Internet over direct broadcast satellites

High-powered direct broadcast television satellites can be used to broadcast high volumes of data directly to home terminals. Using the telephone network or a similar low-speed network, an asymmetrical system can be implemented which offers interactive Internet services. Two such interactive data broadcast systems are described which have been implemented as demonstration platforms for interactive multimedia services; one is based on digital subcarrier techniques for analog television channels, the other on the MPEG-2 and DVB standards. The architecture of the hardware and software is presented, particularly the solutions available for carrying Internet datagrams over MPEG-2 transport systems. A multicast transport protocol with selectable reliability is described which is the basis of a generic distribution application. It exploits the potential benefits of direct broadcast satellites for delivering data to large groups of local caches.