Measurements and test devices for Digital Speech Interpolation systems

DSI (Digital Speech Interpolation) significantly improves the traffic capacity of satellite communications systems but introduces degradation which is not typical of any other transmission devices. The degradations are very difficult to locate and sometimes require subjective measurements. There are two characteristic degradations: degradation due to the voice detection process and degradation due to the voice interpolation process both consisting of clippings of various lengths introduced on the vocal signal. This paper describes laboratory and field measuring equipment for studying DSI degradations. The DSI equipment for laboratory tests consists of a very simple DSI and includes a traffic simulator and auxiliary equipment to verify the characteristics of speech detection and interpolation. Equipment for field speech detector tests on a DSI prototype is described and a diagram illustrating interpolation process test and data collection on live traffic is presented.