Pre-equalization enhancement for telecommunication networks

• US 9,237,040 B1
• Filed: 03/10/2015
• Issued: 01/12/2016
• Est. Priority Date: 03/10/2015
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang
• Primary Examiner(s): Lee, Siu
• Application Number:
  US14/642,979
• Time in Patent Office: 308 Days
• US Class Current: 1/1
• CPC Class Codes: H04L 2025/03808 Transmission of equaliser coefficients
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/03878 Line equalisers; line build-out devices

Abstract

Presented herein are techniques for enhancing pre-equalization operations in a telecommunications network. In one example, a cable modem termination system (CMTS) determines the coherent bandwidth for pre-equalization coefficients associated with upstream transmissions received from a cable modem. The CMTS uses the coherent bandwidth of the pre-equalization coefficients to calculate a time constant for a time domain filter that may be applied to the pre-equalization coefficients. The CMTS also calculates, based on the time constant, filter coefficients for the time domain filter and applies the time domain filter to the pre-equalization coefficients to generate signal-to-noise ratio (SNR)-enhanced pre-equalization coefficients. The CMTS then sends the SNR-enhanced pre-equalization coefficients to the cable modem.

Claims

1. A method comprising:

determining a coherent bandwidth for pre-equalization coefficients associated with upstream transmissions received from a cable modem;

based on the coherent bandwidth of the pre-equalization coefficients, calculating a time constant for a time domain filter for application to the pre-equalization coefficients;

calculating, based on the time constant, filter coefficients for the time domain filter;

applying the time domain filter with the filter coefficients to the pre-equalization coefficients to reduce noise introduced during generation of the pre-equalization coefficients and to generate signal-to-noise ratio (SNR)-enhanced pre-equalization coefficients; and

sending the SNR-enhanced pre-equalization coefficients to the cable modem.

2. The method of claim 1, wherein the time domain filter is a time domain low pass filter.

3. The method of claim 2, further comprising:

selecting a type of time domain low pass filter; and

selecting a filter order for the time domain low pass filter.

4. The method of claim 1, wherein applying the time domain filter to the pre-equalization coefficients comprises:

convolving the filter coefficients with the pre-equalization coefficients.

5. The method of claim 1, further comprising:

assessing the effectiveness of the SNR-enhanced pre-equalization coefficients.

6. The method of claim 5, wherein assessing the effectiveness of the SNR-enhanced pre-equalization coefficients comprises:

computing an SNR of non-equalized probing signals transmitted by the cable modem without performing pre-equalization;

computing an SNR of equalized probing signals transmitted by the cable modem after application of the SNR-enhanced pre-equalization coefficients; and

comparing the SNR of the non-equalized probing signals to the SNR of the equalized probing signals.

7. The method of claim 6, wherein when the SNR of the non-equalized probing signals is less than the SNR of the equalized probing signals, further comprising:

using the SNR-enhanced pre-equalization coefficients for upstream transmissions by the cable modem.

8. The method of claim 6, wherein when the SNR of the non-equalized probing signals is greater than the SNR of the equalized probing signals, further comprising:

scheduling the transmission of non-equalized probing signals from the cable modem;

setting all of the pre-equalization coefficients for the cable modem to a numerical value of one;

sending the pre-equalization coefficients having the numerical value of one to the cable modem; and

using the pre-equalization coefficients having the numerical value of one for upstream transmissions by the cable modem.

9. An apparatus comprising:

one or more interfaces to receive, via a network, upstream traffic from cable modems;

one or more processors that;

determine a coherent bandwidth for pre-equalization coefficients associated with upstream transmissions received from a cable modem;

based on the coherent bandwidth of the pre-equalization coefficients, calculate a time constant for a time domain low pass filter for application to the pre-equalization coefficients;

calculate, based on the time constant, filter coefficients for the time domain low pass filter;

apply the time domain low pass filter with the filter coefficients to the pre-equalization coefficients to reduce noise introduced during generation of the pre-equalization coefficients and to generate signal-to-noise ratio (SNR)-enhanced pre-equalization coefficients; and

send the SNR-enhanced pre-equalization coefficients to the cable modem.

10. The apparatus of claim 9, wherein the processor is configured to:

select a type of time domain low pass filter; and

select a filter order for the time domain low pass filter.

11. The apparatus of claim 9, wherein to apply the time domain low pass filter to the pre-equalization coefficients, the processor is configured to:

convolve the filter coefficients with the pre-equalization coefficients.

12. The apparatus of claim 9, wherein the processor is configured to:

assess the effectiveness of the SNR-enhanced pre-equalization coefficients.

13. The apparatus of claim 12, wherein to assess the effectiveness of the SNR-enhanced pre-equalization coefficients, the processor is configured to:

compute an SNR of non-equalized probing signals transmitted by the cable modem without performing pre-equalization;

compute an SNR of equalized probing signals transmitted by the cable modem after application of the SNR-enhanced pre-equalization coefficients; and

compare the SNR of the non-equalized probing signals to the SNR of the equalized probing signals.

14. The apparatus of claim 13, wherein when the SNR of the non-equalized probing signals is less than the SNR of the equalized probing signals, the processor is configured to:

use the SNR-enhanced pre-equalization coefficients for upstream transmissions by the cable modem.

15. The apparatus of claim 14, wherein when the SNR of the non-equalized probing signals is greater than the SNR of the equalized probing signals, the processor is configured to:

schedule the transmission of non-equalized probing signals from the cable modem;

set all of the pre-equalization coefficients for the cable modem to a numerical value of one;

send the pre-equalization coefficients having the numerical value of one to the cable modem; and

use the pre-equalization coefficients having the numerical value of one for upstream transmissions by the cable modem.

16. A method comprising:

determining pre-equalization coefficients associated with upstream transmissions received from a cable modem;

filtering the pre-equalization coefficients with a time domain low pass filter to reduce noise introduced during generation of the pre-equalization coefficients and to generate signal-to-noise ratio (SNR)-enhanced pre-equalization coefficients;

sending the SNR-enhanced pre-equalization coefficients to the cable modem; and

assessing the effectiveness of the SNR-enhanced pre-equalization coefficients.

17. The method of claim 16, wherein assessing the effectiveness of the SNR-enhanced pre-equalization coefficients comprises:

computing an SNR of non-equalized probing signals transmitted by the cable modem without performing pre-equalization;

computing an SNR of equalized probing signals transmitted by the cable modem after application of the SNR-enhanced pre-equalization coefficients; and

comparing the SNR of the non-equalized probing signals to the SNR of the equalized probing signals.

18. The method of claim 17, wherein when the SNR of the non-equalized probing signals is less than the SNR of the equalized probing signals, further comprising:

using the SNR-enhanced pre-equalization coefficients for upstream transmissions by the cable modem.

19. The method of claim 17, wherein when the SNR of the non-equalized probing signals is greater than the SNR of the equalized probing signals, further comprising:

scheduling the transmission of non-equalized probing signals from the cable modem;

setting all of the pre-equalization coefficients for the cable modem to a numerical value of one;

sending the pre-equalization coefficients having the numerical value of one to the cable modem; and

using the pre-equalization coefficients having the numerical value of one for upstream transmissions by the cable modem.

20. The method of claim 16, further comprising:

determining a coherent bandwidth for the pre-equalization coefficients associated with the upstream transmissions received from the cable modem;

based on the coherent bandwidth of the pre-equalization coefficients, calculating a time constant for the time domain low pass filter; and

calculating, based on the time constant, filter coefficients for the time domain low pass filter.