Interference suppression in full duplex cable network environments

• US 9,966,993 B2
• Filed: 02/24/2016
• Issued: 05/08/2018
• Est. Priority Date: 07/15/2015
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang, Chapman, John T.
• Primary Examiner(s): Towfighi, Afshawn M
• Application Number:
  US15/052,499
• Publication Number:
  US 20170019146A1
• Time in Patent Office: 804 Days
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 3/20 Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04B 3/487 Testing crosstalk effects

Abstract

An example method for interference suppression in full duplex cable network environments is provided and includes providing a baseband (BB) reference signal on a first pathway to a signal processor, converting the BB reference signal to a first radio frequency (RF) signal, transmitting the first RF signal on the first pathway, the first RF signal being reflected back on a second pathway, receiving a second RF signal on the second pathway, the second RF signal including interferences from the reflections, generating an RF reference signal based on signals on the first pathway, providing the RF reference signal to the signal processor, providing the second RF signal to the signal processor, and reducing, by the signal processor, interferences in the second RF signal from reflections of the first RF signal based on the BB reference signal and the RF reference signal.

Claims

1. A method for interference cancellation in a cable network comprising:

providing a baseband (BB) reference signal on a first pathway to a signal processor in a network element;

converting the BB reference signal to a first radio frequency (RF) signal;

transmitting the first RF signal on the first pathway, wherein the first RF signal is reflected back on a second pathway;

receiving a second RF signal on the second pathway, wherein the second RF signal comprises interferences from reflections of the first RF signal on the second pathway, wherein the reflections of the first RF signal comprises time-shifted samples of the first RF signal attenuated by differing amounts;

generating an RF reference signal based on signals on the first pathway;

providing the RF reference signal to the signal processor;

providing the second RF signal as input to the signal processor; and

reducing, by the signal processor, interferences in the second RF signal from the reflections of the first RF signal based on the BB reference signal and the RF reference signal.

2. The method of claim 1, further comprising converting the RF reference signal and the second RF signal to corresponding digital signals prior to providing to the signal processor.

3. The method of claim 1, wherein reducing the interferences by the signal processor comprises executing an adaptive interference cancellation (AIC) algorithm, including convolutions on the second RF signal and the RF reference signal, followed by a cancellation of the convoluted RF reference signal from the convoluted second RF signal.

4. The method of claim 3, wherein the signal processor executes the AIC algorithm separately for each of a plurality of subcarrier frequencies comprised in the RF reference signal.

5. The method of claim 4, wherein the executing the AIC algorithm further comprises:

performing a Fast Fourier Transform (FFT) of the RF reference signal and the second RF signal;

separating out the transformed signals according to the plurality of subcarriers based on information about the plurality of subcarrier frequencies comprised in the BB reference signal; and

executing the AIC algorithm on pairs of transformed RF reference signal and second RF signal corresponding to each of the subcarrier frequencies.

6. The method of claim 1, wherein reducing the interferences by the signal processor comprising executing an AIC algorithm, comprising:

determining time-shifted samples of the RF reference signal;

estimating weighting factors for each time-shifted sample;

estimating an interference signal as a weighted sum of the time-shifted samples;

calculate a residue between the estimated interference signal and the second RF signal;

updating the weighting factors based on the calculated residue;

repeating the estimating the interference signal, calculating the residue and the updating the weighting factors in successive iterations until the residue is below a predetermined threshold, wherein the iterations successively reduce interferences in the second RF signal from reflected signal.

7. The method of claim 1, wherein the network element comprises a transceiver.

8. The method of claim 1, wherein the network element comprises an amplifier, wherein the method further comprises reducing, by the signal processor, interferences in the second RF signal from echoes of itself.

9. The method of claim 8, wherein the method comprises:

reducing, by a first equalizer, interferences in the second RF signal from reflections of the first RF signal, generating a first output signal; and

reducing, by a second equalizer, interferences in the first output signal from echoes of itself.

10. The method of claim 9, wherein the second equalizer generates a second output signal, wherein a BB portion of the second output signal is provided to the signal processor as another BB reference signal, wherein an RF portion of the second output signal is provided to the signal processor as another RF reference signal, wherein interferences on the first pathway in the first RF signal due to reflections of the second RF signal are reduced based on the another BB reference signal and the another RF reference signal.

11. The method of claim 9, wherein the first equalizer executes an AIC algorithm, and the second equalizer executes an echo cancellation algorithm.

12. Non-transitory tangible computer-readable media that includes instructions for execution, which when executed by a processor of a network element, is operable to perform operations comprising:

determining time-shifted samples of a reference signal;

estimating weighting factors for the time-shifted samples;

estimating an interference signal as a weighted sum of the time-shifted samples;

calculating a residue between the estimated interference signal and an input signal;

updating the weighting factors based on the calculated residue; and

repeating the estimating the interference signal, calculating the residue and the updating the weighting factors in successive iterations until the residue is below a predetermined threshold, wherein the iterations successively reduce interferences in the input signal, the reference signal and the input signal comprising communication signals in a full duplex cable network.

13. The media of claim 12, wherein the operations are performed separately for each of a plurality of subcarrier frequencies comprised in the reference signal.

14. The media of claim 13, wherein the operations further comprise:

performing a FFT of the reference signal and the second RF signal;

separating out the transformed signals according to the plurality of subcarriers based on information about the plurality of subcarrier frequencies comprised in the BB reference signal; and

executing the operations on pairs of transformed reference signal and second RF signal corresponding to each of the subcarrier frequencies.

15. The media of claim 13, wherein the reference signal comprises a first RF signal distorted by interferences, the first RF signal being transmitted from the apparatus by the transmitter on a first pathway, wherein the second RF signal is received at the apparatus by the receiver on a second pathway.

16. The media of claim 13, wherein the reference signal comprises time-shifted samples of the input signal for echo cancellation.

17. An apparatus, comprising:

a transmitter;

a receiver;

a memory element; and

a processor operable to execute instructions associated with the data, wherein the processor and the memory cooperate, such that the apparatus is configured for operations comprising;

determining time-shifted samples of a reference signal;

estimating weighting factors for the time-shifted samples;

estimating an interference signal as a weighted sum of the time-shifted samples;

calculating a residue between the estimated interference signal and an input signal;

updating the weighting factors based on the calculated residue; and

repeating the estimating the interference signal, calculating the residue and the updating the weighting factors in successive iterations until the residue is below a predetermined threshold, wherein the iterations successively reduce interferences in the input signal, the reference signal and the input signal comprising communication signals in a full duplex cable network.

18. The apparatus of claim 17, wherein the reference signal comprises a first RF signal distorted by interferences, the first RF signal being transmitted from the apparatus by the transmitter on a first pathway, wherein the second RF signal is received at the apparatus by the receiver on a second pathway.

19. The apparatus of claim 17, wherein the operations are performed separately for each of a plurality of subcarrier frequencies comprised in the reference signal.