Browsing by Autor "Toru Abe"

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    Energy‐Aware Controller Placement With Delay Guarantees for In‐Band SDN
    (Wiley, 2026) T. Kondo; Luis Andrés Guillén; Satoru Izumi; Toru Abe; Takuo Suganuma
    ABSTRACT Software‐defined networking (SDN) enables flexible, programmable networks, but in large deployments, poor controller placement can raise latency and energy use. This paper presents a practical in‐band SDN model and an optimization method that jointly accounts for control‐plane delay and device power consumption to place controllers and configure switches. We formulate the problem as a binary integer programming (BIP) that decides controller locations, which switches remain active, and port bit‐rates and routes. Experiments on a large WAN topology (Janos‐US) show the approach can cut total network energy by up to 15% while keeping control‐plane delays within required bounds, offering network operators a straightforward way to trade responsiveness for energy savings.
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    Spatio-Temporal Kriging for High-Resolution Urban Microclimate Estimation with Fixed and Mobile Sensors
    (2025) Wataru Kunimi; Shinji Takada; Yuya Ito; Luis Andrés Guillén; Toru Abe; Takuo Suganuma
    Urban heat-island (UHI) mitigation requires fine-grained intra-urban meteorology, yet existing interpolation methods rely on fixed search radii or linear time corrections, which blur microclimatic heterogeneity, while dense sensor deployments remain costly. We propose Spatio-Temporal Kriging (ST-Kriging), a probabilistic framework that fuses asynchronous fixed and mobile measurements within a single space–time covariance model, eliminating explicit time correction and reducing dependence on dense sensor grids. Field experiments demonstrate that ST-Kriging achieves high predictive accuracy, with a MAE of 0.29 °C and an RMSE of 0.24 °C—reducing errors by up to 27% compared with existing approaches. These results highlight ST-Kriging as a practical foundation for affordable UHI countermeasures and more broadly for fine-scale environmental monitoring in smart-city applications.