Details of a Researcher - Tokuda, Hideyuki

Papers - Tokuda, Hideyuki

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Real-world product deployment of adaptive push notification scheduling on smartphones

Okoshi T., Tsubouchi K., Tokuda H.

Proceedings of the ACM SIGKDD International Conference on Knowledge Discovery and Data Mining (Proceedings of the ACM SIGKDD International Conference on Knowledge Discovery and Data Mining) 2792 - 2800 2019.07

ISSN 9781450362016

The limited attentional resource of users is a bottleneck to delivery of push notifications in today's mobile and ubiquitous computing environments. Adaptive mobile notification scheduling, which detects opportune timings based on mobile sensing and machine learning, has been proposed as a way of alleviating this problem. However, it is still not clear if such adaptive notifications are effective in a large-scale product deployment with real-world situations and configurations, such as users' context changes, personalized content in notifications, and sudden external factors that users commonly experience (such as breaking news). In this paper, we construct a new interruptibility estimation and adaptive notification scheduling with redesigned technical components. From the deploy study of the system to the real product stack of Yahoo! JAPAN Android application and evaluation with 382,518 users for 28 days, we confirmed several significant results, including the maximum 60.7% increase in the users' click rate, 10 times more gain1compared to the previous system, significantly better gain in the personalized notification content, and unexpectedly better performance in a situation with exceptional breaking news notifications. With these results, the proposed system has officially been deployed and enabled to all the users of Yahoo! JAPAN product environment where more than 10 million Android app users are enjoying its benefit.

Access to Document (DOI)

Cruisers: An automotive sensing platform for smart cities using door-to-door garbage collecting trucks

Chen Y., Nakazawa J., Yonezawa T., Tokuda H.

Ad Hoc Networks (Ad Hoc Networks) 85 32 - 45 2019.03

ISSN 15708705

Due to the advance in information and communication technologies, smart cities have become an increasingly appealing vision. One indispensable basis in the research, development and implementation of smart cities is urban sensing technology. Automotive sensing is a novel urban sensing technology that equips sensors to vehicles, like buses, taxi cabs or garbage trucks and utilizes their mobility to help to conduct urban sensing tasks. In this paper, we present Cruisers, an automotive sensing platform for smart cities, based on the following ideas: a) Garbage collecting trucks are used to host sensors, b) Cellular communication network is used to deliver sensed data to servers, and c) Proxy server(s) are adopted to convert the format of sensed data to required ones, such as sampling rate, spatial interval or pub/sub protocol. To validate the feasibility of Cruisers, we implement a real system that consists of 66 customized sensing modulars integrating typical environmental and mobility sensors and deploy them into the garbage collecting trucks at Fujisawa, a medium-sized city in Japan. Performance evaluation is conducted to investigate the performance of Cruisers in terms of scalability, data publishing delay and spatial coverage.

Access to Document (DOI)

Real-world large-scale study on adaptive notification scheduling on smartphones

Okoshi T., Tsubouchi K., Tokuda H.

Pervasive and Mobile Computing (Pervasive and Mobile Computing) 50 1 - 24 2018.10

ISSN 15741192

Human attention has bottlenecked today's ubiquitous computing environment where users are consuming increasing amounts of information from numerous applications and services. Since the system-to-user provision of information is becoming more proactive, mainly via push notifications that often cause interruption at the users’ side, attention management is becoming very important. Despite the many existing studies concerned with detecting opportune moments to present such push information to the users (in a way that preserves the user's attention and lowers their cognitive load and frustration), there is little evaluation of such systems in the real-world production environments. Overlooked areas of study also include the examination of real users and notification contents. In this paper, we present various results from the first extensive evaluation on user's interruptibility and engagement in the real-world environment with a market-leading smartphone application that boasts a large number of users, including real notification content on the application. Following our previous mobile-sensing and machine learning-based interruptibility estimation approach, which was an effective study in its own right (Okoshi et al., 2015 [18,19]), we embedded a logic with the same approach in the “Yahoo! JAPAN” Android app (one of the most popular applications on the national market). The results from our large-scale in-the-wild user study (that included more than 680,000 users and spanned three weeks) indicate that, in most cases, delaying the notification delivery until an interruptible moment is detected is beneficial to users. The practice results in significant reduction of user response time (49.7%) when compared to delivering the notifications immediately. We observed a higher number of notifications opened in our system and constant improvement in user engagement levels throughout the entire study period. We also observed differences in click rates among different days and time among users with different attributes (e.g., age, gender, and occupation). Additional evaluation of our revised system, which can train and distribute different models for weekdays and weekends, improved the click rates during weekends. This negated the performance degradation previously observed during weekends.

Access to Document (DOI)

Evaluating the spatio-temporal coverage of automotive sensing for smart cities

Chen Y., Yonezawa T., Nakazawa J., Tokuda H.

2017 10th International Conference on Mobile Computing and Ubiquitous Network, ICMU 2017 (2017 10th International Conference on Mobile Computing and Ubiquitous Network, ICMU 2017) 2018-January 1 - 5 2018.04

ISSN 9784907626310

Automotive sensing is a novel and appealing sensing technology in which sensors are installed into vehicles to utilize vehicles' mobility to conduct urban sensing in smart cities. The coverage performance is a major metric to characterizing the quality-of-service of sensing systems. Despite of the coverage metrics studied in static sensor networks that consist of only spatial dimension, the lack of a proper metric to characterizing the spatio-temporal coverage of automotive sensing systems is stunting the research, development and commercialization of such mobile sensing systems. To address this issue, we propose, for the first time to the best of our knowledge, a spatio-temporal coverage metric for automotive sensing. The proposed metric characterizes the coverage in both spatial and temporal dimensions in order to provide a guideline for smart cities application developers to evaluate the quality-of-service that can be expected from an automotive sensing system. Evaluation based on an automotive sensing system implemented in Fujisawa City, Japan is conducted to demonstrate the usage of this metric in a realistic scenario.

Access to Document (DOI)

SpoTrip:観光客リピータ化促進のための隠れスポット情報提供システムの評価

TOKUDA HIDEYUKI

電子情報通信学会技術研究報告 116 ( 508 ) 157 - 163 2017.03

NiSleep:ゲーミフィケーションを適用可能な睡眠評価

TOKUDA HIDEYUKI

情報処理学会研究報告(Web) 2016-UBI-50 ( 2 ) 1 - 6 2016.05

リアルタイムランキングシステムで観測されたコミュニティの共振現象

TOKUDA HIDEYUKI

情報処理学会論文誌ジャーナル(Web) 56 ( 1 ) 148 - 160 2015.01

Wapplet:A Media Access Framework for Wearable Applications

T.Iwamoto, N.Nishio, H. Tokuda

International Conference on Information Networking ( - ) 5D4.1-5D4.11 2002.02

Research paper (scientific journal), Joint Work, Accepted

This paper presents a new framework for constructing applications for wearable computers. We do not consider wearable computing merely as a single self-confined system. Rather, wearable computing can be treated as a cooperative application with information surrounding a person and various devices attached to him/her. We have developed a frameworkof such wearable computing called ``Wapplet.'' Wapplet provides adaptation to the availability of devices as well as a systematic scheme of constructing applications for wearable computing. In this paper, we describe the design and implementation of Wapplet, and show its prototype system.

A Light-weight Transport Protocol for Home Networks

Yoshito Tobe,Hiroto Aida. Hideyuki Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 0 ( 0 ) 179-185 2002.01

Joint Work, Accepted

Dynamic Message-path Generation for Improvised Composition of Networked Appliances Services

Jin Nakazawa, Masayuki Iwai, Hideyuki Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 145-154 2002.01

Joint Work, Accepted

This paper presents a new middleware architecture for integrating heterogeneous information appliances on heterogeneous network for various users, called Virtual Network Appliance (VNA) Architecture. Instead of merely connecting appliances seen in existing approaches, VNA architecture accommodates creating a function alliance called a VNA. VNA Markup Language is our solution to define VNAs independent of specific home networks. Our middleware enables users not only to define VNAs by themselves (bottom-up integration), but also to virtually plug and play pre-defined VNAs (top-down integration).

