System and method for accurately predicting signal to interference and noise ratio to improve communications system performance

• US 6,426,971 B1
• Filed: 09/13/1999
• Issued: 07/30/2002
• Est. Priority Date: 09/13/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sindhushayna, Nagabhushana T., Black, Peter J., Wu, Qiang
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): PHU, PHUONG M
• Application Number:
  US09/394,980
• Time in Patent Office: 1,051 Days
• Field of Search: 375/227, 375/221, 375/222, 375/225, 375/285, 455/226.3
• US Class Current: 375/227
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 17/373 Predicting channel quality or other radio frequency [RF] parameters
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/002 Algorithms with memory of the previous states, e.g. Markovian models
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A system for providing an accurate prediction of a signal-to-interference noise ratio is described. The system includes a first circuit for receiving a signal transmitted across a channel via an external transmitter. A second circuit generates a sequence of estimates of signal-to-interference noise ratio based on the received signal. A third circuit determines a relationship between elements of the sequence of estimates. A fourth circuit employs the relationship to provide a signal-to-interference noise ratio prediction for a subsequently received signal. In the illustrative embodiment, the inventive system further includes a circuit for generating a data rate request message based on the signal-to-noise ratio prediction. A special transmitter transmits the data rate request message to the external transmitter. In the specific embodiment, the relationship between elements of the sequence of estimates is based on an average of the elements of the sequence of estimates. The third circuit includes a bank of filters for computing the average. The bank of filters includes finite impulse response filters. Coefficients of the transfer functions associated with each filter in the bank of filters are tailored for different fading environments. The different fading environments include different Rayleigh fading environments, one environment associated with a rapidly moving system, a second environment associated with a slow moving system, and a third system associated with a system moving at a medium velocity. A selection circuit is connected to each of the filter banks and selects an output from one of the filters in the filter bank. The selected output is associated with a filter having a transfer function most suitable to a current fading environment.

Claims

1. A method for receiving a signal comprising:

measuring the signal to form a sequence of consecutive signal-to-interference noise ratio estimates;

filtering said estimates according to each of a plurality of predetermined fading environments to form a plurality of sequences of signal-to-interference noise ratio predictions, wherein each of said plurality of sequences of signal-to-interference noise ratio predictions corresponds to one of said plurality of predetermined fading environments;

comparing each of said plurality of sequences of signal-to-interference noise ratio predictions to at least one signal-to-interference noise ratio estimate subsequent to said sequence to form a plurality of prediction errors, wherein each of said plurality of prediction errors corresponds to one of said plurality of predetermined fading environments;

forming a predicted signal-to-interference noise ratio based on said plurality of sequences of signal-to-interference noise ratio predictions and said plurality of prediction errors.

2. The method of claim 1 wherein said plurality of predetermined fading environments comprises a slow fading environment.

3. The method of claim 2 wherein said plurality of predetermined fading environments further comprises a fast fading environment.

4. The method of claim 1 wherein said plurality of predetermined fading environments comprises a fast fading environment.

5. The method of claim 1 wherein said filtering comprises performing an average of said estimates.

6. The method of claim 1 wherein said filtering comprises filtering said estimates in accordance with a finite impulse response filter.

7. The method of claim 1 wherein said filtering comprises filtering said estimates in accordance with an infinite impulse response filter.

8. The method of claim 7 wherein said filtering further comprises filtering said estimates in accordance with a finite impulse response filter.

9. The method of claim 1 wherein said forming a predicted signal-to-interference noise ratio comprises selecting one of said plurality of prediction errors.

10. The method of claim 1 further comprising adjusting said predicted signal-to-interference noise ratio by a back-off value.

11. The method of claim 10, wherein said back-off value is constant.

12. The method of claim 10 further comprising adjusting said back-off value in accordance with a changing signal environment.

