[Japanese | Thesis | Researches in Minoh Lab | Minoh Lab]
Various multimedia communication systems over computer networks are available along with widespread use of the Internet. There is a need for large bandwidth to transmit video and sound. Real-time applications providing interaction between classrooms, for example, require also shorter delay for smooth communications.
We cannot avoid packet losses which cause disorder or cutting-off of streaming because resource reservation techniques are still in development. In particular bursty packet losses, contiguous multiple packet losses, have a critical impact on interactive communications because they cause longer breaks of streams. In this paper delay-sensitive real-time applications are supposed to be the target, so in some ways to prevent such a deterioration in quality, we focus on Forward Error Correction and Packet Path Diversity. These two methods can deal with bad effects of packet losses without latency.
Some contemporary techniques deal with the same combination of Forward Error Correction and Packet Path Diversity. But they have some following problems: parameters cannot be changed once streaming begins, extended protocols make them incompatible with other systems, they cannot use Packet Path Diversity unless they have multiple IP addresses, and so on. The network situation such as packet loss rate or bandwidth is always varying so we must modify the parameters during the streaming in order to offer more optimal and reliable transmission. Needless to say, it is obvious advantage for a system to have more versatility, that is, the system should be compatible with other systems and should apply to various circumstances. That is why we have adopted three new methods, RTP over RTP, Relay host, Forward Error Correction over each path, and proposed a new robust system which solves all the problems of previous techniques.
This system can prevent the influence of bursty packet losses very well. It also enables other systems which cannot execute Packet Path Diversity or Forward Error Correction by themselves to utilize the methods by using this proposed system together. Furthermore, this system makes it possible for single-linked hosts which could not take advantage of Packet Path Diversity before to use the technique.
In this paper we have proposed a new method for real-time applications with which longer delay is unacceptable, and we have designed and implemented a system succesfully. We have simulated our system to verify the validity, and by results of experiments we confirmed the effectiveness of our proposed system.