Variable rate speech coder matching the needs of traffic reconfigurability

Voice coding at variable rate could be a simple but effective way to obtain diversity schemes in satellite communications. A microprocessor based implementation of a multirate coder is illustrated. This device allows voice coding from a nominal rate of 9.6 Kbps (good speech quality) to a rate of 2.4 Kbps (standard vocoder quality). Two main tasks are the objective of the proposed system: (1) to maintain satisfactory voice quality (average standard quality) when the BER increases; and (2) to obtain a high degree of service by reducing to a minimum the number of satellite channels requested, while still maintaining an average fair quality. The analysis performed shows that this coder represents a significant advantage in low traffic zones and for remote area communications.