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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.
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.
Cooperative interaction of Angiopoietin-like proteins 1 and 2 in zebrafish vascular development.
Kubota, Yoshiaki,Oike, Yuichi,Satoh, Shinya,Tabata, Yoko,Niikura, Yuichi,Morisada, Tohru,Akao, Masaki,Urano, Takashi,Ito, Yasuhiro,Miyamoto, Takeshi,Nagai, Norihiro,Koh, Gou Young,Watanabe, Sumiko,Sud National Academy of Sciences 2005 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.102 No.38
<P>Angiopoietin-like protein (Angptl) 1 and Angptl2, which are considered orphan ligands, are highly homologous, particularly in the fibrinogen-like domain containing the putative receptor binding site. This similarity suggests potentially cooperative functions between the two proteins. In this report, the function of Angptl1 and Angptl2 is analyzed by using morpholino antisense technology in zebrafish. Knockdown of both Angptl1 and Angptl2 produced severe vascular defects due to increased apoptosis of endothelial cells at the sprouting stage. In vitro studies showed that Angptl1 and Angptl2 have antiapoptotic activities through the phosphatidylinositol 3-kinase/Akt pathway, and coinjection of constitutively active Akt/protein kinase B mRNA rescued impaired vascular development seen in double knockdown embryos. These results provide a physiological demonstration of the cooperative interaction of Angptl1 and Angptl2 in endothelial cells through phosphatidylinositol 3-kinase/Akt mediated antiapoptotic activities.</P>