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Optimized CNN-based channel estimation for zero-padded uplink OFDMA in 5G new radio over fast-fading channels
(2026-07-01)
Mata, Tanairat
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Boonsrimuang, Pisit
This paper addresses a pilot-assisted channel estimation applicable to the uplink orthogonal frequency-division multiple-access with zero-padding in a 5G new radio. The adjacent uplink subchannels in the frequency domain are allocated separately for each user, and each subchannel assigns the pilot signal independently. This paper proposes a convolutional neural network-based channel estimation, including one-dimensional and two-dimensional architectures, designed to optimize the handling of rapid fading channel variations encountered in high-mobility scenarios. The estimation process leverages the subchannels of each user to enhance accuracy. Simulation results demonstrate the effectiveness of the proposed method in offering a better bit-error rate and a higher transmission data rate than the conventional channel estimation methods under challenging conditions. Finally, this paper discusses the considerable computational complexity of aspects of the lightweight two convolutional neural network architectures.
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Robust Channel Estimation for MIMO-OFDM-IM Full-Duplex Relaying under Residual Self-Interference in Time-Varying Fading
(2026-01-01)
Mata, Tanairat
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Boonsrimuang, Pisit
Full-duplex relaying can significantly improve spectral efficiency in vehicular communications, but its practical performance is constrained by residual self-interference (SI) and rapidly time-varying channels. This work proposes a Walsh–Hadamard and null (WHN) pilot with maximum likelihood (ML)–based channel estimation (CE) for MIMO OFDM-IM full-duplex relays. Unlike prior designs that prioritize either low complexity or estimation accuracy, the proposed WHN scheme improves the performance–complexity trade-off by leveraging asymmetric pilot intervals and structured orthogo nalization. Two widely recognized baselines are considered for comparison: (i) cyclic-shifted Zadoff–Chu (CS-ZC) preamble pilots representing the low-complexity DFT-domain benchmark, and (ii) scattered pilot-and-null (PN) patterns with ML refinement representing the high-accuracy benchmark used in LTE/5G systems. Results reveal a consistent carrier-to-noise power ratio (CNR)-dependent crossover: WHN outperforms CS-ZC when CNR≥28dBandsurpassesPNundermoderate-to-high mobility. At 35 dB CNR, WHN provides up to 35% BER reduction with only 29% complexity overhead. A standard-compliant link budget analysis further indicates non-trivial coverage gains under the evaluated Doppler regimes and considered residual SI model. All simulation assumptions, Doppler profiles, and SI models follow V2X guidelines, and results are validated across multiple random seeds. Overall, WHN offers a complexity-aware CE solution for full-duplex V2X systems.
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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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Pilot-Assisted Channel Estimation for SFBC MIMO-OFDM with Index Modulation in Higher Time-Varying Fading Channel
(2024-01-01)
Mata, Tanairat
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Boonsrimuang, Pisit
Orthogonal frequency division multiplexing (OFDM) with Index modulation can provide higher spectral and energy efficiencies. For multiple-input, multiple-output OFDM with space-frequency block coding (SFBC MIMO-OFDM), the transmitter can send the information signal with high transmit diversity gain to the receiver, improving system performance. In this paper, we propose a pilot-assisted channel estimation by using SFBC MIMO-OFDM with index modulation. The proposed system can perform a better bit-error-rate (BER) performance and higher transmission data rate than the conventional system in a higher time-varying fading channel.
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An Effective Channel Estimation for Massive MIMO–OFDM System
(2020-09-01)
Mata, Tanairat
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Boonsrimuang, Pisit
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.
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Proposal of a combined CFR estimation method for practical bidirectional ANC-OFDM system in higher time-varying fading channel
(2019-07-15)
Mata, Tanairat
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Boonsrimuang, Pisit
In bidirectional analogue network coding based on orthogonal frequency division multiplexing (ANC-OFDM) system, two users can transfer their data to each other via the Relay during two timeslots. Each user can demodulate the other user’s data after removing the self-data with equalizing by employing the combined channel frequency response (CFR) estimated at each user in the 2nd timeslot. From this reason, the accurate channel estimation method for the combined CFR acts on the bit-error-rate (BER) performance of the bidirectional ANC-OFDM system. To satisfy the requirement, a combined CFR estimation with Chu code and a combined CFR estimation with Walsh code methods were proposed for bidirectional ANC-OFDM system which can achieve the higher channel estimation accuracy. However, their accuracy of channel estimation would be degraded a lot at the non-Nyquist rate in the practical bidirectional ANC-OFDM system. To solve this problem, this paper proposes a combined CFR estimation method for practical bidirectional ANC-OFDM system which can improve much higher the accuracy of channel estimation and get better BER performance. The silent features of the proposed method are to estimate the combined CFR by applying the maximum likelihood technique with the proposed special pilot subcarrier arrangement which can provide the accurate channel estimation for the combined CFR in the practical bidirectional ANC-OFDM system and to estimate the combined CFR over one OFDM frame by applying the cubic spline interpolation technique which can achieve the higher channel estimation accuracy in higher time-varying fading channel. In the performance evaluations, the normalized mean square error (MSE) as the channel estimation accuracy and BER performances are evaluated by using the computer simulations in higher time-varying fading channel at the non-Nyquist rate. The excellent normalized MSE and BER performances of the proposed method have been verified by the computer simulations in this paper.
