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- 저자 : Kazuki Maruta (검색결과 6 건)
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Kentaro Yonei,Kazuki Maruta,안창준 한국통신학회 2020 ICT Express Vol.6 No.3
This article proposes a novel wireless channel estimation method suited for fast fading environment. Generally, forward error correction (FEC) requires long block code length to raise error correction capability while it deteriorates the channel tracking accuracy in pilot-aided estimation. To meet these trade-off demands, we propose a frame splitting and decision directed channel estimation (DDCE). It splits information data in half and estimate channel state information (CSI) of the former part. That of latter is simply extrapolated using the former CSI. Computer simulation result shows that the proposed method can improve bit error rate performance even at fast fading environment.
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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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Satoshi Taroda,Ken Tezuka,Shoichi Higuchi,안창준,Kazuki Maruta 한국통신학회 2019 ICT Express Vol.5 No.4
Due to large peak-to-average power ratio (PAPR) at the time domain OFDM signal, various peak signal reduction methods for OFDM systems have been proposed. However, in a transmit OFDM beamforming, multiplication of the transmit signal using the weights causes transmit power imbalance between antennas and increases peak signal. We propose two approaches to mitigate these problems. Adding the pseudo-noise to covariance matrix at the process of weight calculation can alleviate the transmit power imbalance. Furthermore, the companding transform of time domain signal can reduce the peak signals. We show details of proposed methods and evaluate PAPR and BER performance.
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Variable-channel Threshold-based Hybrid AF-DF Cooperative Communications with Packet Splitting
Ken Tezuka,Satoshi Taroda,Shoichi Higuchi,Kazuki Maruta,Chang-Jun Ahn 대한전자공학회 2018 IEIE Transactions on Smart Processing & Computing Vol.7 No.5
Cooperative communications has been widely researched as an attractive way to improve wireless communications systems with a small number of antennas and low power consumption. However, forward processing in the relay terminals means consuming the power of relays in other terminals. Therefore, the waste of electricity from forwarding is to be reduced as much as possible. In this paper, we propose and analyze a new relay system for three-node, hybrid, cooperative communications systems, where the relay terminal may choose to transmit messages using amplifyand-forward (AF) with expansion of the channel matrix or using decode-and-forward (DF) with packet-splitting transmission. This is based on the qualities of the channels in the source–relay and source–destination links. Then, in the proposed system, the decision on the forwarding scheme is made in order to calculate a threshold based on the equation of the channel capacity. From the simulation results, the proposed system can improve the bit error rate and reduce the load from forward processing latency at the relay.
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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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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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