Method and system for reducing interferences due to handshake tones
View Patent ↗A method and system of the present inventions reduces both near-end crosstalk (NEXT) and far-end crosstalk (FEXT) interferences due to handshake tones into upstream and downstream neighboring services, both at the customer premises equipment (CPE) and at the central office (CO), when handshake is experienced. An embodiment of the present inventions is directed to significantly reduce the NEXT and/or FEXT interferences due to handshake tones. For example, NEXT and/or FEXT interferences due to G.994.1 handshake tones, identified as, bins 7 and 9 for the Upstream channel and bins 12, 14 and 64 for the Downstream channel may be reduced. An embodiment of the present inventions provides an algorithm that may be used for both NEXT and FEXT Handshake Interferences reduction at the CO and at the CPE. In addition, the algorithm may operate in the time domain and in the frequency domain. Frequency domain algorithm offers two options, both versions taking advantage of the high correlation time of the Handshake tone signals.
1. A method for reducing interference due to handshake tones in the frequency domain in a communication system, the method comprising the steps of:
receiving an input signal X t in the frequency domain at bin q and time-symbol t, wherein the input signal comprises a short correlation time component and a long correlation time component, wherein the long correlation time component corresponds to a disturbance signal due to handshake tones;
attaining near zero correlation for the short correlation time component in the received input signal by delaying the input signal by a time-symbol value N, wherein N is an integer such that the generated delayed signal is X t-N ;
estimating the disturbance signal by generating a prediction signal with long correlation properties based at least in part on the delayed signal;
comparing the input signal and the prediction signal; and
correlating the received input signal to the disturbance signal by reducing a variance between the received input signal and the prediction signal,
wherein the steps are performed in a transceiver within the communication system.
2. The method of claim 1 , wherein the input signal is a corrupted frequency domain Asymmetric Digital Subscriber Line (ADSL) signal at a predetermined bin of a predetermined time-symbol.
3. The method of claim 1 , wherein the time-symbol value N is one symbol, wherein the one symbol represents approximately 512 time domain samples.
4. The method of claim 1 , wherein near-end crosstalk (NEXT) interferences due to handshake tones are reduced.
5. The method of claim 1 , wherein far-end crosstalk (FEXT) interferences due to handshake tones are reduced.
6. The method of claim 1 , wherein the steps are performed at a customer premises equipment (CPE) end.
7. The method of claim 1 , wherein the steps are performed at a central office (CO) end.
8. The method of claim 1 , wherein the prediction signal is generated by a causal filter.
9. The method of claim 1 , wherein the causal filter uses historical data to generate the prediction signal.
10. The method of claim 1 , wherein the causal filter uses at least one past disturbance signal to generate the prediction signal.
11. The method of claim 1 , wherein the step of reducing is performed by at a least mean square algorithm.
12. A system for reducing interference due to handshake tones in the frequency domain, the system comprising:
an input for receiving an input signal in the frequency domain having a short correlation time component and a long correlation time component, wherein the long correlation time component corresponds to a disturbance signal due to handshake tones;
a delay module for generating a delayed signal by delaying the input signal by a delay value equal to an upper bound of the short correlation component; and
a filter for generating a prediction signal based at least in part on the delayed signal to estimate the disturbance signal;
wherein the input signal and the prediction signal are compared and a variance between the input signal and the prediction signal is reduced.
13. The system of claim 12 , wherein the input signal is a corrupted frequency domain Asymmetric Digital Subscriber Line (ADSL) signal at a predetermined bin of a predetermined time-symbol.
14. The system of claim 12 , wherein the delay value is a time-symbol value.
15. The system of claim 12 , wherein the delay value is one symbol, wherein the one symbol represents approximately 512 time domain samples.
16. The system of claim 12 , wherein the delay value comprises a predetermined time symbol value.
17. The system of claim 12 , wherein near-end crosstalk (NEXT) interferences due to handshake tones are reduced.
18. The system of claim 12 , wherein far-end crosstalk (FEXT) interferences due to handshake tones are reduced.
19. The system of claim wherein the system resides at a customer premises equipment (CPE) end.
20. The system of claim 12 , wherein the system resides at a central office (CO) end.
21. The system of claim 12 , wherein the prediction signal is generated by a causal filter.
22. The system of claim 21 , wherein the causal filter uses historical data to generate the prediction signal.
23. The system of claim 21 wherein the causal filter uses at least one past disturbance signal to generate the prediction signal.
24. The system of claim 12 , wherein the variance is reduced by a least mean square algorithm.
25. The system of claim 12 , wherein the input is correlated to a disturbance signal.
26. A system for reducing interference due to handshake tones in the time domain, comprising:
means for receiving an input signal in the frequency domain having a short correlation time component and a long correlation time component;
means for generating a delayed signal by delaying the input signal by a delay value, wherein the delay value is equal to a time-symbol value N, wherein N is an integer such that the generated delayed signal is X t-N , wherein X t is the input signal at bin q and time-symbol t, wherein the value N is based on an upper bound of the short correlation time component, and wherein the long correlation time component exhibits high correlation beyond the upper bound;
means for generating a prediction signal with a high correlation value based at least in part on the delayed signal;
means for comparing the input signal and the prediction signal; and
means for reducing a variance between the input signal and the prediction signal.