An evaluation of the application of video compression in distance learning and satellite communications

The advent of digital TV compression offers the possibility of reducing transponder costs since a smaller bandwidth lease is required to support the transmissions. A project was initiated by ESA to explore the practicability of using digital compression in a distance learning environment, taking into account the reactions of students to any degraded picture quality due to the compression and also taking into account technical factors such as signal degradation due to intermodulation products in a heavily loaded multicarrier transponder. This paper presents the results of this project and gives some trade offs between transponder costs and digital compression equipment costs. The project has demonstrated in practice the benefits of digital TV compression and the advantages that the technology presents to satellite delivered tele-education. In many cases distance learning courses to small groups of users become commercially viable if MPEG digital compression equipment is used whilst they were not viable when using conventional full transponder analogue FM. The satellite trials showed that a EUTELSAT II transponder with 47 dBW EIRP edge of cover can support up to five compressed TV carriers, each at 8.448 Mb/s and can be received by a 0.9 m consumer type TVRO earth station