Ji, Yusheng

Associate Professor, Information Systems Architecture Science Research Division[TITLE]

Quality of service provisioning in advanced communication networks [The title is appropriate,I think. However, note that for some purposes this title is too general because there aremany thousands of papers that deal with this subject.][MAIN BODY]

Communication networks are used for exchanging information between people andcomputers which are located at physically distant points. To enable rapid and accuratetransmission of information in a network, it is important to ensure quality-of-service aspects
such as transmission delay, delay differences, and loss of information. My research is focusedon finding efficient ways to ensure quality of service in advanced communication networks.

Broad latitude in quality requirements

The quality of service required depends on the means and purpose of communication. For
non-real-time transmission of data and e-mail, quality of service implies the assurance ofaccuracy of the information in the transmission, during which small delays will not cause
serious problems. In the case of real-time conversations, such delays are more of an issue,
but minor breaks in communication might not seriously affect the integrity of theinformation. This is because people are relatively sensitive to delays in voice communication,
but they routinely compensate for short interruptions that may be caused by slight losses of
information in the network. For advanced communications between computers such as in thelatest grid computing technology, any loss of data will result in calculation errors, and evenvery small delays can cause serious performance degradation. This makes rigorous assurance

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against data losses and delays an essential requirement for such communications.

When supporting different applications through a single network like the Internet, we haveto allocate network resources such as bandwidth and buffers, as well as determine thepriority of the information being transmitted based on the required communication quality.
The purpose of my research is to develop efficient control methods and procedures (calledprotocols) for assuring quality of service on various kinds of communication networks.

Evolution of communication technologies requiring new control methods

The control methods for ensuring quality of service in communication networks are changing
as a result of the rapid advance of communication technologies. In wireless communications,users can transmit and receive radio signals while they are moving. Such mobility results inconstantly changing radio channel conditions that affect communication quality. Thus,
wireless communications require quality control methods that can accommodate different
situations and respond to fluctuating communication conditions. Furthermore, comparedwith wired communications, wireless communications have stricter limitations on network
bandwidth and power consumption. This makes effective use of limited resources especially
important for assuring high communication quality. On the other hand, quality of service inoptical networks must be supported by means of bandwidth reservation or scheduling. Thisis because the current state of technology can not store light (or photons) within networks forstore-and-forward transmission.

Providing quality of service in communication networks will remain a major issue of study inthe communications field. Emerging communication technologies and new applications willcontinue to mandate development of efficient quality control methods.

(Summary of an interview by Asako Murakami)

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