Satellite controlled power control for personal communication user terminals

• US 6,085,067 A
• Filed: 02/23/1999
• Issued: 07/04/2000
• Est. Priority Date: 12/12/1996
• Status: Expired due to Term

• Current Assignee: Globalstar Incorporated
• Original Assignee: Globalstar Incorporated
• Inventors: Wiedeman, Robert A, Monte, Paul A, Gallagher, Vijaya K
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US09/256,038
• Time in Patent Office: 497 Days
• Field of Search: 455/10, 455/12.1, 455/24, 455/69, 455/504, 455/522, 455/13.1, 455/13.2, 455/102, 455/103, 455/115, 455/127, 455/13.4
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system and method for controlling the transmission power of a user terminal in a satellite communications system of a type that includes a ground segment, comprised of at least one user terminal and at least one terrestrial gateway, and a space segment, comprised of a plurality of satellites in a non-geosynchronous earth orbit. The method includes the steps of (a) transmitting an uplink signal from the user terminal simultaneously to at least two satellites of the space segment and (b) receiving the uplink signal with each of the at least two satellites. The method further includes the steps of (c) determining, in the space segment, a difference value representing a difference between a received signal strength indication and a desired received signal strength indication for each of the at least two satellites; (d) in response to the difference value, generating in the space segment at least one power control command for use by the user terminal; (e) transmitting the at least one generated power control command from the space segment to the user terminal; and (f) adjusting a transmitted power of the uplink signal in accordance with the at least one power control command.

Claims

1. A method for controlling the transmission power of a user terminal in a satellite communications system of a type that includes a ground segment comprised of at least one user terminal, and a space segment comprised of a plurality of satellites in a non-geosynchronous earth orbit, comprising the steps of:

transmitting an uplink signal from the user terminal simultaneously to at least two satellites of the space segment;

receiving the uplink signal with each of the at least two satellites;

determining in the space segment a plurality of difference values individual ones of which represent a difference between a received signal strength indication and a desired received signal strength indication for each of the at least two satellites;

in response to the plurality of difference values, generating in the space segment at least one power control command for use by the user terminal;

transmitting the at least one generated power control command from the space segment to the user terminal; and

adjusting a transmitted power of the uplink signal in accordance with the at least one power control command.

2. A method as set forth in claim 1, wherein the step of receiving the uplink signal includes a step of demodulating the received uplink signal to baseband.

3. A method as set forth in claim 1, wherein the step of receiving the uplink signal includes a step of despreading the received uplink signal with a spreading code assigned to the user terminal.

4. A method as set forth in claim 1, wherein the step of determining is accomplished in each of the at least two satellites, and further including a step of transmitting the determined difference value from each of the at least two satellites to a third satellite in a higher orbit.

5. A method as set forth in claim 4, wherein the third satellite is in one of a medium earth orbit or a geosynchronous earth orbit.

6. A method as set forth in claim 4, wherein the step of generating the at least one power control command is performed by the third satellite.

10. A method as set forth in claim 1, wherein the step of receiving includes a step of transmitting the received uplink signal to a terrestrial gateway for connection to a terrestrial communications network.

7. A method for controlling the transmission power of a user terminal in a satellite communications system of a type that includes a ground segment comprised of at least one user terminal, and a space segment comprised of a plurality of satellites in a non-geosynchronous earth orbit, comprising the steps of:

transmitting an uplink signal from the user terminal simultaneously to at least two satellites of the space segment;

receiving the uplink signal with each of the at least two satellites;

determining in the space segment a plurality of difference values individual ones of which represent a difference between a received signal strength indication and a desired received signal strength indication for each of the at least two satellites;

in response to the plurality of difference values, generating in the space segment at least one power control command for use by the user terminal;

transmitting the at least one generated power control command from the space segment to the user terminal; and

adjusting a transmitted power of the uplink signal in accordance with the at least one power control command, wherein

the step of receiving the uplink signal includes a step of relaying the received uplink signal to a third satellite, and further comprising the steps of demodulating or partially demodulating the relayed uplink signal in the third satellite to determine the plurality of difference values, and wherein the step of generating the at least one power control command is performed by the third satellite.

