Published papers

A smaller graph sampled from a large graph uses an excessively wide range of vertex IDs beyond its graph size, which causes a sparse layout on memory. Gorder is a state-of-the-art graph reordering technique for layout optimization. However, despite providing performance improvement, applying Gorder to a sampled graph requires lengthy and impractical time periods,such as reordering time and waiting time for the completion of sampling. In addition, it is unsuitable for multicore graph computation because high and low degree vertices are separated on memory by reordering. We propose WalkOrder, a technique that conducts gradual graph reordering in parallel with sampling; sampling is performed by the widely used Metropolis-Hastings Random Walk. WalkOrder reduces reordering costs of Gorder and balances workload between cores. Our extensive experiments on six real-world graphs revealed that WalkOrder was faster than baseline techniques by an average of 1.52 times and a maximum of 1.95 times.

Recently, it becomes common to handle large files in computers. However, we have a difficulty to realize file sharing over networks, especially for large files. The problem is that we have extended the system model designed decades ago based on a stand-alone computer model. Assuming that all files are located in data centers, and nobody accesses them at the sites, we can redesign the file sharing system model for higher access speed and efficient storage resource usage. We designed a global secure file sharing system called Content Espresso. In this paper, we describe the difficulty, the design goal for global secure file sharing system, and our approach for it. Finally, we explain the impact of Content Espresso on network. © 2012 IEEE.

In future, spotted access networks will enable users to handle large files. We will be able to download movie and enjoy it at any time. However, the narrow and discontinuous areas will result in throughput decrease for the users moving with high speed (e.g. in a car). To avoid the problem, we show on-demand data prefetching system in which users preserve the files via any access networks before they enters into the spotted network area. The requested files are prefetched in Spool Server located in spotted network so that they can start receiving data as soon as possible. We also show our testbed networks and experimental results.

This paper shows an approach to realize secure session migration between devices by introducing key-insulated public-key cryptosystems.

This paper descrives a session layer mobility support which is a mechanism for service migration.

This paper describes the design and our implementation of Personal Mesh and shows the effectiveness of our system by experiment.

本論文では，自己ルーチングを用いた光パケット転送ネットワークにおいて，ヘッダ長のオーバヘッドを抑えるためのプリアンブル遅延型ラベル更新手法を提案し，その効果を評価する．大容量の光伝送技術を生かした光パケット技術は，光RAMや光論理回路などの光デバイスの欠如からIPヘッダ処理のような複雑な機能を用いて実現することが困難である．これに対して，ヘッダ内に通過する経路上の中継ノード情報をすべて記述することで，中継ノードにおける転送処理を単純化する自己ルーチングの適用が研究されている．しかし既存手法では，任意トポロジーのネットワークにおいてヘッダ長がペイロード長に対して長くなり，帯域利用効率が低下する問題があった．本論文で提案するプリアンブル遅延型ラベル更新手法では，ヘッダの先頭を識別するプリアンブルを転送処理時の読取りデータ長分遅延させることで，光領域でのラベル更新を実現し，短いヘッダ書式の適用を可能とする．シミュレーション結果より，特にネットワーク規模が大きくなる場合に，既存手法に比べてヘッダ長を短く抑えられることが示された．

In this paper we describe the world's first Trans-Pacific and Trans-Atlantic real-time switching and streaming transmission of uncompressed 4K motion pictures. This demonstration, of an advanced networked media application, conveyed the 23rd Kyoto Prize events, held on Nov. 10 and 11, 2007, from Kyoto, Japan to Stockholm, Sweden in real-time with life-like image quality. Multiple live 4K streams from different cameras were switched over the network into a single uncompressed stream at the director's request, and transmitted to Stockholm via 10 Gbit Ethernet connections over 21,000 km using the Global Lambda Integrated Facility (GLIF). We introduce several new technologies, including an uncompressed 4K video streaming system using Internet Protocol (IP) transmission and a shared line approach to gap-less video switching control. The Kyoto Prize 2007 demonstration proves the feasibility of using the IP infrastructure for next generation video switching and distribution networks, even at very high speeds across great distances.

We demonstrate a field trial of 4K uncompressed streaming over multicast-capable 80 (8lambda times 10) Gbps colored optical packet switching network using SOA based broadcast-and-select switch and stacked optical-code label processing.

We, Keio DMC, have tried several experiments related to 4K networking applications. In this paper, we briefly explain what 4K is and why 4K requires networking. Then, we introduce our three experiments based on the expected applications. One is 4K network distribution, one is 4K networked production, and the other is 4K videoconference. These experiments were tested over International communication networks and showed not only its concepts but also its feasibility. Finally, we discuss the similarity between 4K and dome theater applications. Dome theater presentations also need a quite big image size due to the huge screen size. Sometimes, it is eight times bigger than 4K. The networking technology developed for 4K can be used for easy content production. On the other hand, dome theaters are at the turning point to change their systems to digital from the point of business. It opens up new services called alternative content like live broadcasting of natural phenomena using network.

Digital projection is increasingly being deployed to dome theaters that have been mainly used for planetarium. Compared with traditional film projection, digital projection has a flexibility of content. Especially, LIVE presentations are the most unique contents using digital feature. On the other hand, in order to show by digital, we have to prepare high quality digital contents. In planetarium community, it is said that 64 million pixel counts are the ideal, 16 million pixels are the adequate, and 4 million pixels are the minimum even for ten meters small domes. If domes are larger, we need more. In this paper, we focus on LIVE transmission system for digital domes. LIVE dome contents are basically created by the following three steps like other digital LIVE contents; capturing, transmission, and projection. The notable differences are that the image must be captured with big pixels using circle fish eye lens to be qualified for domes, large size data transmission to avoid image quality degradation, and it has to be spatially divided for multi-projector projection keeping its quality. Especially for LIVE system, we have to make sure that each process must be realized in real time. We've developed a LIVE transmission system that consists of existing digital still camera, a newly designed LIVE image sharing tool, and existing digital dome presentation system. It realizes 0.5 frame/second LIVE transmission of 9 million pixels image. We transmitted total solar eclipse from three locations in Asia to a dome in Japan in July 2009 using this system.

