• Title/Summary/Keyword: Fading Time

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Decision-Feedback Detector for Quasi-Orthogonal Space-Time Block Code over Time-Selective Channel (시간 선택 채널에서의 QO-STBC를 위한 피드백 결정 검출기)

  • Wang, Youxiang;Park, Yong-Wan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.12A
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    • pp.933-940
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    • 2009
  • This paper proposes a robust detection scheme for quasi-orthogonal space-time block code over time-selective fading channels. The proposed detector performs interference cancellation and decision feedback equalization to remove the inter-antenna interference and inter-symbol interference when the channel varies from symbol to symbol. Cholesky factorization is used on the channel Gram matrix after performing interference cancellation to obtain feed forward equalizer and feedback equalizer. It is shown by simulations that the proposed detection scheme outperforms the conventional detection schemes and the exiting detection schemes to time-selectivity.

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.

Generalized Principal Ratio Combining of Space-Time Trellis Coded OFDM over Multi-Path Fading Channels (다중 경로 채널에서 공간-시간 트렐리스 부호화된 OFDM의 일반화된 준최적 검파)

  • Kim, Young-Ju
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.3
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    • pp.352-357
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    • 2008
  • We present a space-time trellis coded OFDM system in slow fading channels. Generalized principal ratio combining (GPRC) is also analyzed theoretically in frequency domain. The analysis shows that the decoding metric of GPRC includes the metrics of maximum likelihood(ML) and PRC. The computer simulations with M-PSK modulation are obtained in frequency flat and frequency selective fading channels. The decoding complexity and simulation running times are also evaluated among the decoding schemes.

An Analysis on Signal to Interchannel Interference Ratio of MC-CDMA System in Time Selective Fading Environments (시간선택적 페이딩 환경에서 MC-CDMA 시스템의 신호대 채널간 간섭의 비에 대한 분석)

  • 김명진;김성필;오종갑
    • Proceedings of the Korea Institute of Convergence Signal Processing
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    • 2001.06a
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    • pp.33-36
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    • 2001
  • In MC-CDMA systems effects of delay spread of the channel are reduced with increased symbol duration by simultaneously transmitting data symbols on the parallel subcarriers. However, the increased symbol duration causes the system to be more vulnerable to time selective fading. In this paper, we investigate the effects of time selective fading characteristics of the mobile channel from the viewpoint of desired signal power to inter-carrier interference power ratio at the combiner output of the MC-CDMA receiver.

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Predictive Closed-Loop Power Control for CDMA Systems in Time-Varying Fading Channels (시변 페이딩 채널하에 CDMA 시스템을 위한 예측 폐루프 전력제어)

  • Choe, Sang-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.11A
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    • pp.1021-1026
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    • 2005
  • In this paper, we present a novel predictive CDMA closed-loop power control (CLPC) method with a multi-step least squares (LS) linear predictor for time-varying fading channels. The proposed method effectively compensates multiple power control group delays and provides significant performance gains over nonpredictive CLPCs as well as conventional predictive CLPCs with one-step linear predictor.

Chip Timing Recovery Algorithm Robust to Frequency Offset and Time Variant Fading

  • Kang, Hyung-Wook;Lee, Young-Yong;Park, Hyung-Jin
    • Proceedings of the IEEK Conference
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    • 2002.07c
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    • pp.1948-1951
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    • 2002
  • In this paper, we propose a chip timing recovery algorithm that is robust to frequency offset and time variant fading environments for DS/CDMA. The proposed structure is a modified non-coherent Delay Locked Loop (DLL) that employs a decimator. Analytical expression for the proposed non-coherent DLL S-curve and steady-state timing jitter is derived and confirmed by computer simulation. The results show that the proposed structure can reduce a steady-state timing jitter of the regenerated spreading code replica to frequency offset and time-variant fading in mobile radio channel, especially in very low SNR.

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Performance Analysis of Space-Time Block Coded Cooperative Wireless Transmission in Rayleigh Fading Channels

  • Kong Hyung-Yun;Khuong Ho-Van
    • Journal of Communications and Networks
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    • v.8 no.3
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    • pp.306-312
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    • 2006
  • This paper studies theoretically the bit error rate (BER) performance of cooperative transmission using space-time block code (STBC) in a fully distributed manner. Specifically, we first propose a STBC-based cooperative signaling structure to make the cooperation of three single-antenna terminals possible. Then, we derive the closed-form BER expressions for both cooperation and noncooperation schemes under flat Rayleigh fading channel plus additive white Gaussian noise (AWGN). The validity of these expressions is verified by Monte-Carlo simulations. A variety of numerical and simulation results reveal that the cooperative transmission achieves higher diversity gain and better performance than the direct transmission for the same total transmit power.

Performance of IEEE 802.16j using Cooperative Relaying in Correlated Shadow Fading (음영감쇄 환경에서의 IEEE 802.16j 상호 협조 중계 방식 성능 평가)

  • Ha, Dong-Ju;Kim, Suk-Chan;Park, Dong-Chan;Kim, Young-Il
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.5
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    • pp.47-53
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    • 2007
  • The purpose of IEEE 802.16j is to extend coverage and to enhance throughput by using relay station additionally to conventional IEEE 802.16e . The cellular system experiences performance degradation at the cell edge due to pathloss, shadow and multipath fading. We can get advantage of spatial diversity gain by using relays more than two cooperatively in the IEEE 802.16j system. Cooperative relaying using space-time code provides better performance under multipath fading and has more robustness against the shadow fading than single relaying. In this paper, we investigate the performance of IEEE 802.16j using cooperative relaying by link level simulation. We also show that the cooperative relaying system achieves better performance than the conventional single relaying system. We apply realistic shadow model considering correlations between shadow fadings of different relaying paths. It is shown that the performance of the system depends highly on the spatial location of relay stations.

The Analysis of Performance for W-CDMA System using Channel Coding & Space-Time Code in Wideband Multipath Channel. (광대역 다중 경로 채널에서 채널 코딩과 시공간 부호를 적용한 W-CDMA의 성능분석)

  • 박정현;김정미;정호섭;김철성
    • Proceedings of the IEEK Conference
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    • 2003.11c
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    • pp.277-280
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    • 2003
  • In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the reliability of communications and increase the data rate by channel coding, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve tile performance in multi-Path fading channel environment.

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Comparative Performance of Differential Space-Time Block Codes Over Time-Selective Fading Channels (시변 페이딩 채널에서 검파방식에 따른 차분 공간-시간 블록 부호의 성능 비교)

  • Kang, Sung-Ho;Kim, Young-Ju;Lee, In-Sung
    • The Journal of the Acoustical Society of Korea
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    • v.25 no.8
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    • pp.356-361
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    • 2006
  • We present the performance of differential space-time block decoders. which does not require the channel state information. We suggest the structure of the multiple blocks differential space time decoders. which does not require the channel state information, and analyze the Performances. In quasi-static flat fading channels. the Performance of multiple blocks differential detection (MD-STC) outperforms that of 2 blocks(D-STC) by 1.5dB. But in the time-selective fading channels due to Doppler frequency $(f_d)$, the performance of MD-STC degrades as the vehicular speed is greater than 200km/hr in 802.16e systems, where the data transmission rate is 144kbps.