PRONA:A Proactive Support System for Networked Appliances

IEEE International Workshop on Networked Appliances(IWNA) 145-154 2002.01

Joint Work, Accepted

In this paper, we propose a proactive operational model for home appliances. Recently, users of home appliances often have difficulty in operating appliances due to their high functionality, complex interface, which have many buttons, and users’ lack of knowledge. The current operational model of home appliances is a reactive model, which it is necessary for users to notify appliances of operational information. This causes an increased burden on the user to understanding correct operational information. To cope with these issues we propose a proactive operational model. In this model, appliances acquire the operational information by themselves, and provide users with their services based on that information. Thus, our model eliminates the users’ burden on explicitly expressing requests to the appliances to access their services. It is necessary for programmers to satisfy the autonomy of obtaining information, interaction between users and system, and operation simplification. Based on this model, we have developed a middleware, called Proactive Support System for Networked Appliances (PRONA). PRONA is realized by acquiring information necessary for appliance operation and learning the users’ operational pattern. PRONA consists of three modules, which are the information acquisition module, the suggestion composition module, and the information manager module. The information acquisition module normalizes information gathered from sensors and appliances, and transmits it to the information manager module. The suggestion composition module learns the importance of related sensors when users operate the appliances. We represent the importance of related sensors as a weight, and transmit the weighted data to the information manager module. The suggestion composition module also provides the user suggestions from this weighted data. The information manager module stores this data in its database. We evaluated the use of PRONA in a proactive television application. PRONA’s quantitative evaluation criteria are its processing time, the accuracy of its suggestions for user’ action, and its learning time for the user’ operational pattern while varying the number of proactive components.

Implementation and Evaluation of Wapplet Framework

IEEE International Workshop on Networked Appliances(IWNA) 275-284 2002.01

Joint Work, Accepted

It is important for application programmers and users to easily control networked appliances and devices without the need to be aware of their locations. In particular, network transparent control is essential for the ubiquitous computing environment. This is because end-users accomplish their tasks by coordinating devices that they are wearing, such as wearable computers and cellular phones, with various networked appliances, such as display devices and loud speakers. This paper presents the Wapplet framework, a new application framework that addresses this issue for the ubiquitous computing environment. To show the efficiency of the proposed Wapplet framework, we have evaluated it in terms of processing time. Requirements of the Wapplet framework are as follows: (a) support for object-migration, (b) location transparent method of invocation, and c abstraction of device specifics. Object migration is necessary for the ubiquitous computing environment because it is impractical to pre-install all applications on networked appliances. Thus, applications should be composed of multiple mobile modules. Location transparent control mechanisms like RPC (Remote Procedure Call) help application programmers in coordinating networked appliances. The framework needs to provide device independent Application Program Interfaces (APIs) that define interfaces to networked appliances, which eliminates the need to change device control programs for every appliance. In our implementation of the Wapplet framework we satisfied the above requirements using Java 1.2.2 on FreeBSD-4.2RELEASE as follows. Our object migration system (a) is realized by Java's Serialization mechanism. The system supports multi hop migration of mobile objects, which adapts to changes in available devices caused by users' movement. As for location transparent control (b), we developed a location transparent method invocation (LTMI) protocol that works like Java RMI or Sun RPC. Most conventional protocol, such as Java RMI, forces application programmers to manage the locations of mobile objects. We developed LTMI so application programmers only need to invoke the method name of the object but do not need to know the object's location (e.g. IP addresses). In addition, we provide device independent APIs to easily control and manage various kinds of networked appliances. The device control APIs classify networked appliances by media data types. There are four media types: for text, sound, image, and video. To evaluate the efficiency of LTMI, we measured the processing time of LTMI in comparison with Java RMI. As the result, we found that LTMI is more efficient than Java RMI in both local and remote method invocations.

m-P@gent: A Framework of Environment-Aware Mobile Applications for Small, Networked Appliances

Kazunori Takashio,Masakazu Mori, Hideyuki Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 257-266 2002.01

Joint Work, Accepted

Mobile agent software architecture has attracted a great deal of attention as a basic technology for building such a ubiquitous computing environment. In our framework, a mobile agent is divided into two parts: a core component and a set of add-on functional modules. Each runtime system dynamically collects add-on modules necessary for a new environment, and links them with the core component. This feature allows us to describe an application as seamless against changes of computing environment. For example, we can realize the following application behavior. When the user changed his location, his applications also move to a device that he personalized as though they followed him. Then, they adapt their contexts to the new location and continue to carry out their tasks. On a device that has a small LCD, an application can indicate its progress to a user progress. On another device that has an input interface such as a touch-panel, the application may wait for instructions from the user. We implemented mobile agent systems based on this framework on actual PCs and small, networked devices. Especially, one of the m-P@gent runtime environments, @TINI, designed for the TINI devices provides X-10 protocol libraries. An ‘agent @TINI’ can control appliances connected over X-10 network by using X-10 commands.

Detection of Congestion Signals from Relative One-Way Delay

Yoshito Tobe,Hiroto Aida, Yosuke Tamura, Hideyuki Tokuda

情報処理学会論文誌 42 ( 12 ) 3222-3230 2001.12

Joint Work, Accepted

OR2: A Path Tuning Algorithm for Routing in Ad Hoc Networks

Masato Saito,Hiroto Aida, Yoshito Tobe, Yosuke Tamura, Hideyuki Tokuda

IEEE LCN Workshop on Wireless Local Networks (WLN '01) 560-567 2001.11

Joint Work, Accepted

This paper presents 'OR2'', an adaptive path tuning scheme for mobile ad hoc networks. In OR2, the active path adapts dynamically to node mobility without any link failures based on the local link quality. Most conventional routing protocols accommodate the change of network topology only when the link fails. Unless the movement of intermediate nodes leads to any link failures, they cannot adapt to the network topology even if other routes with less hop count become available. In contrast to these protocols, OR2 reduces the hop count of an active route while data packets are sent without link disconnection. Specifically, by introducing the notion of proximity that indicates the nearness of two communicating nodes, OR2 skips the upstream node in a proximity area and continues to shorten an active route as possible. For delay sensitive TCP flows, reducing the number of hops and path delay significantly improves the performance of TCP. We have implemented OR2 as an extension to DSR on FreeBSD. The experimental results have shown that OR2 is effective in enhancing TCP throughput and reducing end-to-end delay for all relevant flows.

m-P@gent: A Framework for Describing Environment-Aware Mobile Agents on Ubiquitous Computing Environment

Kazunori Takashio,Masakazu Mori, Hideyuki Tokuda

IEEE International Conference on Ubiquitous Computing (Ubicomp 2001), Workshop on Application Models and Programming Tools for Ubiquitous Computing (UbiTools 2001) 2001.09

Joint Work, Accepted

This paper proposes a new framework m-P@gent for environment-aware mobile agents that can run even on resource-limited devices and appliances. In the framework, a mobile agent is divided into a two parts: a core and addon functional modules. Each runtime system dynamically collects add-on modules necessary for a new environment, and links them with the core component. This feature allows us to describe an application seamless against changes of computing environment. We implements mobile agent systems based on the framework on actual PC environments and small PDA devices, and evaluates their basic performance. Our system makes two contributions. One is that it shows a possibility for expanding the field of mobile agent to resource-limited devices. Another is it reduces the cost of an agent migration. The framework will be a core software infrastructure for building ubiquitous computing environment.

Flexible Distributed Event-Driven Programming Framework for Networked Appliances and Sensors

3rd International Symposium on Distributed Objects and Applications (DOA01) (Short Papers Proceed) 61-68 2001.09

Joint Work, Accepted

This paper presents a new framework for constructing flexible event-driven systems for distributed networked devices and appliances, referred to as Dragon. Dragon enables constructing and modifying an event-driven system easily by visualizing distributed services which are handled in an integrated manner. The update of the system is conducted immediately following a modification by Dragon. Dragon is built on Jini/Java and can be executed on any Jini/Java-compliant machines. In addition, Dragon incorporates soft real-time event delivery to enhance the predictability of behavior of the constructed system and composition of distributed services for event management.In this paper, we describe the details of design and implementation of Dragon.

On Dynamic Service Integration in VNA Architecture

Jin Nakazawa,Yoshito Tobe, Hideyuki Tokuda

電子情報通信学会論文誌 ((IEICE Transactions on Hundamentals of Electronics, - Communications and Computer Science)) E84-A ( 7 ) 1610-1623 2001.07

Research paper (scientific journal), Joint Work, Accepted

In forthcoming home network environment, computation capability will be embedded invisibly in home appliances, sensors, walls, ceilings, and floors. People will conduct various tasks using multiple devices simultaneously without consciousness of using computers. In this paper, first, we propose an application model named Virtual Network Appliance (VNA) model which simplify and expand device utilization. In the model, each device has VNA runtime system and function objects, called VNA components, running on it. A user task is defined in an application called VNA which is a logical appliance consisting of abstract function requirements and a message graph among them. Second, we propose Virtual Plug&Play mechanism which is a dynamic service integration mechanism in VNA model implementation. When a user conducts a task, he/she makes a VNA runtime system on a user-side terminal load a VNA definition appropriate for the task. Virtual Plug&Play dynamically discovers required VNA components and establishes the message graph as defined. Since XML documents are used to describe a VNA, users can share and customize it easily. We call the device integration done by Virtual Plug&Play top-down integration, which existing middleware do not aim at. Finally, we show that Virtual Plug&Play affords practical performance for top-down integration by performance evaluation.

