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• A 2x2 MIMO spatial multiplexing 5G signal reception in a 500 km/h high-speed vehicle using an augmented channel matrix generated by a Delay and Doppler Profiler

  Suguru Kuniyoshi, Rie Saotome, Shiho Oshiro, Tomohisa Wada

  IJCSNS International Journal of Computer Science and Network Security ( IJCSNS International Journal of Computer Science and Network Security )  23 ( 10 ) 1 - 10   2023年10月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  　概要を見る

  This paper proposes a method to extend Inter-Carrier Interference (ICI) canceling Orthogonal Frequency Division Multiplexing (OFDM) receivers for 5G mobile systems to spatial multiplexing 2x2 MIMO (Multiple Input Multiple Output) systems to support high-speed ground transportation services by linear motor cars traveling at 500 km/h. In Japan, linear-motor high-speed ground transportation service is scheduled to begin in 2027. To expand the coverage area of base stations, 5G mobile systems in high-speed moving trains will have multiple base station antennas transmitting the same downlink (DL) signal, forming an expanded cell size along the train rails. 5G terminals in a fast-moving train can cause the forward and backward antenna signals to be Doppler-shifted in opposite directions, so the receiver in the train may have trouble estimating the exact channel transfer function (CTF) for demodulation. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceller is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number n to receiver sub-carrier number l is generated. In case of n≠l, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 8 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, 2x2MIMO QPSK and 16QAM modulation schemes, BER (Bit Error Rate) improvement was observed when the number of taps in the multi-tap equalizer was set to 31 or more taps, at a moving speed of 500 km/h and in an 8-pass reverse doppler shift environment.

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• Delay and Doppler Profiler based Channel Transfer Function estimation for 2x2 MIMO Receivers in 5G System Targeting a 500km/h Linear Motor Car

  Suguru Kuniyoshi, Rie Saotome, Shiho Oshiro, Tomohisa Wada

  IJCSNS International Journal of Computer Science and Network Security ( IJCSNS International Journal of Computer Science and Network Security )  23 ( 9 ) 8 - 16   2023年09月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  　概要を見る

  In Japan, high-speed ground transportation service using linear motors at speeds of 500 km/h is scheduled to begin in 2027. To accommodate 5G services in trains, a subcarrier spacing frequency of 30 kHz will be used instead of the typical 15 kHz subcarrier spacing to mitigate Doppler effects in such high-speed transport. Furthermore, to increase the cell size of the 5G mobile system, multiple base station antennas will transmit identical downlink (DL) signals to form an expanded cell size along the train rails. In this situation, the forward and backward antenna signals are Doppler-shifted in opposite directions, respectively, so the receiver in the train may suffer from estimating the exact Channel Transfer Function (CTF) for demodulation. In a previously published paper, we proposed a channel estimator based on Delay and Doppler Profiler (DDP) in a 5G SISO (Single Input Single Output) environment and successfully implemented it in a signal processing simulation system. In this paper, we extend it to 2x2 MIMO (Multiple Input Multiple Output) with spatial multiplexing environment and confirm that the delayand DDP based channel estimator is also effective in 2x2 MIMO environment. Its simulation performance is compared with that of a conventional time-domain linear interpolation estimator. The simulation results show that in a 2x2 MIMO environment, the conventional channel estimator can barely achieve QPSK modulation at speeds below 100 km/h and has poor CNR performance versus SISO. The performance degradation of CNR against DDP SISO is only 6dB to 7dB. And even under severe channel conditions such as 500km/h and 8-path inverse Doppler shift environment, the error rate can be reduced by combining the error with LDPC to reduce the error rate and improve the performance in 2x2 MIMO. QPSK modulation scheme in 2x2 MIMO can be used under severe channel conditions such as 500 km/h and 8-path inverse Doppler shift environment.

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• A Modified Delay and Doppler Profiler based ICI Canceling OFDM Receiver for Underwater Multi-path Doppler Channel

  Catherine Akioya, Shiho Oshiro, Hiromasa Yamada, Tomohisa Wada

  IJCSNS International Journal of Computer Science and Network Security ( IJCSNS International Journal of Computer Science and Network Security )  23 ( 7 ) 1 - 8   2023年07月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  　概要を見る

