A Microprocessor Controlled Digital Interface for Digital Satellite Systems

We describe exploratory work designed to demonstrate the feasibility of directly interfacing terrestrial digital carrier systems to digital satellite systems. Designed to accept up to 30 T1 carrier systems on the terrestrial side, the interface is designed as a common-control, bus-oriented time-division switch using a common time-slot interchanger for simultaneous switching of up- and down-links. The output bit rate is about 50 Mbits/s. The controller is implemented as two Motorola M6800 microcomputer chips and associated memory. The switch can communicate with a variety of terrestrial originating switches, including those using either register-sender or cut-through operation. By proper software, a simultaneous mix of such originating switches can be handled, and either delay-start dial, wink-start or dialtone start outpulse control can be used in either direction of call setup (i.e., to or from a terrestrial switch connected to the satellite earth station).