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- 저자 : Shun Kojima (검색결과 3 건)
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Modified pilot selection for channel estimation of systematic polar coded MIMO-OFDM
Koya Watanabe,Shun Kojima,Takashi Akao,Masato Katsuno,Kazuki Maruta,안창준 한국통신학회 2019 ICT Express Vol.5 No.4
This paper proposes a modified pilot selection for channel estimation of systematic polar coded MIMO-OFDM. Polar codes provably achieve the theoretical limit for communication systems and systematic polar codes generate the codeword that has the same value of information bit. Using this property, an efficient channel estimation scheme was proposed; values of some information bits are fixed to zeros or ones and utilized for pilot symbols. Similarly, we also can fix values of some frozen bit as zeros or ones by exploiting features of the encoding generator. By combining these advantages, pilot signals are selected from the systematic polar coded symbols themselves and we do not need add and insert pilot symbols just to estimate the channel. Leveraging this, we apply the proposed systematic polar coding scheme to MIMO-OFDM system under frequency selective fading channel.
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CNN-based blind SIR classification framework for STPA-BAA spectrum superposing
Hiroaki Kobayashi,Shun Kojima,Kazuki Maruta,Takatoshi Sugiyama,Chang-Jun Ahn 한국통신학회 2023 ICT Express Vol.9 No.1
Spectrum sharing in the spatial domain among the plurality of wireless communication systems should be addressed due to its exhaustion. We previously conceptualized a spectrum superposing enabled by subcarrier transmission power assignment (STPA) and blind adaptive array (BAA), where co-channel interference can be suppressed even without a priori information of interferer. However, it requires knowledge of input signal-to-interference power ratio (SIR) to realize completely blind operation. This paper proposes a blind SIR estimation framework by convolutional neural network (CNN) using power spectrum images. Simulation verifies the proposed scheme can maximize throughput performance based on SIR classification results with 97% accuracy.
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Reducing channel spatial correlation by rotating planar antenna array
Takashi Akao,Koya Watanabe,Shun Kojima,Masato Katsuno,Kazuki Maruta,안창준 한국통신학회 2019 ICT Express Vol.5 No.4
This paper newly proposes a direct antenna array control approach to reduce channel spatial correlation for multiuser spatial multiplexing. Conventional rectangular arrays can form three dimensional beams and have superior signal separation performance compared to linear arrays. However, when the arrival angles of some signals are close, the signal separation (interference cancellation) performance deteriorates since the projection points onto horizontal/vertical axes of several antenna elements overlap and spatial resolution along each axis is degenerated. The key proposal is to improve signal separation performance by mechanically changing the positional relationship of antenna elements. The proposed scheme can achieve better Bit Error Rate (BER) performance by searching the optimal antenna rotation angle.
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