Clear sky determination in uplink power control using dual time constants

1. A machine-implemented method for determining clear sky in uplink power control, the method comprising:

receiving, by a receiver at a receiving station, a reference signal from a satellite, the receiving station being either a satellite terminal or a satellite gateway;

computing, by a component of the receiver, a filtered short-term average downlink signal-to-noise-plus-interference ratio based on samples of the received reference signal over a sampling time period;

estimating, by the component of the receiver, a downlink fade based on a filtered long-term average downlink signal-to-noise-plus-interference ratio and the filtered short-term average downlink signal-to-noise-plus-interference ratio;

when the estimated downlink fade is greater than zero, adjusting, by the receiver, the filtered long-term average downlink signal-to-noise-plus-interference ratio toward the filtered short-term average downlink signal-to-noise-plus-interference ratio based, at least partly, on a value of a first time constant;

when the estimated downlink fade is less than zero, adjusting, by the receiver, the filtered long-term average downlink signal-to-noise-plus-interference ratio toward the filtered short-term average downlink signal-to-noise-plus-interference ratio based, at least partly, on a value of a second time constant, the value of the second time constant being a different value from the value of the first time constant; and

adjusting, by the receiving station, the uplink power control based on the adjusted filtered long-term average downlink signal-to-noise-plus interference ratio and the filtered short-term average downlink signal-to-noise-plus-interference ratio, wherein:

when the estimated downlink fade is greater than zero, the adjusting causes the filtered long-term average downlink signal-to-noise-plus-interference ratio to converge toward the filtered short-term average downlink signal-to-noise-plus interference ratio at a first rate, and

when the estimated downlink fade is less than zero, the adjusting causes the filtered long-term average downlink signal-to-noise-plus-interference ratio to converge toward the filtered short-term average downlink signal-to-noise-plus interference ratio at a second rate that is different from the first rate.

2. The machine-implemented method of claim 1 , wherein the reference signal received by the receiving station is held at a constant power level.

3. The machine-implemented method of claim 1 , wherein the value of the second time constant is less than the value of the first time constant.

4. The machine-implemented method of claim 1 , wherein the adjusting of the filtered long-term average downlink signal-to-noise-plus-interference ratio is performed by an application specific integrated circuit of the receiver.

5. The machine-implemented method of claim 1 , wherein:

the adjusting the long-term average downlink signal-to-noise-plus-interference ratio toward the filtered short-term average downlink signal-to-noise-plus-interference ratio based, at least partly, on a value of a first time constant further comprises:

[

C

N

+

I

⁢

(

+

)

]

DL

l_avg

=

α

l_avg

⁢

_dn

·

[

C

N

+

I

⁢

(

-

)

]

DL

l_avg

+

(

1

-

α

l_avg

⁢

_dn

)

·

[

C

N

+

I

⁢

(

+

)

]

DL

D

l_avg

,

where the α l _ avg _ dn is a first coefficient, the

[

C

N

+

I

⁢

(

-

)

]

DL

l_avg

is a last computed value of the long-term average downlink signal-to-noise-plus-interference ratio, the

[

C

N

+

I

⁢

(

+

)

]

DL

D

l_avg

is a current value of the filtered short-term average downlink signal-to-noise-plus-interference ratio, the

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

l_avg

is an updated value the long-term average downlink signal-to-noise-plus-interference ratio, D l _ avg is a decimation rate with respect to sampling of the reference signal, and the DL refers to a downlink; and

the adjusting the long-term average downlink signal-to-noise-plus-interference ratio toward the filtered short-term average downlink signal-to-noise-plus-interference ratio based, at least partly, on a second time constant further comprises:

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

l_avg

=

α

l_avg

⁢

⁢

_up

·

[

C

N

⁢

+

⁢

I

⁢

⁢

(

-

)

]

DL

l_avg

+

(

1

-

α

l_avg

⁢

⁢

_up

)

·

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

D

l_avg

,

where α l _ avg _ up is a second coefficient.

6. The machine-implemented method of claim 5 , wherein:

the

α

l_avg

⁢

_dn

=

1

-

t

s

·

D

l_avg

τ

l_avg

⁢

_dn

,

where the t s is a sampling time, the D l _ avg is a long-term decimation rate, and the τ l _ avg _ dn is the first time constant, and

the

α

l_avg

⁢

_up

=

1

-

t

s

·

D

l_avg

τ

l_avg

⁢

_up

,

where τ l _ avg _ up is the second time constant.

7. The machine-implemented method of claim 1 , wherein:

the receiving station is the satellite terminal, and

the reference signal is a signal which conforms to a DVB-S standard, a DVB-S2X standard, or a DVB-S2 standard.

8. The machine-implemented method of claim 1 , wherein:

the receiving station is the satellite terminal, and

the reference signal is a beacon signal from the satellite.

9. The machine-implemented method of claim 1 , wherein:

the receiving station is the satellite gateway, and

the reference signal is a beacon signal from the satellite.

