Intelligent power level adjustment for cable modems in presence of noise

• US 6,877,166 B1
• Filed: 01/18/2000
• Issued: 04/05/2005
• Est. Priority Date: 01/18/2000
• 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., Nguyen, Son D., Millet, Mark E.
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): Shang, Annan Q
• Application Number:
  US09/484,610
• Time in Patent Office: 1,904 Days
• Field of Search: 725/111, 725/121, 725/124, 725/125, 725/127, 725/128, 725/130, 455 68- 72, 455/522, 455/67, 4554561-4566
• US Class Current: 725/111
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04N 21/2402 Monitoring of the downstream path of the transmission network, e.g. bandwidth available traffic monitoring in data switching networks H04L43/00; monitoring data switching networks utilization H04L43/0876
• CPC Class Codes: H04N 21/42676 for modulating an analogue carrier signal to encode digital information or demodulating it to decode digital information, e.g. ADSL or cable modem
• CPC Class Codes: H04N 21/437 Interfacing the upstream path of the transmission network, e.g. for transmitting client requests to a VOD server flow control in data networks H04L47/10; streaming protocols, e.g. RTP or RTCP, H04L65/65; scheduling or organising the servicing of application requests in data packet switching networks H04L67/60
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6543 for forcing some client operations, e.g. recording remote booting in general G06F9/4416
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/22 Adaptations for optical transmission

Abstract

A technique is disclosed for selectively adjusting the power and/or frequency of cable modems without relying solely on the most recent measurement of these values to determine whether a change is necessary. Rather, it considers multiple recent measurements and from these makes its assessment. In one approach, the technique employs an average of the recent measurements to determine whether a change in power or frequency is necessary. There are actually at least three determinations that can make use of multiple recent measurements. These include (1) determining whether the signals are fluctuating to an extent that requires a special adjustment technique, (2) determining whether an adjustment is necessary (using the special technique), and (3) determining how large of an adjustment is necessary.

Claims

1. A method of adjusting the power of a cable modem on a cable network, the method comprising:

(a) during execution of a ranging protocol in the cable network, determining that cable modem signals received at or proximate a head-end of the cable network fluctuate in power by more than a defined amount;

(b) at the head-end, calculating a power adjustment using a plurality of recent power measurements of signals taken over a plurality of ranging requests from the cable modem taken at or proximate the head-end of the cable network; and

(c) from the head-end and during the ranging protocol, instructing the cable modem to adjust its power based upon the calculated power adjustment.

2. The method of claim 1, wherein a CMTS performs at least the determining and the calculating.

3. The method of claim 1, wherein the power measurements of signals from the cable modem are taken by an amplitude estimator in a CMTS.

4. The method of claim 1, wherein determining that signals from the cable modem fluctuate more than the defined amount comprises calculating a deviation from an expected power level over multiple recent power measurements of the cable modem'"'"'s signals as received at or proximate the head-end of the cable network.

5. The method of claim 1, wherein the deviation is calculated over eight or sixteen of the recent power measurements.

6. The method of claim 1, wherein determining that signals from the cable modem fluctuate more than the defined amount comprises determining that the cable modem has been instructed to change its power level more than a threshold percentage of opportunities for adjustment.

7. The method of claim 1, wherein calculating the power adjustment comprises calculating an average difference between an actual power and an expected power over at least eight recent power measurements at or proximate the head-end of the cable network.

8. The method of claim 7, wherein calculating the power adjustment further comprises offsetting the average difference by a multiple of the deviation in actual power measurements over recent power measurements at or proximate the head-end of the cable network.

9. The method of claim 1, wherein calculating the power adjustment comprises determining an adjustment associated with a signal to noise ratio detected for upstream signals from the cable modem.

10. The method of claim 1, wherein instructing the cable modem to adjust its power comprises sending a ranging response DOCSIS message from a CMTS to the cable modem.

36. The method of claim 1, wherein instructing the cable modem to adjust its power comprises sending instructions from the headend to the cable modem.

