THE ADAPTIVE DIFFERENTIAL PCM CODEC OF THE DKD-400 DIGITAL SATELLITE-COMMUNICATIONS EQUIPMENT

The availability of digital processors for processing signals has made it possible to construct compact devices for the effective coding of speech, suitable not only for special networks but also for commercial communications. The best compromise between technical complexity of t he codecs, transmission rate, and speech reproduction quality at the o utput of the system is obtained using an adaptive differential PCM cod ec to the CCITT standard G.721 [1], by means of which one can transmit speech signals with high quality over a tone-frequency channel at a r ate of 32 kbit/s [5]. The undoubted advantages of the adaptive differe ntial PCM method also includes the possibility of secondary multiplexi ng the tone-frequency channel with data signals at a rate of up 4800 b its/s, which enables the codec to be used on trunk communications line s. In this paper we present the results of a development an experiment al investigation of an adaptive differential PCM codec designed to cor respond to CCITT Recommendation G.721 for the DKD-400 digital satellit e communications equipment [2]. The codec with elements of an echo sup pressor is constructed using the Russian analog of the well-known TMS 320 C10 digital signal processor.