• Title/Summary/Keyword: 적응 변조

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Unproved AMC-MIMO Multiplexing Systems Using Selection Transmit Diversities (선택적 전송다이버시티를 사용한 개선된 AMC-MIMO 다중화시스템)

  • Kang, Min-goo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.7 no.4
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    • pp.652-657
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    • 2003
  • In this paper, Adaptive Modulation and Coding (AMC) is combined with Multiple Input Multiple Output (MIMO) multiplexing to improve the throughput performance of AMC. In addition, a system that adopts Selection Transmit Diversity (STD) in the AMC-MIMO multiplexing system is proposed. The received SNR is improved by adopting STD techniques. And it increases probability of selecting MCS (Modulation and Coding Scheme) level that supports higher data rate. This leads to an increased throughput of the AMC-MIMO system. STD in our simulation selects 2 transmission antennas from 4 antennas and AMC-MIMO multiplexing process operates with the selected antennas. The computer simulation is performed in flat Rayleigh fading channel. The results show that the proposed system achieves a gain of 1Mbps over the AMC-MIMO multiplexing system with the same number of antennas at 15dB SNR.

Design of Maritime Satellite Communication Systems Sharing Frequency with DVB-S2 (DVB-S2와 주파수 공유하는 해양 위성 통신 시스템 설계)

  • Ryu, Joon-Gyu;Oh, Deock-Gil;Yu, Heejung
    • Journal of Satellite, Information and Communications
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    • v.8 no.4
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    • pp.75-80
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    • 2013
  • In this paper, the Ka-band maritime satellite communication systems for mobile terminals are proposed. The design includes the link budget analysis, determination of modulation and coding schemes and the overall structure of a transmitter. To avoid the harmful effects on the existing DVB-S2 services, the proposed maritime satellite system using the same spectrum with DVB-S2 at the same time employs the very wideband spreading transmission. Additionally, omni-directional low-gain antennas should be equipped in a mobile terminal to reduce the system cost. These two considerations limit the maximum transmission rate of the proposed system. Due to the limitations, the proposed system includes 36 dB or 39 dB spreading gain depending on the modulation scheme and a link-adaptive repetition method depending on the level of rain attenuation. To support short packets with minimal performance loss, the turbo code used in 3GPP instead of LDPC(low density parity check code) is adopted. By combining them, the overall structure of low-rate maritime satellite communication system is designed.

Efficient Adaptive Modulation Technique for Multiuser OFDMA Systems (다중 사용자 OFDMA 시스템에서의 효율적인 적응 변조 및 부호화 기법)

  • Kwon, Jung-Hyoung;Rhee, Do-Ho;Byun, Il-Mu;Whang, Keum-Chan;Kim, Kwang-Soon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.12C
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    • pp.1240-1248
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    • 2006
  • In this paper, we present a new method for user selection, sub-band allocation, and power allocation in order to maximize the system throughput under the constraint of transmit power in multiuser downlink orthogonal frequency division multiple access (OFDMA) systems with partial channel quality information (CQI). In previous schemes, each user in one cell transmits CQI of all sub-bands to the base station, which requires enormous feedback overhead. Therefore, we proposed an efficient power allocation and modulation and coding selection scheme in which each user transmits partial CQI and one additional information to reduce the amount of feedback. Simulation results show that we can greatly reduce the amount of feedback than full feedback system.

An Optical Quenching and Efficiency of Laser for the Virtual Display System (허상 디스플레이에 적용되는 레이저 다이오드의 출력 효율과 파장 변이에 대한 연구)

  • Chi, Yongseok
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.9
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    • pp.129-134
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    • 2016
  • This paper studies the high frequency PWM (pulse width modulation) driving technique to increase an optical efficiency and to prevent an optical color quenching of blue laser for head up display on vehicles using digital micro mirror device (DMD) panel and yellow phosphor wheel. The proposed approach adaptively drives the current pulse width modulated signals of high optical power of blue laser to increase the lifetime and to decrease the stem temperature of laser. This method stabilizes the temperature of laser according to the driving environment and the forward current capacity. By the proposed method, the brightness of blue laser is improved by about 37% compared to the continuous waveform current driving method.