A Software Approach to Channel-State Dependent Scheduling for Wireless LANs

Hiroto Aida,Yoshito Tobe, Masato Saito, Hideyuki Tokuda

The 4th ACM International Workshop on Wireless Mobile Multimedia (WOWMOM 2001) 34-43 2001.07

Joint Work, Accepted

This paper proposes a new practical packet scheduling scheme for wireless LANs called SoCPS and also explores extensively the effectiveness of wireless packet scheduling under a variety of conditions over an actual wireless LAN. One well-known aspect in packet scheduling at the base station is consideration of channel state dependency. In conventional studies, the channel state is expressed in microscopic two states in the Markovian sense. To eliminate a large overhead associated with acquiring such a fine-grain channel state and to establish a software-based enhancement, we introduce the notion of Strength of Connection (SoC) which can be expressed as the long-term strength of the connectivity between the base station and an end host. We examine schemes for identifying the channel state and examine the applicability to packet scheduling. We also design a packet scheduling scheme based on SoC called SoCPS. Finally, we investigate the performance under various conditions of traffic and wireless channel states. We have designed and implemented SoCPS on FreeBSD computers. Our evaluation results obtained with up to eight wireless-LAN nodes have determined the applicability of SoCPS and limitation in wireless packet scheduling for wireless LANs. In particular, while FIFO is sufficient in many cases where TCP traffic is dominant, scheduling with SoC consideration is effective for real-time UDP traffic.

IP Fragment情報を利用したルータにおける効率的なパケット破棄手法

田村陽介,戸辺義人，徳田英幸

情報処理学会論文誌 42 ( 6 ) 1483-1491 2001.06

Joint Work, Accepted

IP層において上位アプリケーションのフレームを考慮するApplication Level Framingは長年の課題である．ルータがIPヘッダ以外の情報をもとにパケットを制御することはスケーラビリティの点で不利である．また同時にルータのパケット中継の作業を複雑にしてしまう恐れがある．本論文で我々は送信ホストはIP Fragmentを積極的に活用することにより，ルータに対してアプリケーションデータの境界線を知らせるべきであると主張する．我々が提案するTransport framE Discard（TED）はルータがパケットを破棄する際に，このIP Fragmentの情報を用いてパケットを破棄する順序を動的に変更させる．TEDを利用することでルータはアプリケーションデータの単位でパケットを破棄することが可能となる．我々はTEDをFIFO，WFQ，RED，Random Drop FIFOに組み合わせて実装し，評価した．その結果，ネットワーク内における全体のパケット欠損率を変化させずに，無駄なパケットの中継を回避し，上位アプリケーションに対して高い通信性能を実現することが実証された．

AMRB: Toward Location Migration Transparency of Services

Noriyuki Harashima,Tadashi Okoshi, Jin Nakazawa, Yoshito Tobe, Hideyuki Tokuda

Proceedings. IEEE International Conference on Parallel and Distributed Systems (ICPADS 2001) 305-312 2001.06

Joint Work, Accepted

In this paper, we present a new mobility-support model for applications, Application Module Request Broker (AMRB). We focus on two types of mobility: host mobility and application code mobility. These two types of mobility dynamically change the binding between applications' name and location in the network. AMRB conceals these changes of binding to reduce a complexity in development of applications. In AMRB, we deal with mobile application codes that communicate with each other as Application Modules (Ams). AMRB provides AM's service transparent communication for applications by using a specifier which does not need to include any network location information. Furthermore, applications can use AM's service transparently of migration by exploiting location management mechanism. In this paper, we describe the design and implementation of AMRB and some evaluations. Also, we demonstrate a sample application that AMRB is effective for developing mobile sensor type applications.

Proceedings. IEEE International Conference on Parallel and Distributed Systems (ICPADS 2001)

Y.Yasuda,N.Nishio, H. Tokuda

IEEE International Workshop on Quality of Service (IWQoS2001)(Lecture Notes in Computer Science Vol.2092) 294-299 2001.06

Joint Work, Accepted

システムソフトウェアの新しい潮流　ASAMA: 適応的なサービス利用管理機構

永田智大,西尾信彦，徳田英幸

情報処理学会論文誌 42 ( 6 ) 1557-1569 2001.06

Joint Work, Accepted

本論文では，周辺のサービスを利用してユーザの要求を実行する超機能分散環境を構築する際に重要となる「サービスの代替利用」と「環境変化の検知」を実現することで，利用可能なサービスが変化してもユーザの要求を継続して実行できる新たなサービスフレームワークを提案し，それを実現する Adaptive Service Availability Management システム (ASAMA) のプロトタイプを実装し，評価を行った． ASAMA は，サービスイニシエータ，サービスプロバイダ，ディレクトリサーバの 3 つのエンティティから構成される．PDA やノート PC などのサービスイニシエータは，装備する資源が貧弱なため，周辺のサービスプロバイダからサービスを提供してもらい，必要な機能を補完する． ASAMA ではサービスを入出力によって定義し，段階的なサービスの検索を行うため，代替可能なサービスも発見でき，メディアデータのやりとりでサービスを利用できる．また，環境変化をサービスイニシエータの物理的移動による能動的環境変化と，サービスプロバイダの起動・終了によって生じる受動的環境変化に分類し，これらを透過的に検知し，より品質の高いサービスに切り替えられる．本論文では，本プロトタイプを典型的な超機能分散環境下で実際に動作させ，目的を実現できるか，実証実験を行い，その利便性を示した．また，各処理に要する時間や受動的環境変化検知に関するネットワークトラフィックを測定し， ASAMA の基本性能を評価した．

システムソフトウェアの新しい潮流　QOSプロファイルハンドラつき資源予約機構の設計と実装

西尾信彦，徳田英幸

情報処理学会論文誌 42 ( 6 ) 1570-1579 2001.06

Joint Work, Accepted

よりpredictableな計算機環境を構築するために，計算機資源の予約は必須であるが，アプリケーションプログラマからは予約すべき資源量の算定が容易ではないうえに，それが通常は動的に変動してしまうために必ずしも利用は容易ではない．本稿では，従来の資源予約オブジェクトごとにQOSプロファイルハンドラを生成することにより，適切な資源量の見積りを動的に実施し，さらに動的な処理内容やシステム状況の変化への適応性を高めることを目標とした統合的資源管理機構の設計と実装について報告する．本実装は，OS内の低レベル資源予約管理と資源予約調停および翻訳のための資源予約管理サーバ，QOSプロファイルハンドラと動的適応するための非同期イベントメッセージを受信するポートを備えたライブラリにより構成し，GUIインタフェースをサーバに与えることにより，よりユーザに明解で抽象度の高いプログラミング環境を提供することができた．

Improvised Assembly Mechanism for Component-Based Mobile Applications

M.Mochizuki, H. Tokuda

((IEICE Transaction on Communications)) E84-B ( 4 ) 910-919 2001.04

Joint Work, Accepted

We propose a mechanism to facilitate the development of component-based mobile applications with adaptive behaviors. The design principles and communication patterns of legacy software systems will greatly change in a forthcoming environment, where a variety of computing devices become embedded in home and office environments, users move around with/without portable computing devices, and all the devices are interconnected through wired/wireless networks. In the proposed mechanism, Improvised Assembly Mechanism (IAM), we realize functionality to compose an application in an ad hoc manner and to achieve the adaptation of applications by adding, replacing, supplementing, and relocating components at system runtime according to various environmental changes such as the locational changes of computing devices and users. The mechanism is implemented as a built-in functionality of the Soul component, which is one of the fundamental elements in the Possession model.

A Mobile Agent Framework for Follow-Me Applications in Ubiquitous Computing Environment

Kazunori Takashio,Gakuya Soeda, Hideyuki Tokuda

Proceedings 21st International Conference on Distributed Computing System Workshop 202-207 2001.04

Joint Work, Accepted

The work described a personal corner and desk-top manager. The PDA device stored the keys, passphrases and location information. This follow-me feature was achieved through a secure call-up protocol. The environmental awareness were imported into the application as marshalled environment events. The environmental awareness provided the basis for QoS adaptation. Internal metrics include display size, CPU and memory, and locale information. External metrics include power service, and evaluation service. The call-up would go back to the previous machine to retrieve the standby agents. The Java applications were suspended by flushing their state to the machine (which might compromise the security model). Research issued identified include policy negotiation, QoS adaptation, and resource policy.

