Journal of Signal Processing
Online ISSN : 1880-1013
Print ISSN : 1342-6230
ISSN-L : 1342-6230
18 巻, 6 号
Special Issue on Nonlinear Circuits, Communications and Signal Processing (Editor-in-Chief: Keikichi Hirose, Editor: Nozomu Hamada, Guest Editor: Hironori Takimoto, Honorary Editor-in-Chief: Takashi Yahagi)
選択された号の論文の5件中1~5を表示しています
  • Shintaro Mori, Koji Ishii, Shigeaki Ogose
    2014 年 18 巻 6 号 p. 275-282
    発行日: 2014/11/25
    公開日: 2014/11/25
    ジャーナル フリー
    For adaptive packet retransmission control, network coding (NC)-based schemes have been proposed to reduce the number of packet retransmissions. However, the NC-based schemes have two fundamental drawbacks; the need for a counterpart packet of member packets and an overhearing packet management method. To mitigate these problems, we propose a novel superposition modulation (SM)-based scheme based on cross-layer design. However, when the SM technique is introduced into the system, the bit error probability increases. Therefore, to decrease the bit error probability, we utilize the soft combining (SC) technique. The effectiveness of our scheme is demonstrated through computer simulations.
  • Tomoya Suzuki, Kiyoharu Tanaka
    2014 年 18 巻 6 号 p. 283-290
    発行日: 2014/11/25
    公開日: 2014/11/25
    ジャーナル フリー
    In Markowitz' s mean-variance portfolio model, the probability distribution of a future return is composed of recent historical prices, and the future return and future risk are estimated as the mean and standard deviation of the distribution, respectively. Namely, the future return is predicted by a simple moving average, and the risk is simply the historical fluctuation. In this study, to improve the prediction accuracy of the future return, we apply a nonlinear prediction method following local spatial dynamics, and to estimate the future risk, we produce a probability distribution by aggregating predicted values by the bagging algorithm. Then, each risk is reduced by making a portfolio, that is, we apply the portfolio effect. Namely, our method attempts to simultaneously improve the prediction accuracy and reduce the risk of its prediction error. To confirm the validity of our method, we performed investment simulations. As a result, we could realize higher profit and lower risk in investment than by the conventional method.
  • Haruna Matsushita, Yoshifumi Nishio , Chi K. Tse
    2014 年 18 巻 6 号 p. 291-302
    発行日: 2014/11/25
    公開日: 2014/11/25
    ジャーナル フリー
    This study proposes a network-structured particle swarm optimizer (NS-PSO), which considers neighborhood distances. All particles of the NS-PSO are connected to adjacent particles in the neighborhood of topological space, and NS-PSO utilizes the connections between them not only to share local best position but also to increase swarm diversification. Each NS-PSO particle is updated depending on the positions of the local best and current best particles. In NS-PSO, the neighborhood distance in the topological space from each particle to the current best position is also considered. This effect promotes the diversification of solutions and avoids the solutions from becoming trapped at local optima. Simulation results and comparisons with conventional particle swarm optimization show that the proposed NS-PSO can effectively enhance the searching efficiency by measuring in terms of accuracy, robustness and parameterdependence. Furthermore, we consider various network topologies, grid, hexagonal, cylinder and toroidal. We investigate their behaviors and evaluate the kind of topology that would be the most appropriate for each benchmark.
  • Zhi Zhu, Katsuhiko Yamamoto, Masashi Unoki, Naofumi Aoki
    2014 年 18 巻 6 号 p. 303-307
    発行日: 2014/11/25
    公開日: 2014/11/25
    ジャーナル フリー
    Speech scrambling aims to eliminate intelligibility of original speech in order to preventing eavesdropping and copyright infringement. There is, however, a problem in that completely recovering scrambled speech into the original speech cannot be achieved with conventional methods. In this paper, we propose a speech scrambling method that uses the random-bit-shift of quantization bits with common keys. We evaluated the confidentiality and efficiency of the proposed method by using two objective measures, SER and PESQ. As a result we confirmed that speech signals can be scrambled into completely unintelligible sounds with the proposed method. Moreover, it is possible to restore a scrambled speech signal into the original one completely. In addition, we also confirmed that the scrambled speech signal could not be descrambled correctly with the wrong key.
  • Takeshi Toda, Yuki Enda, Naoko Ideguchi
    2014 年 18 巻 6 号 p. 309-316
    発行日: 2014/11/25
    公開日: 2014/11/25
    ジャーナル フリー
    This paper presents an implementation of simple and low-cost medication support system for outpatient of cerebral infarction who has to keep medication every day for long term. The system consists of the outpatient and the pharmacist terminals at the dispensing-pharmacy. The outpatient terminal features the displays of compliance status and 3D simulation of cerebral infarction, contact functions to dispensing-pharmacy (e.g. call, text and voice messages). The pharmacist terminal features response functions to contacts from the outpatients, displays of the compliance status and the 3D simulation of cerebral infarction same as the outpatient terminal. The compliance status of the outpatients is automatically transmitted to the pharmacist terminal through e-mail connections each day. We designed different symptoms of the blood flow simulation according to the blood-stuck level which are estimated by weighted moving average of the daily compliance status ("took medicine" or "did not take medicine"). The different symptoms of 3D simulation are also registered in the database on the outpatient and the pharmacist terminals, respectively, and are switched according to the shared compliance status. Conventional medication support system used MySQL database engine on web server for those features and thus needed to introduce web server in dispensing-pharmacy. The proposed system realizes simple and low-cost by making the database of those compliance status data using the SQLite database engine on the terminals.
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