Now showing 1 - 10 of 22
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    Item type:Publication,
    Proposal of channel estimation method for bi-directional OFDM based ANC in higher time-varying fading channel
    (2014-01-01)
    Mata, Tanairat
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    Naito, Katsuhiro
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    Mori, Kazuo
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    Kobayashi, Hideo
    Broadband Analog Network Coding (ANC) based on OFDM has been widely investigated to increase capacity of bi-directional relay communications. The broadband ANC based on OFDM technique is required to estimate channel frequency responses (CFRs) between both user terminals (UTs) and a relay station (RS) precisely so as to remove the self-information data from the received signal and to demodulate the other user's information data with frequency equalization. Many channel estimation methods have been proposed for the OFDM based broadband ANC. However bit error rate (BER) performance of these methods would be degraded relatively in higher time- varying fading channels due to the inaccurate estimation of CFR. To solve this problem, this paper proposes a CFR estimation method which can achieve better BER performance with keeping higher transmission efficiency even in higher time-varying fading channels. The salient features of proposed CFR estimation method are to enable the estimation of combined CFR at the UT for both channels between the UTs and RS by using scattered pilot subcarriers and to enable the demodulation of information data without feedback information of CFR estimated at the RS. This paper presents various simulation results in the higher time-varying fading channels to demonstrate the effectiveness of proposed CFR estimation method for the bi-directional OFDM based ANC.
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    Item type:Publication,
    Proposal of STBC MIMO-OFDM for ITS systems
    (2013-09-02)
    Mata, Tanairat
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    Naito, Katsuhiro
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    Mori, Kazuo
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    Kobayashi, Hideo
    Orthogonal Frequency Division Multiplexing (OFDM) is a popular technique in the wireless communication systems which can achieve high transmission data rate with high signal quality even in the multipath fading channel which is a typical operation condition under wireless communication systems. MIMO (Multi Input-Multi Output)-OFDM is also considered as a promising technique for realizing the future ITS services. In this paper, we propose a new road to vehicle communication system (RVC) for the ITS by using the STBC MIMO-OFDM technique which can achieve a high transmission data rate with high signal quality even under the high mobile ITS environments. © 2013 IEEE.
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    Item type:Publication,
    Performance Evaluation of the M-QAM Enhanced Subcarrier Index Modulation in the Multipath Fading Channel with the Non-Linear Amplifier
    (2023-01-01)
    Mi, Si Sar
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    Siriwanitpong, Aphitchaya
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    Boonsrimuang, Pornpawit
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    One of the specifications of the next-generation mobile communication is to reduce the power consumption to transmit the signal. Enhanced subcarrier index modulation (eSIM-OFDM) is a novel multicarrier modulation scheme. However, the eSIM-OFDM scheme degraded a little frequency utilization than the conventional orthogonal frequency division multiplexing (C-OFDM) scheme at the higher M-QAM modulation techniques. It has a special feature to transmit the signal when compared with the C-OFDM scheme. Its special feature increased the power efficiency and improved the bit error rate (BER) performance than the C-OFDM scheme. In the literature, the BER performance of the eSIM-OFDM scheme is analyzed in the additive white Gaussian noise (AWGN) channel and compared BER performance of the C-OFDM scheme. But in the literature, the BER performance of the eSIM-OFDM scheme and C-OFDM scheme were not evaluated in the multipath fading channel. Because eSIM-OFDM includes a special feature called inactive and active subcarriers. In this paper, we will evaluate the BER performance of higher order modulated eSIM-OFDM signal in the multipath Rician fading channel by using the Zadoff-Chu sequence pilot in the non-linear mobile communication system and will compare the BER performance with the C-OFDM scheme. From the simulation results, we can see that the BER performance of the eSIM-OFDM scheme is much better than the C-OFDM scheme in the multipath Rician fading non-linear channel. In this paper, computer simulation will evaluate the BER performance of the higher order modulated eSIM-OFDM scheme in the multipath Rician fading non-linear channel.
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    Item type:Publication,
    Iterative based ML demodulation method for OFDM signal under higher mobile environments
    (2015-07-01)
    Reangsuntea, Pongsathorn
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    Hourai, Mio
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    Mori, Kazuo
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    Kobayashi, Hideo
    Orthogonal Frequency Division Multiplexing (OFDM) signal would be damaged significantly by inter- carrier interference (ICI) in higher time-varying fading channels which leads fatal degradation of bit error rate (BER) performance due to the loss of orthogonality among subcarriers. To solve this problem, this paper proposes an iterative based maximum likelihood demodulation (MLD) method which can achieve better BER performance with lower computation complexity even in higher time-varying fading channels. The features of proposed method are to employ a time domain training sequence (TS) in the estimation of channel impulse response (CIR) instead of using pilot subcarriers in the frequency domain and to employ a time domain equalization (TDE) method with a maximum likelihood (ML) estimation instead of using a conventional frequency domain equalization (FDE) method. This paper also proposes a low-complexity iterative method for solving the simultaneous equations in the MLD method instead of using an inverse matrix calculation. This paper presents various simulation results in higher time-varying fading channels to demonstrate the effectiveness of proposed method as comparing with the conventional frequency domain equalization method.
