Crosstalk identification for spectrum management in broadband telecommunications systems
View Patent ↗Crosstalk between subscriber loops used to transmit different broadband services through the same bundled telephone cable is a significant limitation to providing digital subscriber line services. A method for estimating the crosstalk, identifying the sources of the crosstalk and predicting additional sources of crosstalk are disclosed. The crosstalk sources are identified in the frequency domain by maximizing the correlation with a “basis set” of received crosstalk PSDs which consist of the cascade of a finite set of known transmit PSDs types times a representative set of crosstalk couplings. Multiple crosstalk types are identified with a technique of successive spectral subtraction. Once a type is identified the crosstalk disturber is compared against all other members of the complete set for that type. Additionally, Multiple Regression (MR) techniques and a Matching Pursuit (MP) algorithm are used to increase the ability of the system and method to identify various crosstalk disturbers. The identification of the crosstalk disturber is then used to perform crosstalk cancellation and spectrum management in a DSL system.
1. A method comprising:
measuring a power spectral density on a subscriber loop;
using a processor to correlate the power spectral density for said subscriber loop with a predetermined set of power spectral densities for a group of possible crosstalk disturbers;
selecting a crosstalk disturber, from the group of possible crosstalk disturbers, having the most closely correlated power spectral density; and,
refining the selection of the crosstalk disturber using a matching pursuit (MP) algorithm.
2. The method of claim 1 further comprising:
subtracting the power spectral density for the refined crosstalk disturber from the measured power spectral density of said subscriber loop using spectral subtraction to generate a residual power spectral density;
correlating the residual power spectral density with the predetermined set of power spectral densities for the group of possible crosstalk disturbers;
selecting an another crosstalk disturber having the most closely correlated power spectral density to the residual power spectral density, and
refining the selection of the another crosstalk disturber using the matching pursuit (MP) algorithm.
3. The method of claim 2 wherein subtracting, correlating the residual power spectral density, selecting the another crosstalk disturber, and refining the selection of the another crosstalk disturber are iteratively performed until a stopping criterion is reached.
4. The method of claim 3 wherein the stopping criterion is a predetermined correlation threshold.
5. The method of claim 2 wherein negative power spectral densities resulting from said subtracting are mapped into a non-negative value.
6. The method of claim 1 further comprising sending the identity of the selected crosstalk disturber to a system for broadband spectrum management.
7. The method of claim 1 further comprising sending an estimated pair-to-pair coupling of the selected crosstalk disturber to a system for broadband spectrum management.
8. A method comprising:
measuring a power spectral density of on a subscriber loop;
using a processor to correlate the power spectral density for said subscriber loop with a predetermined set of power spectral densities for a group of possible crosstalk disturbers;
selecting a crosstalk disturber, from the group of possible crosstalk disturbers, having the most closely correlated power spectral density; and,
refining the selection of the crosstalk disturber using a FOCal Undetermined Problem Solver (FOCUSS).
9. The method of claim 8 further comprising:
subtracting the power spectral density for the refined crosstalk disturber from the measured power spectral density of said subscriber loop using spectral subtraction to generate a residual power spectral density;
correlating the residual power spectral density with the predetermined set of power spectral densities for the group of possible crosstalk disturbers;
selecting an another crosstalk disturber having the most closely correlated power spectral density to the residual power spectral density, and
refining the selection of the another crosstalk disturber using the FOCal Undetermined Problem Solver (FOCUSS).
10. The method of claim 9 wherein subtracting, correlating the residual power spectral density, selecting the another crosstalk disturber, and refining the selection of the another crosstalk disturber are iteratively performed until a stopping criterion is reached.
11. The method of claim 10 wherein the stopping criterion is a predetermined correlation threshold.
12. The method of claim 9 wherein negative power spectral densities resulting from said subtracting step are mapped into a non-negative value.
13. The method of claim 8 further comprising sending the identity of the selected crosstalk disturber to a system for broadband spectrum management.
14. The method of claim 8 further comprising sending an estimated pair-to-pair coupling of the selected crosstalk disturber to a system for broadband spectrum management.
15. A method comprising:
measuring a power spectral density of noise present on a subscriber loop;
matching the power spectral density for said subscriber loop with a predetermined set of power spectral densities for a group of possible crosstalk disturbers using a technique selected from the group consisting of a Matching Pursuit (MP) algorithm and a FOCal Undetermined Problem Solver (FOCUSS) to identify the set of crosstalk disturbers;
wherein the identified set of crosstalk disturbers is in a chosen column of a diagonal matrix.
16. The method of claim 15 wherein the technique is the Matching Pursuit (MP) algorithm.
17. The method of claim 15 wherein the technique is the FOCal Undetermined Problem Solver (FOCUSS).
18. The method of claim 15 , wherein the difference between the measured power spectral density and its projection along the direction of the chosen columns must always be positive.
19. The method of claim 15 wherein when a column is chosen, the column is added to a dictionary and no residual is computed.
20. A tangible computer-readable medium having instructions stored thereon, the instructions comprising:
receiving a power spectral density measurement of a subscriber loop;
correlating the power spectral density for said subscriber loop with a predetermined set of power spectral densities for a group of possible crosstalk disturbers;
selecting a crosstalk disturber, from the group of possible crosstalk disturbers, having the most closely correlated power spectral density; and,
refining the selection of the crosstalk disturber using a Best Basis Set technique.
21. The tangible computer-readable medium of claim 20 wherein the Best Basis Set technique is a matching pursuit (MP) algorithm.
22. The tangible computer-readable medium of claim 20 wherein the Best Basis Set technique is a FOCal Undetermined Problem Solver (FOCUSS).