Cable plant certification procedure using cable modems

• US 7,246,368 B1
• Filed: 01/28/2000
• Issued: 07/17/2007
• Est. Priority Date: 01/28/2000
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Roeck, Guenter E., Leano, Chrisanto, Clark, James A., Millet, Mark E.
• Primary Examiner(s): Kelley; Chris
• Assistant Examiner(s): SHELEHEDA, JAMES R
• Application Number:
  US09/493,405
• Time in Patent Office: 2,727 Days
• Field of Search: 725/107, 725/124, 725/125, 725/121, 725/108, 725/111, 725/126, 348/192, 348/193
• US Class Current: 725/111
• CPC Class Codes: H04L 43/50 Testing arrangements

Abstract

A system for testing a cable network during normal operation interleaves test signals with live data traffic. Installed cable modems are used to generate the test signals. During live communication, such modems send upstream data at allotted time periods. Periodically, there are time slots when no modem is transmitting on the network. During these times, specific modems may be directed to transmit specific test signals. A controller such as a cable modem termination system directs specific modems to transmit signals at defined frequencies and powers during specific time slots. In this manner, the system can monitor the frequency response of the cable network at various locations, and thereby determine “on-the-fly” when maintenance or modification is required.

Claims

1. A method of testing a cable network, using one or more cable modems on the cable network, while allowing live data traffic at an original frequency, the method comprising:

(a) identifying a group of time increments, associated with live data transmission, during which cable modems on the network are not scheduled to transmit data;

(b) instructing a first one of the one or more cable modems

(i) to send a first test signal of a first frequency at a first power during a first one of the time increments, and

(ii) to send the first test signal while the first cable modem is on line and engaged in live data transmission at the original frequency;

(c) measuring the power of the first test signal received at a specified location on the cable network;

(d) instructing the first cable modem

(i) to send a second test signal of a second frequency during an available time increment, and

(ii) to send the second test signal while the first cable modem is on line and engaged in live data transmission at the original frequency;

(e) measuring the power of the second test signal received at the specified location on the cable network; and

(f) recording a power versus frequency spectrum of the first modem at at least the first and second frequencies,

wherein the first and second frequencies belong to different transmission channels.

2. The method of claim 1, further comprising, at the specified location, measuring the power of a plurality of additional signals generated by the first cable modem at a plurality of additional frequencies.

3. The method of claim 2, wherein the plurality of additional signals generated by the first cable modem are sent during a plurality of additional time increments.

4. The method of claim 1, further comprising, at the specified location, measuring and recording a frequency versus power spectrum of a second one of the cable modems during available time increments.

5. The method of claim 1, further comprising;

(i) determining a deviation between the measured power of the first test signal, at the specified location, and an expected value of the measured power at that location;

(ii) instructing the first cable modem to send another test signal at the first frequency, but this time at a power adjusted from the first power by the magnitude of the deviation; and

(iii) measuring and recording the power of the other test signal, at the specified location on the cable network.

6. The method of claim 5, further comprising repeating (i)-(iii) a number of times to obtain statistical data.

7. The method of claim 1, wherein the testing determines whether the c able network is in compliance with a cable network standard.

8. The method of claim 1, wherein the testing determines whether the cable network meets DOCSIS requirements, and where instructing the first cable modem to send the first test signal comprises sending a DOCSIS ranging request from the first cable modem.

9. The method of claim 1, further comprising identifying a range of frequencies at which the one or more cable modems are to send signals.

10. The method of claim 9, wherein the range of frequencies spans at least a substantial portion of the upstream frequency bandwidth allotted to cable modems.

11. The method of claim 9, wherein the range of frequencies includes one or more frequencies in a frequency sub-band over with cable modems on the cable network are currently sending data.

28. The method of claim 1, wherein operations (b) and (d) comprise interleaving the first and second test signals at the first and second frequencies and the live data transmissions at the original frequency.

