Now showing 1 - 10 of 25
  • Some of the metrics are blocked by your 
    Item type:Publication,
    An Effective Channel Estimation for Massive MIMO–OFDM System
    (2020-09-01)
    Mata, Tanairat
    ;
    The massive Multiple-Input and Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO–OFDM) system provides a high data transmission for the next generation mobile communication i.e. 4G, 5G, etc. In the practical MIMO–OFDM system, N points of IFFT/FFT is larger than M data subcarriers (N> M) in each OFDM symbol to reject the aliasing after D/A converter. To demodulate information data, the channel responses for all MIMO channel links need to be estimated so as to employ in MIMO data detection for demodulation at the receiver. The discrete Fourier transform estimator (DFE) was proposed for the system which can estimate the MIMO channels accurately when N= M. However, its accuracy will be hugely degraded when N> M because of the oversampling of data transmission. To improve the estimation accuracy when N> M, the maximum likelihood estimator (MLE) was proposed for the system which can achieve higher estimation accuracy than that of the DFE. However, its accuracy will be degraded a lot in the massive MIMO–OFDM system when N> M, due to the estimation error increased in proportion to the increasing of N<inf>T</inf> transmit antennas. To solve these problems, this paper proposes a direct time-domain estimator (DTE) with preamble symbol with scattered-pilot (preamble-SCP) for the massive MIMO–OFDM system when N> M. In the proposed method, it is presented with three salient features; achieving higher estimation accuracy with keeping almost the same computational complexity as the conventional estimators, improving Bit- Error- Rate (BER) with low-complexity MIMO data detection, and providing higher transmission data rate compared with the MLE. Using the normalizedMSE, BER and throughput evaluated by computer simulations, it can be verified that the proposed DTE with preamble-SCP obviously provides higher estimation accuracy, better BER with low-complexity MIMO data detection, and much higher transmission data rate which is approximately 32.5 Mbps gain over the MLE at 5 MHz-BW respectively.
  • Some of the metrics are blocked by your 
    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
    ;
    Naito, Katsuhiro
    ;
    Mori, Kazuo
    ;
    ;
    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.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    Evolution of STBC-based OFDM-IM for wireless vehicular communication
    (2026-01-01)
    Mata, Tanairat
    ;
    This paper studies wireless vehicular communication (VehCom) in intelligent transportation systems using an orthogonal frequency division multiplexing with index modulation (OFDM-IM). In the concept of IM, data is transmitted not only through the modulated symbols but also via the indices of the active subcarriers. In contrast to the original OFDM, OFDM-IM activates only non-zero subcarriers, increasing energy efficiency. However, the pilot-assisted channel estimation (CE) method is a significant challenge in OFDM-IM, where the desired pilot subcarrier interval is related to the OFDM-IM subblock length. This paper proposes a walsh-scattered pilot-assisted CE for OFDM-IM VehCom. The optimum walsh-scattered pilot assignment is proposed to improve the transmission efficiency. Furthermore, a space-time block code with a high transmit diversity gain is employed for OFDM-IM VehCom to enhance VehCom's signal quality. The results show that the proposed method performs higher CE accuracy and better bit-error rate with significant spectral and energy efficiencies than conventional methods.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    Proposal of time domain channel estimation method for MIMO-OFDM systems
    (2015-01-01)
    Mata, Tanairat
    ;
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    This paper proposes a time domain channel estimation (TD-CE) method for Multi Input Multi Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems. The feature of proposed TD-CE method is to estimate channel frequency responses for all links between transmit and receive antennas in MIMO-OFDM systems by using one scattered pilot preamble symbol in the time domain. The proposed method can achieve higher channel estimation accuracy even when the number of transmission antennas is larger and the transmission signal is sampled by a non-Nyquist rate in which the number of IFFT points is different from the number of data subcarriers due to the insertion of null subcarriers (zero padding) at the both ends of data subcarriers. This paper shows various computer simulation results in the time-varying fading channels to demonstrate the effectiveness of the proposed channel estimation method as comparing with the conventional channel estimation methods.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    Proposal of STBC MIMO-OFDM for ITS systems
