• Title/Summary/Keyword: inter-symbol interference (ISI)

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Performance Improvement of MCMA Equalizer with Parallel Structure (병렬 구조를 갖는 MCMA 등화기의 성능 개선)

  • Yoon, Jae-Sun;Lim, Seung-Gag
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.11 no.5
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    • pp.27-33
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    • 2011
  • In digital communication system that the Modified Constant Modulus Algorithm (MCMA) reduced the use of the adaptive equalization algorithm to combat the Inter-symbol Interference (ISI). MCMA is relatively brief operation. The major point of MCMA that it only achieves moderate convergence rate and steady state mean square error (MSE). In this paper suggest, MCMA equalization improve the performance with parallel structure. It combines Modified Constant Modulus Algorithm(MCMA) and Modified Decision Directed(MDD) algorithm. By exploiting the inherent structural relationship between the 4-QAM signal's coordinates and 16-QAM signal's coordinates, another style of cost function for Modified Constant Modulus Algorithm(MCMA) is defined and If it happen to offset of received signals and MCMA is poor performance in order to overcome this because the paper combines apply for MCMA and MDD(Modified Decision Direct) algorithm. By computer simulation, we confirmed that the proposed PMCMA-MDD algorithm has the fater convergence rate and steady mean square error than the conventional MCMA.

Design and Performance Improvement of Simultaneous Single Band Duplex System Using Turbo Equalizer (터보 등화기를 사용한 SSD 시스템 설계와 성능 개선)

  • An, Changyoung;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39A no.1
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    • pp.28-35
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    • 2014
  • In this paper, we propose a SSD(simultaneous single band duplex) system with turbo equalizer for full-duplex over harsh ISI(inter symbol interference) channel. The proposed system uses RF(radio frequency) cancellation and digital cancellation to cancel self-interference caused by simultaneous single band duplex communication. Also, using turbo equalizer, the proposed system equalizes signal after digital cancellation. In this paper, we design SSD system with turbo equalizer. And then we evaluate BER(bit error rate) performance of the proposed system comparison with SSD system with adaptive equalizer. We use simulink program to confirm BER performance of the proposed system. The simulation results shows that the proposed system equalizes received signal effectively over harsh ISI channel and BER performance of the proposed system is better than BER performance of SSD system with adaptive equalizer.

16-QAM Demodulator Design of Broadband Wireless Local Loop (광대역 무선가입자망용 16-QAM 복조기 설계)

  • 김남일;김응배;이창석
    • Proceedings of the IEEK Conference
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    • 2000.11a
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    • pp.81-84
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    • 2000
  • This paper has been studied the design of 16-QAM demodulator used in broadband wireless local loop subscriber station. In B-WLL systems, transmission signal experience the inter symbol interference(ISI) due to multipath, frequency offset of RF/IF local oscillator and phase offset. In this paper, we discuss the effective data recovery algorithm for 16-QAM demodulator to compensate the distorted signal from ISI, frequency offset and phase offset.

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Performance of Adaptive Equalizer in the Shallow Underwater Acoustic Communication Channel (천해 수중 음향 통신 채널에서 적응 등화기의 성능)

  • Choi, Hyun-Kyu;Lee, Sangmin
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.6 no.1
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    • pp.29-36
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    • 2013
  • The inter-symbol interference(ISI) is one of the main obstacles to reliable high-rate data communication in the shallow underwater acoustic channel. This paper studies on the simulation of adaptive equalizer used as a means of mitigating the ISI in the shallow underwater acoustic communication system. The underwater channel is modeled as a superposition of multiple paths, whose lengths and relative delays are calculated from the channel geometry. Based on this channel model, computer simulations are carried out to investigate the performance of adaptive equalizer in the shallow underwater acoustic channel.

A study on efficient integration model of satellite and underwater communication for improving throughput efficiency (전송효율 향상을 위한 위성 및 수중 통신의 효율적인 융합 모델 연구)

  • Baek, Chang-Uk;Jung, Ji-Won
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.6
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    • pp.535-541
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    • 2016
  • In this paper, we analyzed efficient decoding scheme with FTN(Faster than Nyquist) method that is transmission method faster than Nyquist theory and increase the throughput. Applying the FTN method to satellite and underwater communication, we proposed an efficient transceiver model. To minimize ISI(Inter-Symbol Interference) induced by FTN signal, turbo equalization algorithms that iteratively exchange probabilistic information between Viterbi equalizer based on BCJR algorithm and LDPC decoder are used in satellite communication. In others, for underwater communication, DFE equalizer and LDPC decoder are concatenated to improve performance.

A Study on The Modulation Method for Low Power Communication in Underwater Sensor Network (수중 센서 네트워크에서 저전력 통신을 위한 변조기법의 적용성 연구)

  • Jang, Chul-Hee;Han, Jeong-Woo;Kim, Ki-Man;Lee, Seong-Ro
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.6B
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    • pp.689-696
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    • 2011
  • In this paper, we propose the result of PSSK(Phase Silence Shift Keying) modulation scheme that is mixed PSK(Phase Shift Keying) modulation and PPM(Pulse Position Modulation) method. The performance of underwater communication systems are influenced underwater channel characteristics. In particular, delay spread can make ISI(Inter Symbol Interference) because of reverberation and multi path. It degrade the performance of the communication system. Also underwater sensor networks consider about power efficient due to the particularities of their operating environment. PSSK modulation method transmit two orthogonal symbol and using silence period in a period so it can reduce the power. Increasing the distance of between modulation symbols, to enhance the performance of BER(Bit Error Rate) as well as to improve power efficient. The result of sea trial, QPSK modulation BER is $3.19{\times}10^{-1}$ and PSSK modulation BER is $2.89{\times}10^{-1}$.