8. A method for controlling the transmission power of a user terminal in a satellite communications system of a type that includes a ground segment comprised of at least one user terminal, and a space segment comprised of a plurality of satellites in a non-geosynchronous earth orbit, comprising the steps of:

transmitting an uplink signal from the user terminal simultaneously to at least two satellites of the space segment;

receiving the unlink signal with each of the at least two satellites;

determining in the space segment a plurality of difference values individual ones of which represent a difference between a received signal strength indication and a desired received signal strength indication for each of the at least two satellites;

in response to the plurality of difference values, generating in the space segment at least one power control command for use by the user terminal;

transmitting the at least one generated power control command from the space segment to the user terminal; and

adjusting a transmitted power of the uplink signal in accordance with the at least one power control command, wherein

the steps of generating and transmitting the at least one power control command occur at first intervals, and further comprising a step of generating an override power control command and transmitting the generated override power control command to the user terminal at second intervals, wherein the second intervals are longer than the first intervals.

9. A method as set forth in claim 8, wherein the power control commands that are generated and transmitted at the first intervals are generated by the at least two satellites of a constellation of low earth orbit or medium earth orbit satellites, and wherein the override power control command is generated and transmitted by a third satellite in a higher altitude earth orbit than the at least two satellites.

11. A satellite communications system of a type that includes a ground segment, comprised of at least one user terminal and at least one terrestrial gateway, and a space segment, comprised of a plurality of satellites in a non-geosynchronous earth orbit, and further comprising:

a transmitter in said user terminal for transmitting an uplink signal simultaneously to at least two satellites of said space segment;

a receiver in each of the at least two satellites for receiving the uplink signal;

at least one first controller in said space segment for determining a plurality of difference values individual ones of which represent a difference between a received signal strength indication and a desired received signal strength indication for an individual one of the at least two satellites;

a second controller in said space segment that is responsive to the plurality of difference values for generating at least one power control command for use by said user terminal;

a transmitter in said space segment for transmitting the at least one generated power control command to the user terminal; and

means in said user terminal for adjusting a transmitted power of the uplink signal in accordance with the at least one power control command.

12. A system as set forth in claim 11, wherein said receiver includes circuitry for demodulating the received uplink signal to baseband.

13. A system as set forth in claim 11, wherein said receiver includes circuitry for despreading the received uplink signal with a spreading code assigned to the user terminal.

14. A system as set forth in claim 11, wherein said at least one first controller that determines the plurality of difference values is comprised of a plurality of first controllers individual ones of which are located in each of the at least two satellites, wherein said second controller is comprised of a plurality of second controllers individual ones of which are also located in each of the at least two satellites, and further including means for transmitting at least one of the determined difference values between the at least two satellites directly or through at least one other satellite.

15. A system as set forth in claim 11, wherein said at least one first controller that determines the plurality of difference values is comprised of a plurality of first controllers individual ones of which are located in each of the at least two satellites, wherein said second controller is located in a third satellite in a higher orbit, and further including means for transmitting a determined difference value from each of the at least two satellites and said third satellite.

16. A system as set forth in claim 15, wherein the third satellite is in one of a medium earth orbit or a geosynchronous earth orbit.

20. A system as set forth in claim 11, wherein said receiver has an output coupled to a transmitter for transmitting the received uplink signal to a terrestrial gateway for connection to a terrestrial communications network.

