Narrowband interference and identification and digital processing for cable television return path performance enhancement

• US 7,716,712 B2
• Filed: 06/18/2003
• Issued: 05/11/2010
• Est. Priority Date: 06/18/2003
• Status: Expired due to Fees

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Booth, Ted Nelson, Howald, Robert L.
• Primary Examiner(s): Huynh; Son P
• Application Number:
  US10/465,339
• Publication Number:
  US 20040261118A1
• Time in Patent Office: 2,519 Days
• Field of Search: 725/107, 725121-127, 709222-224, 375/346
• US Class Current: 725/121
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

An adaptive data stream filter removes narrowband interference from the CATV return path prior to these paths being combined in the network. A method for removing narrowband interference from the CATV return path detects potential narrowband interference in real-time and adapts a filter to remove this potential narrowband interference. An exemplary embodiment of the above method uses previously created filters that are combined based on detected interference in an adaptive manner to continually adapt to new interference sources. Another exemplary embodiment of the above method calculates new filter coefficients for the data stream filter based on detected interference. In another embodiment, two filters are operated in a ping-pong manner for each band of interference identified as above threshold. This enables updating of one filter while another filter is performing the data stream filter operation.

Claims

1. A method for eliminating unwanted interference in a digital return path of a cable television network comprising:

receiving an incoming data stream transmitted from a network element, the incoming data stream being configured to provide communications between the cable television network and the network element;

splitting the incoming data stream into two paths;

performing a Fast Fourier Transform on the incoming data stream in a first path to determine characteristics of interference in the incoming data stream;

calculating an adaptable interference threshold based on the determined characteristics, the calculated adaptable interference threshold not being selected from a preset value;

identifying any spectral components of the incoming data stream that exceed the adaptable interference threshold;

creating an adaptive filter to filter any identified spectral components based on the identified spectral components; and

filtering the incoming data stream with the adaptive filter to thereby filter ingress noise, and

loading a first plurality of filter coefficients into a first data stream filter while a second data stream filter is used to filter the data stream; and

upon calculating a second plurality of filter coefficients loading the second plurality of filter coefficients into the second data stream filter while the first data stream filter is used to filter the data stream,

wherein the step of creating an adaptive filter includes creating a plurality of filter coefficients based on the identified spectral components; and

using the newly created plurality of filter coefficients in a next clock cycle when filtering the incoming data stream with the adaptive filter,

wherein the adaptable interference threshold is determined from a running average of accumulated array samples from the result of the Fast Fourier Transform, a database of channel characteristics, learned channel characteristics, a duration and dynamics of any observed interference.

2. The method according to claim 1, wherein the creating occurs on a near real-time basis.

3. The method according to claim 1, further comprising:

selecting, based on the identified spectral components, one or more previously created filters from a filter bank storing a plurality of previously created filters.

4. The method according to claim 3, further comprising:

combining two or more filters of the one or more previously created filters to form the adaptive filter.

5. A method for processing a data stream on a digital return path of a cable network comprising:

receiving an incoming data stream transmitted from a network element, the incoming data stream being configured to provide communications between the cable television network and the network element;

calculating a Fast Fourier Transform on the incoming data stream to determine characteristics of interference in the incoming data stream;

calculating an adaptable interference threshold based on the determined characteristics, the calculated adaptable interference threshold not being selected from a present value;

comparing a result of the Fast Fourier Transform against the adaptable interference threshold;

calculating one or more new filter coefficients based on the comparing;

loading the one or more new filter coefficients into a data stream filter;

filtering the data stream with the data stream filter to thereby filter ingress noise;

loading a first plurality of filter coefficients into a first data stream filter while a second data stream filter is used to filter the data stream; and

upon calculating a second plurality of filter coefficients loading the second plurality of filter coefficients into the second data stream filter while the first data stream filter is used to filter the data stream, p1 wherein the adaptable interference threshold is determined from a running average of accumulated array samples from the result of the Fast Fourier Transform, a database of channel characteristics, learned channel characteristics, a duration and dynamics of any observed interference.

6. An apparatus for reducing interference in a digital return path of a cable network comprising:

a field programmable gate array to receive a data stream in the digital return path which has been transmitted from a network element, the field programmable gate array being programmed to filter potential interference in the data stream in the digital return path, the data stream being configured to provide communications between the network and the network element; and

a digital signal processor coupled to the field programmable gate array to reprogram the field programmable data array to remove the potential interference on an ongoing basis,

wherein the digital signal processor performs a Fast Fourier Transform on the data stream to determine characteristics of interference in the data stream;

calculates an adaptable interference threshold based on the determined characteristics, the calculated adaptable interference threshold not being selected from a preset value;

compares the output of the fast Fourier transform against the adaptable interference threshold to identify potential sources of interferences;

creates new filter coefficients based on the comparison for use by the field programmable gate array to use in subsequent filter operations to thereby filter ingress noise;

loads a first plurality of filter coefficients into a first data stream filter while a second data stream filter is used to filter the data stream; and

upon calculating a second plurality of filter coefficients loads the second plurality of filter coefficients into the second data stream filter while the first data stream filter is used to filter the data stream, and

wherein the adaptable interference threshold is determined from a running average of accumulated array samples from the result of the Fast Fourier Transform, a database of channel characteristics, learned channel characteristics, a duration and dynamics of any observed interference.