Quality of an IP-based Video Conference on SCS : Alternative to the Internet

Paper number

IAC-05-E1.P.01

Author

Dr. Tomoharu Shibuya, National Institute of Multimedia Education, Japan

Coauthor

Dr. Kimio Kondo, National Institute of Multimedia Education, Japan

Coauthor

Dr. Noritaka Osawa, National Institute of Multimedia Education, Japan

Year

2005

Abstract

In 1996, National Institute of Multimedia Education (NIME) developed an inter-university satellite communication network named space collaboration system (SCS) [ hp, kondo], which provides a video conference system based on the ITU-T H.261 protocol. Flexible multi-site operation is possible in SCS using two or three 1.5 Mbps channels simultaneously. Currently, SCS consists of 151 ground stations: a HUB station placed at NIME and other 150 stations placed at institutes of higher education in Japan, such as national and private universities, national colleges of technology, and so on. Moreover, SCS is utilized for more than 2,000 hours a year for a variety of collaborative activities such as lecture, symposiums, and academic meetings. Now, in order to provide more flexible and higher collaboration system for universities, a project named Satellite Collaboration using IP [ ists] is in progress in our institute, which enables an inter-university video conference over IP network on SCS.

In the project, we have already verified that by introducing a few devises to the equipment of current SCS and slightly modifying its configurations, we can build an IP network on SCS that accommodates LAN’s in ground stations participating in SCS [ ists]. As the next step of our project, we had experiments to assess the suitability of the IP network on SCS for an IP-based video conference. In this paper, we shall report the results of the experiments.

In the experiments, we first collected the statistics of UDP packets being exchanged between two ITU-T H.323-based video conference systems communicating through the IP network on SCS. Then we investigate, for instance, the lost rate, the occurrence of sequence errors, and the jitters of relative transit time of those UDP packets. It is well known that loss and sequence errors of UDP packets cause serious degradation of the quality of audio and visual images, i.e. noise on voice, freeze of motion, etc. We observed in the experiments that the rate of packet loss is less than 10 ⁻⁵ and no sequence errors occurred. This means that the quality of audio and visual image scarcely degrade on the IP network on SCS.

Next, we connect two IP-based video conference systems used in the above experiments through the Internet, then again measured the rate of packet loss and the number of sequence errors. This experiment shows that the Internet usually exhibits several percent of packet loss, although which varies depending on the status of the Internet. In addition, we observed that sequence errors of packets occurs very frequently. Theses high packet loss rate and many sequence errors sometimes resulted in intolerably degraded audio and visual image.

From the results described above, we can conclude that the IP network on SCS is much suitable for an IP-based video conference. Moreover, we can also say that with respect to the quality of audio and visual image of a video conference, the IP network on SCS has much advantage toward the Internet. This implies that in some educational program, in which degradation of the quality of audio and visual image sometimes becomes a serious problem, an IP-based video conference over SCS can be a promising alternative to that over the Internet.

References

[hp]

Space Collaboration System Project, http://www.nime.ac.jp/SCS/index_e.html

[kondo]

K. Kondo, “VSAT Application for Inter-university Educational Network,” The Journal of IEICE, vol.79, no.8, pp.777-782, 1996.

[ists]

T Shibuya, K Asai, N Osawa, K Kondo, “ Inter-University Satellite Collaboration Using IP on SCS,” Post Conference CD-ROM of 24th ISTS (Miyazaki, Japan), ISTS2004-u-01, 2004.

Abstract document

IAC-05-E1.P.01.pdf

Manuscript document

IAC-05-E1.P.01.pdf (🔒 authorized access only).

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