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Deep Learning-Based Channel Estimation With 1D CNN for OFDM Systems Under High-Speed Railway Environments
(2025-01-01)
Siriwanitpong, Aphitchaya
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Sanada, Kosuke
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Hatano, Hiroyuki
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Mori, Kazuo
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Boonsrimuang, Pisit
In OFDM wireless communications, channel estimation performance is compromised in high-speed railway environments owing to extremely fast multipath fading and severe Doppler effect. Recently, a deep learning approach has been employed to improve the channel estimation performance, however it encounters significant challenges due to its high computational complexity. In order to deal with these challenges, this paper proposes channel estimation employing deep learning with one-dimensional convolutional neural network (1D CNN) schemes to enhance conventional least squares (LS) estimation. The first scheme provides better performance compared to conventional LS estimation. However, it is only suitable for OFDM systems with full pilot symbols, leading to decreased transmission efficiency and high complexity. In order to address those problems, the second scheme develops 1D CNN-based channel estimation employing scattered pilot symbols to enhance transmission efficiency and reduce computational complexity. In comparison to conventional LS estimation and deep learning-based channel estimation with bi-gated recurrent unit (bi-GRU), the performance evaluation demonstrates that the proposed 1D CNN-based schemes simultaneously improve channel estimation performance, transmission efficiency, and reduce computational complexity.
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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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Boonsrimuang, Pisit
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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Low-complexity based TDE Method for OFDM signal in higher time-varying fading channels
(2020-01-01)
Tanangsanakool, Saha
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Reangsuntea, Pongsathorn
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Mori, Kazuo
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Boonsrimuang, Pisit
Orthogonal Frequency Division Multiplexing (OFDM) signal would be damaged significantly by inter-carrier interference (ICI) in higher time-varying fading channels. The ICI leads to fatal degradation of bit error rate (BER) performance due to the loss of orthogonality among subcarriers. To solve this problem, this paper proposes a high accuracy time-domain channel impulse response (CIR) estimation method and low-complexity based time-domain equalization (TDE) method for solving the simultaneous equations instead of using an inverse matrix calculation which can achieve better BER performance and lower computation complexity even in higher time-varying fading channels. The salient 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 the time domain equalization (TDE) method with 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 instead of using an inverse matrix calculation, which remains the computation complexity up to 7.8% of inverse matrix calculation with the same BER performance but achieves the BER performance when compared with the conventional method. This paper presents various simulation results in higher time-varying fading channels (vehicle speed ≈ 381 km/hrs) to demonstrate the effectiveness of the proposed method as compared with conventional FDE and TDE methods.
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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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Boonsrimuang, Pisit
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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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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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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.
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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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Boonsrimuang, Pisit
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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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Proposal of STBC MIMO-OFDM for ITS systems
(2013-09-02)
Mata, Tanairat
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Naito, Katsuhiro
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Boonsrimuang, Pisit
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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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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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Boonsrimuang, Pisit
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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Proposal of simple PAPR reduction method for OFDM signal by using dummy sub-carriers
(2008-01-01)
Boonsrimuang, Pisit
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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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PAPR reduction of OFDM signal by use of DSI method with time-frequency domain swapping algorithm
(2007-01-01)
Boonsrimuang, Pisit
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Naito, Katsuhiro
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Mori, Kazuo
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Paungma, Tawil
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Kobayashi, Hideo
The main disadvantage of orthogonal frequency division multiplexing (OFDM) is the high time domain PAPR. The larger PAPR signal would fatally degrade BER performance in non-linear channels. This paper proposes an improved DSI method, which can achieve better PAPR and BER performances in the non-linear channel with less computation complexity than the conventional DSI method. The feature of proposed method is to employ the time-frequency domain swapping algorithm in the determination of frequency data for dummy sub-carriers. This paper presents various computer simulation results to verify the effectiveness of proposed DSI method. Copyright © 2007 The Institute of Electronics, Information and Communication Engineers.

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