鹿児島大学 · 理工学研究科

研究キーワードmassive MIMO systems・belief propagation detection・chaos-based communication・signal constellation design・wireless communication・decoding algorithms

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• Kawahara T., Arita K., Fujio S., Higa N., Hata H., Moinuddin F.M., Hanaya R. . Patients of idiopathic normal-pressure hydrocephalus have small dural sac in cervical and upper thoracic levels:2023 · 記述言語： 日本語 出版者・発行元： Surgical Neurology International Background: Idiopathic normal pressure hydrocephalus (iNPH) is a neurological disorder presenting a triad including dementia and ventricular enlargement. The mechanism causing excessive cerebrospinal fluid (CSF) accumulation in the ventricles in iNPH is poorly understood. We hypothesized that the age-related degradation of the spinal shock-absorbing system composed of a spinal dural sac (SDS) and surrounding soft tissue, preventing ventricular enlargement caused by wide CSF pulsation driven by heartbeats, may be involved in the ventricular enlargement observed in iNPH. Methods: Sixty-four patients with iNPH in their seventies who underwent a lumboperitoneal shunt and a control group of 79 people in the same age group who underwent brain check-ups were included in the study. We compared the sizes of the cervical and upper parts of the thoracic SDS using magnetic resonance imaging between the two groups. Results: The anterior-posterior distances of the dural sac at C5 were shorter in patients with iNPH of both sexes than those in the control group (P = 0.0008 in men and P = 0.0047 in women). The number of disc levels with disappeared CSF space surrounding the cervical cord was more in iNPH (P = 0.0176 and P = 0.0003). The midsagittal area of the upper part of the spinal sac, C2-Th4, was smaller in iNPH (P = 0.0057 and P = 0.0290). Conclusion: Narrowing of the cervical dural sac and midsagittal area in the upper part of the SDS in patients with iNPH may reflect the degradation of the shock-absorbing mechanism for CSF pressure pulsations, which may cause iNPH or at least aggravate iNPH by other unknown causes. DOI： 10.25259/SNI_474_2023 Scopus PubMed
• Sakoda K., Hata H., Hata S. . Dynamical Behavior of Belief Propagation Detection Models in Massive MIMO Systems . 2023 6th International Conference on Information Communication and Sig2023 · 記述言語： 日本語 出版者・発行元： 2023 6th International Conference on Information Communication and Signal Processing, ICICSP 2023 Massive multiple input multiple output (MIMO) systems have been proposed as a potential method for high-capacity wireless communications. The belief propagation (BP) detection has recently attracted significant attention owing to its high estimation accuracy and practical computation time in MIMO systems. Although there is a choice of models for evaluating variances of residue components in the BP detection, no comparative analysis has thus far reported. In this study, we compare the bit error rate (BER) and dynamical behavior in iterative estimation among several models. Numerical results show that the models exhibit qualitatively different dynamical behaviors, which lead consequently different decoding accuracy among models. We also discuss potential improvements of the models based on the results. DOI： 10.1109/ICICSP59554.2023.10390786 Scopus
• 迫田 和之, 秦 浩起, 秦 重史 . 信号点間距離一定のカオス暗号と大規模MIMOにおけるBP復号 . 電子情報通信学会論文誌B 通信J105-B ( 7 ) 535 - 542 2022年7月 詳細を見る 記述2022 · 記述言語： 日本語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： 電子情報通信学会 近年，無線通信の需要が高まり続けており，それに伴う技術的な需要として通信容量とセキュリティの向上が挙げられる．通信容量を向上させる技術の中核となる大規模MIMO（Multiple-Input Multiple-Output）の研究が盛んに行われており，その中でも，復号性能の高いBP（Belief-Propagation）法を用いた復号（BP復号）を導入した大規模MIMOが注目されている．セキュリティを向上させる方法として，従来のセキュリティに併用できるカオス暗号がある．それをBP復号を用いた大規模MIMOに適用させた手法（前手法）は，通信容量とセキュリティの向上を同時に実現することが期待できる．しかしながら，前手法は，無符号化時と比べると誤り率が大きく増加する．その原因は，信号空間ダイヤグラム上の信号点間距離の減少にある．本研究では，前手法のカオス暗号を基に，信号点間距離を一定に保つ新たなカオス暗号を導入し，その性能を評価する．数値実験の結果，計算時間は大きく変わらず，誤り率とセキュリティ性能は前手法より優れることが確認できた． DOI： 10.14923/transcomj.2021jbp3039 CiNii Research
• Kazuyuki Sakoda, Hiroki Hata, and Shigefumi Hata2020 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌）

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