Enhanced return path performance using modulation-based alignment criteria

• US 20030028898A1
• Filed: 05/06/2002
• Published: 02/06/2003
• Est. Priority Date: 05/04/2001
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Howald, Robert Landis
• Granted Patent: US 7,684,341 B2
• Time in Patent Office: Days
• US Class Current: 725/129
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level

Abstract

A method of allocating power among a plurality of signals, at least two of the signals employing different signal formats, located on different channels of the return path of a cable data network, divides a total power available for the signals on the return path in accordance with a minimum value of an average BER for all the signals and allocates power to each of the signals in accordance therewith. Specifically, a number of parameters are obtained including modulation type and symbol rate for each signal format employed on the return path, the AWGN noise floor across the reverse link, the nominal maximum available RF power for transmitting signals on the reverse path. A predetermined BER expression for each of the modulation types employed on the return path is then obtained, each of the expressions requiring a plurality of input values that includes the above-noted parameters. An expression is then formulated for an average BER based on the predetermined BER expressions and on a number of channels of each signal format type associated with a corresponding BER expression. The power to be allocated to each signal format by minimizing the average BER is then calculated.

Claims

1. A method of allocating signal power among a plurality of different channels on the return path of a cable data network, each of said channels employing one of a plurality of different signal formats, the method comprising the steps of:

a) obtaining parameters specifying modulation type and symbol rate for each signal format employed on the return path, wherein said parameters thereby provide a parameter of channel bandwidth;

b) obtaining the AWGN noise floor across the reverse link;

c) choosing a nominal maximum available RF power for transmitting signals on the reverse path;

d) obtaining a predetermined BER expression for each of the modulation types employed on the return path, each of said predetermined BER expressions requiring a plurality of input values that includes said at least one parameter obtained in step a) for the signal format associated therewith, the AWGN noise floor across the reverse link obtained in step b), and a maximum available RF power for transmitting signals on the return path obtained in step c);

e) formulating an expression for an average BER based on the predetermined BER expressions obtained in step d) and on a number of channels of each signal format type associated with a corresponding BER expression obtained in said obtaining step d);

e) calculating the power to be allocated to each signal format by minimizing said average BER; and

f) allocating power to each of the plurality of channels associated with each signal format in accordance with the power calculated in step e).

2. The method of claim 1, wherein the BER expression includes FEC, using the BER approximations for coded systems.

3. The method of claim 1, wherein the BER expression includes interference, using the BER approximations that account for C/I.

4. The method of claim 1 wherein the BER expression includes clipping related effects.

5. The method of claim 1, wherein the BER includes non-flat noise floors.

6. The method of claim 1, wherein the modulation type parameters obtained in step a) are obtained by automatic means using DSP algorithms.

7. The method of claim 1, wherein the results of step (d) are downloaded from headend control software with an interface to the CMTS.

8. The method of claim 1, wherein the results of step (d) are delivered as observable information.

9. The method of claim 7, wherein a Cable Modem Termination System (CMTS) directs a proper per-channel setting to achieve optimization of a minimum average BER based on the results of step (d).

10. The method of claim 8, wherein a Cable Modem Termination System (CMTS) directs a proper per-channel setting to achieve optimization of a minimum average BER based on the results of step (d).

11. The method of claim 1, further comprising the step of (g) continually automatically adjusting the power allocated, so as to maintain optimization, based on constant communication with modems in the field.

12. The method of claim 1 wherein the parameter implemented in step (e) is derived from information obtained in step (a).

13. The method of claim 1 wherein the AWGN is calculated using the signal parameters of channel power and channel signal quality.

14. The method of claim 1 further comprising the step of (g) identifying a part of the AWGN spectrum and using that information to optimally allocate signal power in step (f).

15. The method of claim 1 wherein step (e) includes the step of obtaining the number of channels of each signal format type associated with each of the predetermined BERs.

16. The method of claim 1 wherein step (f) includes the step of allocating an equal amount of power to each channel that employs a common signal format.

17. The method of claim 1 wherein said plurality of input values includes an AWGN noise floor across the reverse link thereby providing a signal-to-noise ratio.

18. The method of claim 17 wherein the total available power is a nominal maximum RF total drive level based on plant infrastructure limitations.

19. The method of claim 1 wherein said cable data network is an HFC network.

20. A method of allocating power among a plurality of signals located on different channels of the return path of a cable data network, said method comprising the steps of:

a) dividing a total power available for the signals on the return path in accordance with a minimum value of an average BER for all the signals; and

b) allocating power to each of the signals in accordance with step (a),

wherein at least two of said signals employ different signal formats.