Details of a Researcher - Tokuda, Hideyuki

Papers - Tokuda, Hideyuki

Division display 61 - 80 of about 105 ／ All the affair displays >>

User-level Real-Time Network System on Microkernel-based Operating Systems

T.Nakajim, H. Tokuda

Real-Time Systems The International Journal of Time-Critical Computing Systems 14 ( 1 ) 45-60 1998.01

Joint Work, Accepted

This paper presents the design and implementation of a user-level real-time network system in Real-Time Mach. Traditional network systems for microkernel based operating systems, which tend to focus on high performance and flexibility, are not suitable for real-time communication. Our network system provides a framework for implementing real-time network protocols which require to bound protocol processing time, and it is suitable for implementing on microkernel based operating systems. In this paper, we especially focus on the aspects to avoid the priority inversion problem in order to make network systems more preemptable and predictable. We also describe the feasibility of our network system for building distributed multimedia systems.

End-to-End Channel Redirection for Bandwidth Guarantee:RT-Mach with an ATM Network

Y.Tobe, H.Tokuda

IEEE International Symposium on Communication 1997.12

Joint Work, Accepted

Quality of Service (QoS) control of continuous media such as video and audio with Operating System (OS) support has been extensively studied. On the network side, bandwidth-guaranteed networks are already available. Both the OS and the network are becoming able to support continuous media, but there has not been much discussion on collaboration between them for efficient handling of Variable Bit Rate (VBR) continuous media. We consider QoS control of VBR continous media in both end hosts, a sender and a receiver, and consider the delay of theApplication Data Unit (ADU). We propose ``Channel Redirection,

Implementation and Evaluation of Real-Time Java Threads

A.Miyoshi,T.Kitayama, H. Tokuda

Proceedings IEEE 18th Real-Time Systems Symposium ( - ) 166-175 1997.12

Research paper (scientific journal), Joint Work, Accepted

Java has many benefits such as security in distributed environments, reusability of code, and portability because it is architecture neutral. From those characteristics, Java is beginning to be used in many new environments. Even though Java provides various advantages, it still has problems which must be solved. One issue is that, there are often real-time constraints that should be met in those applications. Current Java execution environment and language specification cannot satisfy those requirements. Our research focuses on the current limits of the Java language and its execution environment, and to seek the possibility for real-time using Java and the technologies we have available today. To investigate issues in real-time Java, we have implemented a prototype real-time Java environment which provides real-time Java threads and real-time synchronization mechanism. Then we evaluated its performance. The results indicate that timing requirements are better met and unbounded priority inversion is avoided in our system.

Performance Improvement of TCP in Mobile Computing Environments.

田村陽介 (慶応大), 徳田英幸 (慶応大環境情報)

情報処理学会シンポジウム論文集 97 ( 8 ) 9-15 1997.11

Research paper (conference, symposium, etc.), Joint Work, ISSN 1344-0640

QOS based Multicast Communications

Y.Onoe, H. Tokuda

Proceedomgs. IEEE International Conference on Protocols for Multimedia Systems and Multimedia Networking 162-171 1997.11

Joint Work, Accepted

In a distributed multimedia integration environment, there is a need for transmission control methods based on real-time communication protocols, that provide a relative Quality Of Service (QOS) to allow a variety of receiving capacities for group members and their requests and that provide a dynamic QOS to cope with temporary CPU overload and network congestion. Therefore, this study proposes a cooperative control method for end-to-end QOS control at a transport layer and for point-to-point control at a network layer. The former is mainly a set of flow-monitoring and flow-adjusting functions, and the latter a set of flow-control functions. The flow-adjusting functions provide in-depth evaluation of (1) the characteristics of the transmission data, (2) end-to-end network performance, and (3) the requirements of receiver applications. The appropriate QOS levels and flow control methods are then determined on the basis of the results.

Real-Time Communication in Distributed Environment --- Real-Time Packet Filter Approach ---

T.Kitayama,A.Miyoshi, T.Saito, H. Tokuda

Proceedings 4th International Workshop on Real-Time Computing Systems and Applications 10-17 1997.10

Joint Work, Accepted

Recent modern operating system technology enables protocol processing in user space using in-kernel packet filter and user-level protocol processing library for flexibility without sacrificing the performance of traditional kernelized protocol processing. This technology can be adapted to build a highly preemptable protocol processing mechanism for distributed real-time environment. In this paper, we discuss the structural difference of various operating systems from the protocol processing point of view, and propose an extended mechanism of packet filter and user-level protocol processing library for real-time communication. Using this mechanism, priority of the client can be handed off to the server without priority inversion problem while protocol processing.

