Katsuya Hakozaki

A proposal of a streaming video system in best-effort networks using adaptive QoS control rules

We propose a streaming video system, which can be used in various system environments. This system has three features for providing real-time video delivery services in the Internet. The first is to use QoS (quality of service) control rules adapting to the system environments. The second is to improve estimation accuracy of the network conditions while a user is watching a stream. The third is to notify QoS degradation factors to the user actively. These features make it possible to provide streaming services with a high level of user satisfaction. We show an experimental system in our laboratory as an implementation example.

Mobile communications - icams: a mobile communication tool using location and schedule information

iCAMS, a new mobile communication tool for cellular phones, uses location and schedule information. By analyzing communication logs and the results from questionnaires and user interviews, we evaluated our systemand found the following: 1) Location information is good for estimating the callees context, and enables serendipitous meetings. 2) The sorted list of communication channels in the callees priority list helps callers and callees find a nexus between the callers demands and the callees wishes. 3) We should switch location-sensing methods according to distances in both real and mental space.

Conceptual design of a virtual library for personal use

This paper proposes a concept of the Yawara personalized virtual library and its prototype design. The main purpose of the library is to provide a user with a personalized information set accessible through a user-friendly interface. In order to attain machine and operating system independence, the library is constructed by VRML and its WWW browsers and, as information sources, HTML data widely distributed on the Internet. The virtual librarian agent helps to find and acquire the data sets based on user behavior. The virtual librarian keeps the users personal characteristics, obtained from his/her reading history, and book characteristics. As the user working space, personal bookshelves are provided to work with the stored books. The system will be a powerful tool for intelligent work fully utilizing the Internet.

Generational Replacement Schemes for a WWW Caching Proxy Server

This paper proposes and evaluates generational replacement schemes that suit access patterns to the World Wide Web (WWW) proxy server cache. The schemes partition a cache into generations and put frequently accessed data into older generations where entries are less likely to be replaced. Using our schemes, the hit rate per page is improved by about 5.2 percentage points over the Least Recently Used (LRU) algorithm on the basis of logs of more than 8 million accesses. This improvement reduces the number of cache misses by about 10.8 percent with respect to LRU. Our improvement is roughly twice as good as the improvement of LRU over the First-In First-Out (FIFO) algorithm.

An analysis of relationship between video contents and subjective video quality for Internet broadcasting

This paper analyzes relationship between video contents and subjective video quality for Internet broadcasting, and applies the results to the rate control methods. In this analysis, we classify video programs into some groups in which a large majority of users feel the same subjective video quality. We investigate the relationship by conducting an experiment with method of paired comparisons, and express that as equations by multiple linear regression analysis.

Development of a High-Accurate Time Server for Measurements of the Internet

The network delay is one of the essential elements h)r the Quality of Service (QoS). The time delay is measured by placing devices at both ends of the network and using the machines internal time clock. The accuracy of the measurement is dependent on the precision of tihe clock, therefore the precision of the clock is very important. Network Time Protocol (NTP) is applied for the time synchronization amnong network nodes; hence, the time accuracy at each NTP server is considered very importmLt. Moreover, the improvement of the accuracy is required for the recent, broadband network.Our objective in this research is to improve the time stability of the top NTP server (stratum1) by developing a server with higher stability. The server, which is called the high-accurate time server, was designed based on external high accurate frequency signal, insted of the crystal oscillator on the motherboard of a Personal Computer (PC). The high-accurate time server is capable of the time stability of several hundred nanoseconds. Also evaluated in this paper is the high precision measurement of network delay, which was proceeded with the server.

A proposal of a streaming video system adapting to various system environments and its implementation

This paper proposes a streaming video system adapting to various system environments. Until now, many studies of adapting QoS (quality of service) control methods have been made in the area of streaming video technologies in the Internet. However, these methods have not been able to provide sufficient service quality to system users under recent diversification of system environments. We therefore design the system based on three ideas. First, the system conducts switching of streaming servers. This switching makes it possible to combine multiple control mechanisms and to use the combination for QoS control. Second, the system adopts simple estimation methods of network conditions. Estimation accuracy is gradually modified while users are watching streams. Third, the system notifies information of network conditions to system users. This makes it possible to provide streaming services with high level of user satisfaction. We conducted implementation experiments using the prototype system. From these experimental results, we found out that the proposed system was adaptable to various system environments and that the QoS notification decreased the level of user dissatisfaction of service quality.

Application QoS management for distributed computing systems

As a large number of distributed multimedia systems are deployed on computer networks, quality of service (QoS) for users becomes more important. This paper defines it as application QoS, and proposes the application QoS management system (QMS). It controls the application QoS according to the system environment by using simple measurement-based control methods. QMS consists of three types of modules. These are a notificator for module detecting QoS deterioration, a manager module for deciding the control method according to the application management policies, and a controller module for executing the control. The QMS manages the application QoS by communicating between these modules distributed on the network. Moreover, this paper especially focuses on the function setting QoS management policies to the QMS and proposes the setting method. By a simulation experiment, we confirmed that the system made it possible to negotiate the QoS among many applications and it was able to manage the whole applications according to the policies.

A proposal of a high quality video delivery method in small-scale best-effort networks

This paper proposes a video delivery method, which makes it possible to glance at high quality videos while working or studying in a PC monitor. The target is a small-scale best-effort network, such as networks in SOHOs and laboratory rooms in universities. This method reduces video frame rate when the users do not fix their eyes on the video, and delivers high quality video when they fix their eyes on it. This is based on the idea that high quality video are not necessary while they do something except watching a video. For detecting the watching, we use mouse clicks. As a result, we can reduce useless video delivery traffic when concentrating on other works and use bandwidth resources effectively.

A Proposal of a QoS Control Method for Digital Video Libraries

Digital video libraries using IP networks have become a practical system from trial one. As a result, we need techniques providing data whose quality of service (QoS) satisfies user request. In this paper, we propose a QoS control method for digital video libraries, which made it possible to transport video according to users system environment. In addition, we developed the experiment system using digital video transport system and conducted the experiment using the system. As a result, we found that a bandwidth control function on video servers improved QoS provided to users.