著者
西田 京介 島田 章平 石川 悟 山内 康一郎
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
電子情報通信学会論文誌 D (ISSN:18804535)
巻号頁・発行日
vol.J91-D, no.1, pp.51-64, 2008-01-01

オンライン学習を行うパターン分類システムにとって,学習対象の様々な変化に対応する能力は実世界問題を扱う上で必要不可欠である.特に,学習システムにとって重大な変化が突然発生した場合,すなわち,変化前の学習結果が新たな学習対象への適応を大きく阻害する場合には,変化をできる限り高速に検出して対応する必要がある.突然かつ重大な変化のみを正確かつ高速に検出可能な手法を実現するために,本研究では柔軟に様々な変化に対応できる人間に着目した.「最近の分類精度が高い状況で確信度の高い回答が短期間に連続して否定されるほど,人間は変化を高速に検出できる」という作業仮説を立てて行動実験を行い,得られた知見からLeaky Integrate-and-Fireモデルをもとにした手法を提案した.その有効性を検証するため計算機実験を行ったところ,ノイズがない場合とノイズや緩やかな変化が存在する場合の両方で,提案手法は従来手法よりも高い検出性能を実現できた.今後の課題は,問題に大きく依存するパラメータ値を学習中に自動で調整することである.
著者
Takaharu Yamanaka Takanori Iwai Ryogo Kubo
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Communications Express (ISSN:21870136)
巻号頁・発行日
vol.10, no.6, pp.301-306, 2021-06-01 (Released:2021-06-01)
参考文献数
8

In networked control systems, the quality of performance (QoP), such as in terms of consistent tracking errors, must be maintained at a constant level. A QoP-aware sleep mechanism in network interfaces can reduce the amount of traffic or the communication rate while maintaining the QoP. However, in a QoP-aware sleep mechanism with a fixed sleep period, the sleep period cannot be entered effectively when the length of the steady-state period is changed; e.g., when the command frequency is changed. This study proposes a variable sleep period control method to reduce the communication rate while adapting to the tracking error. The simulations confirm that, when compared to methods with a fixed sleep period, the proposed method reduces the communication rate regardless of the command frequency.
著者
Song-Ju Kim Hiroyuki Yasuda Ryoma Kitagawa Mikio Hasegawa
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Communications Express (ISSN:21870136)
巻号頁・発行日
pp.2021XBL0165, (Released:2021-10-01)

We propose a simple channel-allocation method based on tug-of-war (TOW) dynamics, combined with the time scheduling based on nonlinear oscillator synchronization to efficiently use of the space (channel) and time resources in wireless communications. This study demonstrates that synchronization groups, where each node selects a different channel, are non-uniformly distributed in phase space such that every distance between groups is larger than the area of influence. New type of self-organized spatiotemporal patterns can be formed for resource allocation according to channel rewards.
著者
Kenichi IGA Yasushi TAKAHASHI
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)
巻号頁・発行日
vol.E61-E, no.9, pp.685-689, 1978-09-25

In this paper, an analysis was made on the variation of oscillating mode numbers of a semiconductor laser at high speed pulse modulation by solving multi-mode rate equations which relate a quasi-Fermi level to photon numbers. The laser gain was assumed to be homogeneous and has a dependency of (), where is ωEg (relative photon energy). Single mode oscillation conditions for short pulse modulation were obtained associated with following two cases. A) One is the criterion how wide the mode separation must be made as of a short cavity laser and of an integrated twin-guide (ITG) laser. B) The other is the condition how large we must give an excess loss to the unwanted modes such as of the ITG laser, of a distributed feedback (DFB) laser, and of a distributed Bragg reflector (DBR) laser.
著者
Fumio KOYAMA Susumu KINOSHITA Kenichi IGA
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)
巻号頁・発行日
vol.E71-E, no.11, pp.1089-1090, 1988-11-25

This is the first report on room temperature CW operation of GaAlAs/GaAs vertical Fabry-Perot cavity surface emitting lasers. A vertical microcavity was formed with a diameter of 7 µm and cavity length of 5.5 µm by a two-step MOCVD growth and fully monolithic technology. The threshold current was 32 mA under CW condition at 22.5. Stable single transverse and longitudinal mode operation was obtained.
著者
Shin'ichi Oishi Kouta Sekine
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
Nonlinear Theory and Its Applications, IEICE (ISSN:21854106)
巻号頁・発行日
vol.12, no.3, pp.575-610, 2021 (Released:2021-07-01)
参考文献数
27

