Method and apparatus for reducing frame error rate through signal power adjustment

• US 6,298,242 B1
• Filed: 07/22/1999
• Issued: 10/02/2001
• Est. Priority Date: 07/22/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Schiff, Leonard N.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): PEREZ GUTIERREZ, RAFAEL
• Application Number:
  US09/358,997
• Time in Patent Office: 803 Days
• Field of Search: 455/69, 455/522, 455/67.1, 455/67.3, 455/67.4, 455/67.5, 455/115
• US Class Current: 455/522
• 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 52/18 TPC being performed according to specific parameters
• CPC Class Codes: H04W 52/20 using error rate

Abstract

A method and apparatus for controlling a signal transmission power. The method of the present invention includes the steps of demodulating a received signal to produce a demodulated signal and distorting the demodulated signal to produce a distorted demodulated signal. The demodulated signal can be distorted by, for example, adding noise. A signal quality measurement, such as signal-to-noise ratio, is then determined based on the distorted demodulated signal rather than the demodulated signal. An adjustment in the transmission power is then requested based on the signal quality measurement of the distorted demodulated signal.

Claims

1. A method for controlling a signal transmission power, comprising the steps of:

(a) demodulating a received signal to produce a demodulated signal;

(b) distorting said demodulated signal to produce a distorted demodulated signal;

(c) determining a signal quality measurement based on said distorted demodulated signal which represents a value directly proportional to signal quality;

(d) requesting an adjustment in the transmission power based on said signal quality measurement comprising;

(i) comparing said determined signal quality measurement to a preselected threshold value; and

(ii) requesting an increase in transmission power if said signal quality measurement exceeds said threshold;

(e) decoding said demodulated signal to produce decision data;

(f) decoding said distorted demodulated signal to produce distorted decision data;

(g) determining a second signal quality measurement based on said distorted decision data; and

(h) adjusting said threshold based on said second signal quality measurement.

2. The method of claim 1, wherein the signal quality measurement represents a value inversely proportional to signal quality and step (d) comprises the steps of:

(i) comparing said determined signal quality measurement to a pre-selected threshold value; and

(ii) requesting a decrease in transmission power if said signal quality measurement exceeds said threshold.

3. The method of claim 2, wherein step (d) further comprises the step of:

(iii) requesting an increase in the transmission power if said signal quality measurement does not exceed said threshold.

4. The method of claim 1, wherein said signal is transmitted by a gateway and received by a user terminal via a satellite, and steps (a)-(d) are performed by the user terminal to control the transmission power at the gateway.

5. The method of claim 1, wherein said signal is transmitted by a base station and received by a user terminal, steps (a)-(d) are performed by the user terminal, and the transmission power at the base station is being controlled.

6. The method of claim 1, wherein said signal is transmitted by a user terminal and received by a gateway via a satellite, and steps (a)-(d) are performed by the gateway to control the transmission power at the user terminal.

7. The method of claim 1, wherein step (d) further comprises the step of:

(iii) requesting a decrease in the transmission power if said signal quality measurement does not exceed said threshold.

8. The method of claim 1, wherein said demodulated signal comprises soft decision data which reflects a measure of confidence of values of corresponding digits of the transmitted signal.

9. The method of claim 8, wherein step (b) comprises distorting said soft decision data to thereby reduce said measure of confidence.

10. The method of claim 1, wherein said signal is transmitted by a user terminal and received by a base station to control the transmission power at the user terminal.

11. The method of claim 1, wherein step (a) comprises correlating said received signal with a plurality of data values to produce said demodulated signal.

12. The method of claim 11, wherein step (a) further comprises quantizing said demodulated signal to produce a quantized demodulated signal, and wherein step (c) comprises determining said signal quality measurement based on said quantized demodulated signal.

13. The method of claim 1, wherein step (b) comprises adding noise to said demodulated signal to produce said distorted demodulated signal.

14. The method of claim 1, wherein step (c) comprises determining a signal-to-noise ratio of said distorted demodulated signal.

15. The method of claim 14, wherein step (d) comprises requesting said transmission power adjustment based on said signal-to-noise ratio.

16. The method of claim 1, further comprising the step of providing said decision data to digital baseband circuitry.

17. The method of claim 1, wherein said second signal quality measurement comprises a measure of frame error.

18. An apparatus for controlling a signal transmission power, comprising:

a demodulator for demodulating a received signal to produce a demodulated signal;

a decoder for decoding said demodulated signal to produce decision data;

a distorter for distorting said demodulated signal to produce a distorted demodulated signal;

a virtual decoder for decoding said distorted demodulated signal to produce distorted decision data;

a signal quality estimator for determining a first signal quality measurement based on said distorted demodulated signal which represents a value directly proportional to signal quality;

an error detector for determining a second signal quality measurement based on said distorted decision data; and

a power command generator for requesting an adjustment in the transmission power based on said first signal quality measurement by comparing it to a threshold and requesting an increase in the transmission power if the first signal quality measurement exceeds said threshold.

19. The apparatus of claim 18, wherein said signal is transmitted by a user terminal and received by a gateway via a satellite, wherein said demodulator, said distorter, said signal quality estimator, and said power command determiner are components of the gateway, and wherein the transmission power at the user terminal is being controlled.

20. The apparatus of claim 18, wherein said signal is transmitted by a gateway and received by a user terminal via a satellite, wherein said demodulator, said distorter, said signal quality estimator, and said power command determiner are components of the user terminal, and wherein the transmission power at the gateway is being controlled.

21. The apparatus of claim 18, wherein said signal is transmitted by a base station and received by a user terminal, wherein said demodulator, said distorter, said signal quality estimator, and said power command generator are components of the user terminal, and wherein the transmission power at the base station is being controlled.

22. The apparatus of claim 18, wherein the signal quality measurement represents a value inversely proportional to signal quality and said power command generator compares said signal quality measurement to a threshold and requests a decrease in the transmission power if said signal quality measurement exceeds said threshold.

23. The apparatus of claim 22, wherein said power command generator requests an increase in the transmission power if said signal quality measurement does not exceed said threshold.

24. The apparatus of claim 18, wherein said power command generator requests a decrease in the transmission power if said first signal quality measurement does not exceed said threshold.

25. The apparatus of claim 18, wherein said demodulator comprises a correlator for correlating said received signal with a plurality of data values to produce said demodulated signal.

26. The apparatus of claim 25, further comprising a quantizer for quantizing the output of said correlator to produce a quantized demodulated signal and wherein said signal quality estimator determines said signal quality measurement based on said quantized demodulated signal.

27. The apparatus of claim 18, wherein said demodulated signal comprises soft decision data which reflects a measure of confidence of values of corresponding digits of the transmitted signal.

28. The apparatus of claim 27, wherein said distorter distorts said soft decision data to thereby reduce said measure of confidence.

29. The apparatus of claim 18, wherein said signal is transmitted by a user terminal and received by a base station, and the transmission power at the user terminal is being controlled.

30. The apparatus of claim 18, wherein said second signal quality measurement determined by said error detector is a measure of frame error.

31. The apparatus of claim 18, further comprising means for adjusting said threshold based on said second signal quality measurement.

32. The apparatus of claim 18, wherein said signal quality measurement comprises signal-to-noise ratio.

33. The apparatus of claim 32, wherein said power command determiner requests said adjustment based on said signal-to-noise ratio.

34. The apparatus of claim 18, wherein said decision data is provided to digital baseband circuitry.

35. The apparatus of claim 18, wherein said distorter adds noise to said demodulated signal.