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Proposal of channel estimation method for wireless two-way relay system of using SFBC MIMO-OFDM technique
(2016-12-01)
Mata, Tanairat
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Boonsrimuang, Pisit
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Mori, Kazuo
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Kobayashi, Hideo
In a two-way relay communication system, two user terminals (UTs) can communicate and exchange their information data through a relay station by using two timeslots. To realize the two-way relay communication system, each UT is required to estimate channel frequency responses (CFRs) both for up and down links in two timeslots efficiently which be employed in the demodulation of the other user’s information data with frequency domain equalization. To satisfy this requirement, this paper proposes a novel CFR estimation method for the wireless two-way relay communication system of using SFBC MIMO-OFDM technique. The salient feature of proposed CFR estimation method is to employ the maximum likelihood estimation method for the proposed scattered pilot subcarriers assignment which can achieve higher CFR estimation accuracy even in higher time-varying fading channel and when the transmission OFDM signal is sampled by the non-Nyquist rate. In the proposed system, the SFBC technique is also employed for the data subcarriers both for the pilot symbols including data subcarriers and data symbols consisting of all data subcarriers in the frequency axis to improve the bit error rate (BER) performance in the two-way relay system. From the computer simulation results, this paper demonstrates the effectiveness of proposed two-way relay communication system of using SFBC MIMO-OFDM technique. To demonstrate the effectiveness of proposed two-way relay communication system of using SFBC MIMO-OFDM technique, this paper conducts various computer simulations as comparing with the conventional methods in higher time-varying fading channel. From the computer simulation results, this paper confirms that the proposed method even at the non-Nyquist rate can achieve higher channel estimation accuracy evaluated by the normalized mean square error (NMSE) and better BER performances by 5 and 22 times, respectively as comparing with the conventional methods when the normalized Doppler frequency (f<inf>d</inf>T<inf>S</inf>) is 10 <sup>- 2</sup> and the carrier to noise power ratio (C/N) is 25 dB.
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Joint iterative channel estimation and decoding under impulsive interference condition
(2016-03-01)
Insom, Patcharin
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Insom, Piyakiat
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Boonsrimuang, Pisit
Even though Low-Density-Parity-Check (LDPC) code which has the decoding performance close to the Shannon Limit and it is designed as a powerful forward-error-correction (FEC) code in the Additive White Gaussian Noise (AWGN) channel, simulation results show that the performance of LDPC decoder is degraded when exposed to the impulsive noise. According to such a impulsive noise impact, joint iterative channel estimation and decoding technique is proposed in this paper so as to decrease the effect of impulsive interference while less complicated in processing. The proposed methods decreases the complexity by implementing the simple way of channel estimation and applying joint iterative technique between channel estimation and LDPC decoding under two kind of impulsive noise; pulsed radio frequency interference(RFI) and symmetric alpha-stable (SαS). In the optimal decoder, channel parameter estimation can be as accurate as possible. Because computed in every time of iterative decoder, channel parameters have been always optimized resulting in the enhancement of LDPC decoder performance.
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Joint iterative channel estimation and decoding under pulsed radio frequency interference condition
(2014-01-01)
Insom, Patcharin
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Liu, Rongke
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Duan, Ruifeng
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Hou, Yi
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Boonsrimuang, Pisit
Pulsed Radio Frequency Interference (RFI) has severely effected on communication system in common. Even though Low-Density-Parity-Check (LDPC) code which has the decoding performance to approach the Shannon Limit and it is designed as a powerful forward-error-correction (FEC) code in the Additive White Gaussian Noise (AWGN) channel, simulation results show that the performance of LDPC decoder is degraded when exposed to the pulsed RFI. According to such a pulsed RFI impact, joint iterative channel estimation and decoding technique is proposed in this paper so as to decrease the effect of pulsed RFI while less complicated in processing. The proposed method decreases the complexity by implementing the simple way of SNR estimation and improves the efficiency and applying joint iterative technique between channel estimation and decoding. For optimal decoder performance, Signal-to-Noise Ratio (SNR) estimation must be as accurate as possible. Because computed in each time of iterative decoder, noise variance has been always change resulting in the performance of LDPC decoder has better in efficiency. The simulation results show that both less complexity and higher outcomes can be achieved by this proposed approach. © 2014 Global IT Research Institute (GIRI).
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Doppler spread mitigation using harmonic transform for wireless OFDM systems in mobile communications
(2010-01-01)
Saiyod, Saiyan
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Thipchaksurat, Sakchai
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Varakulsiripunth, Ruttikorn
In wireless OFDM systems, the system performance is suffered from frequency offset and symbol timing offset due to the Doppler effect. Using the discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) for traditional signal transformation from the time-domain into frequency-domain, and vice versa, the system performance may be severely degraded. To make the OFDM system that can tolerate the above problems, we have considered that the harmonic transform can be applicable to the traditional signal transformation, thereby improving the system performance. In this paper, we combine the good characteristics of harmonic transform and instantaneous frequency to be a novel transformation for wireless OFDM systems. We propose a modified discrete harmonic transform (MDHT) which can be performed adaptively. Our proposed scheme called the modified discrete harmonic transform OFDM (MDHT-OFDM scheme). We derive the equations of the novel discrete harmonic transform which are suitable for wireless OFDM systems and the novel channel estimation cooperated with the novel transformation. The proposed channel estimation is performed in both time-domain and frequency-domain. The performance of a MDHT-OFDM scheme is evaluated by means of a simulation. We compare the performance of a MDHT-OFDM scheme with one of the conventional DFT-OFDM scheme in the term of symbol error rate (SER). MDHT-OFDM scheme can achieve better performance than that of the conventional DFT-OFDM scheme in mitigating the Doppler spread. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers.

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