Impact of speech interpolation and data on FDM/FM transmission
Abstract
Speech interpolation decreases the bandwidth required for a given number of voice channels in an FDM/FM system. The bandwidth decrease is a function of the interpolation gain, g, which is the ratio of the number of channels available without interpolation to that with interpolation. This advantage is partially cancelled by increased multichannel load and the corresponding increase in FM deviation required to restore the proper noise floor. For a given g and for a fixed FM bandwidth, the net result is an FDM/FM carrier voice frequency channel capacity enhancement between g to the 2/3-power and g to the 5/6-power, depending on the number of channels. If the FM deviation is not modified, and the FM bandwidth is reduced by the same amount by which the FDM bandwidth is reduced, i.e., by the factor g, channel performance degrades. Channels with data load decrease the interpolation efficiency and the obtainable carrier capacity enhancement. Assigning data-loaded channels, which have a lighter load than the speech-interpolated channels, to high-frequency FDM baseband positions minimizes the multichannel load deviating the FM carrier.
- Publication:
-
COMSAT Technical Review
- Pub Date:
- 1983
- Bibcode:
- 1983COMTR..13..259S
- Keywords:
-
- Channels (Data Transmission);
- Frequency Division Multiple Access;
- Frequency Modulation;
- Speech Baseband Compression;
- Voice Communication;
- Carrier To Noise Ratios;
- Channel Capacity;
- Interpolation;
- Multichannel Communication;
- Signal To Noise Ratios;
- Tradeoffs;
- Communications and Radar