Terrestrial interface architecture (DSI/DNI)

The 64-kbit/s digital speech interpolation (DSI)/digital noninterpolation (DNI) equipment interfaces the TDMA satellite system with the terrestrial network. This paper provides a functional description of the 64-kbit/s DSI/DNI equipment built at Comsat Laboratories in conformance with the Intelsat TDMA/DSI system specification, and discusses the theoretical and experimental performance of the DSI system. Several DSI-related network and interface issues are discussed, including the interaction between echo-control devices and DSI speech detectors, single and multidestinational DSI operation, location of the DSI equipment relative to the international switching center, and the location and need for Doppler and plesiochronous alignment buffers. The transition from 64-kbit/s DSI to 32-kbit/s low-rate encoding/DSI is expected to begin in 1988. The impact of this transition is discussed as it relates to existing 64-kbit/s DSI/DNI equipment.