (~4 peaks) with ~10 Hz rhythm within 400 ms appear. The thresholds for electrical activation of RGCs are overall more elevated in rd1 mouse retinas compared to wild-type mouse retinas: The thresholds for activation of RGCs in rd1 mouse retinas were on average two times higher (70.5099.87μC/cm2 vs. 37.2361.65μC/cm2) in the experiment of voltage amplitude modulation and five times higher (120.5170.6μC/cm2 vs. 22.6937.57μC/cm2) in the experiment of voltage duration modulation than those in wild-type mouse retinas. This is compatible with the findings from human studies that the currents required for evoking visual percepts in RP patients is much higher than those needed in healthy individuals. These results will be used as a guideline for optimal stimulation parameters for upcoming Korean-type retinal prosthesis.

Optimized Low-Switching-Loss PWM and Neutral-Point Balance Control Strategy of Three-Level NPC Inverters

  • Xu, Shi-Zhou;Wang, Chun-Jie;Han, Tian-Cheng;Li, Xue-Ping;Zhu, Xiang-Yu
    • Journal of Power Electronics
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    • v.18 no.3
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    • pp.702-713
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    • 2018
  • Power loss reduction and total harmonic distortion(THD) minimization are two important goals of improving three-level inverters. In this paper, an optimized pulse width modulation (PWM) strategy that can reduce switching losses and balance the neutral point with an optional THD of three-level neutral-point-clamped inverters is proposed. An analysis of the two-level discontinuous PWM (DPWM) strategy indicates that the optimal goal of the proposed PWM strategy is to reduce switching losses to a minimum without increasing the THD compared to that of traditional SVPWMs. Thus, the analysis of the two-level DPWM strategy is introduced. Through the rational allocation of the zero vector, only two-phase switching devices are active in each sector, and their switching losses can be reduced by one-third compared with those of traditional PWM strategies. A detailed analysis of the impact of small vectors, which correspond to different zero vectors, on the neutral-point potential is conducted, and a hysteresis control method is proposed to balance the neutral point. This method is simple, does not judge the direction of midpoint currents, and can adjust the switching times of devices and the fluctuation of the neutral-point potential by changing the hysteresis loop width. Simulation and experimental results prove the effectiveness and feasibility of the proposed strategy.