Enhancement of FDM-FM satellite capacity by use of compandors

This paper presents the results of a study to determine the satellite capacity enhancement obtainable by using syllabic compandors. Syllabic companding applied to the speech channels of FDM-FM carriers can increase satellite capacity by as much as 100 percent, depending on the number of channels per carrier. Syllabic compandors presently produced by integrated circuit technology are small and inexpensive. Compandors permit a higher level of satellite circuit noise and hence an FM index (and bandwidth) which is smaller than that required for uncompanded channels. The results presented in the paper are based on compandor advantage measurements and single- and multi-channel amplitude distribution measurements for both companded and uncompanded speech signals. For data transmission, it is estimated that about 2-dB degradation may be encountered when long terrestrial access circuits are interconnected via a companded satellite circuit for international transmission.