M. Nakagawa et al., EVALUATION OF THE CHARACTERISTICS OF A MULTIMEDIA INTERACTIVE SATELLITE-COMMUNICATIONS SYSTEM, Electronics & communications in Japan. Part 1, Communications, 81(4), 1998, pp. 12-19
In order to realize a flexible but economical communication system wit
h which users can access multimedia information anytime and anywhere,
Tokai University and NTT are currently conducting studies and experime
nts on a multimedia interactive satellite communications system which
uses a satellite circuit for downlinks and a terrestrial network for u
plinks. We are presently involved in a field trial of the system appli
ed to tele-education. The fundamental characteristics of the system, r
ound-trip times and throughputs of point-to-point data transmission by
TCP and network broadcasting by UDP, have been measured and evaluated
. The round-trip rime of actual TCP/IP applications is estimated from
the round-trip time measured by using pings (ICMP echo) from clients.
The measured TCP throughput is consistent with the throughput estimate
d from the measured round-trip time and shows that the system is capab
le of high-speed file transfer, The UDP network broadcasting throughpu
t is 6 Mbps, which is equal to the bandwidth of the leased line in the
system. It is confirmed that a higher throughput is possible with a l
arger window size and a broader-bandwidth leased line. (C) 1998 Script
a Technica.