17. A satellite communications system of a type that includes a ground segment, comprised of at least one user terminal and at least one terrestrial gateway, and a space segment, comprised of a plurality of satellites in a non-geosynchronous earth orbit, and further comprising:

a transmitter in said user terminal for transmitting an uplink signal simultaneously to at least two satellites of said space segment;

a receiver in each of the at least two satellites for receiving the uplink signal;

at least one first controller in said space segment for determining a plurality of difference values individual ones of which represent a difference between a received signal strength indication and a desired received signal strength indication for an individual one of the at least two satellites;

a second controller in said space segment that is responsive to the plurality of difference values for generating at least one power control command for use by said user terminal;

a transmitter in said space segment for transmitting the at least one generated power control command to the user terminal; and

means in said user terminal for adjusting a transmitted power of the uplink signal in accordance with the at least one power control command, wherein

said receiver is coupled to a transmitter for relaying the received uplink signal to a third satellite, said third satellite comprising means for demodulating or partially demodulating the relayed uplink signal, and said first and second control means.

18. A satellite communications system of a type that includes a ground segment, comprised of at least one user terminal and at least one terrestrial gateway, and a space segment, comprised of a plurality of satellites in a non-geosynchronous earth orbit, and further comprising:

a transmitter in said user terminal for transmitting an uplink signal simultaneously to at least two satellites of said space segment;

a receiver in each of the at least two satellites for receiving the uplink signal;

at least one first controller in said space segment for determining a plurality of difference values individual ones of which represent a difference between a received signal strength indication and a desired received signal strength indication for an individual one of the at least two satellites;

a second controller in said space segment that is responsive to the plurality of difference values for generating at least one power control command for use by said user terminal;

a transmitter in said space segment for transmitting the at least one generated power control command to the user terminal; and

means in said user terminal for adjusting a transmitted power of the uplink signal in accordance with the at least one power control command, wherein

said first and second controller are located in each of said at least two satellites and generate and cause to be transmitted, at first intervals, the at least one power control command, and further comprising, in a satellite that orbits at a higher altitude than said at least two satellites, a further first and second controller for generating an override power control command that is transmitted to said user terminal at second intervals, wherein the second intervals are longer than the first intervals.

19. A system as set forth in claim 18, wherein the at least two satellites are a portion of a constellation of low earth orbit satellites, and wherein the third satellite in one of a medium earth orbit or a geosynchronous earth orbit.

21. A satellite communications system, comprising:

a plurality of user terminals each having a transmitter and a receiver;

at least one gateway bidirectionally coupled to a terrestrial communications network;

a plurality of satellites in earth orbit, at least some of said satellites comprising means for receiving communication signals from said user terminals over communication paths and means for transmitting said received communications signals to said at least one gateway; and

a power control function distributed in said plurality of satellites for generating transmitter power control commands individually for said plurality of user terminals for compensating individual ones of said user terminals for communication path impairments;

wherein said power control function is implemented using at least one controller for determining a plurality of difference values individual ones of which represent a difference, at one of said plurality of satellites, between a received communication signal strength indication from a particular user terminal and a desired received communication signal strength indication, and wherein said at least one controller is responsive to the determined plurality of difference values for a particular one of the user terminals for generating an individual one of said transmitter power control commands for the particular user terminal.

22. A satellite communications system, comprising:

a plurality of user terminals each having a transmitter and a receiver;

at least one gateway bidirectionally coupled to a terrestrial communications network;

a plurality of satellites in earth orbit, at least some of said satellites comprising means for receiving communication signals from said user terminals over communication paths and means for transmitting said received communications signals to said at least one gateway; and

a power control function located in said plurality of satellites for generating transmitter power control commands individually for said plurality of user terminals for compensating individual ones of said user terminals for communication path impairments;

wherein said power control function is implemented using a controller in individual ones of said plurality of satellites for determining a difference value, at said individual one of said plurality of satellites, between an actual received communication signal from a particular user terminal and a desired received communication signal, wherein said controller is responsive to the determined difference value for a particular one of said user terminals for generating

a transmitter power control command for said particular user terminal and for delivering the transmitter power control command to said particular user terminal; and

wherein

said particular user terminal is responsive to a plurality of delivered transmitter power control commands for setting its transmitter power accordingly.