Multiple vocoder mobile satellite telephone system

A communications system comprising:

• a first unit having a first transceiver coupled to a first controller, said first unit further comprising a first plurality of vocoders for encoding and decoding speech signals and a first switching unit being responsive to a first selection signal for enabling one of said first plurality of vocoders 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 second plurality of vocoders for encoding and decoding speech signals received from said first unit and a second switching unit being responsive to a second selection signal for enabling one of said second plurality of vocoders that corresponds to an enabled one of said first plurality of vocoders for operation at any given time, said first and second units transmitting and receiving encoded speech signals, using the selected vocoders, and also signalling information therebetween over an RF communication link, the signalling information including a vocoder selection signal command that is derived based on at least one criterion, wherein said first unit is a user terminal, wherein said second unit is a terrestrial gateway, wherein said RF communication link is made through at least one satellite, and wherein a first one of the first and second plurality of vocoders is comprised of a variable rate vocoder, wherein a second one of the first and second plurality of vocoders is comprised of a fixed rate vocoder, wherein said fixed rate vocoder is selected for use in order to conserve satellite power and to maintain or increase system capacity.

A user terminal comprising:

• an RF transceiver for transmitting modulated RF signals to and for receiving modulated RF signals from at least one satellite, the RF signals being modulated to convey speech and signalling information;
• a signal processor coupled to said RF transceiver for demodulating said received RF signals to digital signals;
• an audio unit for transponding speech signals with a user;
• a plurality of different types of selectable speech encoders/decoders coupled between said signal processor and said audio unit;
• and
• a controller, responsive to signalling information received through said RF transceiver, for selecting during any particular frame of speech one of said plurality of encoders/decoders for coupling between said signal processor and said audio unit, wherein said signalling information is transmitted to said user terminal from a terrestrial gateway through said at least one satellite, and wherein an encoder/decoder selection component of said signalling information is generated in said gateway based on one or more criteria including a predicted communications load.

A user terminal comprising:

• an RF transceiver for transmitting modulated RF signals to and for receiving modulated RF signals from at least one satellite, the RF signals being modulated to convey speech and signalling information;
• a signal processor coupled to said RF transceiver for demodulating said received RF signals to digital signals;
• an audio unit for transponding speech signals with a user;
• a plurality of speech vocoders coupled between said signal processor and said audio unit;
• and
• a controller, responsive to signalling information received through said RF transceiver, for selecting during any particular frame of speech at least one of said plurality of vocoders for coupling between said signal processor and said audio unit, wherein said signalling information is transmitted to said user terminal from a terrestrial gateway through said at least one satellite, and wherein a vocoder selection component of said signalling information is generated in said gateway based on one or more criteria including a predicted communications load.

A user terminal comprising:

• an RF transceiver for transmitting modulated RF signals to and for receiving modulated RF signals from at least one satellite, the RF signals being modulated to convey speech and signalling information;
• a signal processor coupled to said RF transceiver for demodulating said received RF signals to digital signals;
• an audio unit for transponding speech signals with a user;
• a plurality of speech vocoders coupled between said signal processor and said audio unit;
• and
• a controller, responsive to signalling information received through said RF transceiver, for selecting during any particular frame of speech at least one of said plurality of vocoders for coupling between said signal processor and said audio unit, wherein a first one of said plurality of vocoders is comprised of a variable rate vocoder, wherein a second one of said plurality of vocoders is comprised of a fixed rate vocoder, and wherein said fixed rate vocoder operates at an average data rate that differs from an average data rate of said variable rate vocoder.

A method for operating a satellite communications system having at least one gateway, at least one user terminal, and at least one satellite for relaying at least speech and signalling information between the gateway and the user terminal over a communication link, comprising steps of:

• providing the user terminal with a plurality of encoders for encoding speech signals and with a first switching unit responsive to a first selection signal for enabling one of the encoders for operation at any given time;
• providing the gateway with a plurality of decoders for decoding encoded speech signals received from the user terminal and with a second switching unit responsive to a second selection signal for enabling one of the decoders that corresponds to an enabled one of the encoders for operation at any given time;
• transmitting and receiving encoded speech signals and also signalling information between the user terminal and the gateway over the communication link;
• generating a selection signal based on at least one criterion;
• and
• transmitting the selection signal from the gateway to the user terminal over the communication link, wherein said at least one criterion is based on a predicted communications load.

A method for operating a satellite communications system having at least one gateway, at least one user terminal, and at least one satellite for relaying at least speech and signalling information between the gateway and the user terminal over a communication link, comprising steps of:

• providing the user terminal with a plurality of encoders for encoding speech signals and with a first switching unit responsive to a first selection signal for enabling one of the encoders for operation at any given time;
• providing the gateway with a plurality of decoders for decoding encoded speech signals received from the user terminal and with a second switching unit responsive to a second selection signal for enabling one of the decoders that corresponds to an enabled one of the encoders for operation at any given time;
• transmitting and receiving encoded speech signals and also signalling information between the user terminal and the gateway over the communication link;
• generating a selection signal based on at least one criterion;
• and
• transmitting the selection signal from the gateway to the user terminal over the communication link, wherein the at least one criterion is based on extending user terminal talk time.

A method for operating a satellite

• communications system having at least one gateway, at least one user terminal, and at least one satellite for relaying at least speech and signalling information between the gateway and the user terminal over a communication link, comprising steps of:
• providing the user terminal with a plurality of encoders for encoding speech signals and with a first switching unit responsive to a first selection signal for enabling one of the encoders for operation at any given time;
• providing the gateway with a plurality of decoders for decoding encoded speech signals received from the user terminal and with a second switching unit responsive to a second selection signal for enabling one of the decoders that corresponds to an enabled one of the encoders for operation at any given time;
• transmitting and receiving encoded speech signals and also signalling information between the user terminal and the gateway over the communication link;
• generating a selection signal based on at least one criterion;
• and
• transmitting the selection signal from the gateway to the user terminal over the communication link, wherein the at least one criterion is based on reducing power within a satellite beam.

A method for operating a satellite communications system having at least one gateway, at least one user terminal, and at least one satellite for relaying at least speech and signalling information between the gateway and the user terminal over a communication link, comprising steps of:

• providing the user terminal with a plurality of encoders for encoding speech signals and with a first switching unit responsive to a first selection signal for enabling one of the encoders for operation at any given time;
• providing the gateway with a plurality of decoders for decoding encoded speech signals received from the user terminal and with a second switching unit responsive to a second selection signal for enabling one of the decoders that corresponds to an enabled one of the encoders for operation at any given time;
• transmitting and receiving encoded speech signals and also signalling information between the user terminal and the gateway over the communication link;
• generating a selection signal based on at least one criterion;
• and
• transmitting the selection signal from the gateway to the user terminal over the communication link, wherein the plurality of encoders each form a part of one of a first plurality of vocoders, wherein the plurality of decoders each form a part of one of a second plurality of vocoders, wherein a first one of each of the first and second plurality of vocoders is comprised of a variable rate vocoder, wherein a second one of the first and second plurality of vocoders is comprised of a fixed rate vocoder, and wherein the fixed rate vocoder operates at an average data rate that differs from an average data rate of the variable rate vocoder.