Faculty Profiles - TSUKADA Koji

Published Papers - TSUKADA Koji

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3次元仮想空間内でのインフォーマルコミュニケーション支援システムInComの実装と評価

中野雄介, 塚田晃司, 高木佐恵子, 岩崎慶, 吉本富士市

情報処理学会グループウェアとネットワークサービスワークショップ2004論文集 27 - 32 2004.11

中メールシステムの信頼性に関する一考察

中筋香里, 泉裕, 齋藤彰一, 塚田晃司, 上原哲太郎, 國枝義敏

情報処理学会研究報告 2004-DSM-34 13 - 7 2004.07

負荷分散を考慮した不正コンテンツフィルタの提案

月城史行, 泉裕, 齋藤彰一, 塚田晃司, 上原哲太郎, 國枝義敏

情報処理学会研究報告 2004-DSM-34 1 - 6 2004.07

アドホックネットワークプロトコルの評価

長船辰昭, Peng Zhao, 塚田晃司, 松井進

電子情報通信学会アクティブネットワークと応用技術時限研究会 2002.10

A Proposal of An Architecture for Peer -to- Peer Service Systems Suitable for Cellular Phone Networks And Its Implementation

TSUKADA KOJI, HIGASHI KIYOSHI, TOUMURA KUNIHIKO, MATSUI SUSUMU

IPSJ SIG Notes ( Information Processing Society of Japan (IPSJ) ) 2002-GN-44 ( 47 ) 51 - 56 2002.05

携帯電話向けP2Pサービス提供方式の検討とプロトタイプシステムの開発

塚田晃司, 東潔司, 東村邦彦, 松井進

情報処理学会情報家電コンピューティング研究グループ研究報告 2002-IAC-2 33 - 35 2002.03

Voice over IP Enabling Telephony and IP Network Convergence

Hoshi, T, Tsukada, K, Yumoto, K, Tanigawa, K, Nakayama, Y

IEICE Trans. Inf. & Syst. ( IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG ) E84-D ( 5 ) 548 - 559 2001.05 [Refereed]

Voice over IP (VoIP) is a generic name for services, systems and technology for telephony over an IP network. It is also referred to as Internet telephony and IP (Internet Protocol) telephony. Internet telephone client software attracted attention when it first appeared in 1995. Since that, VoIP has rapidly matured into a practical technology, propelled by the popularization and rapid development of the Internet. IP network traffic already exceeds telephone network traffic and is expected to further increase several-fold in the next few years. In future, the telephone network will be integrated into the IP network and telephony will become entirely VoIP. There are three expectations for VoIP. The first is inexpensive telephone service. The second expectation is for integrated telephony and IP network services such as a CTI (Computer Telephony Integration) system in which there is interworking with various Internet applications, such as e-mail and Web call-back for communication services of greater convenience rather than simple replacement of the telephone. The third expectation is for a platform fur providing high-quality voice communication; multicast communication, and other such enhanced voice services that have a high degree of freedom. However, many problems remain to be overcome before the VoIP System is realized. The main problems are real-time transmission of voice that allows a smooth conversation, session control for providing a variety of services, and the proposal of new services. In this paper, we give an overview of VoIP and the problems that must be solved in order to realize it and propose some solutions regarding stream control and applications. We also describe session control and other topics that are being discussed in standardization forums.

Voice Stream Multiplexing between IP Telephony Gateways

Hoshi, T, Tanigawa, K, Tsukada, K

IEICE Trans. Inf. & Syst. ( IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG ) E82-D ( 4 ) 838 - 845 1999.04 [Refereed]

IP telephony systems are expected to be deployed worldwide in the near future because of their potential for integrating the multimedia communication infrastructure over IP networks. Phone-to-phone connection over an IP network via IP telephony gateways (IP-GWs) is a key feature of the system. In ari IP telephony system, a low-bit-rate voice codec is used to improve bandwidth efficiency. However, due to the packet transfer method over the IP network, it is necessary to add packet headers, including IP, UDP, and RTP headers, which increases the header overhead and thus decreases transfer efficiency. Moreover, because there will be large numbers of short voice packets flowing into the IP network, the load on the Internet will increase. We propose voice stream multiplexing between IP-GWs to solve these problems. In this scheme, multiple voice streams are connected between a pair of IP-GWs, enabling multiplexed voice stream transfer. The voice stream multiplexing mechanism can reduce the header overhead as well as decrease the number of voice packets. The voice stream multiplexing we propose is to concatenate RTP packets destined for the same IP-GW at a multiplexing interval period into a single UDP packet. The advantage of this method is that no new additional header is required and the current well-defined H.323 and RTP standards can be applied with minimum changes. We implemented and tested the system. The results show that the proposed method is effective at reducing both the header overhead and the number of packets. In a typical case, the bandwidth is cut by 40% for eight G.723.1-encoded voice streams through header overhead reduction and the number of voice packets is also decreased to 1/8. Furthermore, this method can easily be enhanced to a general RTP packet multiplexing method that is applicable not only to an IP-GW but also to other KTP multiplexing and de-multiplexing applications.