A Location-Adaptive Virtual Networked Appliance

A.Kusumoto, J.Nakazawa, Y.Tobe, H. Tokuda

Proceedings 21st International Conference on Distributed Computing System Workshop 214-219 2001.04

Joint Work, Accepted

This work explored location-based virtual plug-and-play. It allowed functional manipulation of objects through the run-time for applications (known as Serdget). A mark-up language (VML) described the functional components of virtual networked appliances (VNA). Some issued include dynamic locations, adaptation, wireless mobile devices, and heterogeneous network. Devices were represented with some structure indicating who else were in the same location. The devices themselves were decentralised. The location mapping mechanism provided lookup, registrar, location update, and event notification. The mechanism addressed issues pertaining to its overhead, modularity of search and autonomy. The area manager appears to be hierarchical rather than peers, which imposed total ordering and partial ordering respectively.

Smart Space Laboratory Project: Toward the Next Generation Computing Environment

T.Okoshi,S.wakayama, Y.Sugita, S.Aoki, T.Iwamoto, J.Nakazawa, D.Furusaka, M.Iwai, A.Kusumoto, N.Harashima, J.Yura, N.Nishio, Y.Tobe, Y.Ikeda, H.Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 2001.03

Joint Work, Accepted

This paper describes the Smart Space Lab (SSLab) project toward the next generation computing environment, ``{sf Smart Space}.'' As numerous types of networked appliances, such as A/V devices, home appliances, or sensors, are connected to each other via both wired and wireless networks, computational intelligence can be regarded as being distributed and embedded into users' surrounding space, rather than on a specific device such as users' PCs or PDAs. We call such a space with embedded computation ``Smart Space.'' In Smart Space, users can have their computing environment relying on not only computation of their carrying devices, but one in Smart Space. Toward the realization of Smart Space, SSLab Project is now addressing three research issues, (A)physical structure of Smart Space, (B)network architecture with support of dynamism and heterogeneity, and cadaptive middleware architecture and applications.

An Application Framework for Wearable Network Computing

T.Iwamoto, N.Nishio, H. Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 2001.03

Joint Work, Accepted

Today, new computing environment called wearable computing is getting popular in research. However, many of these research issues are mainly focused on the user interface or the miniaturization of PC platform. These hardware related researches may achieve some results, however these researches do not present an application and a software organization that are suitable and needed for wearable computing environment.We propose wearable computing environment named `` Wearable Network computing'' which supports cooperation of many devices and appliances around user's body. In {it Wearable Network} computing environment, the application may be distributed into various devices and appliances around user's body and accomplish user's task by using the function of these devices. In this environment the wearable computer controls the distributed application adapting to changes of user's context and to availability of devices.In this paper, we describe the an applicaton framwork for wearable computing environment which may provide context-awareness, device coordination, distributed and migratable application.

Adaptive Service Availability Management Mechanism for Wearable Network Computing

T.Nagata, N.Nishio, H.Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 2001.03

Joint Work, Accepted

A Top-down Integration Scheme for Networked Appliances using VNA Markup Language

Jin Nakazawa,Tadashi Okoshi, Yoshito Tobe, Hideyuki Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 96-101 2001.03

Joint Work, Accepted

SONA: Applying Mobile Agent to Networked Appliance Control

Soko Aoki, Satoshi Makino, Jin Nakazawa,Tadashi Okosh, Hideyuki Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 78-83 2001.03

Joint Work, Accepted

This paper proposes Smart Operation of Networked Appliances (SONA) system, a new control system for networked appliances using mobile agents. By adopting mobile agents to the control system, the SONA system can control networked appliances autonomously and asynchronously. This can relieve users from direct and complicated operations of the appliances. In addition, the SONA system facilitates the control of networked appliances with limited system resources. In this paper, we present the design and implementation of SONA system.

An Application Framework for Wearable Network Computing

T.Iwamoto, N.Nishio, H. Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 2000.12

Joint Work, Accepted

Dragon: Soft Real-Time Event Delivering Architecture for Networked Sensors and Appliances

Masayuki Iwai,Jin Nakazawa, Tokuda H

Proceedings IEEE The 7th International Conference on Real-Time Computing System and Applications 425-432 2000.12

Joint Work, Accepted

This paper presents a new framework for constructing flexible event-driven systems for distributed networked devices and appliances, referred to as Dragon. Dragon enables constructing and modifying an event-driven system easily by visualizing distributed services which are handled in an integrated manner. The update of the system is conducted immediately following a modification by Dragon. Dragon is built on to of Jini/Java and can be executed on any Jini/Java-compliant machines. In addition, Dragon incorporates soft real-time event delivery to enhance the predictability of behavior of the constructed system. In this paper, we describe in detail of design and implementation of Dragon.

Wearable Network: Architecture and Implementation

N.Nishio,T.Iwamoto, T.Nagata, H.Tokuda

IEEE International Workshop on Networked Appliances(IWNA) 2000.12

Joint Work, Accepted

Today, Wearable Computers are popular in research, however, they are dedicated almost for methods of human interface design. We do not expect WC's as a merely super-compact notebook computer or its extension, which includes everything and runs the same OS as desktop PC's do. Meanwhile, short-range radio-networking technology as Bluetooth, is emerging. We envision that a WC plays a role as a control center which conducts and collaborates with the devices or gadgets also worn by a person in response to the environmental changes. All these appliances should be networked in any way, and a person does not wear appliances but rather the network itself. We named it as wearable network, and are constructing the software architecture for this. This article describes the wearable network architecture, from the device layer, which captures and collects raw data of evironmental information around the owner, a database module which consists of the knowledge on the real-world and the owner's intention, to the application layer, which enables the adaptable coordination among the services timely available. We also explain a current state-of-the-art wearable network implementation.

Achieving Moderate Fairness for UDP Flows by Path-Status Classification

Yoshito Tobe,Yosuke Tamura, Anastasio Molano, Sourav Ghosh, Hideyuki Tokuda

Proceedings 25th Annual IEEEConference on Local Computer Network. (LCN2000) 252-261 2000.11

Joint Work, Accepted

Wireless Packet Scheduling with Signal-to-Noise Ratio Monitoring

H. Aida,Y. Tamura, Y. Tobe, H. Tokuda

Proceedings 25th Annual IEEEConference on Local Computer Network. (LCN2000) 32-41 2000.11

Joint Work, Accepted

A key challenge in packet scheduling over a wireless channel is to achieve effective throughput against bursty errors. Although there have been several proposals on packet scheduling for a wireless channel, they are only based on bi-modal channel states: good or bad. In this paper we propose a new packet scheduling scheme for wireless links based on the receiver's signal to noise ratio (SNR). The scheme is referred to as SNR-based packet scheduling (SPS). In SPS, outgoing packet flows are scheduled such that the flows with higher SNR values have larger weights in scheduling. SPS can achieve effectiveness by adopting a flexible mapping between weight and SNR. We present measured results of the relationship between throughput and SNR as well as the design and implementation of SPS. In our experiments, SPS has shown its effectiveness in enhancing total throughput for hosts with good and bad wireless connectivity over a wireless LAN.

ポゼッションウェア：「間に合わせ」手法によるアプリケーション構成ツールキット

望月祐洋，徳田英幸

日本ソフトウェア科学会論文誌コンピュータソフトウェア 17 ( 6 ) 521-533 2000.06

Joint Work, Accepted

本論文では，「間に合わせ」手法に基づいてアプリケーションの動的構成を支援するためのツールキットであるポゼッションウェアの設計・実装について述べる．ポゼッションウェアは，遍在するデバイスやソフトウェア部品を抽象化したBodyコンポーネントと，それらを統合してアプリケーションを構成する実体であるSoulコンポーネント，および基盤システムから成る．Soulコンポーネントが，基盤システムを通じてディレクトリサービスやコンポーネントレポジトリと通信することで，ユーザの近隣に遍在する部品を探索・選択し，アプリケーションを動的に構成する．本論文では，ポゼッションウェアにおけるアプリケーション構成の基本となる「間に合わせ」手法について述べ，本手法に基づくアプリケーション構成例のいくつかを応用事例として示す．

VNA: An Object Model for Virtual Network Appliances

Jin Nakazawa,Tadashi Okoshi, Masahiro Mochizuki, Yoshito Tobe, Hideyuki Tokuda

2000 Digest of Technical Papers. IEEE International Conference on Consumer Electronics (ICCE2000) 2000.06

Joint Work, Accepted

SF-FC: A Neighbor-State Based Flow Control with Soft Fairness

Y.Tamura,Y.Tobe

The 10th International Workshop on Network and Operating System Support for Digital Audio and Video(NOSSDAV) 2000.06

