In network virtualization, it has been considered that virtual networks are constructed over a physical network where conventional data transmission services have been utilized. Here, virtual networks have to be constructed while keeping qualities of the conventional services. In this paper, we propose a new virtual network construction in order to construct many virtual networks while keeping the robustness of a physical network by using network resources effectively. The proposed method consists of three processes: K-shortest path algorithm and Prim's minimum spanning tree algorithm, path splitting, and path migration. In the proposed method, at first, multiple topologies are designed by using the K-shortest path algorithm and the Prim's MST algorithm according to the user's request. After the topology design is completed, an admission control with network robustness of the physical network is performed. Then, if one of the designed topologies can satisfy the construction conditions, a virtual network is constructed and provided with the user. Otherwise, the path splitting and path migration are performed. Here, the path splitting is utilized to design another topology of a virtual network and path migration is used to change the topologies of the virtual networks that have already been constructed. These processes are formulated as optimization problems and those are processed by solving the optimization problems. In numerical examples, we show that our proposed method can construct a higher number of virtual networks while keeping the robustness of a physical network by comparing with the conventional method where only the Kou-Markowsky-Berman algorithm is used. Int. J. Commun. Syst. 2017; 30: e2958 1 of 21 Y. URAYAMA AND T. TACHIBANA flow table that describes each action for each data packet. Data packets can be forwarded to a corresponding virtual network according to the flow table in the OpenFlow controller.Here, the amount of available network resources is limited in the physical network, and hence, each virtual network has to be constructed so that the network resources are utilized efficiently. Some methods for designing the topology of a virtual network and allocating the network resources to the virtual network have been proposed in the literatures.In [10], in order to construct a virtual network simply over a large physical network, a topology of the virtual network is designed by combining two or more small star topologies. Yu et al. [11] has proposed a construction method of a virtual network with path splitting and path migration.In this method, a service provider obtains the revenue from a user after a virtual network was constructed. In order to maximize the revenue, virtual networks are constructed over a physical network by using the path splitting and path migration.In particular, by using the path migration, the topologies of constructed virtual networks are redesigned periodically. In [12], an architecture called DaVinci has been proposed so that network resources can be allocated to each ...

In this paper, we propose a construction scheduling of virtual networks to utilize network resources effectively while keeping robustness of a physical network. In the proposed method, a service provider determines a schedule of virtual network construction for user's requests that are received during a waiting time. For this method, we consider two scheduling methods and two redesign methods. We evaluate with simulation our proposed method.

Recently, a network virtualization technology has attracted considerable attention as one of new generation network technologies. In this paper, in order to permit the rapid changing for a topology of a virtual network, we propose a new virtual network construction method based on the shortest path betweenness. In our proposed method, at first, a service provider receives a user's request for the reconfiguration of the constructed virtual network. In this case, the service provider reconfigures the topology of the constructed virtual network rapidly based on shortest path betweenness. We evaluate the performance of our proposed method with simulation, and we show the effectiveness of our proposed method.

