• Title/Summary/Keyword: 직교진폭변조

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Joint Optimization of Source Codebooks and Channel Modulation Signal for AWGN Channels (AWGN 채널에서 VQ 부호책과 직교 진폭변조신호 좌표의 공동 최적화)

  • 한종기;박준현
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.6C
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    • pp.580-593
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    • 2003
  • A joint design scheme has been proposed to optimize the source encoder and the modulation signal constellation based on the minimization of the end-to-end distortion including both the quantization error and channel distortion. The proposed scheme first optimizes the VQ codebook for a fixed modulation signal set, and then the modulation signals for the fixed VQ codebook. These two steps are iteratively repeated until they reach a local optimum solution. It has been shown that the performance of the proposed system can be enhanced by employing a new efficient mapping scheme between codevectors and modulation signals. Simulation results show that a jointly optimized system based on the proposed algorithms outperforms the conventional system based on a conventional QAM modulation signal set and the VQ codebook designed for a noiseless channel.

Comprehensive Performance Analysis and Comparison of various Digital Communication Systems in an Multipath Fading Channel with additive Mixture of Gaussian and Impulsive Noise [Part-1] (가우스성 잡음과 임펄스성 잡음이 혼재하는 다중전파 페이딩 전송로상에서의 제반 디지털 통신 시스템 특성의 종합분석 및 비교에 관한 연구(제 1 부))

  • 김현철;고봉진;공병옥;조성준
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.14 no.3
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    • pp.263-279
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    • 1989
  • In part-1 of this paper, the error rate equations of digitally modulated signals transmitted though the Gaussian/Impulsive noise channel have been derived. Using the derived equations for the error probabilities of ASK, QAM, CPSK, DPSK, FSK and MSK signals, the error rate performances of digital modulation systems have been evaluated and represented in the figures as the functions of carrier-to-noise power ratio(CNR), impulsive index, and the ration of Gaussian noise power component to impulsive noise power component. The results are shown in graphs to known how much impulsive noise effects on digital signals than Gaussian noise.

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Multi-code Biorthogonal Code Keying with Constant Amplitude Coding Combined with $Q^{2}PSK$ to Increase Bandwidth Efficiency (정 진폭 부호화된 Multi-code Biorthogonal Code Keying시스템에서 대역폭 효율 개선을 위해 $Q^{2}PSK$를 이용하는 방안)

  • Kim Sung-Pil;Kim Myoung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.5A
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    • pp.484-492
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    • 2006
  • A multi-code biorthogonal code keying(MBCK) system consists of multiple waveform coding block, and the sum of output codewords is transmitted. Drawback of MBCK is that it requires amplifier with high linearity because its output symbol is multi-level. MBCK with constant amplitude preceding blcok(CA-MBCK) has been proposed, which guarantees sum of orthogonal codes to have constant amplitude. Redundant bits of CA-MBCK for constant amplitude coding are not only used to make constant amplitude signal but also used to improve the bit error rate(BER) performance at receiver. In this paper, we proposed a transmission scheme which combine CA-MBCK with $Q^{2}PSK$ to improve bandwidth efficiency of CA-MBCK. The BER performance of the scheme is same that of CA-MBCK in additive white gaussian noise(AWGN). And we showed that BER performance of the proposed system can be improved using redundant bits of constant amplitude preceding.

CACB-Q2AM Modulation for High Bandwidth Efficiency and Constant Amplitude Signal Transmission (높은 대역폭 효율과 정진폭 신호 전송을 위한 CACB-Q2AM 변조)

  • Hong, Dae-Ki;Kang, Sung-Jin
    • Journal of Internet Computing and Services
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    • v.9 no.1
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    • pp.21-32
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    • 2008
  • In this paper, we propose new modulation schemes using the conventional CACB (Constant Amplitude Coded Multicode Biorthogonal) 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 $Q^2$AM (Quadrature-Quadrature Amplitude Modulation) and CA-$Q^2$AM (Constant Amplitude-$Q^2$AM) are used. We explain the simplest combining modulation scheme of CACB and $Q^2$AM (i.e., CACB-$Q^2$AM). However, this modulation scheme cannot support the constant amplitude property. Hence the first CACB-CA-$Q^2$AM (or CACB-CA-$Q^2$AM 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-$Q^2$AM (or CACB-CA-$Q^2$AM II) modulation scheme is proposed retaining the constant amplitude and the spectral efficiency. Computer simulations show that the proposed CACB-CA-$Q^2$AM II is the efficient modulation scheme.