Joint Work, Accepted

Many audio and video stream applications in the Internet require good network performance but not perfect reliability. Such applications should employ congestion control and should not shut down the TCP flows by restricting buffering too much. However, the Internet is not a small local community, and it is impossible to rely on all developers to incorporate end-to-end congestion control in their Internet applications. The network should take part in controlling its own resource utilization. Most research for fair queuing tend to focus on reducing processing overhead and achieving exact fairness for each flow. In this paper we claim that perfect fair queuing is not effective for end users in the current complicated network environment. We propose Soft Fair Flow Control(SF-FC) which is a light weight router mechanism that employs simple FIFO queuing, and shows high performance than other fair queuing. SF-FC provides fair network resource allocation to non-adaptive and adaptive flows. Each SF-FC router informs the upstream SF-FC router of its link state. Based on the received state, SF-FC dynamically sets the packet discard rate of the non-adaptive flows. '

Load-Sensitive Handover Scheme over Wireless Local Area Networks

Daichi Furusaka,Takeshi Iwamoto, Tomohiro Nagata, Hideyuki Tokuda

IEEE ICDCS Workshop on Wireless Networks and Mobile Computing (IWWNMC '00) D12-19 2000.04

Joint Work, Accepted

This paper proposes a new load-sensitive handover scheme called LSH to manage wireless LANs. Future wireless LANs will is difficult to guarantee the network quality in current wireless LANs because of poor network resources including narrow bandwidth, high latency and high error rate. Under these conditions, mobile station should share resources efficiently. LSH utilizes information about the network load. By quantitative measurement and update messages, each base station maintains the cell information including a number of mobile stations, transmit/receive throughput and loss rate. Mobile stations in the cell overlapped area can select the most suitable cell by using cell information. It works to balance the network load of each cell.

Detection of Change in One-Way Delay for Analyzing the Path Status

Yoshito Tobe,Hiroto Aida, Yosuke Tamura, Hideyuki Tokuda

Passive and Active Measurement Workshop 2000.04

Joint Work

The objective of detecting the change in one-way delay is to capture a congestion signal that should be reflected to a rate control of an RTP/RTCP-type unicast stream communication. Although a packet of the RTP flow may not be lost, the delay of the flow will increase due to an increase in queuing delay at the link. Therefore, only a change in delay instead of the absolute value of delay should be obtained for the rate control. Measuring the change in delay is also significant for a path that includes an error-prone wireless link. In such a wireless link,some packet losses may be irrelevant to congestion. Therefore, congestion control depending on packet loss ratio alone results in an erroneously low rate. In this paper, we describe the design and the implementation of Estimation of Skew with Reduced Samples (ESRS). We have measured changes in delay using the scheme over a path between Keio University (Japan) and Carnegie Mellon University (U.S.), and a path between Keio University and CESAT (Spain). The variation in one-way delay obtained with ESRS is shown to include the path status of the flow.

MobileSocket: Session Layer Continuous Operation Support for Java Applications

T.Okoshi,M.Mochizuki, Y.Tobe, H. Tokuda

Proceedings Eight International Conference on Computer Communications and Networks(Cat. No.99EX370) 41 ( 2 ) 50-57 2000.02

Joint Work, Accepted

This paper proposes the session layer communication continuity support for Java applications toward a continuous operation for the users. In a mobile computing environment, mobile hosts move around thedifferent network segments even during applications communicate with the remote endpoint.In such a situation, maintenance of thecommunication continuity between the applications is significant.In order to retain the communication continuity, not only the mobilitysupport but the virtual circuit continuity support is required forapplications.Existing approaches on the network, the transport and the sessionlayers do not provide the complete mobility and virtual circuitcontinuity for applications, although they require the complicatedimplementation.``MobileSocket'' is a user-level enhanced socket library written inJava, and provides the library-based session layer mobility andvirtual circuit continuity support for applications. Two mechanisms, Dynamic Socket Switching (DSS) and Application LayerWindow (ALW) enforce MobileSocket and enable the implementationsimplicity.MobileSocket applications can be used in the Java mobile applications and the agents, as well as in ordinary network applications.In this paper, after we clarify the communication continuity andexisting approaches, we present the MobileSocket design, mechanism, and evaluation results.

TCP-Rate-Probing-Based Adaptation for Continuous Media Communications

Y.Tobe,Y.Tamura, H.Tokuda

情報処理学会論文誌 41 ( 2 ) 297-311 2000.02

Joint Work, Accepted

Rate control of continuous media (CM) UDP flows over the Internet should retain TCP-friendliness.Despite many efforts to create TCP-friendly algorithms,it is often difficult to adjust parameters pertaining to the algorithmsin order to achieve exact fairness with TCP flows.In this paper, we propose a scheme called TCP-Rate-Probing-Based Adaptation (TPBA).In TPBA, a CM flow intermittently changes its transport protocol to TCP to measurea TCP-exact rate, and uses the rate with UDP.We have built an experimental system with FreeBSD PCs andshown that TCP-friendly rate control can easily be achievedfor both a shorter and a longer round-trip-time connections.

A Neighbor-state Based Congestion Control Schemefor Adaptive Bandwidth Sharing

Y.Tamura,Y.Tobe, H. Tokuda

情報処理学会論文誌 41 ( 2 ) 210-221 2000.02

Joint Work, Accepted

In this paper, we propose the Neighbor-state Based Queuing（NBQ）for improving the performance of flows sharing link bandwidth under various transfer protocols. Each router with NBQ　informs the next upstream router of its link status. According to the received status, NBQ dynamically sets the packet discard ratio of the non-adaptive flows. NBQ　reduces the wasted non-adaptive flows and provides available bandwidth for the adaptive flows. We have demonstrated dramatic improvements of adaptive flow's throughputusing our scheme through simulations.

Software Traffic Management Architecture for Multimedia Flows over a Real-Time Microkernel

Y.Tobe,Y.Tamura, H.Tokuda

((IEICE Transactions on Communications)) E82B ( 12 ) 2116-2125 1999.12

Joint Work, Accepted

Traffic management schemes such as Connection Admission Control (CAC), policing, and traffic shaping are important to provide multimedia communications with better Quality of Service (QoS). In the conventional model, admission control and policing are done at intermediate nodes, and traffic shaping is done at the edge of a network. However, QoS of communications should be defined between tasks or threads rather than between hosts. Therefore traffic management inside a host is as important as that in networks. We propose software-based traffic management architecture over a real-time microkernel. The architecture focuses on the interface between a network driver and user threads calling the driver. We categorized services of communication threads into three classes: Real-Time at Guaranteed Rate (RT-GR), Real-Time at Available Rate (RT-AR), and Best-Effort (BE). Our architecture is designed for an environment containing a mixture of these services. In the architecture, a sender periodic thread of RT-GR or RT-AR is executed such that the sending rate matches a user-specified rate. The network driver monitors the per-flow rate of injected data and discards the data if the injected rate exceeds the user-specified rate. To avoid the continuous discarding of data, the sending thread can adjust its sending rate by periodically looking at logged data concerning the rate. RT-AR service can achieve more than the specified rate when bandwidth is available. The scheme of software traffic management is effective in attaining higher throughput not only for full-duplex Ethernet but also for ATM because the difference of rate between hardware and software is reduced. In this paper, we describe the design and implementation of the software-based traffic management architecture on Real-Time Mach. The results of performance evaluations demonstrate that our traffic management scheme performs well for full-duplex Ethernet.

NBQ: Neighbor-state Based Queuing for Adaptive Bandwidth Sharing

Yosuke Tamura,Yoshito Tobe, Hideyuki Tokuda

Proceedings Seventh International Conference on Network Protocol(ICNP'99) 135-144 1999.11

Joint Work, Accepted

In this paper, we propose the Neighbor-state Based Queuing (NBQ) for improving the performance of flows sharing link bandwidth under various transfer protocols. Each router with NBQ informs the next upstream router of its link status. According to the received status, NBQ dynamically sets the packet discard ratio of the non-adaptive flows. NBQ reduces the wasted nonadaptive flows and provides available bandwidth for the adaptive flows. We have demonstrated dramatic improvements of adaptive flow's throughput using our scheme through simulations.