Symbol Timing Synchronization Algorithm on OFDM System for Speed Up (OFDM 시스템에서 속도 향상을 위한 심볼 타이밍 동기 기법)

  • 진상욱;이태홍
    • Proceedings of the Korea Multimedia Society Conference
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    • 2001.11a
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    • pp.56-59
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    • 2001
  • OFDM 시스템은 부반송파의 직교성을 이용하는 특징으로 인하여 신호치 시간동기 및 주파수동기가 맞지 않은 경우 수신신호를 정확히 복조하기가 거의 불가능하다. 보호구간(Guard Interval)은 신호의 데이터 구간 일부분을 복사하여 심볼의 앞에 추가하는 CP(Cyolic Prefix)방식을 사용하고 있으며, 채널에서 발생하는 ISI(InterSymbol Interference)를 흡수하는 중요한 역할을 한다. 본 논문에서는 시간동기에 사용되어지는 보호구간을 여러 부구간으로 나눈 후, 이를 이용하여 심볼 타이밍 동기를 추정하고자 한다. 제안된 방법은 기존의 방법에 비해 성능의 손실없이 많은 계산량을 줄이는 방법으로서 수신기의 구조를 단순화시킬 수 있다. 여러 채널 환경에서의 모의 실험을 통해 제안한 방법과 기존의 방법을 비교하였다.

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Performance Evaluation of the Complex-Coefficient Adaptive Equalizer Using the Hilbert Transform

  • Park, Kyu-Chil;Yoon, Jong Rak
    • Journal of information and communication convergence engineering
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    • v.14 no.2
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    • pp.78-83
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    • 2016
  • In underwater acoustic communication, the transmitted signals are severely influenced by the reflections from both the sea surface and the sea bottom. As very large reflection signals from these boundaries cause an inter-symbol interference (ISI) effect, the communication quality worsens. A channel estimation-based equalizer is usually adopted to compensate for the reflected signals under the acoustic communication channel. In this study, a feed-forward equalizer (FFE) with the least mean squares (LMS) algorithm was applied to a quadrature phase-shift keying (QPSK) transmission system. Two different types of equalizers were adopted in the QPSK system, namely a real-coefficient equalizer and a complex-coefficient equalizer. The performance of the complex-coefficient equalizer was better than that of two real-coefficient equalizers. Therefore, a Hilbert transform was applied to the real-coefficient binary phase-shift keying (BPSK) system to obtain a complex-coefficient BPSK system. Consequently, we obtained better results than those of a real-coefficient equalizer.

An Electronic Domain Chromatic Dispersion Monitoring Scheme Insensitive to OSNR Using Kurtosis

  • Kim, Kyoung-Soo;Lee, Jae-Hoon;Chung, Won-Zoo;Kim, Sung-Chul
    • Journal of the Optical Society of Korea
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    • v.12 no.4
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    • pp.249-254
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    • 2008
  • In this paper we present an electronic domain solution for chromatic dispersion (CD) monitoring algorithm based on the estimated time domain channel in electronic domain using channel estimation methods. The proposed scheme utilizes kurtosis as a CD measurement, directly computed from the estimated inter-symbol-interference (ISI) channel due to the CD distortion. Hence, the proposed scheme exhibits robust performance under OSNR variation, in contrast to the existing electronic domain approach based on minimum mean squared error (MMSE) fractionally-spaced equalizer taps [1]. The simulation results verify the CD monitoring ability of the proposed scheme.

A Frame Structure of Modified ATSC Transmission Systems for Terrestial 3D HDTV Broadcasting (지상파 3D HDTV 전송을 위한 수정된 ATSC 전송 시스템의 프레임 구조에 관한 연구)

  • Oh, Jong-Gyu;Kim, Joon-Tae
    • Journal of Broadcast Engineering
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    • v.15 no.6
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    • pp.803-814
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    • 2010
  • In this paper, we propose a frame structure for modified ATSC transmission systems which is used for a terrestrial 3D HDTV broadcasting. The modified ATSC transmission systems [2] see the potential of increasing a transmission capacity at reasonable TOV (Threshold of Visibility) by modifying channel codes of conventional ATSC systems and varying modulations. We use PN symbols (Pseudorandom Noise) in a guard interval which is used for avoiding the ISI (Inter Symbol Interference) to estimate and compensate the time-varying multi path channel effectively with a maximum transmission payload. With PN symbols in the guard interval, a CIR (Channel Impulse Response) in a time domain can be estimated and a compensation in a frequency domain can be achieved for the accurate channel estimation and compensation. The prosed frame structure is applied to the modified ATSC systems and computer simulations are performed for SER (Symbol Error Rate) performances in TU (Typical Urban)-6 Channel.