초록 ▼

A user terminal (16) includes an RF transceiver (30) for transmitting modulated RF signals to a gateway (14) and for receiving modulated RF signals from the gateway via at least one satellite (112). The satellite may be a GEO or a non-GEO satellite. The user terminal further includes a signal proces

A user terminal (16) includes an RF transceiver (30) for transmitting modulated RF signals to a gateway (14) and for receiving modulated RF signals from the gateway via at least one satellite (112). The satellite may be a GEO or a non-GEO satellite. The user terminal further includes a signal processor (32) coupled to the RF transceiver for demodulating received RF signals to digital signals, an audio unit (90,92,94) for transponding speech signals with a user, and a plurality of encoders/decoders (2A,2B) and/or vocoders (82,84,86) between the signal processor and the audio unit for encoding and decoding speech signals passing to and from the audio unit. A first vocoder can be a variable rate vocoder, a second vocoder can be a fixed rate vocoder, where the fixed rate vocoder operates at an average data rate that differs from, e.g., is less than, an average data rate of the variable rate vocoder. The encoder/decoder or vocoder selection is made in the gateway based on one or more criterion such as a presence of an RF signal impairment or RF interference, a predicted and/or actual communications system, a user-selected voice quality, and/or a signal quality received from the user terminal. In one embodiment the vocoder selection command is generated in the terrestrial gateway in response to a request from the user terminal, and in this case the criterion is based on a quality of a signal received from the terrestrial gateway at the user terminal. The selection can be made on the fly on a frame or multi-frame basis.

대표청구항 ▼

1. A communications system comprising:a first unit having a first transceiver coupled to a first controller, said first unit further comprising a plurality of encoders for encoding speech signals and a first switching unit being responsive to a first selection signal for enabling one of said encoder

1. A communications system comprising:a first unit having a first transceiver coupled to a first controller, said first unit further comprising a plurality of encoders for encoding speech signals and a first switching unit being responsive to a first selection signal for enabling one of said encoders for operation at any given time; and a second unit having a second transceiver coupled to a second controller, said second unit further comprising a plurality of decoders for decoding encoded speech signals received from said first unit and a second switching unit being responsive to a second selection signal for enabling one of said decoders that corresponds to an enabled one of said encoders for operation at any given time, said first and second units transmitting and receiving encoded speech signals and also signalling information therebetween over an RF communication link, the signalling information including a selection signal command that is derived based on at least one criterion, wherein the at least one criterion is based on a predicted communications system load.