MobileSocket: Toward Continuous Operation for Java Applications

Tadashi Okoshi,Masahiro Mochizuki, Yoshito Tobe, Hideyuki Tokuda

Proceedings IEEE 8th International Conference on Computer Communications and Networks 50-57 1999.10

Joint Work, Accepted

This paper proposes'MobileSocket'which realizes session layer communication continuitysupport for Java Applications towards the continuousoperations for mobile applications. In the mobile com-putting environment where mobile hosts moves aroundthe network even during applications are communi-cating with the remote, maintenance of the commu-nication continuity between the applications is signif-icant. Not only the mobility support but the virtualcircuit continuity support is required for communi-cation continuity. Existing approaches have not pro-vided the complete communication continuity for ap-plications. 'MobileSocket'is a user-level enhancedsocket library written in Java, and provides library-based session layer mobility and virtual circuit conti-nuity support for applications. Two mechanisms, Dy-namic Socket Switching (DSS) and Application LayerWindow (ALW) were developed for MobileSocket andenable a simple implementation. MobileSocket appli-cations can be used in Java mobile applications and the agents, as well as for ordinary network applica-tions. In this paper, after we clarify the communi-cation continuity and existing approaches, we presentthe MobileSocket design, mechanism, and results ofevaluation.

ホスト透過型オブジェクト移送システムMogulの実現

中澤仁,望月祐洋，徳田英幸

情報処理学会論文誌 40 ( 6 ) 2573-2584 1999.06

Joint Work, Accepted

既存アプリケーションのホスト透過的な移送を実現する, ホスト透過型オブジェクト移送モデルを提案する. 本モデルは, プロセス移送や分散ウィンドウシステムにはないプラットホーム独立性を提供し, さらにオブジェクトを単位として移送の粒度を柔軟に制御できるのが特徴である. 本研究で Java 言語によって実現したホスト透過型オブジェクト移送システム Mogul は, 既存アプリケーションコードに対する変更をともなわずに, ホスト透過的なアプリケーション移送を実現する. Mogul では, アプリケーションを移送可能オブジェクトとホスト依存オブジェクトとに動的に分離し, それらの間のメソッド呼び出しをリダイレクトする, 動的メソッドリダイレクションによって透過性を確保している. 本論文では, アプリケーション移送の実現手法を比較検討したうえで, Mogul の機能および特徴を示し, 実装と評価について報告する.

Possession System: Adaptation Support Middleware for Collaborative Multimedia Applications in Java

M.Mochizuki, H. Tokuda

Proceedings IEEE 19th International Conference on Multimedia Computing and Systems ( - ) 339-344 1999.06

Research paper (scientific journal), Joint Work, Accepted

Possession System is middleware which realizes a simple framework to deal with the adaptation of collaborative multimedia application. The system is based on Possession Model which provides users with a consistent view of application components, networked sensors, and distributed devices by introducing two separated abstractions: Body and Soul. The adaptation is achieved through the changes of relationships among Bodies and Souls with a simple operation named possession. The adaptation actions can be invoked both manually and automatically by monitoring the changes of the environment underlying beneath the applications. The middleware is applicable to adaptive systems in mobile and ubiquitous computing environment where unpredictable changes in available computing resources, device configuration, and geographics location frequently occure. We describe how collaborative multimedia applications using our middleware adaptively behave.

Rate Probing Based Adaptation at End Hosts

Y.Tobe,Y.Tamura, H.Nishino, H. Tokuda

IEEE Workshop on QoS Support for Real-Time Internet Applications 1999.06

Joint Work, Accepted

Rate control of continuous media UDP flows over the Internet should retain TCP-friendliness.Despite many efforts to create TCP-friendly algorithms, it is often difficult to adjust parameters pertaining to the algorithms in order to achieve exact fairnesswith TCP flows. In this paper, we propose a novel scheme, Rate Probing Based Adaptation (RPBA). In RPBA, a continuous media flow intermittently changes its transport protocol to TCP to measure its available rate and uses the rate with UDP. We have built an experimental system with FreeBSD PCs and shown that TCP-friendly rate control can easily be achieved both for a shorter and a longer round-trip time connections.

通信環境に適応する動的プロトコルスタック構成モデル

戸辺義人,田村陽介，徳田英幸

電子情報通信学会論文誌 J82B ( 5 ) 783-798 1999.05

Joint Work, Accepted

ネットワーク上で連続メディアの配送を行うサーバとの間で通信を行うクライアントにおいて，クライアントが接続される位置に依存して，経由するネットワークの状況に応じて通信品質に差が生じる．本論文では，ネットワークに接続されたクライアントが，サーバとの通信時のデータ配送の信頼性，スループットに応じて，通信開始時及び通信持続中の両方の場合に，フローごとにプロトコルスタックを動的に変更するDPC（Dynamic Protocol stack Configuration）モデルを提案する．更に，サーバ，クライアント間で協調してプロトコルスタックを変更するためのプロトコルとして，DPCP（Dynamic Protocol stack Configuration Protocol），及びDPCモデルに対応してsocketを拡張したdsocketを定義する．本モデルをFreeBSDに実装した計算機間を無線LAN及びインターネットで接続したシステムにおいて，ネットワークの負荷の変化に対してTCPとUDPとの間の動的変更を適用し，DPCモデル適用の有効性が示された．

EFR: Efficient Fast Retransmit Scheme for TCP in a Wireless Multiple Access

Yosuke Tamura,Yoshito Tobe, Hideyuki Tokuda

((Transactions of Media & Governance)) 40 ( 1 ) 46-56 1999.01

Joint Work, Accepted

In this paper, we propose a new and efficient fast retransmit scheme for wireless LANs. Wireless LANs are becoming popular, and providing and efficient protocol over a wireless link is important. In our experiments with 2.4 GHz WaveLAN, the poor TCP performance observed was attributed to frequent expiration of the retransmission timer. To avoid unnecessary expiration of the retransmission timer, we propose a scheme in which fast retransmission is performed efficiently. The proposed modification only affects a TCP sender, and our version of TCP with the change is interoperable with existing TCP implementations. The change is especially effective in wireless LAN environments, where we have demonstrated dramatic improvements in throughput, 10-15%, via experiments with 2.4 GHz WaveLAN.

Reliable, Real-Time and Reconfigurable System (R3-System)

H.Tokuda,T.Hagino, N.Nishio, Y.Tobe, S.Moriai, S.Kihara, Y.Matsui, T.Okamoto, M.Mochizuki, Y.Tamura, T.Nagata, T.Iwamoto

IEEE International Workshop on Networked Appliances(IWNA) 1998.11

Joint Work, Accepted

SMAF:A Framework for Future Embedded Systems

T.Kitayama,T.Nakajima, T.Watanabe, K.Gondow, I.Satoh, H. Tokuda

IEEE International Workshop on Networked Appliances(IWNA) s2-1 1998.11

Joint Work, Accepted

In this paper, we describe the research topics and the goals of the Seamless Migratory Application Framework (SMAF) project. The project aims to provide the common framework for building future distributed embedded applications. In the future computing environment, various types of computers will be embedded in home and office appliances, which are connected through networks. Many kinds of application may run in variety of environment, and they need to aware and adapt to the computing environment and user preferences. The SMAF project focuses on how the applications need to execute efficiently in these environments, and we are building the SMAF system framework.

EFR: A Retransmit Scheme for TCP in Wireless LANs

Y.Tamura,Y.Tobe, H. Tokuda

Proceedomgs 23rd IEEE Annual Conference on Local Computer Network (LCN'98) 2-11 1998.10

Research paper (scientific journal), Joint Work, Accepted

Rate-Based QoS Control of Multiple Flows over a Real-Time OS

Y.Tobe,Y.Tamura, H. Tokuda

Proceedings IEEE Fifth International Conference on Real-Time Computing Systems and Applications (RTCSA'98), 83-90 1998.10

Joint Work, Accepted

We propose a framework of Quality of Service (QoS) management inside a sending host that controls execution of sending threads in consideration of utilization of processor capacity and network bandwidth. To distinguish from flows which require only best-effort service, we call a flow which requires a specific rate of service ``reserved flow.'' To guarantee QoS of such reserved flow both in processor- and network-intensive cases in a sending host, processor capacity reserve is allocated such that the rate of each reserved flow is attained and non-conforming data are policed before they are transmitted. Processor Capacity Manager and the network device driver exchange information in a cooperative manner to support the rate adaptive allocation of processor capacity reserve.

