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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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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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Boonsrimuang, Pisit
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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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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Channel Estimation for Enhanced Subcarrier Index Modulation OFDM Using Zadoff-Chu Sequence Pilot in Nonlinear Channel
(2022-01-01)
Mi, Si Sar
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Siriwanitpong, Aphichaya
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Boonsrimuang, Pornpawit
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Boonsrimuang, Pisit
Orthogonal Frequency Division Multiplexing with Index Modulation (OFDM-IM) is a digital modulation scheme that conveys additional information bits by using the index of subcarriers. OFDM with enhanced subcarrier index modulation (OFDM-SIM) has been recently proposed to improve the bit error rate (BER) performance of multicarrier communication systems. It is challenging to estimate channel variation of the OFDM-SIM system in wireless communication systems for coherent detection at the receiver side. This paper proposes a new pilot data information Zadoff-Chu sequence for the channel estimation OFDM-SIM system. And OFDM-SIM channel estimation will be done by using the conventional OFDM-SIM symbol pilot and the proposed Zadoff-Chu sequence pilot in the multipath Rician fading channel. And evaluate the simulation results by using BER performance. BER results of channel estimation OFDM-SIM with proposed Zadoff-Chu sequence pilot decreased than BER results of channel estimation OFDM-SIM using conventional OFDM-SIM symbol pilot. And we evaluate the proposed Zadoff-Chu sequence channel estimation OFDM-SIM in a nonlinear multipath Rician fading channel. We can see that the proposed Zadoff-Chu sequence pilot outperformed than conventional OFDM-SIM symbol pilot in every input back off (IBO)=0 dB,-2dB,-4dB, and-6dB. Our proposed channel estimation method is evaluated by using computer simulation.
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A low-complexity PAPR reduction for space-time block code MIMO-OFDM by using modified-PTS with ABC-concurrent algorithm
(2020-01-01)
Boontra, Pitchaya
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Mata, Tanairat
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Boonsrimuang, Pisit
One of the problems of using Orthogonal Frequency Division Multiplexing (OFDM) technique is the higher Peak-to-Average Power Ratio (PAPR) which leads to the fatal degradation of the system performance in the non-linear channel. To solve this problem, the partial transmit sequence (PTS) was proposed for Space-Time Block Code (STBC) with Multi-Input and Multi-Output (MIMO)-OFDM as STBC MIMO-OFDM system which can reduce the PAPR effectively. However, its complexity in the PAPR reduction process becomes higher in proportion to the increase of its considered cluster number. To solve this problem, this paper proposes a low-complexity PAPR reduction by using the modified-PTS with artificial bee colony (ABC) and concurrent algorithm as ABC-Concurrent algorithm for STBC MIMO-OFDM system which can improve better PAPR with low-complexity and can perform better Bit-Error-Rate (BER) in the non-linear channel. The silent features of the proposed modified-PTS with ABCConcurrent algorithm are to reduce the PAPR with decreasing side information (SI) to half by modifying PTS with the concurrent algorithm and to reduce the complexity in PAPR reduction process by applying ABC algorithm for STBC MIMO-OFDM system. From the various results by using computer simulation, it can be confirmed that the proposed modified-PTS with ABC-Concurrent algorithm can reduce PAPR by approximately 3.4 and 0.4 dB at CCDF 10<sup>-3</sup> as comparing with the original STBC MIMO-OFDM and conventional PTS methods respectively, and can use the complexity approximately only 19% in PAPR reduction process which is decreased a lot from using the conventional PTS method. Moreover, the proposed method can perform the better BER in the non-linear channel than the original STBC MIMO-OFDM and the conventional. PTS methods which is close to that of operating in nonlinear channel.
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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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Evaluation of rotated constellation in DVB-T2 based on measurement data
(2019-07-01)
Suwansukho, Nattapan
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Promwong, Sathaporn
This paper describes the result of using Rotated Constellation Feature that include Digital Terrestrial Television second generation network in Thailand. The measured results were carried out from 20 measured location, located in Bangkok, Thailand.
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A PAPR reduction scheme based on improved PTS with ABC algorithm for OFDM signal
(2018-07-02)
Mata, Tanairat
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Boonsrimuang, Pisit
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Boontra, Pitchaya
A high PAPR is well known as the serious problem of OFDM system because of a huge degradation of its signal quality, especially in the non-linear channel. From the reason, many PAPR reduction schemes have been proposed for solving this problem. The Partial Transmit Sequence (PTS) scheme is one of the PAPR reduction schemes which can improve the PAPR performance effectively. However, its computational complexity would be increased which is proportional to the increasing number of symbol clusters in the optimum PAPR value for a PAPR reduction process. To solve this problem, this paper proposes the PAPR reduction scheme based on the improved PTS with Artificial Bee Colony (ABC) algorithm for OFDM system. The potential capability of the proposed scheme is the PAPR reduction performance with low computational complexity which leads to the improvement of signal quality in the OFDM system. The excellent PAPR reduction performance with the low computational complexity of the proposed scheme has been verified by the computer simulations in this paper.
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Proposal of channel estimation scheme for practical V-BLAST MIMO-OFDM system
(2017-07-01)
Inkamchua, Nakarin
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Boonsrimuang, Pisit
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Mata, Tanairat
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Sopin, Anan
In wireless communication, multiple input and multiple output technique is often applied with orthogonal frequency division multiplexing (MIMO-OFDM) because of its many advantages such as spectral efficiency, link reliability, diversity gain and so on. In the practical MIMO-OFDM system, it has a signal aliasing problem due to the mismatch of sampling from adding zero padding at both front and rear of data transmission in each OFDM symbol. To solve this problem, the channel estimation by using the new comb-type pilot symbol arrangement scheme is proposed for the practical MIMO-OFDM system. From the computer results, it can be shown that the proposed channel estimation scheme can perform higher system performances than the conventional scheme in the practical V- BLAST MIMO-OFDM system.
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An adaptive demodulation for OFDM signal
(2017-01-18)
Manosueb, Anchalee
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Koseeyaporn, Jeerasuda
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Wardkein, Paramote
This paper presents a novel method for OFDM demodulation based on LMS adaptive filter. In this proposed method, data symbol is reconstructed from amplitude of reference signal without using fast Fourier transform and thus this method can be applied for real time system. In addition, the convergence rate of adaptive filter can be promoted by using the proper initial weights. The proposed technique will be applied for BASK-OFDM, BPSK-OFDM and QAM-OFDM demodulation. The obtained simulation results of the proposed method compared to the conventional scheme show that the proposed technique can be applied for real time processing of OFDM demodulation.

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