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Author: search.filters.author.Reangsuntea, Arttapol

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    Transmit diversity for TS-OFDM signal in higher time-varying fading channels
    (2017-11-03)
    Danchai, Anusan
    ;
    Reangsuntea, Arttapol
    ;
    Boonsrimuang, Pisit
    ;
    Reangsuntea, Pongsathorn
    ;
    Mori, Kazuo
    This paper proposes a channel estimation and equalization methods for a transmit diversity system of using time domain training sequence inserted orthogonal frequency division multiplexing (TS-OFDM) signal in higher time-varying fading channels. The salient feature of the proposed channel impulse response (CIR) estimation method for the transmit diversity system with a space frequency block coding is to employ a new design of training sequence (TS) signal which can reduce the leakage of power spectrum density (PSD) and keep higher CIR estimation accuracy. In the proposed equalization method, the estimated CIR at every sampling time and the known TS signals are employed at the receiver for removing the inter-symbol interference (ISI) caused in higher time-varying fading channels so as to employ the overlap and add (OLA) operation. This paper presents various simulation results to demonstrate the effectiveness of the proposed transmit diversity system as comparing with the conventional methods.
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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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    A low-complexity PS based radix IFFT method for PAPR reduction in OFDM systems
    (2014-01-01)
    Reangsuntea, Arttapol
    ;
    Boonsrimuang, Pornpawit
    ;
    Reangsuntea, Pongsathorn
    ;
    Boonsrimuang, Pisit
    ;
    Kobayashi, Hideo
    We have proposed one of the distortion-less PAPR reduction methods which employs the Permutation Sequence (PS) in the frequency domain with embedded side information. However, the proposed PS method has high computation complexity. To improve the computation complexity for the previous proposed PS method, this paper proposes a low-complexity PS method which can keep the better peak-to-average power ratio (PAPR). In the proposed PS method, the signals at the middle stages of an N-point radix IFFT using decimation in frequency (DIF) is considered for PS processing. This paper shows that the proposed method has a lower multiplicative complexity than conventional PS method with keeping the PAPR reduction performance. The proposed method is called PS based radix IFFT, where DIF-IFFT is assigned through different stages of the IFFT transform. This proposed method can reduce the multiplicative complexity relatively with keeping the similar PAPR reduction to other methods such as C-PTS and C-PS. The proposed method also can reduce the side information as compared with the C-PTS. This paper presents the various computer simulation results to verify the effectiveness of proposed method. © 2014 Global IT Research Institute (GIRI).