家庭内ネットワークにおける機器制御方式

橋本幹生,寺本圭一, 斉藤健, 岡本利夫，徳田英幸

電子情報通信学会講演論文集 1998 B2-267 1998.09

Joint Work

TMR: Traffic Management of Segregated Flows into an Egress Link over a Real-Time Operating System

Y.Tobe,Y.Tamura, H.Tokuda

System for Programming and Applications(SPA'98) (電子情報通信学会) 1998.03

Joint Work

QOSの3階層指定とその翻訳を用いたセッションの単純化調停方式

西尾　信彦,徳田　英幸

情報処理学会論文誌 39 ( 2 ) 328-336 1998.02

Joint Work, Accepted

マルチメディアシステムでは，新しいセッションを生成したり，連続メディアセッションが終了するときに返還される資源の再分配にセッション間の調停方式が重要である．エンドユーザはセッションのサービスの質（Quality of Service; QOS）を何KBといった厳密なメモリサイズやネットワークバンド幅を指定したくはないが，このような定量値はアドミッション制御には欠かせない．そこで，我々は3-階層化したQOS指定と層間のQOSの翻訳機構を導入してシステムが定量値を扱えるようにした．それでも，セッション間の調停には複雑で時にはNP-完全問題に相当する計算量が必要となる．そこで，QOS指定に単調性の制約をつけることによって，セッション間調停を単純化し実装運用が可能になった．本論文では，Real-Time Mach 3.0上の Conductor/Performerシステムを用いて，QOSの翻訳と複数セッション間調停の実装を報告する．

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.

Comprehensive operating system for highly parallel machine

Saito-N; Hagino-T; Oikawa-S; Yonezawa-A; Matsuoka-S; Inohara-S; Tada-Y; Sunahara-H; Ishii-S; Shibayama-E; Shinoda-Y; Tokuda-H

In Proceedings of the 1994 International Symposium on Parallel Architectures, Algorithms and Networks (ISPAN) 435-442 1994

Joint Work, Accepted

This paper describes the design and implementation of a comprehensive operating system (COS) for highly parallel machine. This is one of the research themes in the Japanese University Highly Parallel Research Project supported by the Special Grant of the Research Funds of Ministry of Education. The target machine is called JUMP-1 originally developed in this project. Several design policies are discussed, and the user service classes are defined. COS architecture is based on the micro kernel, and it includes both Partition OS and Service OS. The development environment is also discussed briefly

Integrated Management of Priority Inversion in Real-Time Mach

T. Nakajima, T.Kitayama, H. Arakawa, H. Tokuda

In Proceedings of 14th IEEE Real-Time Systems Symposium 120-130 1993.12

Joint Work, Accepted

Synchronization and communication are two common sources of priority inversion which may make the behavior of systems unpredictable and unanalyzable. In microkernel-based systems, they are heavily used for building operating system servers and decomposing applications into several tasks. The management of priorities in IPC and synchronization should be integrated using a uniform mechanism since priority inversion occurs if such integration is not supported. Also, a highly preemptable server structure should be provided because the execution in a server may take up too much time. In this paper, we propose an integrated real-time resource management model, and a real-time server model which solve the above problems. We implemented and evaluated the models in Real-Time Mach using a uniform mechanism. Our approach enables us to build operating system servers and to decompose applications into several tasks without incurring priority inversion.

Dynamic QOS Control based on RealTime Threads

Kitayama, T, Tokuda, H

Proc. Fourth International Workshop on Network and Operating System Support for Digital Audio and Video 114-123 1993.10

Joint Work, Accepted

Processor capacity reserves: An abstraction for managing processor usage

C. W. Mercer, S. Savage, H. Tokuda

In Proc. Of the 4th Workshopon Workstation Operating Systems (WWOS-IV) 129-134 1993.10

Joint Work, Accepted

This paper briefly motivates and describes processor capacity reserves and a prototype implementation of reserves in Real Time Mach. The reservation mechanism provides a way for application programs to specify their reservation requests and incorporates a scheduling framework which supports an admission control policy. The reservation system accurately measures processor usage of individual threads, even when these threads invoke user-level servers to do work on their behalf, and the scheduler enforces reservations by relegating reserves to a time-sharing pool after their reservations have been consumed.

RT-IPC: An IPC Extension for Real-Time Mach

Takuro Kitayama, T.Nakajima, H. Tokuda

In Proceedings of the 2nd Microkernel and Other Kernel Architectures 91-104 1993.09

Joint Work, Accepted

Interprocess communication (IPC) provides the fundamental mechanism for the Mach microkernel to be extensible and flexible. Mach IPC provides efficient communication mechanisms for many applications. However, it does not provide sufficient functionality for real-time applications which have rigid timing constraints among threads. In Real-Time Mach (RT-Mach), we have extended Mach IPC to be priority inversion free for real-time applications. This paper describes the Real-Time IPC (RT-IPC) facilities, its implementation, and the evaluation results. We used the Distributed Hartstone (DHS) real-time benchmark for the evaluation and the results show that RT-IPC can reduce priority inversion and improve CPU utilization for real-time applications.

Continuous Media Communication with Dynamic QOS Control Using ARTS with an FDDI Network

Y. Tobe, S. T. C. Chou, and J. M. F. Moura, H. Tokuda

Proceedings of the ACM SIGCOMM'92 Symposium on Communications Architectures and Protocols 88-98 1992.10

Joint Work, Accepted

Continuous media communication requires timely delivery of data such as digital video and audio packets. Quality of Service (QOS) parameters specify the temporal and spatial characteristic of such continuous media data. To insure timely delivery of continuous media data, the system needs to minimize the communication delay by securing required processor and network resources. We have extended the Capacity-Based Session Reservation Protocol(CBSRP), which was proposed to realizing predictable real-time communications, to support dynamic control of QOS. We have implemented a QOS control scheme by which the network dynamically adjusts the allocations of network bandwidth on a Fiber Distributed Data Interface(FDDI) network. In this paper, we describe the definition of our QOS model, the extension of CBSRP to support dynamic control of QOS, and the implementation and evaluation of extended CBSRP in our distributed systems testbed, Advanced Real-Time System(ARTS).

An object-oriented real-time programming language

Y. Ishikawa, C. W. Mercer, H.Tokuda

IEEE Computer 25 ( 10 ) 66-73 1992.10

Joint Work, Accepted

Microkernel operating system architecture and Mach

D.L. Black, D. B. Golub, D.P. Julin, R.F. Rashid, R. P. Draves, R. W. Dean, A. Florin, J. Barrera, G. Malan, and D. Bohman, H. Tokuda

In Proceedings of theUsenix Workshop on Microkernels and Other Kernel Architectures 11-31 1992.10

Joint Work, Accepted

Modular architectures based on a microkernel are suitable bases for the design and implementation of operating systems. Prototype systems employing microkernel architectures are achieving the levels of functionality and performance expected and required of commercial products. Researchers at Carnegie Mellon University, the Open Software Foundation, and other sites are investigating implementations of a number of operating systems that use the Mach microkernel. The paper describes the Mach microkernel, its use to support implementations of other operating systems, and the status of these efforts.

Evaluation of realtime synchronization in Real-Time Mach

H. Tokuda, T. Nakajima

In Proc. Of the Second Mach Symposium 213-221 1991.10

Joint Work, Accepted

Real-Time Mach provides real-time thread and real-time synchronization facilities. A real-time thread can be created for a periodic or aperiodic activity with a timing constraint. Threads can be synchronized among them using a real-time version of the monitor-based synchronization mechanism with a suitable locking protocol. Real-time Mach has several locking policies, such as kernelized monitor, basic priority priority inheritance protocol, priority ceiling protocol, and restartable critical section, for real-time applications. It can also avoid an unbounded priority inversion problem. The authors describe the real-time synchronization facilities in Real-Time Mach and its implementation and performance evaluation. The evaluation results demonstrated that a proper choice of locking policy can avoid unbounded priority inversions and improve the processor schedulability for real-time applications.

Microkernel operating system architecture and Mach

Black-DL; Golub-DB; Julin-DP; Rashid-RF; Draves-RP; Dean-RW; Forin-A; Barrera-J; Malan-G-R; Bohman-D, Tokuda-H

Journal-of-Information-Processing 14,4 442-453 1991

Joint Work, Accepted

Modular architectures based on a microkernel are suitable bases for the design and implementation of operating systems. Prototype systems employing microkernel architectures are achieving the levels of functionality and performance expected and required of commercial products. Researchers at Carnegie Mellon University, the Open Software Foundation, and other sites are investigating implementations of a number of operating systems (e.g., Unix, MS-DOS) than use the Mach microkernel. The paper describes the Mach microkernel, its use to support implementations of other operating systems, and the status of these efforts.

