• Title/Summary/Keyword: high-order modulation

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Soft Decision Detection Method for Turbo-coded STBC Using High-order Modulation Schemes (고차원 변조 방식에서의 터보 부호화된 시공간 블록 부호 기술을 위한 최적의 연판정 검출 방법)

  • Kim, Young-Min;Kim, Soo-Young
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.6C
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    • pp.562-571
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    • 2010
  • Forward error correction (FEC) coding schemes using iterative soft decision detection (SDD) information are mandatory in most of the next generation wireless communication system, in order to combat inevitable channel imparirnents. At the same time, space-time block coding (STBC) schemes are used for the diversity gain. Therefore, SDD information has to be fed into FEC decoder. In this paper, we propose efficient SDD methods for turbo-coded STBC system using high order modulation such as QAM. We present simulation results of various SDD schemes for turbo-coded STBC systems, and show that the proposed methods can provide almost approximating performance to maximum likelihood detection with much less computational load.

Optimal Control of Dynamic Positioned Vessel Using Kalman Filtering Techniques (칼만필터를 이용한 부유체운동의 최적제어)

  • Lee, Pan-Muk;Lee, Sang-Mu;Hong, Sa-Yeong
    • Journal of Ocean Engineering and Technology
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    • v.2 no.2
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    • pp.37-45
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    • 1988
  • A dynamically positioned vessel must be capable of maintaining a specified position and direction by controlling the thruster devices. The motions of a vessel are often assuned to tne sum of low frequency(LF)motions and high frequency(HF)motions. The former is mainly due to wind, current and second order wave forces, while the latter is mainly due to first order wave forces. In order to avoid the high frequency thruser modulation, the control system must include filters to estimate the low frequency motions from the measured motion signals, This paper presents a control system based on Kalman filtering technique and optimal control tyeory. Using the combined kalmam filter, LF motion estimates and HF ones are achieved from the motion measurement of the vessel. The estimated low frequency motions are used as inputs to the dynamic positioning system. The thruster modulation is minimized using the optimal control theory; Linear Quadratic Gaussian(LQG)controller. The performances of the Kalman filter and the dynamic positioned vessel are investigated by computer simulation.

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Fundamental second-order and third-order Nonlinear Distortions in Semiconductor Lasers (반도체 레이저에서의 2차 및 3차 비선형 왜곡의 특성)

  • 이경식;문용수
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.5
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    • pp.18-26
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    • 1994
  • We express fundamental second-order and third- order harmonic distortions and intermodulation distortions in terms of the laser parameters. Compared to the Darcie `s result only limited to the high frequency (f >1GHz), these expression are quite valid in the entire modulation frequency region. It is found that the fundamental nonlinear distortions are strongly effected by the spontaneous emission to lasing mode as well as the gain compresion damping in the low frequency region.

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High Efficiency Strategy of High Input Voltage SMPS (고전압 입력용 SMPS의 고효율 전략)

  • Woo, Dong-Young;Park, Seong-Mi;Park, Sung-Jun
    • Journal of the Korean Society of Industry Convergence
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    • v.22 no.3
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    • pp.365-371
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    • 2019
  • Recently, the demonstration and research on the power transmission using high voltage DC such as HVDC(High Voltage DC), Smart Grid, DC transmission and distribution have been actively conducted. In order to control the power converter in high-voltage DC power transmission system, SMPS(Switching Modulation Power Supply) for power converter control using high-voltage DC input is essential. However, the demand for high-pressure SMPS is still low, so the development is not enough. In the low-output SMPS using the high-voltage input, it is difficult to achieve high efficiency due to the switching transient loss especially at light load. In this paper, we propose a new switching scheme for high power SMPS control for low output power. The proposed method can provide better efficiency increase effect in the light load region compared to the existing PWM method. To verify the feasibility of the proposed method, a 40 W SMPS for HVDC MMC(Modulation Multi-level Converter) was designed and verified by simulation.

Dynamic Modulation Transfer Function Analysis of Images Blurred by Sinusoidal Vibration

  • Du, Yanlu;Ding, Yalin;Xu, Yongsen;Sun, Chongshang
    • Journal of the Optical Society of Korea
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    • v.20 no.6
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    • pp.762-769
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    • 2016
  • The dynamic modulation transfer function (MTF) for image degradation caused by sinusoidal vibration is formulated based on a Bessel function of the first kind. The presented method makes it possible to obtain an analytical MTF expression derived for arbitrary frequency sinusoidal vibration. The error obtained by the use of finite order sum approximations instead of infinite sums is investigated in detail. Dynamic MTF exhibits a stronger random behavior for low frequency vibration than high frequency vibration. The calculated MTFs agree well with the measured MTFs with the slant edge method in imaging experiments. With the proposed formula, allowable amplitudes of any frequency vibration are easily calculated. This is practical for the analysis and design of the line-of-sight stabilization system in the remote sensing camera.