12. A method of testing a cable network, using one or more cable modems on the cable network, while allowing live data traffic at an original frequency, the method comprising:

(a) identifying a group of time increments during which cable modems on the network are not scheduled to transmit data at the original frequency;

(b) instructing a first one of the one or more cable modems

(i) to send a first test signal of a first frequency at a first power during a first one of the time increments, and

(ii) to send the first test signal while the first cable modem is on line and engaged in live data transmission at the original frequency;

(c) measuring the power of the first test signal received at a specified location on the cable network;

(d) instructing the first cable modem

(i) to send a second test signal of a second frequency during an available time increment at the original frequency, and

(ii) to send the second test signal while the first cable modem is on line and engaged in live data transmission at the original frequency;

(e) measuring the power of the second test signal received at the specified location on the cable network; and

(f) recording a power versus frequency spectrum of the first modem at least the first and second frequencies,

wherein the one or more cable modems are selected by a method comprising;

identifying separate geographic regions of the cable network for testing; and

selecting at least one cable modem at each geographic location.

13. A method of testing a cable network while allowing live data traffic at an original frequency, the method comprising:

(a) instructing a first cable modem

(i) to send test signals of a first frequency and power during a first group of time increments at which times cable modems on the network are not scheduled to transmit data, and

(ii) to send the test signals of the first frequency while the first cable modem is on line and engaged in live data transmission at the original frequency;

(b) measuring and recording at least one of the frequency and the power of the test signals from the first cable modem;

(c) instructing a second cable modem

(i) to send test signals of a second frequency and power during a second group of time increments at which times cable modems on the network are not scheduled to transmit data, and

(ii) to send the test signals of the second frequency while the second cable modem is on line and engaged in live data transmission at the original frequency; and

(d) measuring and recording at least one of the frequency and the power of the test signals from the second cable modem,

wherein the first and second frequencies belong to different transmission channels.

14. The method of claim 13, wherein the test signals from the first and second cable modems are measured at a single specified location on the cable network.

15. The method of claim 13, wherein the testing determines whether the cable network is in compliance with requirements of DOCSIS.

16. The method of claim 13, further comprising identifying a range of frequencies at which the first and second cable modems are to send test signals.

17. The method of claim 16, wherein the range of frequencies spans at least a substantial portion of the upstream frequency bandwidth allotted to cable modems.

18. The method of claim 16, wherein the range of frequencies includes one or more frequencies in a frequency sub-band over with cable modems on the cable network are currently sending data.

19. A cable network headend allowing testing of the cable network, the headend comprising:

(a) an amplitude detector that can measure, at a specified location in the cable network, the amplitude of a signal received from a cable modem in the cable network;

(b) a MAC layer means for identifying a group of time increments, associated with live data transmission at an original frequency, during which cable modems on the cable network are not scheduled to transmit data; and

(c) test logic means for instructing a cable modem on the cable network

(i) to send test signals at least two different frequencies during one or more of the time increments, and

(ii) to send the test signals while the cable modem is on line and engaged in live data transmission at the original frequency and for directing the headend to record the power of said test signals at said different frequencies as detected by the amplitude detector,

wherein the different frequencies belong to different transmission channels.

20. The headend of claim 19, further comprising an upstream receiver in communication with the amplitude detector;

and

a downstream transmitter in communication with the MAC layer means.

21. The headend of claim 19, wherein the test logic means selects one or more cable modems in the cable network to generate test signals at multiple frequencies.

22. The headend of claim 21, wherein the test logic means selects multiple cable modems and the individual selected cable modems reside at separate geographic regions.

23. The headend of claim 19, wherein at least one of the frequencies at which the cable modem sends test signals is within a frequency band over which cable modems on the cable network are currently sending data.

24. The headend of claim 19, wherein the test logic means determines from one or more power versus frequency spectra of one or more of the cable modems in the cable network whether the cable network complies with a cable network standard.

25. A cable network headend allowing testing of the cable network, the headend comprising:

(a) an amplitude detector that can measure, at a specified location in the cable network, the amplitude of a signal received from a cable modem in the cable network;

(b) one or more processors configured to (i) identify a group of time increments, associated with live data transmission at an original frequency, during which cable modems on the cable network are not scheduled to first data and (ii) to generate instructions to cause specific cable modems on the cable network to transmit test signals of specified power and frequencies and to transmit said test signals while the cable modems are on lie and engaged in live data transmission at the original frequency, which signals can be measured by the amplitude detector; and

(c) memory coupled to the one or more processors and storing power and frequency data for the specific cable modems,

wherein the test frequencies belong to different transmission channels.

26. The cable network headend of claim 25, further comprising a modulator/transmitter and a demodulator/receiver.

27. The cable network headend of claim 25, wherein the power and frequency data are power versus frequency spectra over a range of upstream transmission frequencies for the specific cable modems.