  An Orthogonal Frequency Division Multiplexing (OFDM) based wireless communication system has drawn wide attention for its high transmission rate and high spectrum efficiency in not only radio but also Underwater Acoustic (UWA) applications. Because of the narrow sub-carrier spacing of OFDM, orthogonality between sub-carriers is easily affected by Doppler effect caused by the movement of transmitter or receiver. Previously, Doppler compensation signal processing algorithm for Desired propagation path was proposed. However, other Doppler shifts caused by delayed Undesired signal arriving from different directions cannot be perfectly compensated. Then Receiver Bit Error Rate (BER) is degraded by Inter-Carrier-Interference (ICI) caused in the case of Multi-path Doppler channel. To mitigate the ICI effect, a modified Delay and Doppler Profiler (mDDP), which estimates not only attenuation, relative delay and Doppler shift but also sampling clock shift of each multi-path component, is proposed. Based on the outputs of mDDP, an ICI canceling multi-tap equalizer is also proposed. Computer simulated performances of one-tap equalizer with the conventional Time domain linear interpolated Channel Transfer Function (CTF) estimator, multi-tap equalizer based on mDDP are compared. According to the simulation results, BER improvement has been observed. Especially, in the condition of 16QAM modulation, transmitting vessel speed of 6m/s, two-path multipath channel with direct path and ocean surface reflection path; more than one order of magnitude BER reduction has been observed at CNR=30dB.

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• An ICI Canceling 5G System Receiver for 500km/h Linear Motor Car

  Suguru Kuniyoshi, Rie Saotome, Shiho Oshiro, Tomohisa Wada

  IJCSNS International Journal of Computer Science and Network Security ( IJCSNS International Journal of Computer Science and Network Security )  23 ( 6 ) 27 - 34   2023年06月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  　概要を見る

  This paper proposed an Inter-Carrier-Interference (ICI) Canceling Orthogonal Frequency Division Multiplexing (OFDM) receiver for 5G mobile system to support 500 km/h linear motor high speed terrestrial transportation service. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceler is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number n to receiver sub-carrier number l is generated. In case of n≠l, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 2 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, for modulation schemes below 16QAM, we confirmed that the difference between BER in a 2 path reverse Doppler shift environment and stationary environment at a moving speed of 500 km/h was very small when the number of taps in the multi-tap equalizer was set to 31 taps or more. We also confirmed that the BER performance in high-speed mobile communications for multi-level modulation schemes above 64QAM is dramatically improved by the use of a multi-tap equalizer.

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• Performance Comparison of Autoencoder based OFDM Communication System with Wi-Fi

  Shiho Oshiro, Takao Toma, Tomohisa Wada (担当範囲: 執筆、実験)

  IJCSNS International Journal of Computer Science and Network Security ( IJCSNS International Journal of Computer Science and Network Security )  23 ( 5 ) 171 - 176   2023年05月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  　概要を見る

  In this paper, performance of autoencoder based OFDM communication systems is compared with IEEE 802.11a Wireless Lan System (Wi-Fi). The proposed autoencoder based OFDM system is composed of the following steps. First, one sub-carrier’s transmitter - channel ? receiver system is created by autoencoder. Then learning process of the one sub-carrier autoencoder generates constellation map. Secondly, using the plural sub-carrier autoencoder systems, parallel bundle is configured with inserting IFFT and FFT before and after the channel to configure OFDM system. Finally, the receiver part of the OFDM communication system was updated by re-learning process for adapting channel condition such as multipath channel. For performance comparison, IEEE802.11a and the proposed autoencoder based OFDM system are compared. For channel estimation, Wi-Fi uses initial long preamble to measure channel condition. but Autoencoder needs re-learning process to create an equalizer which compensate a distortion caused by the transmission channel. Therefore, this autoencoder based system has basic advantage to the Wi-Fi system. For the comparison of the system, additive random noise and 2-wave and 4-wave multipaths are assumed in the transmission path with no inter-symbol interference. A simulation was performed to compare the conventional type and the autoencoder. As a result of the simulation, the autoencoder properly generated automatic constellations with QPSK, 16QAM, and 64QAM. In the previous simulation, the received data was re-learned, thus the performance was poor, but the performance improved by making the initial value of reception a random number. A function equivalent to an equalizer for multipath channels has been realized in OFDM systems. As a future task, there is not include error correction at this time, we plan to make further improvements by incorporating error correction in the future.