Fixed Priority Scheduling Theory for Hard Real-Time Systems,

J. P. Lehoczky, L. Sha, J. K. Strosnider, H. Tokuda

in Foundations of Real-Time Computing, Scheduling and Resource Management (A. M. Tilborg and G. M. Koob, eds.), ch. 1 chap 1 1-30 1991

Joint Work

An Evaluation of Priority Consistency in ProtocolArchitectures

Clifford W. Mercer, Hideyuki Tokuda

In Proceedings of the IEEE 16th Conference on Local Computer Networks 386-396 1991

Joint Work, Accepted

Workstations for digital audio and video applications must support predictable processing, presentation, and transmission of continuous media data while making efficient use of limited hardware resources. The authors present techniques for managing network resources and processing messages in a predictable fashion. Their solutions use a novel structure for the protocol processing software, and they examine several alternatives and discuss the engineering tradeoffs associated with each. Using simulation, they evaluate their protocol processing structures and show that the more sophisticated structures can improve the response time and predictability of time-constrained messages. The ideas presented in this paper can be applied to resource management in the operating system and to the structuring of application-level servers. The designers of gateway machines (for internetwork routing) which handle both time-constrained traffic and non-time-constrained traffic may also benefit from this study.

The ARTS Real-Time Object Model

Clifford W. Mercer, Hideyuki Tokuda

Proceedings of the 11th Real-Time Systems Symposium, 2-10 1990.12

Joint Work, Accepted

In this paper, we present the motivation for using object model for real-time operating systems and we describe the object model used in the ARTS Kernel, a real-time operating system developed in the ART project at Carnegie Mellon University. We discuss our novel object classification and the priority inheritance properties which arise from this taxonomy. We also discuss various methods for implementing critical regions and give some guidelines as to the use of each. 　　　　　　　

Distributed Hartstone: a distributed real-time benchmark suite

Y. Ishikawa,C. W. Mercer, H. Tokuda

Proceedings. The 10th International Conference on Distributed Computing Systems 70-77 1990.10

Joint Work, Accepted

An extension of the uniprocessor Hartstone benchmark for the distributed real-time environment, called the Distributed Hartstone benchmark, is described. The Distributed Hartstone measures system performance in the critical areas of communication latency and bandwidth, protocol preemptability, and priority queueing at the protocol and media access levels. Areas of the system which are particularly important for distributed, real-time computing are described. On the basis of the requirements that specify various areas of the system that a distributed real-time benchmark must stress, a series of task sets in the style of the Hartstone benchmarks are given. The benchmark results from a distributed real-time operating system (ARTS testbed) are given

Object-oriented real-time language design: constructs for timing constraints

Y. Ishikawa,C. W. Mercer, H. Tokuda

In Proc. Of ECOOP/OOPSLA 289-298 1990.10

Joint Work, Accepted

We propose a new object-oriented programming language called RTC++ for programming real-time applications. RTC++ is an extension of C++ and its features are to specify I) a real-time object which is an active entity, ii) timing constraints in an operation as well as in statements, and iii) a periodic task with rigid timing constraints. In this paper, we first discuss real-time programming issues and what language support should be provided for building real-time applications. Then, the key features of RTC++ are described. Some programming examples are shown to demonstrate RTC++'s expressive power. A comparison to other programming languages are also discussed.

Real-Time Mach: Towards a Predictable Real-Time System

H. Tokuda, T. Nakajima, P. Rao

In Proceedings of USENIX Mach Workshop 73-82 1990.10

Joint Work, Accepted

Distributed real-time systems play a very important role in our modern society. They are used in aircraft control, communication systems, military command and control systems, factory automation, and robotics. However, satisfying the rigid timing requirements of various real-time activities in distributed real-time systems often requires ad hoc methods to tune the system's runtime behavior The objective of Real-Time Mach is to develop a realtime version of the Mach kernel which provides users with a predictable and reliable distributed real-time computing environment. In this paper, we describe a real-time thread model, real-time synchronization, and the ITDS scheduler in Real-Time Mach. We also discuss the implementation issues, a real-time toolset, and the current status of the system.

Mach: a system software kernel

Rashid-RF, Tokuda-H

Computing-Systems-in-Engineering 1,2-4 163-169 1990.04

Joint Work, Accepted

Priority inversions in real-time communication

H. Tokuda, C. W. Mercer, Y. Ishikawa, T. E. Marchok

In Proceedings of 10th IEEE Real-Time Systems Symposium 348-359 1989.12

Joint Work, Accepted

ARTS: A distributed real-time kernel

H. Tokuda, C. W. Mercer

ACM Operating Systems Review 23 ( 3 ) 29-53 1989.07

Joint Work, Accepted

ARTS is a distributed real-time operating system designed for a real-time systems testbed being developed at Carnegie Mellon University. The objective of the testbed is to develop and verify advanced real-time computing technologies for a distributed environment. The paper gives an overview of the ARTS kernel and ARTS real-time toolset. In particular, it introduces a real-time object model and the integrated time-driven scheduling model. It then describes the basic primitives and major components of the ARTS kernel and the real-time toolset which consists of the schedulability analyzer, Scheduler 1-2-3, and real-time monitor/debugger, ARM.

A real-time tool set for the ARTS kernel

Tokuda. H, M. Kotera

Proceedings of 9th IEEE Real-Time Systems Symposium 289-299 1988.12

Joint Work, Accepted

An integrated real-time tool set is described that consists of a schedulability analyzer and a real-time monitor/debugger for the ARTS kernel, which is being built for a distributed real-time testbed. The schedulability analyzer, called Scheduler 1-2-3, is an X11 window-based interactive tool and can verify whether the given real-time tasks can meet their deadlines under a specific scheduling policy. An advanced real-time monitor, ARM, also runs on the X11 window and visualizes the target system's runtime behavior in real time. ARM can be used with Scheduler 1-2-3 to analyze simulated runs and its monitorability

Scheduler 1-2-3: an interactive schedulability analyzer for real-time systems

Kotera-M, Tokuda-H

Proceedings COMPSAC 88 211-219 1988.10

Joint Work, Accepted

Scheduler 1-2-3 is an interactive analysis tool that can perform schedulability analysis for the development of real-time computing systems. The schedulability analysis can verify whether all hard real-time tasks in a target system will be completed by their deadlines at the system design phase. Scheduler 1-2-3 is a window-based stand-alone tool that can also be used as a synthetic workload generator in an integrated tool set that consists of a timing tool, a schedulability analyzer, and a real-time monitor/debugger.

A real-time monitor for a distributed real-time operating system

H. Tokuda, M. Kotera, and C. W. Mercer

SINGPLAN-Notice 24 ( 1 ) 68-77 1988.05

Joint Work, Accepted

Implementation of a time-driven scheduler for real-time operating systems

Hideyuki Tokuda., J.W. Wendorf, and H.Y. Wang

Proceedings of 8th IEEE Real-Time Systems Symposium 271-280 1987.12

Joint Work, Accepted

In the time-driven scheduling (TDS) model, both the importance value and timing criticality of each task are given together as a function of time. The TDS scheduler attempts to maximize the total value of completed tasks. A practical TDS model that has been implemented in the Mach operating system kernel is described. Some of the important design considerations for a flexible TDS scheduler are discussed, with emphasis on policy/mechanism separation as a system structuring principle. The structure of a TDS scheduler that was actually implemented is explained. The practicality of the TDS scheduler is demonstrated by performance results.

Distributed Computing in a Network of 529 Type Workstation

In Proceedings of IEEE Workshop on Large Grain Parallelism, Providenc ?? 1986.10

Single Work, Accepted

A time driven scheduling model for real-time operating system

E.D. Jensen, C.D. Locke, Hideyuki Tokuda

Proceedings IEEE Real-Time Sytems Symposium 112-122 1985.12

Joint Work, Accepted

Process scheduling in real-time systems has almost invariably used one or more of three algorithms, namely, fixed priority, FIFO or round robin. The reasons for these choices are simplicity and speed in the operating system, but the cost to the system in terms of reliability and maintainability have not generally been assessed. The notion that the primary distinguishing characteristic of a real-time system is the concept that completion of a process or a set of processes has a value to the system which can be expressed as a function of time is discussed. This notion is described in terms of a time-driven scheduling model for real-time operating systems and provides a tool for measuring the effectiveness of most of the currently used process schedulers in real-time systems. Applying this model, a multiprocessor real-time system simulator was constructed with which a numberf well-known scheduling algorithms such as shortest process time, deadline, shortest slack time, FIFO and a fixed priority scheduler are measured with respect to the resulting total system values. This approach to measuring the process scheduling effectiveness is a first step in the longer term effort to produce a scheduler which will explicitly schedule real-time processes in such a way that their execution times maximize their collective value to the system, either in a shared-memory multiprocessing environment or in multiple nodes of a distributed processing environment.

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