Ingress Suppression for Communication Systems

• US 20130010810A1
• Filed: 07/07/2011
• Published: 01/10/2013
• Est. Priority Date: 07/07/2011
• Status: Active Grant

• Current Assignee: Vecima Networks Incorporated
• Original Assignee: Vecima Networks Incorporated
• Inventors: Pelet, Eric R.
• Granted Patent: US 9,059,786 B2
• Time in Patent Office: Days
• US Class Current: 370/479
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/71 the interference being narrowband interference
• CPC Class Codes: H04B 1/7101 with estimation filters
• CPC Class Codes: H04B 2001/1063 using a notch filter
• CPC Class Codes: H04L 25/03267 with decision feedback equalisers
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults

Abstract

A method used in the receiver of a communication system is provided to suppress narrow band interferences, known as ingress, that are present in the communication channel, which is shared by a plurality of transmitters each having a channel pre-equalizer, by means of a Time Division Multiple Access (TDMA) scheme or Synchronous Code Division Multiple Access (SCDMA) scheme. The method comprises filtering the interferences using Infinite Impulse Response (IIR) notch filters, and providing IIR all-pass filters devised to compensate for substantially all phase distortions introduced by the notch filters. The method also includes an algorithm to detect the narrow band interferences and an adaptive equalizer to equalize the channel by computing the coefficients of the transmitters'"'"' pre-equalizers, and arranged such that the equalization of the channel is isolated from the suppression of the interferences.

Claims

1. A method for use in a receiver of a communication system for suppressing one or several narrow band interferences present in a communication channel, the method comprising:

receiving at the receiver a communication signal from the communication channel;

filtering in the signal each interference to be suppressed in turn with a respective one of a plurality of Infinite Impulse Response (IIR) notch filters configured to suppress the respective one of the interferences;

and providing for each of the notch filters a respective one of a plurality of IIR all-pass filters devised to compensate for substantially all phase distortions introduced by the respective notch filter.

2. The method according to claim 1 wherein the communication channel is shared by a plurality of transmitters by means of a Time Division Multiple Access (TDMA) scheme and wherein a Decision Feedback Equalizer (DFE) is used to compensate for the distortions introduced by the notch filters not compensated by the IIR all-pass filters.

3. The method according to claim 1 wherein the communication channel is shared by a plurality of transmitters by means of a Synchronous Code Division Multiple Access (S-CDMA) scheme.

4. The method according to claim 1 wherein there is provided an algorithm to detect the narrow band interferences in the communication channel, and configure the notch filters to suppress the detected interferences.

5. The method according to claim 4 wherein the algorithm comprises Fast Fourier Transforms, frequency interpolations, filtering, down-sampling, and up-sampling operations.

6. The method according to claim 1 including isolating or decoupling the equalization of the communication channel from the suppression of the interferences.

7. The method according to claim 6 wherein the equalization of the communication channel is isolated or decoupled from the suppression of the interferences by using an adaptive equalizer in the receiver wherein during the training mode, the desired response of the equalizer is a replica of the communication signal if only distorted by the notch and all-pass filters.

8. The method according to claim 7 wherein the transmitter pre-distorts the communication signal using a pre-equalizer to cancel the effect of the channel at the receiver, and the adaptive equalizer in the receiver is used to compute the coefficients of the transmitter'"'"'s pre-equalizer.

9. The method according to claim 1 wherein the communication system is a Cable Television (CATV) network having a plurality of Cable Modems for communicating data in a return path and the method operates on the return path to suppress narrow band interferences that enter the return path through defective shields.