Customer premise SELT based method for detecting the presence of a micro-filter on a VDSL connection

1. A method comprising:

transmitting, from a customer premises modem, a signal on a line connected to the customer premises modem;

receiving data corresponding to a reflection of the transmitted signal;

processing the data to obtain an estimated loop length of the line; and

analyzing the data in accordance with the obtained loop length to determine whether a micro-filter is connected on the line.

2. A method according to claim 1 , wherein the steps of transmitting, receiving and analyzing are incorporated into single ended line test (SELT) tests performed by the customer premises modem.

3. A method according to claim 1 , wherein transmitting includes transmitting a high frequency signal and analyzing includes determining whether the line includes a short circuit.

4. A method according to claim 3 , wherein determining includes:

determining a phase response associated with the transmitted signal; and

comparing the phase response to a threshold associated with a short circuit condition.

5. A method according to claim 1 , wherein transmitting includes transmitting a low frequency signal and analyzing includes determining whether the line includes an open circuit.

6. A method according to claim 5 , wherein determining includes:

determining a phase response associated with the transmitted signal; and

comparing the phase response to a threshold associated with an open circuit condition.

7. A method according to claim 1 , wherein transmitting includes transmitting a wideband signal and analyzing includes determining whether the line is terminated by approximately 100 ohms.

8. A method according to claim 7 , wherein determining includes:

determining a ratio of transmitted and received energy associated with the wideband signal; and

comparing the ratio to a threshold associated with a 100 ohm line termination condition.

9. A method according to claim 1 , wherein the micro-filter is a ADSL/VDSL micro-filter/splitter.

10. A modem comprising:

a transmitter adapted to transmit a signal on a line connected to the modem;

a receiver adapted to receive data corresponding to a reflection of the transmitted signal; and

a chipset programmed to process the data to obtain an estimated loop length of the line and to analyze the data in accordance with the estimated loop length to determine whether a micro-filter is connected on the line.

11. A modem according to claim 10 , wherein the signal is a high frequency signal and wherein the analyzing performed by the chipset includes determining whether the line includes a short circuit.

12. A modem according to claim 11 , wherein determining includes:

determining a phase response associated with the transmitted signal; and

comparing the phase response to a threshold associated with a short circuit condition.

13. A modem according to claim 10 , wherein the signal is a low frequency signal and wherein the analyzing performed by the chipset includes determining whether the line includes an open circuit.

14. A modem according to claim 13 , wherein determining includes:

determining a phase response associated with the transmitted signal; and

comparing the phase response to a threshold associated with an open circuit condition.

15. A modem according to claim 10 , wherein the signal is a wideband signal and wherein the analyzing performed by the chipset includes determining whether the line is terminated by approximately 100 ohms.

16. A modem according to claim 15 , wherein determining includes:

determining a ratio of transmitted and received energy associated with the wideband signal; and

comparing the ratio to a threshold associated with a 100 ohm line termination condition.

17. A modem according to claim 10 , wherein the micro-filter is a ADSL/VDSL micro-filter/splitter.

18. A method comprising:

transmitting, from a customer premises modem, a high frequency signal on a line connected to the customer premises modem;

receiving first data corresponding to a reflection of the transmitted high frequency signal;

transmitting, from the customer premises modem, a low frequency signal on the line connected to the customer premises modem;

receiving second data corresponding to a reflection of the transmitted low frequency signal;

transmitting, from the customer premises modem, a wideband signal on the line connected to the customer premises modem;

receiving third data corresponding to a reflection of the transmitted high frequency signal;

analyzing some or all of the first, second and third data to determine whether a micro-filter is connected on the line.

19. A method according to claim 18 , wherein analyzing includes determining that the micro-filter is connected if the first data indicates that a short circuit condition is present on the line, and if the second data indicates that an open circuit condition is present on the line, and if the third data indicates that the line is not terminated by approximately 100 ohms.

20. A method according to claim 19 , wherein analyzing includes comparing a phase response associated with the high frequency and low frequency signals to respective thresholds.

21. A method according to claim 4 , further comprising obtaining the threshold for use in the comparing by looking up the threshold in a table of short circuit threshold values using the estimated loop length.

22. A method according to claim 6 , further comprising obtaining the threshold for use in the comparing by looking up the threshold in a table of open circuit threshold values using the estimated loop length.