Multi-step Modulation Techniques in PWM Inverter for a Variable-Speed Induction Motor Driving (가변속 유도전동기의 구동을 위한 PWM인버터의 다단변조 기법)

  • 박충규;정헌상;김국진;정을기;손진근
    • The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.6 no.6
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    • pp.32-41
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    • 1992
  • In this paper, an advanced Pulse Width Modulation Inverter strategy for driving a variable-speed induction motor is introduced. A switching pattern making use of the near-proportionality of voltage and frequency in AC machines operating with constant flux was computed. At low magnitudes and ow frequencies of the fundamental, many more harmonics are eliminated than at high magnitudes and frequencies. In order to keep the inverter switching frequency constant over the output frequency range, the chopping frequency is diminished as the frequency of the fundamental increases. Using these modulation strategy, the harmonics components of PWM inverter are efficiently eliminated.

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Improved Differential Detection Scheme of Space Time Trellis Coded MDPSK For MIMO (MIMO에서 시공간 부호화된 MDPSK의 성능을 향상시키기 위한 차동 검파 시스템)

  • Kim, Chong-Il;Lee, Ho-Jin;Yoo, Hang-Youal;Kim, Jin-Yong;Kim, Seung-Youal
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • v.9 no.2
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    • pp.164-167
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    • 2005
  • Recently, STC techniques have been considered to be candidate to support multimedia services in the next generation mobile radio communications and have been developed the many communications systems in order to achieve the high data rates. In this paper, we propose the Trellis-Coded Differential Space Time Modulation system with multiple symbol detection. The Trellis-code performs the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER performance without sacrificing bandwidth and power efficiency.

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CACB-Q2PSK Modulation for Efficient Bandwidth Utilization and Constant Amplitude Signal Transmission (효율적인 대역폭 이용과 정진폭 신호 전송을 위한 CACB-Q2PSK 변조)

  • Hong, Dae-Ki
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.1
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    • pp.93-99
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    • 2008
  • In this paper, we propose new modulation schemes using the conventional CACB modulation with constant amplitude property. Also the proposed modulation schemes supports high transmission data rate by increasing the spectral efficiency. In order to obtain the high spectral efficiency, the $Q^2$PSK and CA-$Q^2$PSK are used. We explain the simplest combining modulation scheme of CACB and $Q^2$PSK (i.e., CACB-$Q^2$PSK). However, this modulation scheme cannot support the constant amplitude property. Hence the first CACB-CA-$Q^2$PSK (or CACB-CA-$Q^2$PSK I) modulation scheme is proposed for the constant amplitude property. In the modulation scheme, the redundant constant amplitude encoding (spectral efficiency decrease) is required. Therefore, the second CACB-CA-$Q^2$PSK (or CACB-CA-$Q^2$PSK II) modulation scheme is proposed retaining the constant amplitude and the spectral efficiency. Computer simulations show that the proposed CACB-CA-$Q^2$PSK II is the efficient modulation scheme.

Natural Balancing of the Neutral Point Potential of a Three-Level Inverter with Improved Firefly Algorithm

  • Gnanasundari, M.;Rajaram, M.;Balaraman, Sujatha
    • Journal of Power Electronics
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    • v.16 no.4
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    • pp.1306-1315
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    • 2016
  • Modern power systems driven by high-power converters have become inevitable in view of the ever increasing demand for electric power. The total power loss can be reduced by limiting the switching losses in such power converters; increased power efficiency can thus be achieved. A reduced switching frequency that is less than a few hundreds of hertz is applied to power converters that produce output waveforms with high distortion. Selective harmonic elimination pulse width modulation (SHEPWM) is an optimized low switching frequency pulse width modulation method that is based on offline estimation. This method can pre-program the harmonic profile of the output waveform over a range of modulation indices to eliminate low-order harmonics. In this paper, a SHEPWM scheme for three-phase three-leg neutral point clamped inverter is proposed. Aside from eliminating the selected harmonics, the DC capacitor voltages at the DC bus are also balanced because of the symmetrical pulse pattern over a quarter cycle of the period. The technique utilized in the estimation of switching angles involves the firefly algorithm (FA). Compared with other techniques, FA is more robust and entails less computation time. Simulation in the MATLAB/SIMULINK environment and experimental verification in the very large scale integration platform with Spartan 6A DSP are performed to prove the validity of the proposed technique.

Performance of OFDM wireless communication system for modulation techniques (변조방식에 따른 OFDM 무선통신 시스템의 성능평가)

  • 김창선;김성곤;변건식
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2001.05a
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    • pp.741-744
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    • 2001
  • In this study, a OFDM mode, unlike traditional single carrier mode, is that a great number of carrier in multi-channel environment is transmitted by modulating objective Data parallel in order to execute high speed Data translation and make frequency orthogonal to offer high spectrum efficiency. As a result, this method is adopted to a variety of fields and is being actively studied. In this papers, the efficiency of OFDM wireless-communication systems is evaluated by modulation methods through computer simulation. M-PSK and M-QAM are used as modulation methods. The simulation is executed in a real channel and a virtual channel included multi-path, AWGN, Peak Power clipping, Frame Start Time Error As a result of simulation, it is confirmed that M-QAM method is superior to M-PSK in OFDM systems in terms of the transmission methods.

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