Speech Compression: A Key to Low-Cost Telephony Systems for Developing Countries.
Geraldo Lino de Campos · IFIP Congress · 1994
Speech compressing techniques have evolved to a point were a rate of 4.8 Kb/s is sufficient to transmit voice with quality that exceeds normal telephone grade voice. As carriers still use 64 Kb/s for transmission of a voice signal, this effectively wastes more than 90% of the world’s long range transmission capacity, a scarce, valuable and expensive resource. This waste is specially significant for developing countries, where capital is the most scarce resource. This paper proposes the use of voice-only phone lines, using compression techniques and 4.8 kb/s per channel, multiplexing up to 26 subscribers in one line (subscriber loop), using the chips and technologies already developed for ISDN, and multiplexing up to 13 voice channels in each toll connecting trunk, as well in intertoll trunks. This will result in a low-cost system for developing countries. In this paper all references will be to the international telephony standards; the same reasonings, with slightly changed figures, apply to the American standards.