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    Item type:Publication,
    Proposal of simple PAPR reduction method for OFDM signal by using dummy sub-carriers
    (2008-01-01) ;
    Mori, Kazuo
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    Paungma, Tawil
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    Kobayashi, Hideo
    One of the disadvantages of using OFDM is the larger peak to averaged power ratio (PAPR) in its time domain signal as compared with the conventional single carrier modulation method. The larger PAPR signal would course the fatal degradation of bit error rate (BER) performance due to the inter-modulation noise occurring in the non-linear amplifier. To overcome this problem, this paper proposes a simple PAPR reduction method by using dummy sub-carriers, which can achieve the better PAPR performance with less computational complexity than the conventional method. This paper presents various computer simulation results to verify the effectiveness of proposed method as comparing with the conventional method in the non-linear channel. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.
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    Item type:Publication,
    Proposal of improved PTS method for STBC MIMO-OFDM systems
    (2010-01-01)
    Mata, Tanairat
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    Boonsrimuang, Pornpawit
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    Kobayashi, Hideo
    This paper proposes a new Partial Transmit Sequence (PTS) method in conjunction with the concurrent algorithm for Space Time Block Code Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (STBC MIMO-OFDM) systems. The feature of proposed PTS method is that each cluster is divided into two parts and these two parts employ the different weighting factors to achieve the better Peak to Average Power Ratio (PAPR) with keeping the same size of side information and almost the same size of computational complexity as that for the conventional concurrent PTS method. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers.
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    Item type:Publication,
    Iterative based time domain equalization method for OFDM signal under high mobile environments
    (2014-01-23)
    Reangsuntea, Pongsathorn
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    Mori, Kazuo
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    Kobayashi, Hideo
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    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.
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    Item type:Publication,
    Proposal of PAPR reduction method for OFDM signal by re-ordering of clusters
    (2013-01-01)
    Mata, Tanairat
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    Naito, Katsuhiro
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    Mori, Kazuo
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    Kobayashi, Hideo
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    One of the major disadvantages of OFDM technique is the high PAPR in the time domain signal. The larger PAPR signal would cause the fatal degradation of BER performance and un-desirable spectrum regrowth in the nonlinear channel. One of the promising PAPR reduction methods is the Partial Transmit Sequence (PTS) method which can achieve better PAPR performance with reasonable computation complexity. But the PTS method is required to inform the side information to the receiver for the correct demodulation of data information by using the separate channel. To solve the above problem, this paper proposes a new PAPR reduction method without requiring the separate channel. The salient feature of the proposed method is to reduce the PAPR performance by reordering of clusters in the frequency domain at the transmitter and reconstructing the clusters by using the cluster ID under embedded in the data information at the receiver. The proposed method can achieve almost the same PAPR performance and computation complexity as those for the PTS method without requiring the transmission of side information. This paper presents various computer simulation results to verify the effectiveness of the proposed method. © 2013 IEEE.
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    Item type:Publication,
    A Deep Learning-Based Channel Estimation for High-Speed Train Environments
    (2022-01-01)
    Siriwanitpong, Aphitchaya
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    Boonsrimuang, Pornpawit
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    Mori, Kazuo
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    A communication system in the railway track environment provides constant channel coefficient property as trains travel on a predetermined route and speed. This channel characteristic provides advantages in designing a channel estimation. This paper proposes a channel estimation algorithm based on a deep learning network called the Convolutional Neural Network (CNN). The CNN has trained with an average Channel Frequency Response (CFR) dataset on railway track environments with different multi-path fading and noises. The CFR can be estimated using a known pilot symbol as conventional methods. The estimated CFR is also used to select the right CFR for multi-path fading compensation. The CNN will then classify the estimated CFR by recognizing estimated channel characteristics and determining the most matched estimated channel for equalization of received signals in a data channel. The simulation results show that the performance of the deep learning algorithms outperforms that of the conventional algorithms. Furthermore, the proposed method delivers better Bit Error Rate (BER) performance since the deep learning-based channel estimation can categorize the features of the channel characteristics with different multi-path and doppler shifts.
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    Item type:Publication,
    A new weighting factor with concurrent PAPR reduction algorithm for STBC MIMO-OFDM
    (2009-12-01)
    Mata, Tanairat
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    Boonsrimuang, Pornpawit
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    Kobayashi, Hideo
    Partial Transmit Sequences (PTS) method seems to be attractive for the reduction of Peak to Average Power Ratio (PAPR) in the Orthogonal Frequency Division Multiplexing (OFDM) system, since it can obtain better PAPR property by modifying OFDM signals without any degradation of BER performance. Meanwhile it also shows the potential capability to be utilized in MIMO-OFDM system with a concurrent PAPR reduction algorithm based on the property of orthogonal Space-Time Block Coded (STBC)[1]. On the other hand, the PTS method can improve the PAPR reduction performance very well as increasing the number of weighting factors and clusters. However, the size of side information proportionally increases as increasing the number of weighting factors or/and clutters, which are required to the receiver for recovering the original data. In this paper, we propose a new determination method for the weighting factor of PTS in conjunction with the concurrent [2] algorithm for the STBC MIMO-OFDM systems, which can improve the PAPR performance, computation complexity without any increasing of side information, and improve the BER (Bit Error Rate) performance. ©2009 IEEE.