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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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Evolution of STBC-based OFDM-IM for wireless vehicular communication
(2026-01-01)
Mata, Tanairat
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Boonsrimuang, Pisit
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.
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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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Efficient reduction of peak-to-average power ratio in multiple-input multiple-output orthogonal frequency-division multiplexing system by shuffling cluster sequences
(2024-12-01)
Mi, Si Sar
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Mata, Tanairat
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Boonsrimuang, Pornpawit
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Boonsrimuang, Pisit
We propose a shuffling cluster sequence technique without separate side information (SI) for multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. In the proposed technique, the active subcarriers over two consecutive OFDM symbols are divided into (Formula presented.) clusters, and each cluster (packet frame) includes a header for ID#cluster and payload for (Formula presented.). The (Formula presented.) clusters are shuffled to reduce the peak-to-average power ratio (PAPR) of the time-domain OFDM signal, which includes the information data and SI signals, with a low computational complexity. At the receiver, the information data can be correctly reconstructed by ID#cluster in the header of each cluster, achieving a smaller bit error rate than the conventional MIMO-OFDM system without PAPR reduction. Moreover, our technique is comparable with the conventional partial transmit sequence technique without the impact of a separate SI signal even when increasing the number of transmitter antennas in a nonlinear multipath fading channel.
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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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PAPR Reduction in FBMC-OQAM Systems Using Trellis-based D-SLM with ABC Algorithm
(2020-06-01)
Jirajaracheep, Panya
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Mata, Tanairat
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Boonsrimuang, Pisit
For the next age of mobile and wireless communications systems. Filter bank multicarrier conjunction with offset quadrature amplitude modulation (FBMC-OQAM) is the non-orthogonal multicarrier modulation techniques, which is mention as an essential and prominent player. It has several advantages, such as higher spectral efficiency, as compared to the traditional methods. Nevertheless, FBMC-OQAM still has a critical weakness similar to OFDM system, which is a high peak-to-average power ratio (PAPR) at the transmitter. There are several varieties of the technique presented to defeat the severe PAPR issue. The Trellis-based D-SLM technique is presented to employ and achieve a significantly improve PAPR curtailment performance. However, The Trellis-based method still has a limitation of its high computational complexity. This study presents the Trellis-based D-SLM scheme with artificial bee colony (ABC) phase optimization, which achieves lower computational complexity. The results of PAPR performance evaluation through computer simulation, the proposed technique can deliver a performance of PAPR reduction similar to the conventional Trellis-based D-SLM technique, but the proposed technique requires around 10% computation complexity of the conventional technique.
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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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