実オフィスワーク環境に基づいたマルチプロジェクト環境支援システムに関する研究

塚田晃司

慶應義塾大学 1999.02 [Refereed]

IPテレフォニ技術の動向

星徹, 谷川桂子, 塚田晃司

電子情報通信学会研究報告 IN98-110 53 - 60 1998.10

情報へのアクセスの形態に着目した情報共有モデルの一提案

塚田晃司, 岡田謙一, 松下温

情報処理学会論文誌 39 ( 10 ) 2802 - 2810 1998.10 [Refereed]

IPテレフォニシステムにおけるゲートウェイ間高効率通信方式の提案

星徹, 谷川桂子, 塚田晃司, 小山俊明, 石川亨, 高橋亨

情報処理学会マルチメディア，分散処理，協調とモーバイルシンポジウム 496 - 475 1998.07

Design and experiment of a global management model for Internet telephone

新美誠, 直江宏一, 渡辺晴美, 塚田晃司

報処理学会分散システム運用技術シンポジウム98 1998 5 - 10 1998.02

現在、インターネット電話サービスが商業サービスとして多数立ち上がっている。しかし、現状では、いくつかの問題点があり、不必要な「電話とインターネットのゲートウェイ」の乱立や、汎用性の低い「特化されたサービス」の乱立を招き、インターネットの重要な要素である分散協調性を低下させ、「多様なメディアが流れるバックボーンとしてのインターネット」におけるメディア間相互透過性を損ねている。そこで、本論文では、これら問題点を解消すべく、まず、インターネット上でのインターネット電話管理運用モデルを作成し、 3点に分類したIn these days, Internet telephone service has become popular as commercial service. But such service causes some problems in the Internet environment. There are too many gateways between telephone and the Internet and specially customized systems that hav

オフィスワークにおける効果的な時間管理手法の一提案

塚田晃司, 岡田謙一, 松下温

情報処理学会論文誌 38 ( 2 ) 359 - 369 1997.02 [Refereed]

The Multi-Project Support System Based on Multiplicity of Task

Tsukada, K, Okada, K, Matsushita, Y

Proceedings of the 18th IEEE Annual International Computer Software and Applications Conference ( I E E E, COMPUTER SOC PRESS ) 358 - 369 1994.11 [Refereed]

A Cooperative Support System Based on Multiplicity of Task

Tsukada, K, Okada, K, Matsushita, Y

Proceedings of the IFIP 13th World Computer Congress ( ELSEVIER SCIENCE PUBL B V ) II 69 - 74 1994.08 [Refereed]

In an office working environment it is very unusual that a worker is engaged in a single task until the task is completed. Generally multitasking is the norm, so workers will belong to several project groups aad work on one of the projects and then, before completing that, switch to another. This paper, focusing on how to manage resources effectively and how to support performing tasks in the environment in which workers belong: to multiple projects, examines the provision of appropriate mechanisms to support a collaborative work in the environment. Based upon a examination we suggest a manage method using a 3-level structure which consists of personal-level, working-level and sharing-level as the method for a resource management anti describe implementation of the Multi-project Support System which is capable of supporting interrelations among workers, resources and projects.

Multi - Project Support System Based on Subjectivity of Workers

Tsukada Koji, Okada Ken'ichi, Matsushita Yutaka

IPSJ SIG Notes ( Information Processing Society of Japan (IPSJ) ) 94-GW-6 ( 33 ) 31 - 36 1994.04

In a real office working environment it is very unusual that a job is assigned to a worker who will be employed duration of that task. Generally multitasking is the norm, so workers will belong to several project groups and work on one of the projects and then, before completing that, switch to another. This paper, focusing on how to support performing and shifting tasks in the environment in which workers belong to multiple projects with subjectivity of workers, examines the provision of appropriate mechanisms to support a collaborative work in the environment and describes implementation of a prototype system.

作業の多重性に着目した協調作業支援に関する研究

塚田晃司

慶應義塾大学 1993.03 [Refereed]

作業の多重性に着目した協調作業支援

塚田晃司, 岡田謙一, 松下温

情報処理学会グループウェア研究グループ研究報告 92-GW-3 25 - 32 1992.12

A Multi-layered Architecture Suitable for Concurrent Collaborative Work

Tsukada, K, Okada, K, Matsushita, Y

Proceedings of 7th International Joint Workshop on Computer Communications 61 - 68 1992.07 [Refereed]

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Published Papers - TSUKADA Koji