13. An apparatus for receiving a signal comprising:

a signal-to-interference ratio circuit for measuring the signal to form a sequence of consecutive signal-to-interference noise ratio estimates;

a bank of filters for filtering said estimates according to each of a plurality of predetermined fading environments to form a plurality of sequences of signal-to-interference noise ratio predictions, wherein each of said plurality of sequences of signal-to-interference noise ratio predictions corresponds to one of said plurality of predetermined fading environments;

a prediction selector for comparing each of said plurality of sequences of signal-to-interference noise ratio predictions to at least one signal-to-interference noise ratio estimate subsequent to said sequence to form a plurality of prediction errors, wherein each of said plurality of prediction errors corresponds to one of said plurality of predetermined fading environments, and forming a predicted signal-to-interference noise ratio based on said plurality of sequences of signal-to-interference noise ratio predictions and said plurality of prediction errors.

14. The apparatus of claim 13 wherein said bank of filters comprises a slow fading signal-to-interference noise predictor.

15. The apparatus of claim 14 wherein said bank of filters further comprises a fast fading signal-to-interference noise predictor.

16. The apparatus of claim 14 wherein said bank of filters further comprises a hold filter predictor.

17. The apparatus of claim 13 wherein said bank of filters comprises a fast fading signal-to-interference noise predictor.

18. The apparatus of claim 13 wherein said bank of filters comprises a hold filter predictor.

19. The apparatus of claim 13 wherein said bank of filters comprises a finite impulse response filter.

20. The apparatus of claim 13 wherein said bank of filters comprises an infinite impulse response filter.

21. The apparatus of claim 20 wherein said bank of filters further comprises a finite impulse response filter.

22. The apparatus of claim 13 further comprising a back-off circuit for adjusting said predicted signal-to-interference noise ratio by a back-off value.

23. The apparatus of claim 22, wherein said back-off circuit is configured to provide a constant back-off value.

24. The apparatus of claim 22 wherein said back-off circuit is configured to adjust said back-off value in accordance with a changing signal environment.

25. A method for receiving a signal comprising:

means for measuring the signal to form a sequence of consecutive signal-to-interference noise ratio estimates;

means for filtering said estimates according to each of a plurality of predetermined fading environments to form a plurality of sequences of signal-to-interference noise ratio predictions, wherein each of said plurality of sequences of signal-to-interference noise ratio predictions corresponds to one of said plurality of predetermined fading environments;

means for comparing each of said plurality of sequences of signal-to-interference noise ratio predictions to at least one signal-to-interference noise ratio estimate subsequent to said sequence to form a plurality of prediction errors, wherein each of said plurality of prediction errors corresponds to one of said plurality of predetermined fading environments;

means for forming a predicted signal-to-interference noise ratio based on said plurality of sequences of signal-to-interference noise ratio predictions and said plurality of prediction errors.

26. The apparatus of claim 25 wherein said plurality of predetermined fading environments comprises means for filtering said estimates according to a slow fading environment.

27. The apparatus of claim 26 wherein said plurality of predetermined fading environments further comprises means for filtering said estimates according to a fast fading environment.

28. The apparatus of claim 25 wherein said plurality of predetermined fading environments comprises means for filtering said estimates according to a fast fading environment.

29. The apparatus of claim 25 wherein said filtering comprises means for performing an average of said estimates.

30. The apparatus of claim 25 wherein said filtering comprises filtering said estimates in accordance with a finite impulse response filter.

31. The apparatus of claim 25 wherein said filtering comprises an infinite impulse response filter.

32. The apparatus of claim 31 wherein said filtering further comprises a finite impulse response filter.

33. The apparatus of claim 25 wherein said means for forming comprises means for selecting one of said plurality of prediction errors.

34. The apparatus of claim 25 further comprising means for adjusting said predicted signal-to-interference noise ratio by a back-off value.

35. The apparatus of claim 34, wherein said means for adjusting is configured to apply a constant back-off value.

36. The apparatus of claim 34 further comprising means for adjusting said back-off value in accordance with a changing signal environment.