    (2013-09-02)
    Mata, Tanairat
    ;
    Naito, Katsuhiro
    ;
    ;
    Mori, Kazuo
    ;
    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.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    A low complexity improved-PTS phase coefficient searching algorithm for OFDM system
    (2011-08-12)
    Pantiko, Panus
    ;
    Mata, Tanairat
    ;
    ;
    Kobayashi, Hideo
    The Partial Transmit Sequence (PTS) is well known algorithm for reducing peak-to-average ratio (PAPR) in OFDM system. The PTS can improve PAPR reduction performance relatively as increasing a number of weighting factors and clusters. However, the size of side information and computation complexity proportionally increase as increasing the number of weighting factors or/and clusters. The higher computational complexity in the phase coefficient searching makes it difficult to implement in the actual OFDM system. In this paper, we propose a low computation complexity PTS phase coefficient searching algorithm conjunction with new weighting factor. The proposed method can achieve better PAPR reduction performance and computation complexity than those for the conventional PTS method. © 2011 IEEE.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    Proposal of improved PTS method for STBC MIMO-OFDM systems
    (2010-01-01)
    Mata, Tanairat
    ;
    Boonsrimuang, Pornpawit
    ;
    ;
    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.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    A PAPR Reduction for FBMC-OQAM Signals using ABC-OPTS Scheme
    (2019-04-29)
    Boontra, Pitchaya
    ;
    Mata, Tanairat
    ;
    Dataesatu, Arif
    ;
    Mori, Kazuo
    ;
    Partial Transmit Sequence (PTS) scheme has been applied to the OFDM signal for solving the high PAPR problem which can achieve better PAPR performance. However, because of the structure of the FBMC-OQAM signal which is different from the OFDM signal, the PTS scheme is not suitable for the FBMC-OQAM signal. For this reason, this paper considers the PAPR reduction for FBMC-OQAM signal. This paper proposes an overlapped PTS (OPTS) with Artificial Bee Colony (ABC) algorithm. The silent features are to improve the PAPR by modifying the PTS scheme as OPTS scheme and less computational complexity in the PAPR optimization process by using the ABC algorithm. The PAPR reduction effectiveness of the proposed method has been confirmed by the simulation results in the paper.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    Channel estimation method for SFBC MIMO-OFDM based wireless two-way relay system in time-varying fading channel
    (2014-10-03)
    Mata, Tanairat
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    ;
    This paper proposes SFBC MIMO-OFDM based two-way relay system to improve signal quality with keeping higher transmission efficiency. In the two-way relay system, each user terminal (UT) is required to estimate channel frequency responses (CFRs) for up and down links between both UTs and RS (Relay Station) precisely which are used in the demodulation of the other user's information data with frequency domain equalization. To satisfy the above requirement, this paper proposes a novel CFR estimation method for the SFBC MIMO-OFDM based two-way relay system which can achieve better CFR estimation accuracy and better BER performance even in the higher time-varying fading channel. The salient features of proposed system are to employ the SFBC technique both for data subcarriers in the pilot symbols and data symbols and to apply the Maximum Likelihood (ML) and Cubic Spline Interpolation methods to the estimated CFR at pilot subcarriers with Walsh codes in the estimation of CFR for the frequency axis and time axis, respectively. From the computer simulation results, this paper demonstrates the effectiveness of proposed system which can achieve higher signal quality with keeping higher transmission efficiency even in the higher time-varying fading channel.
  • Some of the metrics are blocked by your 
    Item type:Publication,
    Proposal of PAPR reduction method for OFDM signal by re-ordering of clusters
    (2013-01-01)
    Mata, Tanairat
    ;
    Naito, Katsuhiro
    ;
    Mori, Kazuo
    ;
    Kobayashi, Hideo
    ;
    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.