• Title/Summary/Keyword: Multipath Channel

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W-CDMA Systems Using Turbo Code over Wideband Multipath Channel (광대역 다중경로 채널에서 터보부호를 적용한 W-CDMA 시스템의 성능 분석)

  • 윤성재;조성철;김철성
    • Proceedings of the IEEK Conference
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    • 2000.09a
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    • pp.41-46
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    • 2000
  • In this paper, we analyze the performance of W-CDMA systems using turbo code in the wideband multipath channel. The strength of each multipath component is assumed to be Rayleigh distributed. Turbo codes of long block sizes have been known to show very good performance in a AWGN channel. Recently, turbo codes of short block sizes suitable for real time communication systems have attracted a lot of attention. Thus, in this paper we consider the turbo code of 1/3 code rate and short frame size of 192 bits in wideband mobile multipath channel. We analyze the performance of W-CDMA systems with 10MHz bandwidths in the case of employing RAKE receiver with not only MRC diversity but also turbo code.

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Performance Analysis of the CDMA system with the RAKE Receiver over a Multipath Fading Channel (다경로 페이딩 채널에서 RAKE 수신기를 적용한 CDMA 시스템의 성능 분석)

  • 고영훈;박성경;홍대식;강창언
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.4
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    • pp.47-55
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    • 1994
  • This paper presents the CDMA system using the RAKE receiver over a multipath fading channel and in multi-user environments. The interference between the propagation paths in a multipath fading causes a serious degradation in the mobile communication environment. In order to derive the path inteference and reduce the fading effect, the RAKE receiver is used. In a computer simulation, the path number of a fading channel and the branch number of the RAKE receiver are modified. As a result, the CDMA system using the RAKE receiver gives a better performance than the conventional CDMA system over a multipath fading channel and in multi-user environments.

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Performance analysis of TDL for tracking of a direct-sequence spread-spectrum system in a multipath fading channel (다중경로 페이딩 전송로에서 직접시퀀스 확산대역 시스템이 추적을 위한 TDL의 성능분석)

  • 김진영;이재홍
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.3
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    • pp.10-17
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    • 1996
  • The performance of tau-dither loop (TDL) is evaluated for a direct-sequence spread-spectrum system in a multipath fading channel. The multipath fading channel is modeled as a two-ray rayleight fading channel. The code tracking perfomrance of TDL is analyzed in terms of tracking jitter and mean-tiem-to-lose-lick (MTLL). The tracking jitter performance is degraded while MTLL perfomrance is improved with increasing discriminator offset and decreasing power ratio of main to second paths. It is shown that for a large bit SNR, the effect of multipath fading becomes more significant. And it is also shown that tracking jitter and MTLL performance is less sensitive to delay spacing and discriminator offset for a small bit SNR than for a large bit SNR.

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Underwater Acoustic Communication Research using Blind Channel identification (블라인드 채널추정기법(Blind Channel Identification)을 이용한 수중통신 연구)

  • Kim, Kap-Su;Cho, A-Ra;Choi, Young-Chol;Lim, Yong-Kon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2007.10a
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    • pp.165-169
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    • 2007
  • Due to the complexity of underwater acoustic channel, signal estimation in underwater acoustic communication field is considerably affected from time-varying multipath fading channels. On this reason, the original signals should have many long training signals to estimate the channel and the purposed signals, and the bit rate of signals having information may have small rate. In order to avoid this loss of efficiency in underwater communication, this paper employed a blind channel identification method which don't use training signals. Simulations have predicted performance of the employed method in multipath environment and an aquatic plant experiment has verified the simulation results.

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Power Line Channel Model Considering Adjacent Nodes with Reduced Calculation Complexity due to Multipath Signal Propagation and Network Size Using Infinite Geometric Series and Matrices (무한 등비급수와 행렬을 이용하여 멀티 패스 신호 전송과 네트워크 크기에 의한 계산의 복잡성을 줄이고 근접 노드의 영향을 고려한 전력선 통신 채널 모델)

  • Shin, Jae-Young;Jeong, Ji-Chai
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.2
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    • pp.248-255
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    • 2009
  • We proposed a power line channel model. We adopted advantages of other power line channel models to calculate channel responses correctly and simply. Infinite geometric series reduced the calculation complexity of the multipath signal propagation. Description Matrices were also adopted to handle the network topology easily. It represents complex power line network precisely and simply. Newly proposed model considered the effect of the adjacent nodes to channel responses, which have been not considered so far. Several simulations were executed to verify the effect of the adjacent nodes. As a result we found out that it affected channel responses but its effect was limited within certain degree.

