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Guimaraes C.,University of Aveiro | Corujo D.,University of Aveiro | De La Oliva A.,Charles III University of Madrid | Ohba Y.,Toshiba Corporate Randnter | Aguiar R.L.,University of Aveiro
Computer Networks | Year: 2014

Currently we are witnessing an explosion of devices able to connect to a variety of wired and wireless access network technologies. This connectivity is increasingly integrating networks composed by sensors, actuators and even utility devices that use private and public networks to relay important information and measurements. The deployment of the so-called Smart Grid technologies allied to the rise of Machine-to-Machine communications require new mechanisms to optimally manage the change of point of attachment to the network of these huge clouds of nodes, assisting in tackling the scale of the problem. With this problematic in mind, the IEEE 802.21 WG started on March 2012 a new project, named IEEE 802.21d, group management services. This amendment establishes the required changes to the original specification, in order to manage the mobility of groups of nodes. This work follows closely the progress of the Task Group on the use cases, requirements and gap analysis, providing in addition a potential solution, integrating new group mechanisms, extensions to the MIH Protocol and associated security enhancements. This solution has been implemented and validated in a custom built testbed, with results showing that the utilisation of Group Control procedures through multicast signalling achieves a lower cost when compared with unicast signalling, in group handover and sensor information dissemination scenarios. © 2014 Elsevier B.V. All rights reserved.


Ohba Y.,Toshiba Corporate Randnter | Kanda M.,Toshiba Corporate Randnter
Proceedings of the IEEE Power Engineering Society Transmission and Distribution Conference | Year: 2012

The recent growth of Smart Grid and energy services introduced resource-constrained Internet communications devices such as smart meters, consumer electric devices, sensors, lighting devices and so on. In this paper, we propose a new proxy scheme designed for authentication and key establishment protocols for authenticating resource-constrained end-devices. The proposed scheme leverages key hierarchy in a way that the end-device can delegate the main protocol tasks of authentication and key establishment to the proxy and only a cryptographic and key management module including the root key of the key hierarchy needs to be retained by the end-device. The proposed scheme can reduce 70% and 28% of persistent storage for Class 1 and Class 2 memory-constrained devices, respectively. Also, the total memory reduction effect in the system consisting of a single proxy and multiple end-devices increases as the number of end-devices connected to one proxy increases. © 2012 IEEE.


Nakasaki Y.,Toshiba Corporate Randnter | Hirano I.,Toshiba Corporate Randnter | Kato K.,Toshiba Corporate Randnter | Mitani Y.,Toshiba Corporate Randnter
Microelectronic Engineering | Year: 2011

An atomic-scale model for the degradation of Hf silicates (HfSiON) gate stacks triggered by atomic hydrogen strongly influencing oxygen vacancy (V O) generation in HfSiON and its interfacial layer is proposed based on first-principles calculations. We found that the atomic hydrogen is always negatively charged in the high-k stacks and diffuses fast as interstitials with very low energy barriers along electric fields irrespective of the Fermi level of the whole system. These characteristics of the atomic hydrogen induce bias-polarity dependent degradations of the high-k stacked dielectrics. It agrees well with the experimental results, especially evident in high-k p-FETs. We also found that although both oxygen vacancies and substitutional nitrogen atoms at the oxygen sites (N O) attract each other and stabilize the atomic hydrogen, substitutional nitrogens have also possibility to act as preserving a puckered configuration of the VO2+ accompanied by a hydrogen interstitial under a hole existence. These H atom complexes accompanied by V Os and N Os may also enhance the degradation of the high-k stacks. © 2011 Elsevier B.V. All rights reserved.


Kaji S.,Toshiba Corporate Randnter | Kobayashi T.,Toshiba Corporate Randnter | Saito A.T.,Toshiba Corporate Randnter
Journal of Physics: Conference Series | Year: 2010

The substitution effects have been measured on the magnetization and lattice parameters of Gd100-xZrx and Gd 100-yYy alloys. The magnetic transition temperatures are affected by Zr more effectively than by Y. The Curie temperature decreases with increasing Zr content; the coefficient is -3.6 K/at.%. The effect on spin-reorientation transition temperature is of particular note. With increasing Zr content, it increases with the coefficient +7.9 K/at.%, which is about three times as large as that of Gd100-yYy alloy. From the measurement of lattice parameters, it is confirmed that Zr-substitution affects the temperature dependence of c-axis value more than that of a-axis one. © 2010 IOP Publishing Ltd.

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