Interference resistant satellite link power control using uplink noise measurements

1. A method for determining an effective isotropic radiated power (EIRP) adjustment for user terminals in a satellite communications system, the method comprising:

determining a return uplink thermal noise estimate at a gateway, the return uplink thermal noise estimate determined at each of a plurality of different frequencies using total power measurements;

obtaining a target return uplink signal density relative to thermal noise density based on end to end link characteristics and off-axis emissions from the user terminals;

determining a target signal power at a gateway in the satellite communications system for one or more frequency channels, the target signal power based at least in part on the return uplink thermal noise and the target return uplink signal density relative to the thermal noise density;

obtaining a message signal power at the gateway of one or more messages from a user terminal, the message signal power determined by a demodulator at the gateway; and

determining the EIRP adjustment for the user terminal based at least in part on a difference between the target signal power and the message signal power.

2. The method of claim 1 further comprising obtaining an automatic gain control of one or more demodulators at the gateway and obtaining a satellite beacon signal power at a beacon receiver of the gateway, wherein the target signal power is based at least in part on the return uplink thermal noise, the target return uplink signal density relative to the thermal noise density, the satellite beacon signal power, and the automatic gain control of the one or more demodulators.

3. The method of claim 1 further comprising sending the EIRP adjustment to the user terminal.

4. The method of claim 1 wherein obtaining the message signal power comprises measuring a signal power of the one or more message at the gateway.

5. The method of claim 1 wherein the return uplink thermal noise is determined at a specified frequency during a time period in which there are no transmissions in the satellite communications system at the specified frequency.

6. The method of claim 1 wherein the return uplink thermal noise is determined at a plurality of frequencies within a return channel group.

7. The method of claim 1 wherein determining the return uplink thermal noise comprises performing a series of total power measurements and determining a minimum total power measurement from the series.

8. The method of claim 1 wherein the target signal power is based at least in part on a channel symbol rate.

9. A method for controlling power of return link transmissions in a satellite communications system, the method comprising:

obtaining a return uplink thermal noise estimate at one or more frequencies, the return uplink thermal noise estimate based at least in part on a total power measurement from a series of total power measurements;

obtaining a target return uplink signal density relative to thermal noise density;

determining a target signal power at a gateway for one or more frequency channels, the target signal power based at least in part on the return uplink thermal noise estimate and the target return uplink signal density relative to thermal noise density;

obtaining a message signal power at the gateway of a message from a user terminal; and

determining an EIRP of the user terminal based at least in part on a difference between the target signal power and the message signal power.

10. The method of claim 9 further comprising sending the EIRP to the user terminal.

11. The method of claim 9 wherein the series of total power measurements are obtained during a specified time period.

12. The method of claim 9 wherein the total power measurement is a minimum of the total power measurements.

13. The method of claim 9 wherein the total power measurement is statistically near a minimum of the total power measurements.

14. An apparatus for determining an effective isotropic radiated power (EIRP) adjustment for user terminals in a satellite communications system, comprising:

an obtaining module comprising hardware configured to:

obtain a return uplink thermal noise estimate at a gateway, the return uplink thermal noise estimate obtained at each of a plurality of different frequencies using total power measurements;

obtaining a target return uplink signal density relative to thermal noise density based on end to end link characteristics and off-axis emissions from the user terminals; and

obtain a message signal power at a gateway in the satellite communications system of a message from a user terminal;

a determining module comprising hardware configured to:

determine a target signal power at the gateway based at least in part on the return uplink thermal noise estimate and the target return uplink signal density relative to thermal noise density; and

determine the EIRP adjustment for the user terminal based at least in part on a difference between the target signal power and the message signal power.

15. The apparatus of claim 14 further comprising a sending module configured to send the EIRP adjustment to the user terminal.

16. The apparatus of claim 14 wherein the obtaining module is further configured to obtain a satellite beacon signal power at a beacon receiver of the gateway, and the determining module is further configured to determine the target signal power at the gateway for one or more frequency channels based at least in part on the return uplink thermal noise estimate, the satellite beacon signal power, and the target return uplink signal density relative to thermal noise density.

17. The apparatus of claim 14 wherein the obtaining module is configured to obtain the return uplink thermal noise estimate at a specified frequency during a time period in which there are no transmissions in the satellite communications system at the specified frequency.

18. The apparatus of claim 14 wherein the obtaining module is configured to obtain the return uplink thermal noise estimate from a series of total power measurements.