• Title/Summary/Keyword: Quadrature Amplitude Modulation

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A Method to Avoid Mutual Interference in a Cooperative Spectrum Sharing System

  • Tran, Truc Thanh;Kong, Hyung Yun
    • Journal of Communications and Networks
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    • v.16 no.2
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    • pp.110-120
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    • 2014
  • This article proposes a spectrum sharing method which can avoid the mutual interference in both primary and secondary systems. The two systems make them a priority to use two single-dimension orthogonal signals, the real and imaginary pulse amplitude modulation signals, if the primary system is not in outage with this use. A secondary transmitter is selected to be the primary relay and the active secondary source to perform this. This allows a simultaneous spectrum access without any mutual interference. Otherwise, the primary system attempts to use a full two-dimensional signal, the quadrature amplitude modulation signal. If there is no outage with respect to this use, the secondary spectrum access is not allowed. When both of the previous attempts fail, the secondary system is allowed to freely use the spectrum two whole time slots. The analysis and simulation are provided to analyze the outage performance and they validate the considerable improvement of the proposed method as compared to the conventional one.

Design and Implementation of phase sensitive RF Modulator/Demodulator using Amplitude Modulation (진폭변조방식을 이용한 Phase Sensitive RF Modulator/Demodulator의 설계 및 제작)

  • Kim, Jun-Woo;Chung, Jae-Ho;Mun, Chi-Woong;Oh, Chang-Hyun;Yi, Yun
    • Proceedings of the KOSOMBE Conference
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    • v.1995 no.05
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    • pp.167-170
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    • 1995
  • A quadrature-channel MODEM using amplitude modulation was constructed. To test the MODEM, 6.4 MHz sinusoidal wave 1 KHz triangular wave were modulated, then the modulated signal was fed into the demodulator, to reconstruct the triangular wave.

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PAPR Improvement of OFDM-CQAM System through Optimum Position based Impulse Insertion in Frequency Domain (주파수영역 최적위치기반 임펄스 삽입에 따른 OFDM-CQAM 시스템의 PAPR 개선)

  • Kwak, Jae-min
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2019.05a
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    • pp.597-599
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    • 2019
  • When frequency domain high amplitude impulse is inserted before IFFT in OFDM transmitter, the PAPR of OFDM signal in tme domain can be effectively reduced. In this paper, the degree of PAPR improvement of OFDM communication system with CQAM subcarrier modulation is analysed by adopting impulse insertion technique before IFFT of transmitter. Furthermore, it is verified that additional PAPR performance improvement can be obtained by finding optimum position of impulse insertion for maximizing PAPR reduction.

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Performance of a 3-Dimensional Signal Transmission System (3차원 신호 전송시스템의 성능)

  • Kwon, Hyeock Chan;Kang, Seog Geun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.11
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    • pp.2021-2026
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    • 2016
  • In this paper, a system model for transmission of 3-dimensional (3-D) signals is presented and its performance is analyzed. Unlike 2-D signals, no quadrature form expression for the 3-D signals is available. Exploiting a set of orthogonal basis functions, the 3-D signals are transmitted. As a result of computer simulation using very higher-level signal constellations, the 3-D transmission system has significantly improved error performance as compared with the 2-D system. It is considered that the principal reason for such performance improvement is much increased minimum Euclidean distance (MED) of the 3-D lattice constellations compared with the corresponding 2-D ones. When the MEDs of 2-D and 3-D lattice constellation are compared to confirm the analysis, the MED of 3-D 1024-ary constellation is around 2.6 times larger than that of the quadrature amplitude modulation (QAM). Expanding the constellation size to 4096, the MED of 3-D lattice constellation is increased by 3.2 times of the QAM.

A Study on Performance Requirement of I/Q Impairments for RF Implementation in W-CDMA User Equipment (W-CDMA 사용자장치 RF 구현을 위한 I/Q 열화성능요구규격 연구)

  • Lee, Il-Kyoo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.1
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    • pp.148-154
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    • 2005
  • This paper deals with performance degradations caused by RF I/Q impairments such as amplitude mismatch and phase mismatch in W-CDMA user equipment which uses QPSK(Quadrature Phase Shift Keying) modulation. The impacts of I/Q impairments on the BER(Bit Error Rate) are analyzed by using the variations of adjacent symbol distance. The BER versus amplitude mismatch and phase mismatch with QPSK constellation is reviewed through Matlab simulation. Performance degradation produced by RF I/Q impairments is measured with the implemented RF transceiver and modulation/demodulation test equipments through EVM(Error Vector Magnitude). The minimum performance requirements of amplitude mismatch and phase mismatch in W-CDMA user equipment are presented from the point of hardware implementation and the test method of the impairments is also included.