Analysis of Nonlinearity of RF Amplifier and Back-Off Operations on the Multichannel Wireless Transmission Systems. (다 채널 무선 전송 시스템의 RF증폭기의 비선형 및 백-오프 동작 분석)

  • 신동환;정인기;이영철
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.8 no.1
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    • pp.18-27
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    • 2004
  • In this paper, we presents an analytical simulation procedure for evaluation in baseband digital modulated signals distortions in the present of RF power amplifier(SSPA) nonlinear behavior and backoff operations of OFDM wireless transmission system. we obtained the optimum nonlinear transfer function of designed SSPA with the SiGe HBT bias currents of OFDM multi-channel wireless transmission system and compared this transfer function to SSPA nonlinear modeling functions mathematically, we finds optimum bias conditions of designed SSPA. With the derived nonlinear modeling function of SSPA, We analysed the PSD characteristics of in-band and out-band output powers of SSPA EVM measurement results of distorted constellation signals with the input power levels of SSPA. The results of paper can be applied to find the SSPA linearly with optimum bias currents and determine the SSPA input backoff bias for AGC control circuits of SSPA.

Controlling the Intensity Distribution of Light at the Output of a Multimode Optical Fiber Using a Polar-coordinate-based Transmission-matrix Method (극좌표 기반 투과 매트릭스 방법을 이용한 다중모드 광섬유 출력단에서의 빛의 세기 분포 제어)

  • Park, Jaedeok;Jo, Jaepil;Yoon, Jonghee;Yeom, Dong-Il
    • Korean Journal of Optics and Photonics
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    • v.33 no.6
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    • pp.252-259
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    • 2022
  • We have conducted a study to control the light-intensity distribution at the output end of a multimode optical fiber via estimating the transmission matrix. A circularly arranged Hadamard eigenmode phase distribution was implemented using a spatial light modulator, and the transmission matrix of a multimode optical fiber was experimentally obtained using a four-phase method. Based on the derived transmission matrix, the spatial phase distribution of light incident upon the optical fiber was adjusted via the spatial light modulator in advance, to focus the light at a desired position at the optical fiber output. The light could be focused with an intensity up to 359.6 times as high as that of the surrounding background signal at a specific position of the multimode fiber's output end, and the intensity of the focused beam was on average 104.6 times as large as that of the background signal, across the area of the multimode fiber's core.

The Optimal Turbo Coded V-BLAST Technique in the Adaptive Modulation System corresponding to each MIMO Scheme (적응 변조 시스템에서 각 MIMO 기법에 따른 최적의 터보 부호화된 V-BLAST 기법)

  • Lee, Kyung-Hwan;Ryoo, Sang-Jin;Choi, Kwang-Wook;You, Cheol-Woo;Hong, Dae-Ki;Kim, Dae-Jin;Hwang, In-Tae;Kim, Cheol-Sung
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.6 s.360
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    • pp.40-47
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    • 2007
  • In this paper, we propose and analyze the Adaptive Modulation System with optimal Turbo Coded V-BLAST(Vertical-Bell-lab Layered Space-Time) technique that adopts the extrinsic information from MAP (Maximum A Posteriori) Decoder with Iterative Decoding as a priori probability in two decoding procedures of V-BLAST; the ordering and the slicing. Also, we consider and compare the Adaptive Modulation System using conventional Turbo Coded V-BLAST technique that is simply combined V-BLAST with Turbo Coding scheme and the Adaptive Modulation System using conventional Turbo Coded V-BLAST technique that is decoded by the ML (Maximum Likelihood) decoding algorithm. We observe a throughput performance and a complexity. As a result of a performance comparison of each system, it has been proved that the complexity of the proposed decoding algorithm is lower than that of the ML decoding algorithm but is higher than that of the conventional V-BLAST decoding algorithm. however, we can see that the proposed system achieves a better throughput performance than the conventional system in the whole SNR (Signal to Noise Ratio) range. And the result shows that the proposed system achieves a throughput performance close to the ML decoded system. Specifically, a simulation shows that the maximum throughput improvement in each MIMO scheme is respectively about 350 kbps, 460 kbps, and 740 kbps compared to the conventional system. It is suggested that the effect of the proposed decoding algorithm accordingly gets higher as the number of system antenna increases.

