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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
    ;
    Siriwanitpong, Aphitchaya
    ;
    Boonsrimuang, Pornpawit
    ;
    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
    ;
    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
    ;
    Siriwanitpong, Aphichaya
    ;
    Boonsrimuang, Pornpawit
    ;
    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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    An efficient uplink OFDMA channel estimation under high-speed mobile environment
    (2017-11-03)
    Aiempo, Pimracha
    ;
    Boonsrimuang, Pisit
    ;
    Mata, Tanairat
    ;
    Anunvrapong, Pramote
    OFDMA (Orthogonal Frequency Division Multiple Access) was known extensively for operating in various mobile communication systems. In OFDMA system, there are two parts of communication link, uplink which the uplink OFDMA is considered in this paper, and downlink. In uplink OFDMA communication, all users send their information signals to base station at the same time. Each channel between user and base station requires to be estimated from the combined received signals at base station. From this reason, this paper proposes a channel estimation method for actual uplink OFDMA system which N points IFFT/FFT is larger than M data subcarriers (N>M) which can provide more accuracy for channel estimation. In the computer simulation results, the normalized mean square error (NMSE) performance is evaluated for the channel estimation accuracy under high-speed mobile environment. There is 12dB gain at 10<sup>-1</sup> of NMSE for the proposed method over the conventional method as shown in the result.
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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
    ;
    Mata, Tanairat
    ;
    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.