橘：本日は座談会に御参加頂きまして，ありがとうござ います．最初に，現在取り組んでいる研究テーマにつ いて，簡単に教えて頂けますでしょうか？ 永島：研究テーマは， 「無線給電システムの高効率化」 です．無線給電システムは基本的に， インバータ， 無線 結合部，整流器で構成されます．システム全体を高効 率化するためには，三つの構成要素全ての高効率化が 重要です．現在は特に，高効率を達成可能な新しいシ ステム構成及びその設計手法の提案を行っています． 豊田：研究テーマは「セキュリティ & プライバシー」 です．具体的な研究内容としては，センサ端末やス マートフォン向けの軽量な端末間の認証方式，IP 電 話の普及に伴う迷惑電話発信者の検知手法， RFID(電 波による個体識別)を用いた安全な物流管理システム の検討などを行っています． 沈 ：私は，将来大容量通信を支える基盤となる「光ネッ トワーク技術」を研究しています．今までの通信需要 に応じて可変帯域を割り当てる検討は，高い周波数使 用率を達成できる一方，高コスト化が課題となりま す．そこで私は，各通信需要の必要帯域ごとに一定の 周波数配置間隔を設定するコスト面で優れた方式を 提案し，その効果を実証しています． 下平：広い範囲に信号が伝送できる「マクロ基地局」と， 限られた狭い範囲に信号を伝送する「ピコ基地局」を 組み合わせた「ヘテロジニアスセルラネットワーク」 と呼ばれる次世代の携帯電話ネットワークに関して， 基地局の設置位置や，通信リソース配分，及び端末の 接続基地局の最適化等を行っています． 村上：アンテナの課題である薄形・小形設計を，自然界 に存在しない特性を持つ 「メタマテリアル」 を用いて解 決する方法があります．メタマテリアルの一例として， 表面での反射位相が 0°の特性を持つものなどがありま す．私の研究は，そのメタマテリアルを用いたアンテ ナ設計の最適化と設計法の確立を行うことです． 藤橋：多様なネットワーク上での効率的な「複数視点映 像の伝送手法」について研究しています．複数視点映 像は，3D 映像や自由視点映像といった次世代の映像 技術を支える技術として注目されています．この研究 を進めることで，部屋にいながら，まるで別の場所に 座談会参加者： 金井謙治 Kenji Kanai，早稲田大学 D3 豊田健太郎 Kentaroh Toyoda，慶應義塾大学 D2 沈 志舒 Zhi-shu Shen，名古屋大学 D3 永島和治 Tomoharu Nagashima，千葉大学 D2 村上靖宜 Yasutaka Murakami，福井大学 D3 下平英和 Hidekazu Shimodaira，東京工業大学 D1 諶 璐 Lu Chen，大阪大学 D2 藤橋卓也 Takuya Fujihashi，大阪大学 D1 司会： 記録係： 橘 拓至 Takuji Tachibana 浦山康洋 Yasuhiro Urayama，福井大学 D1 情報通信技術の研究・開発分野では，世界の舞台で活躍するために「博士号」が必要となる場合があり ます．この博士号を取得するには，博士後期課程(博士課程)に進学して課程を修了することで博士号を 取得する方法(課程博士)と，論文審査により研究能力を認定されて博士号を取得する方法(論文博士) の 2 通りがあります．本座談会では，博士後期課程に進学して博士号の取得を目指している学生の皆さん に集まって頂き，博士後期課程での研究活動や生活，博士号取得後の進路などについて語って頂きました． この座談会を通じて，博士後期課程が一体どんなところか，博士後期課程の学生がどんな生活をしている のか，といった疑問に少しでも答えられたらと思います．また，博士後期課程学生の皆さんが博士号取得 に向けて頑張っているということを，読者の皆様に知って頂けたらと思います． 258 通信ソサイエティマガジン No.32 春号 2015 ⓒ電子情報通信学会 2015 博士後期課程ってどんなところ？ ─博士後期課程学生の座談会─ 解 説 研究者を目指すには

The regional activation is an important issue for regional areas. In order to resolve this issue, we propose a live video streaming service for regional activation with the network virtualization technology. In our proposed service, a live video of each tourist spot is delivered to tourists and local residents though a dedicated virtual network. By watching the live video, it is expected to increase the interest of the tourists and the local residents for the tourist spot and they may visit the tourist spot. We suppose that the dedicated virtual networks are readied over a substrate network where existing services have already been performed. Therefore, we propose two topology designs for virtual networks so as to keep the performance of the existing services. One of the two topology designs embeds the dedicated virtual networks by solving an optimization problem based on network robustness of the substrate network, and the other embeds the dedicated virtual networks by solving an optimization problem based on the amount of resources in the virtual networks. We investigate the performance of our proposed topology designs with simulation. From numerical examples, we show that our proposed topology designs can effectively embed multiple virtual networks regardless of the number of tourist spots and the position of tourist spots, and we also show that our proposed live video streaming service is effective for the regional activation.