Nonlinear device detection

1. A method of detecting one or more unfiltered devices that interfere with communication signals comprising:

transmitting a device detection signal at a frequency S from a device;

measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

instructing a user to install one or more microfilters.

2. The method of claim 1 , further comprising transmitting additional signals concurrently and one or more of measuring received signals at frequencies that are multiples of the transmitted frequencies and at frequencies that are sums and differences of multiples of the transmitted frequencies.

3. The method of claim 1 , further comprising:

measuring background noise on a communications channel; and

comparing the received signal to one or more predetermined thresholds.

4. The method of claim 1 , wherein the device detection signal is a sinusoid.

5. The method of claim 1 , wherein the one or more unfiltered devices are telephones, answering machines, fax machines, home security systems, cable TV set-top boxes, satellite TV set-top boxes and other modems.

6. The method of claim 1 , further comprising determining if background noise is higher than a harmonic.

7. The method of claim 1 , further comprising determining if harmonic power is higher than one or more predetermined thresholds.

8. The method of claim 1 , wherein the method is performed by a multicarrier modem.

9. A method of detecting one or more unfiltered devices that interfere with communication signals comprising:

transmitting a device detection signal at a frequency S from a device;

measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

informing a user that one or more devices that interfere with communications have been detected.

10. A method of detecting one or more unfiltered devices that interfere with communication signals comprising:

transmitting a device detection signal at a frequency S from a device;

measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

waiting for a transmitting modem to go quiet.

11. A method of detecting one or more unfiltered devices that interfere with communication signals comprising:

transmitting a device detection signal at a frequency S from a device;

measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

transmitting raw data corresponding to the measured received signal to an interpreter.

12. A method of detecting one or more unfiltered devices that interfere with communication signals comprising:

transmitting a device detection signal at a frequency S from a device;

measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

generating a message to a user with corrective action instructions.

13. A system configured to detect one or more unfiltered devices that interfere with communication signals comprising:

a transmitter adapted to transmit a device detection signal at a frequency S from a device;

a signal analysis module adapted to measure a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

an interpretation module adapted to detect the presence of the one or more unfiltered devices that interfere with the communication signals; and

a user interface that instructs the user to install one or more microfilters.

14. The system of claim 13 , further comprising a user interface module adapted to inform a user that one or more devices that interfere with communications have been detected.

15. The system of claim 13 , wherein the transmitter further transmits additional signals concurrently and a receiver in cooperation with the signal analysis module are adapted to one or more of measuring received signals at frequencies that are multiples of the transmitted frequencies and measuring received signals that are at frequencies that are sums and differences of multiples of the transmitted frequencies.

16. The system of claim 13 , further comprising a noise measurement module adapted to measure background noise on a communications channel.

17. The system claim 13 , wherein the device detection signal is a sinusoid.

18. The system of claim 13 , wherein the one or more unfiltered devices are telephones, answering machines, fax machines, home security systems, cable TV set-top boxes, satellite TV set-top boxes and other modems.

19. The system of claim 13 , wherein the system is associated with a multicarrier modem.

20. A system configured one or more unfiltered devices that interfere with communication signals comprising:

a transmitter adapted to transmit a device detection signal at a frequency S from a device;

a signal analysis module adapted to measure a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device; and

an interpretation module adapted to detect the presence of the one or more unfiltered devices that interfere with the communication signals, wherein the transmitter is further adapted to wait for a transmitting modem to go quiet.

21. A system configured to detect one or more unfiltered devices that interfere with communication signals comprising:

a transmitter adapted to transmit a device detection signal at a frequency S from a device;

a signal analysis module adapted to measure a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

an interpretation module adapted to detect the presence of the one or more unfiltered devices that interfere with the communication signals; and

a raw data collection module adapted to collect and transmit raw data corresponding to the measured received signal to one or more remote interpretation modules.

22. A system configured to detect one or more unfiltered devices that interfere with communication signals comprising:

a transmitter adapted to transmit a device detection signal at a frequency S from a device;

a signal analysis module adapted to measure a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

an interpretation module adapted to detect the presence of the one or more unfiltered devices that interfere with the communication signals; and

a noise measurement module adapted to determine if background noise is higher than a harmonic.

23. A system configured to detect one or more unfiltered devices that interfere with communication signals comprising:

a transmitter adapted to transmit a device detection signal at a frequency S from a device;

a signal analysis module adapted to measure a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

an interpretation module adapted to detect the presence of the one or more unfiltered devices that interfere with the communication signals, wherein the signal analysis module is further adapted to determine if harmonic power is higher than one or more predetermined thresholds.

24. A system configured to detect one or more unfiltered devices that interfere with communication signals comprising:

a transmitter adapted to transmit a device detection signal at a frequency S from a device;

a signal analysis module adapted to measure a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

an interpretation module adapted to detect the presence of the one or more unfiltered devices that interfere with the communication signals; and

a user interface module adapted to generate a message to a user with corrective action instructions.

25. A means for detecting one or more unfiltered devices that interfere with communication signals comprising:

means for transmitting a device detection signal at a frequency S from a device;

means for measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

means for detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

means for instructing a user to install one or more microfilters.

26. The means of claim 25 , further comprising means for transmitting additional signals concurrently and one or more of measuring received signals at frequencies that are multiples of the transmitted frequencies and at frequencies that are sums and differences of multiples of the transmitted frequencies.

27. The means of claim 25 , further comprising means for measuring background noise on a communications channel.

28. The means of claim 25 , wherein the device detection signal is a sinusoid.

29. The means of claim 25 , wherein the one or more unfilted devices are telephones, answering machines, fax machines, home security systems, cable TV set-top boxes, satellite TV set-top boxes and other modems.

30. The means of claim 25 , further comprising means for determining if background noise is higher than a harmonic.

31. The means of claim 25 , further comprising means for determining if harmonic power is higher than one or more predetermined thresholds.

32. The means of claim 25 , wherein the means is performed by a multicarrier modem.

33. A means for detecting one or more unfiltered devices that interfere with communication signals comprising:

means for transmitting a device detection signal at a frequency S from a device;

means for measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

means for detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

means for informing a user that one or more devices that interfere with communications have been detected.

34. A means for detecting one or more unfiltered devices that interfere with communication signals comprising:

means for transmitting a device detection signal at a frequency S from a device;

means for measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

means for detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

means for waiting for a transmitting modem to go quiet.

35. A means for detecting one or more unfiltered devices that interfere with communication signals comprising:

means for transmitting a device detection signal at a frequency S from a device;

means for measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

means for detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

means for transmitting raw data corresponding to the measured received signal to an interpreter.

36. A means for detecting one or more unfiltered devices that interfere with communication signals comprising:

means for transmitting a device detection signal at a frequency S from a device;

means for measuring a received signal at frequencies that are multiples of the transmitted frequency S and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device;

means for detecting the presence of the one or more unfiltered devices that interfere with the communication signals; and

means for generating a message to a user with corrective action instructions.

37. In a multicarrier modulation transceiver, a method of detecting one or more unfiltered devices comprising:

transmitting at least one tone at a first subcarrier index S IDD from a device;

measuring a received signal of at least one received tone at a second subcarrier index that is multiple of the first subcarrier index S IID and at frequencies that are sums and differences of multiples of the transmitted frequencies at the device; and

determining whether one or more of the unfiltered devices require a microfilter.