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Noise Reduction Characteristics of A Modulated Orthogonal Sequence Under Weak-Signal Communication Channels (약한 신호 통신로에서 한 변조 직교수열의 잡음 줄임 특성)

  • 박성일;김윤희;김홍길;송익호;이성로
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.23 no.7
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    • pp.1824-1830
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    • 1998
  • In this paper, we investigate a noise reduction scheme, based on the inherent characteristic of an orthogonal sequence. The modulated orthogonal code generates sequences of length $N^{2}$ from N information symbols. Using the amplitudes of the received symbols, we first estimate the location of the smallest amplitude noise. Then the noise is reduced by the suggested system. The performance of the scheme is confirmed by computer simulation results.

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Analysis on Spectral Regrowth of Bandwidth Expansion Module by Quadrature Modulation Error in Digital Chirp Generator (디지털 첩 발생기에서의 직교 변조 오차에 의한 대역 확장 모듈에서의 스펙트럴 재성장 분석)

  • Kim, Se-Young;Sung, Jin-Bong;Lee, Jong-Hwan;Yi, Dong-Woo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.7
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    • pp.761-768
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    • 2010
  • This paper presents an effective method to achieve the wideband waveform for high resolution SAR(Synthetic Aperture Radar) using the frequency multiplication technique. And also this paper analyzes the root causes for the spectral regrowth due to 3rd-order intermodulation in chirp bandwidth expansion scheme using quadrature modulator and frequency multipliers. The amplitude and phase imbalance requirement are defined based on the simulation results in terms of quadrature channel imbalance. This minimizes the degradation of range resolution, peak sidelobe ratio and integrated sidelobe ratio. The wideband chirp generator using the frequency multiplier and memory map scheme was manufactured and the compensation technique was presented to reduce the spectral regrowth of SAR waveform by minimizing the amplitude and phase imbalance. After I and Q channel imbalance adjustment, the carrier level reduces -28.7 dBm to -53.4 dBm. Chirp signal with 150 MHz bandwidth at S-band expands to 600 MHz bandwidth at X-band. The sidelobe levels are reduced by about 8 to 9 dB by compensating the amplitude balance between I and Q channels.

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.

2N-Point FFT-Based Inter-Carrier Interference Cancellation Alamouti Coded OFDM Method for Distributed Antennas systems (분산안테나 시스템을 위한 2N-점 고속푸리에변환 기반 부반송파 간 간섭 자체제거 알라무티 부호화 직교주파수분할다중화 기법)

  • Kim, Bong-Seok;Choi, Kwonhue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.12
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    • pp.1030-1038
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    • 2013
  • The proposed Alamouti coded OFDM effectively cancels Inter Carrier Interference (ICI) due to frequency offset between distributed antennas. The conventional Alamouti coded OFDM schemes to mitigate ICI utilize N-point Inverse Fast Fourier Transform/Fast Fourier Transform (IFFT/FFT) operations for OFDM modulation and demodulation processes with total N subcarriers. However, the performance degrades because ICI is also repeated in N periods due to the property of N-point IFFT/FFT operation. In order to avoid this problem, null data are used at the subcarriers with large ICI and thus, data rate decreases. The proposed scheme employs 2N-point IFFT/FFT instead of N-point IFFT/FFT in order to increase sampling rate. By increasing sampling rate, the amount of interference significantly decreases because the period of ICI also increases. The proposed scheme increases the data rate and improves the performance by reducing amount of ICI and the number of null-data. Furthermore, the gain of the performance and data rate of the proposed scheme is significant with higher modulation such as 16-Quadarature Amplitude Modulation (QAM) or 64-QAM.

Improving the performance of turbo code by optimizing QAM constellation points (QAM 변조방식의 성상도 최적화를 통한 터보 부호의 성능 개선 연구)

  • Lee, Keun-Hyung;Kang, Dong-Hoon;Lee, Ji-Yeon;Oh, Wang-Rok
    • Proceedings of the IEEK Conference
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    • 2009.05a
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    • pp.9-11
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    • 2009
  • It is well-known that the performance of turbo codes can be improved by allocating different energies per code symbol. In this paper, based on this observation, we propose a joint encoding and modulation scheme for quadrature amplitude modulated turbo code systems. In the proposed scheme, the amount of energy difference between the turbo coded symbols is optimized by optimizing the constellation of quadrature amplitude modulation(QAM). The proposed scheme offers better coding gain compared to the conventional combination of binary turbo code and QAM at the bit error rate of $10^{-5}$.

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