Traffic routing for satellite communication system

Abstract

Methods and apparatus which route, control and manage traffic throughout a Satellite Communication System operating in low Earth orbit are disclosed. Voice, video and data traffic from terrestrial gateways (G) and from portable (P), mobile (M) or fixed (F) terminals are directed up through the constellation of satellites (S) and back down to destinations on Earth. The satellites provide continuous worldwide communication services while insuring uniform end-to-end transmission delays. The satellite network is highly adaptive to the constantly changing network topology, and will offer a synchronous circuit switched communication service that provides sequential delivery of user data, regardless of the type of the data transmitted. The network employs datagram switching, as opposed to conventional virtual circuit switching techniques. Packets associated with a single phone call do not necessarily travel along the same route, and consequently arrive at their common destinations at different times with a variable transmission delay. Packets (26) received from a portable (P), mobile (M) or fixed (F) terminal, from a satellite (S), or from a stationary gateway (G) are dispatched from an origin node (OUR.sub.-- NODE) to a destination node (DEST.sub.-- NODE) according to address instructions carried in the packet header (28). At each node, propagation delay vectors OUR.sub.-- DELAY.sub.-- EST [DEST.sub.-- NODE, ] are calculated using local computers. These delay vectors estimate a time delay which the packet (26) encounters in traveling from the origin node (OUR.sub.-- NODE) to the destination node (DEST.sub.-- NODE). An optimal route (opt.sub.-- link) is then selected from the set of calculated delay vectors, and the packet (26) is routed to the destination node (DEST.sub.-- NODE) via the pathway (opt.sub.-- link) that insures both the lowest end-to-end delay and the best overall traffic management of the network.