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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
;
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
;
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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Pilot-Assisted Channel Estimation for SFBC MIMO-OFDM with Index Modulation in Higher Time-Varying Fading Channel
(2024-01-01)
Mata, Tanairat
;
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
;
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
;
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
;
Boonsrimuang, Pisit
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Mori, Kazuo
;
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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