VoR: A Network System Framework for VBR over Reserved Bandwidth

Y.Matsui, H. Tokuda

ACM European Workshop on Interactive Distributed Multimedia Systems and Telecommunication Services (IDMS'97) 189-198 1997.09

Joint Work, Accepted

Distributed multimedia systems must handle multiple continuous media streams at once. The network subsystem must thus be able to transmit aggregation of VBR streams effectively. Data smoothing and shaping is necessary for high quality transmission. Flexibility is also required to handle different types of data formats and contents. In this paper, we propose the VoR system, a network subsystem framework for VBR continuous media transmission. It controls stream multiplexing by the scheduler in the network driver along with the QoS coordinator middleware. The system provides a way for application programs to interact with the underlying network. The system is designed on the principle of policy and mechanism separation, which enables to flexibly adapt to application dependent inter- and intra-stream QoS tradeoffs. Our preliminary result using MPEG2 streams indicates that while simple multiplexing gains some bandwidth utilization, better multiplexing can be achieved by providing more elaborate data dependent policies.

実時間通信のための次世代インターネットプロトコルサーバ・ライブラリ

尾上裕子,木原誠司, 舩渡大地, 松井康範,徳田英幸

電子情報通信学会技術報告 97 ( 42 ) 17-23 1997.09

Joint Work

次世代インターネットプロトコル IPv6 では、24 ビットのフローラベルや優先度フィールドなど、実時間通信処理サービスへの要求に応じた QOS サポートが考慮されており、今後の課題として(1)フローラベル毎のフロー制御、(2) ATM の QOS コネクションとのマッピング、(3)ルーティングプロトコルやNDP (Neighbor Discovery Protocol) とのキャッシュ情報の一貫性管理、(4)キューでの優先度制御、(5)パスと資源予約制御が挙げられる。さらに、慶應大学を中心とした次世代マイクロカーネル(MKng)研究プロジェクトにおける、RT- Mach (Realtime Mach) OS 上でのリアルタイムスレッドを用いた次世代インターネットプロトコルサーバ・ライブラリの実装と、通常のファイル転送プロトコル(ftp)による輻輳時のジッタの評価結果について述べる。

講座マルチメディアコンピューティング第5回 --- 連続メディア処理のためのミドルウェアとツールキット ---

西尾信彦，徳田英幸

電子情報通信学会電子通信情報学会誌 80 ( 9 ) 969-975 1997.09

Joint Work, Accepted

Simplified Method for Session Coordination Using Multi-level QOS Specification and Translation

N.Nishio, H.Tokuda

IFIP5th IFIP Intl. Workshop on Quality of Service 335-346 1997.05

Joint Work, Accepted

In multimedia systems, session coordination technique is important to accommodate a new session and re-distribute reclaimed resources when tough continuous media session is exiting. Although end-users do not want to specify the quality of service (QOS) in an exact memory size like in KB or KB/s of bandwidth, such rigid usages are necessary for admission control and coordination. Therefore, we introduce the multi-level quality specification and QOS translation mechanism to put it into the quantitative expression which the system can handle. Nonetheless, session coodination have demanded complicated computation or presented an NP-complete problem. Constraining QOS specification, we invent a simplified session coordination method which is feasible enough to actually implement. This paper reports experiments on QOS translation and multiple session coordination using the Conductor/Performer system on top of Real-Time Mach 3.0.

A Real-Time Java Server for Real-Time Mach

A.Miyoshi, H.Tokuda

Proceedings of the Joint Workshop on Parallet Distributed Systems.Fifth International Workshop on Parallel and Distributed Real-Time Systems(WPDRTS) and the Third Workshop on Object-Oriented Real-Time Systems(OORTS) 319-325 1997.04

Joint Work, Accepted

Java has many benefits such as security in distributed environments, reusability of code, and portability because it is architecture neutral. From those characteristics, Java is beginning to be used in many environments where more popular languages such as C and C＋＋ were originally used. Even though Java provides benefits, still it has problems which must be overcomed. There are often real-time constraints that should be met in those applications. Current Java execution environment and language specification cannot satisfy those requirements. Our research focuses on the current limits of the Java language and its execution environement, and to seek the posibility for real-time using Java and the technologies we have available today. To investigate issues in real-time Java, we have implemented a prototype real-time Java environment and Real-Time Java thread.

