Method and apparatus for gauge identification based on single ended line testing (SELT)
View Patent ↗The present invention relates generally to characterizing loops in a communication system, and more particularly to methods and apparatuses for loop gauge identification. In accordance with certain aspects, embodiments of the invention extract some information from the SELT signal. From SELT, the loop impedance, or equivalently input impedance, is determined. This information is then used for gauge identification.
1. A method for identifying a gauge of a loop, comprising:
receiving, at a central office (CO) device, a reflection of a signal on the loop, the reflection having a value for each of a plurality of tones in the signal;
determining a plurality of impedance values of the loop using the reflection, wherein the plurality of impedance values are average impedance values over a respective plurality of windows of the plurality of tones; and
identifying the gauge of the loop using the plurality of impedance values.
2. A method according to claim 1 , wherein the loop is included in a xDSL system and the signal is a single ended line test (SELT) signal.
3. A method according to claim 2 , wherein the SELT signal comprises a REVERB symbol modulating each of the plurality of tones.
4. A method according to claim 1 , wherein identifying the gauge includes comparing the plurality of impedance values to a respective plurality of threshold values.
5. A method according to claim 1 , wherein identifying the gauge comprises identifying the gauge as either 24-AWG or 26-AWG.
6. A method according to claim 4 , wherein the respective plurality of threshold values are obtained from experiments conducted using signals reflected from loops having different gauges, and wherein identifying includes determining one of the different gauges for which the most threshold values are met by the plurality of impedance values.
7. A method according to claim 4 , wherein identifying the gauge comprises identifying the gauge as either 24-AWG or 26-AWG, and wherein the respective plurality of threshold values are obtained from experiments conducted using signals reflected from loops having either 24-AWG or 26-AWG gauges, and wherein identifying includes determining the gauge for which the most threshold values are met by the plurality of impedance values.
8. A method for identifying a gauge of a loop, comprising:
receiving, at a central office (CO) device, a reflection of a signal on the loop, the reflection having a value for each of a plurality of tones in the signal;
determining a plurality of impedance values of the loop using the reflection, wherein the plurality of impedance values are average impedance values over a respective plurality of windows of the plurality of tones;
forming an initial estimate of the gauge of the loop using the plurality of impedance values;
estimating a length of the loop using the initial estimate of the gauge; and
identifying the gauge of the loop using the estimated length of the loop and the plurality of impedance values.
9. A method according to claim 8 , wherein identifying includes:
looking up a stored value of a minimum impedance value using the estimated length and the initial estimate of the gauge;
comparing the stored value to a minimum one of the determined plurality of impedance values; and
identifying the gauge of the loop as the initial estimate of the gauge of the loop if the stored value and the one minimum determined value are within a threshold.
10. A method according to claim 8 , wherein identifying the gauge comprises identifying the gauge as either 24-AWG or 26-AWG.
11. A method according to claim 9 , wherein identifying the gauge comprises identifying the gauge as either 24-AWG or 26-AWG, and wherein if the stored value and the one minimum determined value are not within the threshold, the method further comprises:
changing the initial estimate of the gauge of the loop to the other of either 24-AWG or 26-AWG;
re-estimating the length of the loop using the changed initial estimate of the gauge; and
looking up another stored value of the minimum impedance value using the re-estimated length and the changed initial estimate of the gauge;
comparing the another stored value to the minimum one of the determined plurality of impedance values; and
identifying the gauge of the loop as the changed initial estimate of the gauge of the loop if the stored value and the one minimum determined value are within the threshold.
12. A method according to claim 8 , wherein the loop is included in a xDSL system and the signal is a single ended line test (SELT) signal.
13. A method according to claim 12 , wherein the SELT signal comprises a REVERB symbol modulating each of the plurality of tones.
14. A method according to claim 8 , wherein forming the initial estimate of the gauge includes comparing the plurality of impedance values to a respective plurality of threshold values.
15. A method according to claim 14 , wherein the respective plurality of threshold values are obtained from experiments conducted using signals reflected from loops having different gauges, and wherein forming the initial estimate of the gauge includes determining one of the different gauges for which the most threshold values are met by the plurality of impedance values.