11. A method of controlling the power at which a cable modem sends data upstream on a cable network, wherein at or proximate a cable network head-end, the cable network periodically determines the power of upstream signals from the cable modem, the method comprising:

(a) during execution of a ranging protocol in the cable network, adjusting the cable modem power by an amount calculated based on a first technique that does not average recent cable modem power measurements;

(b) determining that upstream signals from cable modem contain more than a threshold level of noise or fluctuation; and

(c) from the head-end and during the ranging protocol, sending instructions for adjusting the cable modem power by an amount calculated based upon a second technique that averages recent cable modem power measurements.

12. The method of claim 11, wherein adjusting the cable modem power based upon the first technique comprises:

(i) determining a difference between an actual power and an expected power of an upstream signal from the cable modem; and

(ii) instructing the cable modem to adjust its power based upon the difference.

13. The method of claim 11 wherein adjusting the cable modem power based upon a second technique comprise:

(i) calculating a power adjustment based upon a plurality of recent differences between actual power and expected power of upstream signals from the cable modem; and

(ii) instructing the cable modem to adjust its power based upon the calculated power adjustment.

14. The method of claim 11, wherein cable modem upstream power levels are determined using DOCSIS ranging requests.

15. The method of claim 11, further comprising:

after instructing the cable modem to adjust its power, determining that the upstream signals from the cable modem contain less than the threshold level of noise or fluctuation; and

returning to the first technique for adjusting the cable modem power.

37. The method of claim 11, further comprising sending instructions from the headend to the cable modem to adjust the cable modem power by amount determined using the second technique.

16. A cable modem termination system comprising:

(a) a receiver arranged to detect received power levels from transmissions of a cable modem;

(b) means for implementing a cable network ranging to protocol that (i) uses a plurality of the detected power levels taken over a plurality of ranging requests to determine that cable modem signals fluctuate at the cable modem termination system by more than a defined amount and (ii) calculates a single power level adjustment for the cable modem based upon the plurality of the detected power levels; and

(c) means for generating instructions, as part of the ranging protocol, to the cable modem to make the calculated power adjustment.

17. The apparatus of claim 16, wherein the receiver determines differences between the detected power levels and an expected power level, where the means for calculating receives the differences from the receiver and calculates the single power level adjustment based upon the differences.

18. The apparatus of claim 16, wherein the receiver is a hardware device, and wherein the means for calculating and the means for generating are implemented as software.

19. The apparatus of claim 16, wherein the means for calculating calculates the power level adjustment by calculating an average based upon the plurality of detected power levels.

20. The apparatus of claim 19, wherein the means for calculating calculates the power level adjustment by offsetting the average by a multiple of a deviation ia the detected power levels.

21. The apparatus of claim 16, wherein the means for calculating calculate the power level adjustment based on a signal-to-noise ratio determined from the plurality of detected power levels.

22. The apparatus of claim 16, wherein the means for generating generates a DOCSIS ranging response indicating the power level adjustment.

23. The apparatus of claim 16, further comprising means for determining whether signals from a cable modem contain more than a threshold level of noise.

24. A method of adjusting the frequency of a cable modem on a cable network, the method comprising:

(a) during execution of a ranging protocol in the cable network, calculating a frequency adjustment using a plurality of recent frequency measurements of signals taken over a plurality of ranging request from the cable modem taken at or proximate the head-end for the cable network; and

(b) from the head-end and during the ranging protocol, instructing the cable modem to adjust its frequency based con the calculated frequency adjustment.

25. The method of claim 24, wherein a cable modem termination system performs at least the detecting and the calculating.

26. The method of claim 24, wherein calculating the frequency adjustment comprises calculating an average difference between an actual frequency and an expected frequency over at least eight frequency measurements at or proximate the head-end of the cable network.

38. The method of claim 24, wherein instructing the cable modem to adjust its frequency comprises sending instructions from the headend to the cable modem.

27. A computer program product comprising a machine readable medium on which are provided program instructions for adjusting the power of a cable modem on a cable network, the program instructions comprising instructions for:

(a) during execution of a ranging protocol in the cable network, determining that cable modem signals received at or proximate a head-end of the cable network fluctuate in power by more than a defined amount;

(b) at the head-ed, calculating a power adjustment using a plurality of recent power measurement of signals taken over a plurality of ranging requests from the cable modem taken at or proximate the head-end of the cable network; and

(c) from the head-end and during the ranging protocol instructing the cable modem to adjust its power based upon the calculated power adjustment.

