New trends in digital circuit multiplication technology
J. Piasetzky · International Journal of Satellite Communications · 1990
Abstract This paper discusses the achievements and the unsolved problems of the first generation of Digital Circuit Multiplication Systems (DCMS) DCMS is an abbreviation for Digital Circuit Multiplication Systems. DCME is an abbreviation for Digital Channel Multiplication Equipment. Both refer to the same technique of combining digital speech interpolation and low rate encoding. . The following summarizes proposed improvements in DCMS technology. A major improvement in DCMS gain may be achieved by implementation of facsimile demodulation. The design considerations of this technique are discussed. The CCITT activities on standardization of a 16 kb/s speech coding algorithm are reviewed. In order to adapt this algorithm to implementation in a DCMS, the operation of the algorithm has been modified to enable variable bit rate operation at rates between 12·8 and 24 kb/s. The implementation of such an algorithm in DCMS will further increase the overall compression gain. The first generation of DCMS has been implemented mainly on heavy traffic routes. A DCMS terminal which is optimized for operation on ‘thin’, or smaller, routes, using an IDR link operating at 512 kb/s, is described. Tandem operation of DCMS is becoming an increasingly important consideration on both international and national routes. The accumulation of qdu's (quantization distortion units) when two pairs of DCME/S terminals are operated in tandem can be avoided by an arrangement without ADPCM decoding/encoding in the transit terminals so that the ADPCM decoding is carried out only at the final destination DCMS terminal.