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Author: search.filters.author.Kobayashi, HideoSubject: search.filters.subject.training sequence (TS)

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    Low-complexity FDE method for TS-OFDM signal under higher time-varying channels
    (2016-09-06)
    Reangsuntea, Pongsathorn
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    ;
    Reangsuntea, Arttapol
    ;
    Boonsrimuang, Pisit
    A losing of orthogonality among subcarriers in higher time-varying fading channels causes an inter-carrier interference (ICI) in orthogonal frequency division multiplexing (OFDM) signal which leads a fatal degradation both for the channel estimation accuracy and bit error rate (BER) performances. To solve this problem, this paper firstly proposes a channel estimation method with a new design of time domain training sequence (TS) of using a triangular window function which can achieve higher channel estimation accuracy with keeping lower leakage of power spectrum density (PSD) at the outside of OFDM allocated frequency bandwidth than the conventional TS signal. Secondly, this paper proposes a low-complexity frequency domain equalization (FDE) method which can achieve better BER performance than the conventional one-tap FDE method. The feature of proposed FDE method is to enable the reduction of complexity by using a Maclaurin's expansion algorithm in the inverse matrix calculation. This paper presents various computer simulation results to demonstrate the effectiveness of proposed FDE method as comparing with the conventional FDE methods.
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    Iterative based time domain equalization method for DFTS-OFDM under highly mobile environments
    (2016-09-06)
    Reangsuntea, Arttapol
    ;
    Boonsrimuang, Pisit
    ;
    Reangsuntea, Pongsathorn
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    Under highly mobile environments, the bit error rate (BER) performance of DFT spreading-orthogonal frequency division multiplexing (DFTS-OFDM) signal with a frequency domain equalization method would be degraded relatively due to the loss of orthogonality among subcarriers. To solve this problem, this paper proposes an iterative based time domain equalization (TDE) technique with a time domain channel impulse response (CIR) estimation method for the DFTS-OFDM signal. The salient features of proposed method are to employ a time domain training sequence (TS) in the estimation of CIR instead of using the conventional pilot subcarriers method and to employ the TDE technique with a maximum likelihood (ML) estimation method instead of using the conventional minimum mean square error frequency domain equalization (MMSE-FDE) method. This paper also proposes a low-complexity iterative method for the TDE method by using the preconditioned conjugate gradient squared (PCGS) algorithm for solving the simultaneous equations instead of using a direct calculation of inverse matrix. This paper presents various simulation results under highly mobile environments to demonstrate the effectiveness of proposed iterative based TDE with the CIR estimation method for the DFTS-OFDM signal as comparing with the conventional MMSE-FDE method.
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    Time domain equalization method for DFTS-OFDM signal without GI under high mobile environments
    (2015-08-17)
    Reangsuntea, Pongsathorn
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    ;
    Boonsrimuang, Pisit
    In higher time-varying fading channels, the DFT Spreading-Orthogonal Frequency Division Multiplexing (DFTS-OFDM) signal would be damaged significantly by inter-channel interference (ICI) due to the loss of orthogonality among subcarriers which leads a fatal degradation of bit error rate (BER) performance. To solve this problem, this paper proposes a time domain equalization (TDE) technique in conjunction with a time domain channel impulse response (CIR) estimation method for the DFTS-OFDM signal. The salient features of proposed method are to employ a time domain training sequence (TS) in the estimation of CIR at every sampling time instead of using the conventional scattered pilots inserted in the frequency domain and to employ the TDE with a maximum likelihood (ML) estimation method in the demodulation of received time domain signal at every symbol instead of using the conventional frequency domain equalization (FDE) method. This paper presents various simulation results to demonstrate the effectiveness of proposed method for the DFTS-OFDM signal as comparing with the conventional FDE method.
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    Iterative based time domain equalization method for OFDM signal under high mobile environments
    (2014-01-23)
    Reangsuntea, Pongsathorn
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    ;
    Boonsrimuang, Pisit
    A loss of subcarrier orthogonality in orthogonal frequency division multiplexing (OFDM) signal due to time-varying multipath fading channel causes an inter-carrier interference (ICI) which would lead fatal degradation of bit error rate (BER) performance. To solve this problem, this paper proposes a high accuracy time domain channel impulse response (CIR) estimation method and a time domain equalization (TDE) method of using estimated CIR at every sampling time in conjunction with a low-complexity iterative method instead of using an inverse matrix calculation. The salient feature of proposed method is to employ a time-domain training sequence (TS) for the estimation of CIR at every sampling time and low-complexity iterative method for solving the simultaneous equations which are required in the TDE method. This paper presents various simulation results to demonstrate the effectiveness of proposed TDE method as comparing with the conventional frequency domain equalization (FDE) method.