28. The computer program product of claim 27, wherein the instructions for determining that signals from the cable modem fluctuate more than the defined amount comprises instructions for calculating a deviation from an expected power level over multiple recent power measurements of the cable modem'"'"'s signals as received at or proximate the head-end of the cable network.

29. The computer program product of claim 27, wherein the instructions for calculating the power adjustment comprises instructions for calculating an average difference between an actual power and an expected power over at least eight recent power measurements at or proximate the head-end of the cable network.

30. The computer program product of claim 29, wherein the instructions for calculating the power adjustment further comprises instructions for offsetting the average difference by a multiple of the deviation in actual power measurements over recent power measurements at or proximate the head-end of the cable network.

31. The computer program product of claim 27, wherein the instructions for calculating the power adjustment comprises instructions for determining an adjustment associated with a sign to noise ratio detected for upstream signals from the cable modem.

39. The computer program product of claim 27, wherein instructions for instructing the cable modem to adjust its power comprises instructions for sending instructions from the head-end to the cable modem.

32. A computer program product comprising a machine readable medium on which are provided program instructions for controlling the power at which a cable modem sends data upstream on a cable network, wherein at or proximate a cable network head-end, the cable network periodically determines the power of upstream signals from the cable modem, the program instructions comprising instructions for:

(a) dung execution of a ranging protocol in the cable network, adjusting the cable modem power by an amount calculated based on a first technique that does not average recent cable modem power measurements;

(b) determining that upstream signals from the cable modem contain more than a threshold level of noise or fluctuation; and

(c) from the head-end and during the ranging protocol, sending instructions for adjusting the cable modem power by an amount calculated based upon a second technique that averages recent cable modem power measurements.

33. The computer program product of claim 32, wherein the instructions for adjusting the cable modem power based upon the first technique comprise instructions for:

(i) determining a difference between an actual power and an expected power of an upstream signal from the cable modem; and

(ii) instructing the cable modem to adjust its power based upon the difference.

34. The computer program product of claim 32, wherein the program instructions for adjusting the cable modem power based upon a second technique comprises instructions for;

(i) calculating a power adjustment based upon a plurality of recent different between actual power and expected power of upstream signals from the cable modem; and

(ii) instructing the cable modem to adjust its power based upon the calculated power adjustment.

35. The computer program product of claim 32, further comprising program instructions for:

after instructing the cable modem to adjust its power, determining that the upstream signs from the cable modem contain less than the threshold level of noise or fluctuation; and

returning to the first technique for adjusting the cable modem power.

40. The computer program product of claim 32, wherein the program instructions further comprise instructions for sending instructions from the headend to the cable modem to adjust the cable modem power by amount determined using the second technique.

41. Apparatus for adjusting the power of a cable modem on a cable network, the apparatus being located in a head-end of the cable network and comprising:

(a) means for determining, during execution of a ranging protocol in the cable network, that cable modem signals received at or proximate a head-end of the cable network fluctuate in power by more than a defined amount;

(b) means for instructing a power adjustment using a plurality of recent power measurements of signals taken over a plurality of ranging requests from the cable modem taken at or proximate the head-end of the cable network; and

(c) means for instructing the cable modem, from the head end and during the ranging protocol, to adjust its power based upon the calculated power adjustment.

42. Apparatus for controlling the power at which a cable modem sends data upstream on a cable network, wherein at or proximate a cable network heads the cable network periodically determines the power of upstream signals from the cable modem, the apparatus comprising:

(a) means for adjusting the cable modem power, during execution of a ranging protocol in the cable network, by an amount calculated based on a first technique that does not average recent cable modem power measurements;

(b) means for determining that upstream signals from the cable modem contain more than a threshold level of noise or fluctuation; and

(c) means for sending instructions for adjusting the cable modem power from the head-end and during the ranging protocol, by an amount calculated based upon a second technique that averages recent cable modems power measurements.