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論文査読・海外派遣等、研究諸活動 【 表示 ／ 非表示 】

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• Journal of Marine Science and Technologyの査読者

  学術論文査読件数 

  2023年11月

  -

  継続中

   

  　概要を見る

  Journal of Marine Science and Technology（JMST）の査読者として推薦され、査読を行った。

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• ⽔中⾳響通信による⽔中ドローンの群制御システム

  研究費種類: 財団・社団法人等の民間助成金  参画方法: 研究代表者

  研究種別: 研究助成  事業名: 公益財団法人トランスコスモス財団 学術・科学技術等の分野への助成事業

  研究期間: 2021年04月  -  2022年03月 

  代表者: 大城　史帆  資金配分機関: 琉球大学

  直接経費: 1,000,000（円）  金額合計: 1,000,000（円）

  　概要を見る

  近年国内外で海底資源の探索や⽔中ドローンを⽤いた海中の⽣態調査が盛んになっ てきている。現段階では⽔中⾳響通信の技術も進歩してきているが、まだ課題も多く 安定的な通信を可能にする事は難しいとされている。そして⽔中ドローンも有線接続 で使⽤する機体が多く、使⽤できる範囲もケーブルの⻑さにどうしても制限が掛かっ てしまう。そのため、⽔中⾳響通信技術を使⽤した無線の⽔中ドローンを提案する。 後に機体を複数機使⽤した群集合の開発に取り組む予定である。

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• ArduPilot Podcast #11 華麗にゲスト登場！美らファーストペンギン大城さん (1/3)  テレビ・ラジオ番組

  Spotify, ApplePodcast, AmazonPodcast  ArduPilot Podcast  2023年6月

  執筆者： 本人以外 

  　概要を見る

  ドローンエンジニア養成塾の講師である我田さん、川村さんのPodcast【ArduPilot Podcast】にゲストとして出演しました。 ＃11では『私がどんな人なのか』について話しています。 収録を終え、講師のお二人にとって「この回は受験生や人生について悩んでるそこのあなたに聴いて欲しい」そんな回だったそうです。

• [2022年英語版vol.14] SDGs特別版  新聞・雑誌

  科学技術振興機構  サイエンスウィンドウ  pp. 22 - 25  2023年3月

  執筆者： 本人以外 

• [2022年SDGs特集号] ダイバーシティーはいま  新聞・雑誌

  科学技術振興機構  サイエンスウィンドウ  pp. 22 - 25  2022年11月

  執筆者： 本人以外 

  　概要を見る

  【特集】ダイバーシティーはいま 「誰一人取り残さない」という理念を掲げる国連の「持続可能な開発目標（Sustainable Development Goals、SDGs）」。その実現のため、異なる特徴や特性を持つ者がともに存在する状態を指す「ダイバーシティー（多様性）」が大切なキーワードになっています。人権尊重の視点とともに“多様性がある方がより良いアイデアや解決策が生まれ、社会が強くなる”という考えから、組織やコミュニティーづくり、働き方、文化、生態系など、さまざまな分野で語られています。 2019年から発行している「Science Window」SDGs特集号では、SDGs達成に向けた科学技術の担い手たちの未来ビジョンや取り組みを紹介してきました。今回はジェンダー、国籍、障がい、地域など、さまざまな多様性に着目し、その取り組みや担い手たちの声を盛り込みました。社会や科学技術の世界のダイバーシティーについて、一緒に考えてみましょう。 【目次】 イノベーション加速の原動力に 《行木陽子さんインタビュー》 一人の高校生の願いから生まれた「だれでもピアノ」 《新井鴎子さんインタビュー》 障がい者の埋もれた能力を掘り起こそう ジェンダー平等がもたらすより良い社会 《佐々木成江さんインタビュー》 燃料デブリの取り出しに挑む 《岩渕美咲さんインタビュー》 ポジティブな出産、適切な情報提供が後押し 世界で学んだコンビ、水中ドローンを開発 雨水をもっと暮らしに活かそう 世界を舞台に、今後の活躍を期待 《羽ばたく女性研究者賞の受賞者に聞く》 「STI for SDGs」アワード2022 受賞取組一覧

• [2022年夏号] ダイバーシティーで目指すもの  新聞・雑誌

  科学技術振興機構  サイエンスウィンドウ  Chapter 5 世界で学んだコンビ、 水中ドローンを開発  2022年10月

  執筆者： 本人以外 

  　概要を見る

  【特集】ダイバーシティーで目指すもの 私たちは未来に向け、さまざまな課題を克服しながら歩む必要があります。世の中のあらゆる人々が加わり、互いを尊重し、多様な視点を活かすことは、豊かな社会を築いていく新しい活力になりそうです。 【目次】 CHAPTER 01 イノベーション加速の原動力に《行木陽子さんインタビュー》 CHAPTER 02 障がい者の埋もれた能力を掘り起こそう CHAPTER 03 ポジティブな出産、適切な情報提供が後押し CHAPTER 04 人と生き物の関係を問い直す CHAPTER 05 世界で学んだコンビ、水中ドローンを開発 COLUMN 企業のダイバーシティー&インクルージョンを評価―独自指数で「何をすれば良いか」に挑むアワード―