Computations of DSI (TASI) Overload as a Function of the Traffic Offered

This paper presents an analysis of the performance of a digital speech interpolation (DSI) system as a function of the traffic offered to the system. We assume that the DSI overload degradation occurs as clipping or freezeout. This is identical to TASI freezeout. Unlike conventional analysis, which assumes all of the trunks entering the DSI system are busy all the time, we calculate the freezeout fraction as a function of the traffic offered. In almost all practical situations the freezeout fraction, computed based on traffic assumptions, is considerably less than that computed assuming all trunks are busy. When a DSI system is used to compress trunks down into channels, there is always a tradeoff between the blocking probability in the trunk group and the degradation introduced by the DSI system. This tradeoff depends on the traffic offered and is explored in this paper.