Digital projection systems are now becoming popular in planetariums. One of the biggest advantages of the digital projection system is live viewing capability that enables audiences in planetariums to see phenomena observed at remote locations. Although several trials of live viewing in a planetarium have been carried out, a live viewing system has not yet been standardized and it is still a challenge to realize higher image quality in large digital domed theaters by multiple projectors. In this paper, we describe our live viewing system consisting of acquisition by digital cameras, transmission through networks, pre-processing for projection, and projection in domed theaters. In addition, we introduce our live viewing trial of the total solar eclipse from three locations in Asia to a digital domed theater in Sendai, Japan in 2009. In the trial, we accomplished 0.5 frame/second live viewing of nine million pixels images by two 4K x 2K projectors in a 250 seat 25m domed theater.

We demonstrate for the first time a field trial of 80 (10 × 8λ) Gbps colored optical packet switching of 4K and 2K uncompressed streaming using SOA based broadcast-and-select switch and optical-code label processing. keywords: {Optical packet switching;Optical switches;Optical receivers;High speed optical techniques;Optical transmitters;Semiconductor optical amplifiers;Converters

4K that became a digital cinema standard in 2005 is now recognized as the next high quality image technology of HD in the market. This paper describes what 4K is, the status of 4K, and 4K applications other than digital cinema. We introduces three 4K applications, 4K alternative content with live transmission, 4K usage in dome theaters, and 4K video conference with our proof-of-concept experiments over the world. ©2010 IEEE.

Live streaming of high quality media requires high quality network in terms of packet loss rate and jitter. However, the current IP or Ethernet network does not assure the bandwidth or jitter for streaming in general. In addition, the existing network monitoring system does not have the functionality to measure these network quality. My precise network monitoring is a packet-by-packet network monitoring to observe switching or routing latency inside of a switch, router, or network, and provide the statistics of a flow that is specified by user on-demand. We implemented this system, installed it in the existing network, and evaluated its functionality. It shows the impact of cross-traffic on a measured flow. © 2011 IEEE.

The aesthetic potentials of 4K digital cinema are an impetus for creative practitioners of cinematic arts to undertake full investigations of the methods and expressive possibilities of this end-to-end digital medium. This includes new approaches to production, distribution and the forum of theatrical experience. A group of artists, film-makers and computer scientists have been developing a series of 4K digital cinema projects that have diffused and grown the manner in which 4K cinema is experienced between Brazil, the US and Japan. The recent culmination of this was an event in July 2009 in which a 4K feature length movie had its world premiere on three continents, streamed from Brazil to the US and Japan. This was accompanied by an HD video teleconference (VTC) between the three sites. To the knowledge of the participants, this was both the first uncompressed HD VTC between the northern and southern hemispheres as well as the first feature length 4K film to be streamed across three continents. Through this work, the new creative affordances of 4K cinema were highlighted, along with the new capabilities of cinematic distribution, production and experience.

The high definition of 4K motion pictures makes them applicable to a wide variety of purposes. The development of 4K image equipment such as cameras, displays, and playback systems has made easy viewing of 4K video possible. Video frame rates have also become higher, enabling 4K-60 fps progressive (60p) video streams to be transmitted over IP networks. However, problems remain in increasing video image resolution to 8K or more so as to build systems in which many people collaborate at the same time. This paper describes a video transmission system that attains image resolution of 8K-60p or higher by synchronizing multiple 4K transmission systems we have developed. Since 8K-60p transmission over IP networks has extremely high traffic rates, schemes for achieving robust transmission such as forward error correction (FEC) must also have very high rates. We have also developed techniques for attaining reliable transmission, i.e., the use of low-density generator matrix (LDGM) codes to achieve high throughput FEC, application-layer multicasting, and monitoring network status at multiple points.

The progress of technologies in image industries and the rapid spread of broadband networks allow us to put high quality video communications to use for remote collaboration. We have developed a 4K/2K layered video streaming system with JPEG 2000 codec. It offers three main advances; support of various video formats to realize a media exchange platform, 4K/2K layered streaming with multicast to utilize 4K images even if the environment has no 4K equipment, and robust transmission using a forward error correction (FEC) scheme that can deal with bandwidths beyond 800 Mbit/s. Using the system, we conducted the world's first multi-point ''shared collaborative space'' experiment with a large audience in CineGrid International Workshop 2008. It proved the feasibility of the new environment for 4K remote collaboration between multiple points including those that did not have 4K equipment. This paper details the system and implemented technologies.

This paper proposes a live transmission system to dome theaters with multiple-projector projection systems. Our live transmission to dome theaters solves three issues between the sender and the receiver: slicing, image size, and clock synchronization. These issues make it difficult to apply a conventional streaming approach to dome theaters. We propose a file-based approach, which we call live image file feeding. We realize live file transfer by checking the file status periodically, transmitting reliably at a constant bit rate, and retransmitting immediately if packets are lost. We implemented this system, named it the Kaneko file system (KFS), and evaluated its functionality. Furthermore, we tested the entire live transmission system using the KFS, a digital still camera and a dome theater during the total solar eclipse in 2009 and showed that it worked well with 3K×3K image pixels. © 2010 Elsevier B.V. All rights reserved.