A satellite based ATM switch

When the asynchronous transfer mode was adopted in 1987 as the target communications technology for the IBCN, it was recognised that the deployment of an ubiquitous terrestrial infrastructure to support this technology would take many years. A traditional chicken-and-egg situation was in prospect: without a network there would be no user demand; without user demand there would be no network. The satellite, with its broad geographical coverage and relatively fast deployment (and redeployment) capabilities, suggested itself as an obvious transmission gap-filler, but there were difficulties in providing low cost satellite paths at the 155 and 622 Mb/s rates conventionally associated with ATM. In the cell-based ATM environment it could also be expected that source streams, of whatever rate, would contain a proportion, perhaps a high proportion, of empty cells. The prospect of wasting valuable satellite capacity on the transmission of empty cells prompted a change in focus; the gaps between cells became as important as the cells themselves: they cried out to be filled. But a cell-gap filler is, in effect, a cell switch: the concept of a satellite-based ATM switch, an ATM exchange-in-the-sky, presented itself