System and method for estimating noise power level in a multi-signal communications channel

• US 7,555,064 B2
• Filed: 08/27/2007
• Issued: 06/30/2009
• Est. Priority Date: 08/27/2007
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Beadle, Edward R.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US11/845,186
• Publication Number:
  US 20090060015A1
• Time in Patent Office: 673 Days
• Field of Search: 375/130, 375/136, 375132-134, 375/147, 375/150, 375/152, 375/340, 375/343, 375/354, 375362-368, 375/285, 375/346, 375/140, 375143-145, 375/148, 375/316, 370504-515
• US Class Current: 375/316
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/206 for modulated signals

Abstract

A system estimates noise power in a scalar, multi-signal communications channel. A data sampler collects N data samples from communications signals received from the communications channel. A module forms a covariance matrix of the N data samples based on a model order estimate. A module also computes the eigenvalue decomposition of the covariance matrix and ranks resultant eigenvalues from the minimum to the maximum for determining the noise power.

Claims

1. A system of estimating noise power in a scalar, multi-signal communications channel, comprising:

a data sampler for collecting N data samples from communications signals received from the communications channel;

a module for forming a temporal covariance matrix of the N data samples based on a model order estimate; and

a noise power estimator module for computing the eigenvalue decomposition of the temporal covariance matrix and ranking resultant eigenvalues from the minimum to the maximum for determining the noise power and setting a noise threshold based on an input signal using said temporal covariance matrix that is formed of N data samples of the signal input based on said model order estimate.

2. The communications system according to claim 1, and further comprising a module for estimating the model order based on a number to overbound a maximum possible number of possible individual signals from a transmitter.

3. The communications system according to claim 1, and further comprising a module for estimating the model order based on one of at least a Multiple Signal Classifier, Pisarenko Harmonic Decomposition, Auto-regression, Pade Approximation, Bayesian Information Criterion, Akaike'"'"'s Information Criterion and Minimum Description Length algorithm.

4. The communications system according to claim 1, and further comprising a receiver having a signal input for receiving the communications signal having data and synchronization pulses over a scalar, multi-signal communications channel, a first filter matched to a synchronization pulse, a second filter inversely matched to the synchronization pulse, a detector that determines the synchronization pulse based on outputs from the first and second filters, wherein said noise power estimator is coupled to the detector and estimates the noise power and sets a noise threshold based on the input signal using a covariance matrix that is formed of the N data samples of the signal input based on the model order estimate.

5. The communications system according to claim 4, and further comprising an integrator coupled to an output of at least one of first and second filters for integrating samples accumulated by the first and second filters over N observation intervals.

6. The communications system according to claim 5, and further comprising a constant false alarm rate (CFAR) detector coupled to the noise power estimator and integrator for comparing samples to the noise threshold.

7. The communications system according to claim 6, wherein said CFAR detector comprises a processor for processing a control parameter of said CFAR detector in accordance with a priori knowledge of information that is extrinsic to the receiver.

8. The communications system according to claim 4, wherein said first filter comprises a matched filter and said second filter comprises an orthogonal filter.

9. A receiver comprising:

a signal input for receiving a communications signal having data and synchronization pulses over a scalar, multi-signal communications channel;

a first filter matched to a synchronization pulse;

a second filter inversely matched to the synchronization pulse;

a detector that determines the synchronization pulse based on outputs from the first and second filters; and

a noise power estimator coupled to the detector for estimating the noise power and setting a noise threshold based on the input signal using a covariance matrix that is formed of the N data samples of the signal input based on a model order estimate.

10. The receiver according to claim 9, wherein said noise power estimator is operative for computing the eigenvalue decomposition of the covariance matrix and ranking resultant eigenvalues from a minimum to a maximum for determining the noise power.

11. The receiver according to claim 9, wherein said noise power estimator is operative for selecting a number to overbound a maximum number of possible individual signals from a transmitter.

12. The receiver according to claim 9, wherein said noise power estimator is operative for estimating a model order using one of at least a Multiple Signal Classifier, Pisarenko Harmonic Decomposition, Auto-regression, Pade Approximation, Bayesian Information Criterion, Akaike'"'"'s Information Criterion and Minimum Description Length algorithm.

13. The receiver according to claim 9, and further comprising an integrator coupled to an output of at least one of first and second filters for integrating samples accumulated by the first and second filters over N observation intervals.

14. The receiver according to claim 13, and further comprising a constant false alarm rate (CFAR) detector coupled to the noise power estimator and integrator for comparing samples to the noise threshold.

15. The receiver according to claim 14, wherein said CFAR detector comprises processor for processing a control parameter of said CFAR detector in accordance with a priori knowledge of information that is extrinsic to the receiver.

16. The receiver according to claim 9, wherein said first filter comprises a matched filter and said second filter comprises an orthogonal filter.

17. A method of estimating noise power in a scalar, multi-signal, communications channel, comprising:

collecting within a data sampler N data samples from communications signals received within the communications channel;

forming a temporal covariance matrix of the N data samples based on a model order estimate;

computing the eigenvalue decomposition of said temporal covariance matrix within a noise power estimator module to obtain eigenvalues; and

ranking the eigenvalues from the minimum to the maximum for determining the noise power and setting the noise threshold based on said temporal covariance matrix and said model order estimate.

18. The method according to claim 17, which further comprises forming the covariance matrix using single channel data.

19. The method according to claim 17, which further comprises averaging the smallest eigenvalues for determining the noise power.

20. The method according to claim 19, which further comprises using the mean or median for determining the noise power.

21. The method according to claim 17, which further comprises estimating a model order by selecting a number to overbound a maximum number of possible individual signals on a transmitter.

22. The method according to claim 17, which further comprises estimating a model order using data based techniques.

23. The method according to claim 17, which further comprises estimating a model order using one of at least a Multiple Signal Classifier, Pisarenko Harmonic Decomposition, Auto-regression, Pade Approximation, Bayesian Information Criterion, Akaike'"'"'s Information Criterion and Minimum Description Length algorithm.

24. The method according to claim 17, which further comprises forming a covariance matrix having a limited dimension greater than the number of expected signals.

25. The method according to claim 24, which further comprises choosing an extra dimension corresponding to the noise dimension.

26. A method of estimating noise power in a scalar, multi-signal, communications channel, comprising:

collecting within a data sampler N data samples from communications signals received within the communications channel;

forming a covariance matrix of the N data samples based on a model order estimate and having a limited dimension greater than the number of expected signals;

computing the eigenvalue decomposition of the covariance matrix within a noise power estimator module to obtain eigenvalues; and

ranking the eigenvalues from the minimum to the maximum for determining the noise power.