10. An uplink power control system for use in a satellite terminal or a satellite gateway, the uplink power control system comprising:

a receiving station operable to transmit uplink signals to and receive downlink signals from a satellite and comprising a programmable processing device or an application specific integrated circuit, the receiving station being either the satellite terminal or the satellite gateway;

the programmable processing device or the application specific integrated circuit produces a value of a filtered short-term average downlink signal-to-noise-plus-interference ratio based on samples of a reference signal over a sampling time period, the processing device or the application specific integrated circuit updates a value of a filtered long-term average downlink signal-to-noise-plus-interference ratio based on the value of the filtered short-term average downlink signal-to-noise-plus-interference ratio;

a power control module adjusts transmit power for the uplink signals based on the updated value of the filtered long-term average downlink signal-to-noise-plus-interference ratio and the filtered short-term average downlink signal-to-noise-plus-interference ratio received from the processing device or the application specific integrated circuit, wherein:

when the value of the filtered long-term average downlink signal-to-noise-plus-interference ratio is greater than the value of the filtered short-term average downlink signal-to-noise-plus-interference ratio, the programmable processing device or the application specific integrated circuit adjusts the filtered long-term average downlink signal-to-noise-plus-interference ratio toward the filtered short-term average downlink signal-to-noise-plus-interference ratio at a first rate based on a first time constant, and

when the value of the filtered long-term average downlink signal-to-noise-plus-interference ratio is not greater than or equal to the value of the filtered short-term average downlink signal-to-noise-plus-interference ratio, the programmable processing device or the application specific integrated circuit adjusts the filtered long-term average downlink signal-to-noise-plus-interference ratio toward the filtered short-term average downlink signal-to-noise-plus-interference ratio at a second rate based on a second time constant, a value of the second time constant being different from a value of the first time constant and the first rate being different from the second rate.

11. The uplink power control system of claim 10 , wherein the second rate is faster than the first rate.

12. The uplink power control system of claim 10 , wherein:

the receiving station is a satellite terminal,

the reference signal received by the satellite terminal is held at a constant power level and conforms to a DVB-S standard, a DVB-S2 standard or a DVB-S2X standard, and

the reference signal originates from a satellite gateway and is repeated by the satellite.

13. The uplink power control system of claim 10 , wherein:

the receiving station is a satellite terminal, and

the reference signal received by the satellite terminal is held at a constant power level and is a beacon signal received from the satellite.

14. The uplink power control system of claim 13 , wherein the beacon signal is generated by the satellite.

15. The uplink power control system of claim 10 , wherein:

when the filtered long-term average downlink signal-to-noise-plus-interference ratio is greater than the filtered short-term average downlink signal-to-noise-plus-interference ratio, the programmable processing device or the application specific integrated circuit adjusts the filtered long-term average downlink signal-to-noise-plus-interference ratio according to:

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

l_avg

=

α

l_avg

⁢

⁢

_dn

·

[

C

N

⁢

+

⁢

I

⁢

⁢

(

-

)

]

DL

l_avg

+

(

1

-

α

l_avg

⁢

⁢

_dn

)

·

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

D

l_avg

,

where the α l _ avg _ dn is a first coefficient, the

[

C

N

⁢

+

⁢

I

⁢

⁢

(

-

)

]

DL

l_avg

is a last computed value of the filtered long-term average downlink signal-to-noise-plus-interference ratio, the

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

D

l_avg

is a current value of the filtered short-term average downlink signal-to-noise-plus-interference ratio, the

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

l_avg

is an updated value of the filtered long-term average downlink signal-to-noise-plus-interference ratio, the D l _ avg is a decimation rate, and the DL refers to a downlink, and

when the filtered long-term average downlink signal-to-noise-plus-interference ratio is not greater than the filtered short-term average downlink signal-to-noise-plus-interference ratio, the programmable processing device or the application specific integrated circuit adjusts the filtered long-term average downlink signal-to-noise-plus-interference ratio according to:

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

l_avg

=

α

l_avg

⁢

⁢

_up

·

[

C

N

⁢

+

⁢

I

⁢

⁢

(

-

)

]

DL

l_avg

+

(

1

-

α

l_avg

⁢

⁢

_up

)

·

[

C

N

⁢

+

⁢

I

⁢

⁢

(

+

)

]

DL

D

l_avg

,

where α l _ avg _ up is a second coefficient.

16. The uplink power control system of claim 15 , wherein:

the

α

l_avg

⁢

_dn

=

1

-

t

s

·

D

l_avg

τ

l_avg

⁢

_dn

,

where the τ s is a sampling time, the D l _ avg is the decimation rate, and the τ l _ avg _ dn is the first time constant, and

the

α

l_avg

⁢

_up

=

1

-

t

s

·

D

l_avg

τ

l_avg

⁢

_up

,

where τ l _ avg _ up is the second time constant, the second time constant being less than the first time constant.

17. The uplink power control system of claim 10 , wherein:

the receiving station is a satellite terminal,

and the reference signal is either a beacon signal or a signal conforming to a standard from a group of standards consisting of a DVB-S standard, a DVB-S2X standard, and a DVB-S2 standard.

18. The uplink power control system of claim 10 , wherein:

the receiving station is a satellite gateway, and

the reference signal is a beacon signal from the satellite.

19. The uplink power control system of claim 10 , wherein:

the receiving station is a satellite gateway,

the reference signal is a beacon signal from the satellite, and

the beacon signal is held at a constant power level by the satellite.

20. The uplink power control of claim 19 , wherein the beacon signal originates from the satellite.