A computer assisted proof is presented for the existence of various periodic solutions for forced Suarez-Schopf's equation, which are delay differential equations modeling El Niño. Tight inclusions of periodic solutions are calculated through numerical verification method by utilizing a structure of Galerkin's equation for forced Suarez-Schopf's equation effectively. The existence of various periodic solutions has been proved via computer assisted proofs including various subharmonics. Especially, coexistence of several subharmonics are proved and numerical simulations are presented suggesting an appearance of chaos.
著者
Hiroyuki Tsuda
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Electronics Express (ISSN:13492543)
巻号頁・発行日
vol.17, no.22, pp.20202002, 2020-11-25 (Released:2020-11-25)
参考文献数
77
被引用文献数
7

This paper reviews recent progress in silicon photonics and compares it with other optical device platforms. The key components for optical communication systems, including arrayed waveguide gratings, optical switches, modulators and optical functional devices fabricated on silicon photonics platforms are explained. The integration of III-V compounds, lithium niobate, polymers, phase change and other functional materials are necessary to strengthen silicon photonics platforms. These are also reviewed, and the feasibilities are discussed. Finally, I express my personal view as to the best research direction for silicon photonics.
著者
福田 明
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
電子情報通信学会論文誌 B (ISSN:03736105)
巻号頁・発行日
vol.J64-B, no.11, pp.1303-1304, 1981-11-25

後ろから他パケットが重なってもその前までは正しく受信されるよう,パケットをブロック構造とした純アロハ方式の特性を考察する.
著者
Neisei Hayashi Yosuke Mizuno Heeyoung Lee Kentaro Nakamura Sze Yun Set Shinji Yamashita
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Electronics Express (ISSN:13492543)
巻号頁・発行日
vol.17, no.12, pp.20200139, 2020-06-25 (Released:2020-06-25)
参考文献数
39
被引用文献数
2 5

We present a method for generating cascaded forward Brillouin scattering (CFBS) on the basis of a counter-propagated pump-probe technique with backward stimulated Brillouin scattering used as its seed. The CFBS, induced by forward stimulated Brillouin scattering (FSBS), is generated via the energy transfer from the probe light to other acoustic resonance frequencies. The CFBS spectrum generated in a 390-m-long highly nonlinear fiber exhibits a high signal-to-noise ratio (SNR), and the center frequencies of its acoustic resonance peaks agree with theoretical values. In addition, the SNR dependence on pump/probe powers and the CFBS frequency shift dependence on temperature are investigated.
著者
齋藤 宏文 金子 智喜 河野 宜幸 村上 圭司 國井 喜則 友田 孝久 田中 孝治 平子 敬一 中須賀 真一 白坂 成功
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
電子情報通信学会論文誌 B (ISSN:13444697)
巻号頁・発行日
vol.J104-B, no.7, pp.669-672, 2021-07-01

低高度地球観測衛星からのデータダウンリンクの高速化を目的に,シンボルレート300 Msps,64APSK変調,及び256APSK変調,左右円偏波多重方式のデータダウンリンクの軌道上実証実験を行った.64APSK変調にて2.65 Gbit/sec,256APSK変調にて3.3 Gbit/secの低高度衛星からの世界最高の通信速度が確認された.
著者
Kimiko MOTONAKA Tomoya KOSEKI Yoshinobu KAJIKAWA Seiji MIYOSHI
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences (ISSN:09168508)
巻号頁・発行日
pp.2021EAP1013, (Released:2021-06-01)
被引用文献数
2

The Volterra filter is one of the digital filters that can describe nonlinearity. In this paper, we analyze the dynamic behaviors of an adaptive signal-processing system including the Volterra filter by a statistical-mechanical method. On the basis of the self-averaging property that holds when the tapped delay line is assumed to be infinitely long, we derive simultaneous differential equations in a deterministic and closed form, which describe the behaviors of macroscopic variables. We obtain the exact solution by solving the equations analytically. In addition, the validity of the theory derived is confirmed by comparison with numerical simulations.
著者
Yang OU Kyung Hyune RHEE
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Transactions on Information and Systems (ISSN:09168532)
巻号頁・発行日
vol.E93.D, no.5, pp.1020-1030, 2010-05-01 (Released:2010-05-01)
参考文献数
50
被引用文献数
3 6

