Closed-loop power control apparatus for mobile satellite communication system and method thereof

• US 7,254,117 B2
• Filed: 10/21/2002
• Issued: 08/07/2007
• Est. Priority Date: 10/20/2001
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Soo-Young, Lim, Kwang-Jae, Choi, Kwon-Hue
• Primary Examiner(s): Nguyen; Lee
• Application Number:
  US10/493,158
• Publication Number:
  US 20040246928A1
• Time in Patent Office: 1,751 Days
• Field of Search: 370/318, 370/335, 370/342, 455/69, 455/522
• US Class Current: 370/318
• 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

Abstract

Apparatus and method for closed-loop power control in mobile satellite communication system, which can compensate round trip delay. The apparatus for closed-loop power control includes the means of; a) converting power control order from base earth station into power control step; b) measuring channel change rate from power of pilot channel; c) making tab coefficient using said channel change rate; d) compensating channel change due to loop delay using power control step; and e) renovating received signal power using said power control step.

Claims

1. A closed-loop power control apparatus that can compensate for round trip delay (RTD) in an up-link satellite channel of a satellite Code Division Multiple Access (SAT-CDMA) mobile communication system, the apparatus comprising:

a power control level determining means for determining a power control level based on a power control command transmitted from a base station;

a channel variation rate estimation means for estimating a channel variation rate based on received power of a pilot channel;

a filter coefficient generation means for generating a filter coefficient by using the channel variation rate;

a compensation means for receiving the power control level and compensating for the channel variation caused by the round trip delay; and

a transmit power updating means for updating transmit power by using the power control level received from the compensation means.

2. The apparatus as recited in claim 1, wherein the transmit power updating means includes:

a sample delay means for delaying the output of the compensation means by 1 sample substantially; and

an adding means for adding the output of the compensation means and the output of the sample delay means.

5. The apparatus as recited in claim 1 or 3, wherein the channel variation rate estimation means includes:

a first delay means for receiving the pilot channel power and delaying the pilot channel power by m sample, m being a natural number;

a first computing means for calculating a gradient of the pilot channel power based on the pilot channel power and the output of the first delay means;

a sign alteration detection means for detecting sign alteration of the output of the first computing means;

a comparison means for comparing the sign of the output of the sign alteration detection means and the sign of an output which is n sample before the output of the sign alteration detection means, n being a natural number, and outputting a comparison result;

a mean estimation means for estimating a mean value of the signal alteration of the gradient of the pilot channel power during a w sample period, w being a natural number; and

a second computing means for calculating a channel variation rate based on the output of the mean estimation means.

6. The apparatus as recited in claim 5, wherein the first computing means calculates the gradient of the pilot channel power by subtracting the output of the first delay means from the pilot channel power.

7. The apparatus as recited in claim 5, wherein the sign alteration detection means detects alteration in the sign of the output of the first computing means based on an equation as:

$\begin{array}{cc}\mathrm{Sign}<br><br>\left(x\right)=1,& x><br><br>0\\ 0,& \mathrm{otherwise}.\end{array}$

8. The apparatus as recited in claim 5, wherein the comparison means compares the sign of the output of the sign alteration detection means and the sign of an output n sample before the output of the sign alteration detection means, and if the both are the same, outputs ‘

1’

, or if the both are not the same, outputs ‘

0’

.

9. The apparatus as recited in claim 8, wherein the larger the correlation value of the sign alteration of the continued gradient of the pilot channel becomes, the more ‘

1’

is outputted from the comparison means.

10. The apparatus as recited in claim 5, wherein the mean estimation means estimates the mean of the output of the comparison means during a w sample period.

11. The apparatus as recited in claim 10, wherein the second computing means subtracts 0.5 from the output of the mean estimation means substantially.

12. The apparatus as recited in claim 5, wherein the mean estimation means estimates the number of ‘

1’

outputted from the comparison means during a w sample period.

13. The apparatus as recited in claim 12, wherein the second computing means subtracting w/2 from the output of the mean estimation means.

14. The apparatus as recited in claim 1 or 3, wherein the compensation means and the channel variation amount estimation means include:

a first filter for feedforward;

a second filter for feedback; and

a third computing means for calculating the output of the power control level determining means and the output of the second filter.