Adaptive Object Management for a Reconfigurable Microkernel

Oikawa-S, Sugiura- K, Tokuda-H

Proceedings of the 5 th International Workshop on Object Orientation in Operating Systems (IWOOOS'96) 67-71 1996.10

Joint Work, Accepted

Keio-MMPプロジェクトの分散マルチメディア統合環境

和田英彦 (横河電機), 藤井敬三 (システムコア), 萩野達也, 徳田英幸, 斎藤信男 (慶応大環境情報)

電気学会情報処理研究会資料 lP-96 ( 23-30 ) 69-78 1996.09

Research paper (scientific journal), Joint Work

Dynamic QOS Control Based on the QOS-Ticket Model

Kawachiya, K., Tokuda, H

Proceedings 3rd IEEE Intl. Conference on Multimedia Computing and Systems (ICMCS'96) 78-85 1996.06

Joint Work, Accepted

QOS-Ticket: A New Resource-Management Mechanism for Dynamic QOS Control of Multimedia

Kawachiya, K, Tokuda, H

Proc. Multimedia Japan '96 14-21 1996.04

Joint Work, Accepted

In an interactive multimedia environment that handles multiple sessions dynamically, a mechanism for controlling the QOS among sessions is very important. It is, however, difficult to achieve such QOS control without any system support. A new resourcemanagement mechanism and QOS-control architecture for multimedia applications are needed. This paper first discusses features required for such architecture, and then proposes a new QOS-control architecture based on ''QOS-Ticket.'' In this QOS-Ticket model, resource management and QOS control are achieved through the cooperation of an operating system, a QOS Manager, and individual continuous-media sessions.'

Q-Thread: A New Execution Model for Dynamic QOS Control of Continuous-Media Processing

Kawachiya, K, Tokuda, H

In Proc. 6th Intl. Workshop on Network and Operating System Support for Digital Audio and Video (NOSSDAV96) 149-156 1996.04

Joint Work, Accepted

Efficient Timing Management for User-Level Real-Time Threads

Oikawa S, Tokuda, H

In Proceedings of the IEEE Real-Time Technology and Applications Symposium 27-32 1995.05

Joint Work, Accepted

Evaluation of QOS-Control servers on real-time mach

Kiyokuni Kawachiya, Masanobu Ogata, Nobuhiko Nishio, Hideyuki Tokuda

Proc. 5th Intl. Workshop on Network and Operating System Support for Digital Audio and Video 123-126 1995.04

Joint Work, Accepted

User-level real-time threads

Oikawa S, Tokuda, H

In Proceedings of the 11th IEEE Workshop on Real-Time Operating Systems and Software 7-11 1994.05

Joint Work, Accepted

Continuous-media applications require more efficient and flexible support from real-time threads than traditional real-time systems. It includes functionalities such as the dynamic management of thread attributes and the support of multiple thread models. In this paper, we will describe the design and implementation of user-level real-time threads on the RT-Mach micro kernel. Since they are implemented at user-level, both of the fast management of thread attributes and the support of multiple thread models are possible

Processor Capacity Reserves: Operating System Support for Multimedia Applications.

Clifford W. Mercer, Stefan Savage, H. Tokuda

In Proc. Of the IEEE International Conference on Multimedia Computing and Systems 90-99 1994.05

Joint Work, Accepted

Multimedia applications have timing requirements that cannot generally be satisfied using the time-sharing scheduling algorithms of general purpose operating systems. Our approach is to provide the predictability of real-time systems while retaining the flexibility of a timesharing system. We designed a processor capacity reservation mechanism that isolates programs from the timing and execution characteristics of other programs in the same way that a memory protection system isolates them from outside memory accesses. In this paper, we describe a scheduling framework that supports reservation and admission control, and we introduce a novel reserve abstraction, specifically designed for the microkernel architecture, for measuring and controlling processor usage. We have implemented processor capacity reserves in Real-Time Mach, and we describe the performance of our system on several types of applications.

　 Previous page - Next page 　