Performance of 8SQAM System in a Nonlinearly Amplified SCPC-FDMA Channel Interference Environment (비선형 증폭 SCPC-FDMA 채널 간섭 환경에서 8SQAM 시스템의 성능)

  • 성봉훈;서종수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.7C
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    • pp.678-687
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    • 2003
  • 8SQAM(8-state Superposed Quadrature Amplitude Modulation) being a new modem technique for use in power and bandwidth limited digital communication system generates output signals which have a mか and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Also, 8SQAM signal is free of inter-symbol interference(ISI), and has a compact power spectrum. Accordingly 8SQAM, as compared with a conventional 8PSK, is influenced a little by inter-modulation(IM), inter-symbol interference(ISI) and adjacent channel interference(ACI) in a nonlinearly amplified multi-channel(SCPC-FDMA) environment. In this paper, the performance of 8SQAM system in a nonlinearly amplified multi-channel interference environment is analyzed via computer simulation The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of $\alpha$ = 0.3 by 2.7dB in CNR to maintain BER=1$\times$10$^{-4}$ when input back-off(IBO) of HPA is 1dB and channel space is 41.7% of the data bit rate(i.e., spectral efficiency = 2.40b/s/Hz).

Performance of 8SQAM System in a Nonlinearly Amplified Channel Environment (비선형 증폭 채널 환경에서 8SQAM 시스템의 성능)

  • 성봉훈;서종수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.7C
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    • pp.669-677
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    • 2003
  • A new Modem technique - 8SQAM(8-state Superposed Quadrature Amplitude Modulation) - for use in power and bandwidth limited digital communication system is proposed. 8SQAM is free of inter-symbol interference(ISI) and generates output signals which have a smooth and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Accordingly, 8SQAM, as compared with a conventional 8PSK, is influenced a little by ISI and inter-modulation(IM) caused by nonlinear distortions. In this paper, the performance of the 8SQAM system, in a nonlinearly amplified channel impaired by additive white Gaussian noise(AWGN), ISI and IM, is analyzed via computer simulation. The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of $\alpha$=0.25 by 2.5dB in CNR to maintain BER=1$\times$10$^{-4}$ when input back-off(IBO) of HPA is 3dB.

Generalized BER Analysis of Arbitrary Rectangular QAM (임의의 사각형 QAM의 일반화된 비트 오율 분석)

  • Yoon Dong-Weon;Cho, Kyong-Kuk;Suh, Ki-Bum
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.10A
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    • pp.962-968
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    • 2002
  • Reliable high-speed data communications over insufficient channel bandwidth is one of the major challenges of harsh wireless environments that push the achievable spectral efficiency far below its theoretical limits. A Quadrature amplitude modulation (QAM) scheme is a userful modulation technique for achieving high data rate transmission without increasing the bandwidth of wireless communication systems. The exact general bit error rate (BER) expression of arbitrary rectangular quadrature amplitude modulation has not yet been derived. In this paper, a generalized closed-form expression for the BER performance of rectangular QAM with Gray code bit mapping is derived and analyzed in the presence of additive white Gaussian noise (AWGN) channel. First we analyze the BER performance of an I-ary PAM scheme. Regular patterns in the k-th bit error probability are observed while developing the EBR expression. From these patterns we provide the exact and general closed-from EBR expression of an I-ary PAM. Then we present a general closed-from expression for BER of an arbitrary IXJ rectangular QAM by considering that this signaling format consists of two PAM scheme, i.e., I-ary and J-ary PAM. A simple approximate BER expression for rectangular QAM is given as well.

Performance Evaluation of Turbo coded Adaptive QAM Systems for High-speed Mobile Multimedia Communications (고속 이동 멀티미디어 통신을 위한 터보 부호 적응 QAM 시스템의 성능 분석)

  • 백흥현;정연호
    • Journal of the Institute of Convergence Signal Processing
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    • v.5 no.3
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    • pp.216-222
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    • 2004
  • Frequency selective fading is a limiting factor for transmission rate and performance in high-speed multimedia communications. In this paper, we propose a turbo coded adaptive quadrature amplitude modulation (QAM) system for efficient high-speed transmission. By making use of a user-friendly simulation platform of SPW, the proposed turbo coded adaptive QAM system(TuAQAM) is developed and its performance is evaluated in terms of throughput and BER performance. Two channel models having delay spreads of 700ns and 1400ns are created for the simulations. It is shown that the proposed TuAQAM system provides a performance improvement of approximately 3dB and improved throughput for the channel model whose delay spread is 700ns. Similarly, a performance improvement is also achieved for the channel model whose delay spread is 1400ns.

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A deep learning method for the automatic modulation recognition of received radio signals (수신된 전파신호의 자동 변조 인식을 위한 딥러닝 방법론)

  • Kim, Hanjin;Kim, Hyeockjin;Je, Junho;Kim, Kyungsup
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.23 no.10
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    • pp.1275-1281
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    • 2019
  • The automatic modulation recognition of a radio signal is a major task of an intelligent receiver, with various civilian and military applications. In this paper, we propose a method to recognize the modulation of radio signals in wireless communication based on the deep neural network. We classify the modulation pattern of radio signal by using the LSTM model, which can catch the long-term pattern for the sequential data as the input data of the deep neural network. The amplitude and phase of the modulated signal, the in-phase carrier, and the quadrature-phase carrier are used as input data in the LSTM model. In order to verify the performance of the proposed learning method, we use a large dataset for training and test, including the ten types of modulation signal under various signal-to-noise ratios.