15. The apparatus as recited in claim 14, wherein the first and second filters are discrete linear filters.

16. The apparatus as recited in claim 15, wherein the first and second filters are finite impulse response (FIR) filters.

17. The apparatus as recited in claim 14, wherein if the first filter has two tabs, the filter coefficients are generated based on an equation as:

$\mathrm{Tab}<br><br><br><br>1=\{\begin{array}{cc}\mathrm{Gp}<br><br><br><br>1& \mathrm{if}<br><br><br><br>\mathrm{channel}<br><br><br><br>\mathrm{alteration}<br><br><br><br>\mathrm{rate}><br><br>T\\ 1& \mathrm{otherwise}\end{array}<br><br><br><br>\mathrm{Tab}<br><br><br><br>2=\{\begin{array}{cc}-\mathrm{Gp}<br><br><br><br>2& \mathrm{if}<br><br><br><br>\mathrm{channel}<br><br><br><br>\mathrm{alteration}<br><br><br><br>\mathrm{rate}><br><br>T\\ 1& \mathrm{otherwise},\end{array}$

wherein Gp1 and Gp2 are gains of the first filter, and T is a threshold of the channel variation rate.

18. The apparatus as recited in claim 14, wherein the filter coefficient of the second filter is 0 substantially.

19. The apparatus as recited in claim 1 or 3, wherein the filter coefficient generation means generates an optimum filter coefficient based on the channel variation rate in a pre-stored memory table.

3. A closed-loop power control apparatus that can compensate for round trip delay (RTD) in a down-link satellite channel of a SAT-CDMA mobile communication system, the apparatus comprising:

a power error computing means for calculating a power error of a received signal;

a channel variation rate estimation means for estimating a channel variation rate based on received power of a pilot channel;

a filter coefficient generation means for generating a filter coefficient by using the channel variation rate;

a channel variation amount estimation means for estimating a channel variation amount after a loop delay time;

a power error compensation means for compensating for the power error by using the output of the channel variation rate estimation means; and

a power control command generation means for generating a power control command based on the compensated power error.

4. The apparatus as recited in claim 3, wherein the power error computing means calculates the difference between a signal-to-interference ratio (SIR) of the received signal and a reference SIR.

20. A closed-loop power control method that can compensate for round trip delay (RTD) in an up-link satellite channel of a SAT-CDMA mobile communication system, the method comprising the steps of:

a) receiving power of a pilot channel and a power control command;

b) estimating a channel variation rate from the pilot channel power and generating a filter coefficient based on the channel variation rate; and

c) compensating transmit power by using the filter coefficient.

21. The method as recited in claim 20, further comprising the step of:

d) updating the transmit power.

22. A closed-loop power control method that can compensate for round trip delay (RTD) in a down-link satellite channel of a SAT-CDMA mobile communication system, the method comprising the steps of:

a) receiving power of a pilot channel and a signal-to-interference ratio of a received signal;

b) estimating a channel variation rate based on the pilot channel power and generating a filter coefficient based on the channel variation rate; and

c) compensating a power error based on the filter coefficient.

23. The method as recited in claim 22, further comprising the step of:

d) calculating the power error based on the received SIR.

24. The method as recited in claim 22, further comprising the step of:

d) generating a power control command based on the compensated power error.

25. A computer-readable recording medium for recording a program that implements a closed-loop power control method which can compensate for round trip delay in an up-link satellite channel of a SAT-CDMA mobile communication system, the method comprising the steps of:

a) receiving power of a pilot channel and a power control command;

b) estimating a channel variation rate from the pilot channel power and generating a filter coefficient based on the channel variation rate; and

c) compensating transmit power by using the filter coefficient.

26. A computer-readable recording medium provided with a processor for recording a program that implements a closed-loop power control method which can compensate for round trip delay in a down-link satellite channel of a SAT-CDMA mobile communication system, the method comprising the steps of:

a) receiving power of a pilot channel and a signal-to-interference ratio of a received signal;

b) estimating a channel variation rate from the pilot channel power and generating a filter coefficient based on the channel variation rate; and

c) compensating a power error based on the filter coefficient.