Proof-of-principle Experimental Study of the CMA-ES Phase-control Algorithm Implemented in a Multichannel Coherent-beam-combining System (다채널 결맞음 빔결합 시스템에서 CMA-ES 위상 제어 알고리즘 구현에 관한 원리증명 실험적 연구)

  • Minsu Yeo;Hansol Kim;Yoonchan Jeong
    • Korean Journal of Optics and Photonics
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    • v.35 no.3
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    • pp.107-114
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    • 2024
  • In this study, the feasibility of using the covariance-matrix-adaptation-evolution-strategy (CMA-ES) algorithm in a multichannel coherent-beam-combining (CBC) system was experimentally verified. We constructed a multichannel CBC system utilizing a spatial light modulator (SLM) as a multichannel phase-modulator array, along with a coherent light source at 635 nm, implemented the stochastic-parallel-gradient-descent (SPGD) and CMA-ES algorithms on it, and compared their performances. In particular, we evaluated the characteristics of the CMA-ES and SPGD algorithms in the CBC system in both 16-channel rectangular and 19-channel honeycomb formats. The results of the evaluation showed that the performances of the two algorithms were similar on average, under the given conditions; However, it was verified that under the given conditions the CMA-ES algorithm was able to operate with more stable performance than the SPGD algorithm, as the former had less operational variation with the initial phase setting than the latter. It is emphasized that this study is the first proof-of-principle demonstration of the CMA-ES phase-control algorithm in a multichannel CBC system, to the best of our knowledge, and is expected to be useful for future experimental studies of the effects of additional channel-number increments, or external-phase-noise effects, in multichannel CBC systems based on the CMA-ES phase-control algorithm.

On Adaptive Narrowband Interference Cancellers for Direct-Sequence Spread-Spectrum Communication Systems (주파수대역 직접 확산 통신시스템에서 협대역 간섭 신호 제거를 위한 적응 간섭제거기에 관한 연구)

  • 장원석;이재천
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.10C
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    • pp.967-983
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    • 2003
  • In wireless spread-spectrum communication systems utilizing PN (pseudo noise) sequences, a variety of noise sources from the channel affect the data reception performance. Among them, in this paper we are concerned with the narrowband interference that may arise from the use of the spectral bands overlapped by the existing narrowband users or the intentional jammers as in military communication. The effect of this interference can be reduced to some extent at the receiver with the PN demodulation by processing gain. It is known, however, that when the interferers are strong, the reduction cannot be sufficient and thereby requiring the extra use of narrowband interference cancellers (NIC's) at the receivers. A class of adaptive NIC's are studied here based on different two cost functions. One is the chip mean-squared error (MSE) computed prior to the PN demodulation and used in the conventional cancellers. Since thses conventional cancellers should be operated at the chip rate, the computational requirements are enormous. The other is the symbol MSE computed after the PN demodulation in which case the weights of the NIC's can be updated at a lot lower symbol rate. To compare the performance of these NIC's, we derive a common measure of performance, i.e., the symbol MSE after the PN demodulation. The analytical results are verified by computer simulation. As a result, it is shown that the cancellation capability of the symbol-rate NIC's are similar or better than the conventional one while the computational complexity can be reduced a lot.

Long-range multiple-input-multiple-output underwater communication in deep water (심해에서의 장거리 다중입출력 수중통신)

  • Kim, Donghyeon;Kim, Daehwan;Kim, J.S.;Hahn, Joo Young
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.5
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    • pp.417-427
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    • 2021
  • Long-range communication in deep waters must overcome the low data rate due to limited bandwidth. This paper presents the performance of Multiple-Input-Multiple-Output (MIMO) system to increase the data rate. In MIMO system, communication performance is degraded by crosstalk between users and an adaptive passive Time Reversal Processing (TRP) is widely used to eliminate this. In October 2018, long-range underwater acoustic communication experiment was conducted in deep water (1,000 m ~) off the east of Pohang, South Korea. During the experiment, a vertical line array was utilized and communication signals modulated by binary phase shift keying and quadrature phase shift keying with a symbol rate of 512 sps were transmitted. To generate MIMO communication signals, received signals from ranges of 26 km and 30 km is synthesized. Compared to the conventional passive TRP, the adaptive passive TRP eliminates the crosstalk between users and achieves error-free performance with an increase of output signal-to-noise ratio. Therefore, two users separated by 4 km in range achieves an aggregate data rate of 1,024 symbols/s.