• Title/Summary/Keyword: 다중 반송파

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Selective Mapping of Partial Tones (SMOPT) Scheme for PAR Reduction in OFDM Systems (OFDM 시스템에서 PAR을 줄이는 SMOPT 기법)

  • Yoo Seung soo;Yoon Seok ho;Kim Sun yong;Song Iick ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.4C
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    • pp.230-238
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    • 2005
  • An orthogonal frequency division multiplexing (OFDM) system consists of a number of independently modulated subcarriers and, thus, a high peak-to-average power ratio (PAR) can occur when the subcarriers are added coherently. The high PAR brings such disadvantages as an increased complexity of the analog-to-digital (ADC) and digital-to-analog (DAC) converters and a reduced efficiency of the radio frequency (RF) power amplifier. In this paper, we propose a novel PAR reduction scheme called selective mapping of partial tones (SMOPT). The SMOPT scheme has a reduced complexity, lower sensitivity to peak reduction tones (PRT) positions, and a shorter processing time as compared with the conventional tone reservation (TR) scheme. The performance of the SMOPT scheme is analyzed based on the IEEE 802.1la wireless local area network(WLAM) physical layer model. Numerical results show that the SMOPT scheme outperforms the TR scheme under various scenarios.

Research Trend on Continuous Variable Quantum Communication (연속 변수 양자 통신 연구 동향)

  • Kim, YoungJun;Ko, Young-chia
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2014.11a
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    • pp.224-225
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    • 2014
  • 본 논문에서는 양자 통신을 실제적인 환경에서 구현하고자 하는 노력의 일환으로 개발된 연속 변수 양자 통신 기법에 대해 소개한다. 연속 변수 양자 통신 전반에 대한 설명에 이어 이를 이용한 최신 응용 기술들을 소개한다. 연속 변수 환경에서 구현된 다중 접속 채널, 최소 제곱 예측법, 그리고 다중 반송파 기법을 소개하고 그 효과와 한계를 서술한다.

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PAPR Reduction for WPM Schemes using Filter Design Schemes (필터 설계 기법을 통한 WPM의 PAPR 감소에 관한 연구)

  • Lee, Kyu Seop;Choi, Gin Kyu
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.13 no.1
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    • pp.49-54
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    • 2013
  • WPM(Wavelet Packet Modulation) is multicarrier system which is suitable for high speed transmission. The main advantage of using the WPM system is the fact that the flexible system effectively can be realized by the combination of filter coefficient. On the other hand, the major problem of multicarrier system is known to be the high PAPR. In this paper we propose WPM system that has a minimum PAPR by using filter coefficient adjustment method. We first derive the filter coefficient equation and then select the coefficient that has a minimum PAPR. we conduct WPM system by using a selected coefficient and we demonstrate the system performance by using computer simulation.

Quantized Channel State Information Feedback Scheme for Multi-carrier Systems (다중 반송파 시스템을 위한 양자화된 채널 상태 정보 피드백 기법)

  • Seo Hee-Jung;Kim Seayoung;Kim Nak-Myeong;Kim Kiho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.12A
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    • pp.1146-1152
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    • 2005
  • In this paper, we propose a compressed quantized channel state information (CQCSI) feedback scheme for multi-carrier mobile communication systems. The proposed CQCSI figures out the contiguous subsequences of equal QCSI's as separate types of runs across the subcarriers, and then encodes the types of runs using a truncated Huffman coding algorithm. Computer simulation shows that the proposed algorithm can reduce the QCSI feedback up to one tenth of the uncompressed, while providing a comparable performance with the conventional QCSI feedback schemes. To cope with special cases when the frequency selective fading is very high, we also propose a restricted CQCSI feedback scheme. The restricted CQCSI feedback has been proved under vehicular B channel model.

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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Performance Analysis of OFDM for Wireless Communication Applications (이동 무선 통신 응용을 위한 OFDM의 성능 해석)

  • 김창선;김성곤;변건식
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.2
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    • pp.251-256
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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-OAM method is superior to M-PSK in OFDM systems in terms of the transmission methods.

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Performance Analysis of Coded-OFDM for Wireless Multimedia Communication (무선멀티미디어 통신을 위한 Coded-OFDM의 성능 해석)

  • 김창선;김성곤;이창호;변건식
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.3B
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    • pp.196-201
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    • 2002
  • OFDM(orthogonal Frequency Division Multiplex) modulates transmitting data with many carriers in parallel. As a result, high-speed data transmission is carried out and high spectral efficiency is provided by overlapping orthogonal frequencies. Therefore, OFDM is applied to many communication systems. In this paper, according to modulation methods(M-PSK and M-QAM), coded-OFDM wireless communication is simulated. Turbo code is used and two channels(virtual and real channel) are used. both channels have multipath delay spread, Gaussian noise, and peak power clipping. As a result of the simulation, coding gain is about 3dB and it is proved that M-QAM modulation is better than M-PSK. Start after striking space key 2 times.

Performance Degradation of OFDMA Systems owing to Multi-User Interference (OFDMA 시스템에서 다중 사용자 간섭에 의한 성능 열화)

  • Choi, Seung-Kuk
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.12
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    • pp.2226-2234
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    • 2016
  • Orthogonal Frequency Division Multiplexing (OFDM) technique uses multiple sub-carriers for the data transmission. Therefore, Inter Carrier Interference(ICI) is generated because of nonlinear high power amplifier and carrier frequency offset. Wireless OFDM transmission over Doppler fading channels also causes ICI. In OFDMA(Orthogonal Frequency Division Multiplexing Access), multiple sub-carriers are allocated to each user. Therefore, inter carrier interference causes interference to other users. I evaluate the BER performance of OFDMA systems in frequency selective fading channel, considering Multi-User Interference (MUI) owing to the carrier frequency offset, the nonlinear high power amplifier, and the Doppler fading. In the uplink OFDMA, multi-user interference introduces larger BER degradation than in the downlink. I explain the reason and obtain the required characteristics of the nonlinear amplifier and the value of frequency offset for good BER performance. And I also analyze the BER degradation upon Doppler fading channel.

A Study on OFDM Technique for High-speed Data Transmission in Underwater (수중에서 고속 데이터 전송을 위한 OFDM 기법 적용성 연구)

  • Han, Jeong-Woo;Kim, Se-Young;Kim, Ki-Man
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.10
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    • pp.1780-1786
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    • 2008
  • The performance of underwater wireless communication system is influenced on channel characteristic. Especially, a delay spread cause by reverberation and multi-path happen the ISI (Inter Symbol Interference) and reduces the communication performance. In this paper, we study the application of high speed data transmission in underwater to use the OFDM (Orthogonal Frequency Division Multiplexing) technique for robust the reverberation and multi-path. we confirm the performance of communication in underwater to use the model for actually underwater channel simulation model. As a result, we acquired the BER of modulation techniques. The BER of single carrier is $2{\times}10^{-1}$ and BER of multi currier is $8{\times}10^{-2}$ in 1000m. Transmission of single carrier is 5 kbps.