The traditional cryptographic hash functions are sensitive to even one-bit difference of the input message. While multimedia data always undergo compression or other signal processing operations, which lead to the unsuitability of multimedia authentication using cryptographic hash. The image hashing has emerged recently which captures visual essentials for robust image authentication. In this paper, we give a comprehensive survey of image hashing. We present an overview of various image hashing schemes and discuss their advantages and limitations in terms of security, robustness, and discrimination under different types of operations on the image.
著者
Nobutaka Funaki Kazuki Maruta Chang-Jun Ahn
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Communications Express (ISSN:21870136)
巻号頁・発行日
vol.10, no.6, pp.324-330, 2021-06-01 (Released:2021-06-01)
参考文献数
6
被引用文献数
1

This letter proposes adaptive null-space expansion (NSE) for multiuser massive MIMO according to users’ mobility. NSE can improve the robustness of multi-user spatial multiplexing in a time-varying channel by expanding null-steering to multiple past channels. Its superiority was verified under the unified moving speed among users. In a realistic environment, users with different speeds coexist. Null-space dimension, which is the number of nullified channels per user terminal, should be optimized in accordance with users’ mobility so as to maximize the beamforming gain and nullification capability. In our proposal, we first show that user mobility can be classified by observing the singular value of time-varying channels. Computer simulation then clarifies that output SINR can be improved by assigning null space dimensions respective to user moving speeds.
著者
Yuji MIZUTANI Hiroto KURIKI Yosuke KODAMA Keiichi MIZUTANI Takeshi MATSUMURA Hiroshi HARADA
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Transactions on Communications (ISSN:09168516)
巻号頁・発行日
vol.E103.B, no.4, pp.467-475, 2020-04-01 (Released:2020-04-01)
参考文献数
20

The conventional universal filtered-DFT-spread-OFDM (UF-DFTs-OFDM) can drastically improve the out-of-band emission (OOBE) caused by the discontinuity between symbols in the conventional cyclic prefix-based DFTs-OFDM (CP-DFTs-OFDM). However, the UF-DFTs-OFDM degrades the communication quality in a long-delay multipath fading environment due to the frequency-domain ripple derived from the long transition time of the low pass filter (LPF) corresponding to the guard interval (GI). In this paper, we propose an enhanced UF-DFTs-OFDM (eUF-DFTs-OFDM) that achieves significantly low OOBE and high communication quality even in a long-delay multipath fading environment. The eUF-DFTs-OFDM applies an LPF with quite short length in combination with the zero padding (ZP) or the CP process. Then, the characteristics of the OOBE, peak-to-average power ratio (PAPR), and block error rate (BLER) are evaluated by computer simulation with the LTE uplink parameters. The result confirms that the eUF-DFTs-OFDM can improve the OOBE by 22.5dB at the channel-edge compared to the CP-DFTs-OFDM, and also improve the ES/N0 to achieve BLER =10-3 by about 2.5dB for QPSK and 16QAM compared to the UF-DFTs-OFDM. For 64QAM, the proposed eUF-DFTs-ODFDM can eliminate the error floor of the UF-DFTs-OFDM. These results indicate that the proposed eUF-DFTs-OFDM can significantly reduce the OOBE while maintaining the same level of communication quality as the CP-DFTs-OFDM even in long-delay multipath environment.
著者
Takafumi KUBOTA Kenji KONO
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Transactions on Information and Systems (ISSN:09168532)
巻号頁・発行日
vol.E104.D, no.1, pp.126-137, 2021-01-01 (Released:2021-01-01)
参考文献数
52

Build systems are essential tools for developing large software projects. Traditionally, build systems have been designed for high incremental-build performance. However, the longer build times of recent large C++ projects have imposed a requirement on build systems: i.e., unity builds. Unity builds are a build technique for speeding up sequential compilation of many source files by bundling multiple source files into one. Unity builds lead to a significant reduction in build time through removal of redundant parsing of shared header files. However, unity builds have a negative effect on incremental builds because each compiler task gets larger. Our previous study reported existing unity builds overlook many better bundle configurations that improve unity-build performance without increasing the incremental-build time. Motivated by the problem, we present a novel build system for better performance in unity builds. Our build system aims to achieve competitive unity-build performance in full builds with mitigating the negative effect on incremental builds. To accomplish this goal, our build system uses sophisticated bundle strategies developed on the basis of hints extracted from the preprocessed code of each source file. Thanks to the strategies, our build system finds better bundle configurations that improve both of the full-build performance and the incremental-build performance in unity builds. For example, in comparison with the state-of-the-art unity builds of WebKit, our build system improves build performance by 9% in full builds, by 39% in incremental builds, and by 23% in continuous builds that include both types of the builds.
著者
Minseok KIM Jun-ichi TAKADA Kentaro SAITO
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE TRANSACTIONS on Communications (ISSN:09168516)
巻号頁・発行日
vol.E101-B, no.2, pp.293-308, 2018-02-01
被引用文献数
12

