ABSTRACT
The major consequence of the geostationary orbital position is that signals experience a propagation delay of no less than 119 ms on an uplink (longer for earth stations at northern latitudes or for earth stations looking at satellites that are significantly offset longitudinally compared with the earth station itself §), and no less than 238 ms for an uplink and a downlink or a oneway end-to-end transmission path. A two-way interactive session with a typical communications protocol, such as TCP, will experience this roundabout delay twice (no less than 476 ms) because the information is making two round trips to the satellite and back. One-way or broadcast (video or data) applications easily deal with this issue, as the delay is not noticeable to the video viewer or the receive data user. However, interactive data applications and voice backhaul applications typically have to accept (and adjust to) this predicament imposed by the limitations
of the speed of light, which is the speed that radio waves travel. Satellite delay compensation units and “spoofing” technology have successfully been used to compensate for these delays in data circuits. Voice transmission via satellite presently accounts for only a tiny fraction of overall transponder capacity, and users are left to deal with the satellite delay individually; only a few find it to be objectionable.
