Packet communications via satellite with buffer and multiple downlinks

The Pacsat (packet satellite) system described by DeRosa et al. (1979) is extended to include multiple downlinks. In this extended system, only the FIFO (first-in-first-out) buffer is considered. Whereas the FIFO buffer treated by DeRosa et al. was of finite size, an infinite buffer that demonstrates the limit of the system performance is investigated here. Typical performance measures, such as system throughput and packet delay, are derived. An alternative derivation, believed to be more straightforward and easier to understand than that given by DeRosa et al., is given for the expected number of retrials that any packet may have to go through before it can be successfully transmitted. It is also demonstrated, through examples, that on-board storage provides gains in throughput, efficiency and margin against instability equivalent to multiple uplinks.