| 摘要 |
PROBLEM TO BE SOLVED: To provide a satellite communication system having a function for switching plural vocoders having respectively different rates based on a line state and using the selected vocoder. SOLUTION: In the system consisting of a user terminal 16, a gateway and a satellite, the terminal 16 includes a transceiver 30, a signal processor 32, voice units 90, 92, 94, encoders/decoders for encoding/decoding respective voice signals, and vocoders 82, 84, 86. Vocoders of a variable rate and a fixed rate are included. The selection of an encoder/decoder or a vocoder is executed by the gateway based on respective references such as the damage or interference of an RF signal, a predicted or practical communication system, the quality of a voice selected by a user and/or the quality of a signal received from the user terminal 16. It is also available that the user terminal 16 outputs a request based on the quality of a signal received from the gateway and the gateway outputs a vocoder selection command. |