In order to utilize higher frequency bands above 6GHz, which is an important technical challenge in fifth generation mobile systems, radio propagation channel properties in a large variety of deployment scenarios should be thoroughly investigated. The authors' group has been involved in a fundamental research project aimed at investigating multiple-input-multiple-output (MIMO) transmission performance and propagation channel properties at microwave frequency above 10GHz from 2009 to 2013, and since then they have been conducting measurement and modeling for high frequency bands. This paper aims at providing comprehensive tutorial of a whole procedure of channel modeling; multi-dimensional channel sounding, propagation channel measurement, analysis, and modeling, by introducing the developed MIMO channel sounders at high frequency bands of 11 and 60GHz and presenting some measurement results in a microcell environment at 11GHz. Furthermore, this paper identifies challenges in radio propagation measurements, and discusses current/future channel modeling issues as future works.
著者
Tomu Katsumata Muneki Yasuda
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
Nonlinear Theory and Its Applications, IEICE (ISSN:21854106)
巻号頁・発行日
vol.12, no.3, pp.377-390, 2021 (Released:2021-07-01)
参考文献数
29
被引用文献数
2

A deep Boltzmann machine (DBM) is a probabilistic deep learning model; DBM learning consists pretraining and fine-tuning stages. This study focuses on the fine-tuning stage, and it develops a new and effective fine-tuning method based on spatial Monte Carlo integration (SMCI), which is an extension of the standard Monte Carlo integration (MCI). It has been proved that SMCI is statistically more accurate than the standard MCI. Fine-tuning methods based on first-order and semi-second-order SMCI methods are formulated. The numerical experiments demonstrate that the proposed fine-tuning methods are superior to the conventional method in terms of both training and generalization errors.
著者
Takaaki SAEKI Yuki SAITO Shinnosuke TAKAMICHI Hiroshi SARUWATARI
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE TRANSACTIONS on Information and Systems (ISSN:09168532)
巻号頁・発行日
vol.E104-D, no.7, pp.1002-1016, 2021-07-01
被引用文献数
2

This paper proposes two high-fidelity and computationally efficient neural voice conversion (VC) methods based on a direct waveform modification using spectral differentials. The conventional spectral-differential VC method with a minimum-phase filter achieves high-quality conversion for narrow-band (16 kHz-sampled) VC but requires heavy computational cost in filtering. This is because the minimum phase obtained using a fixed lifter of the Hilbert transform often results in a long-tap filter. Furthermore, when we extend the method to full-band (48 kHz-sampled) VC, the computational cost is heavy due to increased sampling points, and the converted-speech quality degrades due to large fluctuations in the high-frequency band. To construct a short-tap filter, we propose a lifter-training method for data-driven phase reconstruction that trains a lifter of the Hilbert transform by taking into account filter truncation. We also propose a frequency-band-wise modeling method based on sub-band multi-rate signal processing (sub-band modeling method) for full-band VC. It enhances the computational efficiency by reducing sampling points of signals converted with filtering and improves converted-speech quality by modeling only the low-frequency band. We conducted several objective and subjective evaluations to investigate the effectiveness of the proposed methods through implementation of the real-time, online, full-band VC system we developed, which is based on the proposed methods. The results indicate that 1) the proposed lifter-training method for narrow-band VC can shorten the tap length to 1/16 without degrading the converted-speech quality, and 2) the proposed sub-band modeling method for full-band VC can improve the converted-speech quality while reducing the computational cost, and 3) our real-time, online, full-band VC system can convert 48 kHz-sampled speech in real time attaining the converted speech with a 3.6 out of 5.0 mean opinion score of naturalness.
著者
Noboru MURAYAMA
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)
巻号頁・発行日
vol.E72-E, no.5, pp.661-669, 1989-05-25

A polynomial for automatic contour vector coding of the binary picture pattern is proposed. The proposed polynomial is the expansion of the Bezier polynomial to have the more flexibility. It is easy to be implemented and the generated curve is easy to be estimated from the given control points. This advantage is confirmed by the automatic contour coding of both English and Japanese fonts.