An Implementation of Modulation/ Demodulation System Based on the Multipath Analyses for the Acoustic-based Communication (Multipath를 고려한 수중 초음파 통신시스템의 구현)

  • 임용곤;박종원;김천석;이영철
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.1 no.1
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    • pp.95-104
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    • 1997
  • This paper deals with an analysis of multipath which affect a transmission performance in underwater acoustic channel. For the test of autonomous underwater vehicle(AUV), underwater acoustic channel with multipath structure is introduced to mathmatical modelling for a basin environment. In this paper, SMR(Signal to Multipath Ratio) which is defined as a parameter of mulipath's effect is presented as a mathmatical equation, and the equation or SMR is simulated by MATLAB program.

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Receiver Techniques for Ultra-wide-band Multiuser Systems over Fading Multipath Channels

  • Zhou, Xiaobo;Wang, Xiaodong
    • Journal of Communications and Networks
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    • v.5 no.2
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    • pp.167-173
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    • 2003
  • We treat the problem of channel estimation and interference cancellation in multiuser ultra-wide-band (UWB) communication systems over multipath fading channels. The UWB system under consideration employs a random time-hopping impulse radio format. We develop a channel estimation method based on linear weighted algorithm. An iterative channel estimation and interference cancellation scheme is proposed to successively improve the receiver performance. We also consider systems employing multiple transmit and/or receive antennas. For systems with multiple receive antennas, we develop a diversity receiver for the wellseparated antennas. For systems with multiple transmit antennas, we propose to make use of Alamouti’s space-time transmission scheme, and develop the corresponding channel estimation and interference cancellation receiver techniques. Simulation results are provided to demonstrate the performance of various UWB receiver techniques developed in this paper.

Performance of COFDM in Underwater Acoustic Channel with Frequency Selective Fading (주파수 선택적 페이딩을 갖는 수중 음향 채널에서 COFDM의 성능)

  • Seo, Chulwon;Park, Jihyun;Park, Kyu-Chil;Yoon, Jong Rak
    • The Journal of the Acoustical Society of Korea
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    • v.32 no.5
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    • pp.377-384
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    • 2013
  • In this paper, performance of COFDM (Coded Orthogonal Frequency Division Multiplexing) which is OFDM with a forward error correction code, is studied in frequency selective fading underwater acoustic communication channel. The OFDM is a multiplexing technique resistant to frequency selective multipath channel. In OFDM, a broadband information signal is transformed into several narrow band signals and transmits narrow band signals whose bandwidths are less than the channel coherence bandwidth. However, its performance is degraded in a specific narrow band signal due to its deep fading by multipath. To mitigate this degradation, COFDM which is OFDM with convolution code as a forward error correction code, is evaluated. The performance of COFDM is found to be better than that of OFDM in multipath channel.

Error rate performance of DS / SSMA system in multipath fading channel (다경로 페이딩 채널에서 DS/SSMA 시스템의 오율특성)

  • 박성경;송왕철;강창언
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.6 no.1
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    • pp.66-76
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    • 1995
  • In this paper, the error rate performance of DS/SSMA system in multipath fading channel is calculated by computer simulation. At first, the multipath fading channel is modeled with TDL(Tap Delay Line) model. The characteristics of channels, including multipath fading effects and error pattern, are examined by doppler frequency and signal bandwidth, and time spread variation. Using the multipath fading channel model, the error rateperformance of block code and convolutional code is compared, thus the coding sys- tem is applied to the DS / SSMA system. The BER results of DS / SSMA system show that the proposed receiver gives about 2~3[dB] improve- ment compared with the conventional receiver.

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Time-Varying Multipath Channel Estimation with Superimposed Training in CP-OFDM Systems

  • Yang, Qinghai;Kwak, Kyung-Sup
    • ETRI Journal
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    • v.28 no.6
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    • pp.822-825
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    • 2006
  • Based on superimposed training methods, a novel time-varying multipath channel estimation scheme is proposed for orthogonal frequency division multiplexing systems. We first develop a linear least square channel estimator, and meanwhile find the optimal superimposed sequences with respect to the channel estimates' mean square error. Next, a low-rank approximated channel estimator is obtained by using the singular value decomposition. As demonstrated in simulations, the proposed scheme achieves not only better performance but also higher bandwidth efficiency than the conventional pilot-aided approach.

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