HFC reverse path using an intelligent dynamic switch

• US 20030121056A1
• Filed: 12/21/2001
• Published: 06/26/2003
• Est. Priority Date: 12/21/2001
• Status: Abandoned Application

• Current Assignee: Scientific-Atlanta LLC (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta LLC (Cisco Systems, Inc.)
• Inventors: Job, David M., Sorenson, Donald C., West, Lamar E. Jr.
• Application Number:
  US10/026,283
• Publication Number:
  US 20030121056A1
• Time in Patent Office: Days
• US Class Current: 725/125
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04N 7/104 Switchers or splitters
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

The present invention provides an apparatus and method for reducing the amount of ingress noise that is present in the reverse path of a two-way communication network. The present invention employs intelligent dynamic switches (200) that determine whether desirable reverse signals are present at that point in the network. If so, the reverse signals, which also probably include some amount of ingress noise, are allowed to pass further upstream. If no desirable reverse signals are present at that point in the network, the IDS (200) blocks the transmission of any reverse signal further upstream, thereby blocking the transmission of any ingress signals. Although ingress noise is allowed to travel upstream with desirable reverse signals, the performance of the overall network is improved because ingress signals are blocked at various points in the network, thereby reducing the total amount of cumulative ingress noise signals that would otherwise be present in the network.

Claims

1. A method for reducing ingress signals in a communication network, comprising the steps of:

receiving an input signal, the input signal including at least one of a desirable signal and ingress signals;

determining if the input signal includes a desirable signal;

if the input signal includes a desirable signal, allowing the input signal to proceed through the communication network;

otherwise, preventing the transmission of the input signal.

2. The method of claim 1, wherein the determining step comprises determining whether the input signal includes at least one RF carrier signal.

3. The method of claim 2, wherein determining whether the input signal includes at least one RF carrier signal comprises determining whether the signal power level exceeds a threshold level.

4. The method of claim 1, wherein the determining step comprises the steps of:

delaying the input signal for a predetermined period of time; and

determining whether the input signal includes at least one RF carrier signal during the predetermined period of time.

5. A dynamic switch for reducing the amount of ingress signals in a communication network, comprising:

an input for receiving a first RF input signal from a first portion of the communication network, the first RF input signal including at least one of a desirable input signal and an ingress signal;

an analog-to-digital converter for converting the first RF input signal to a digital input signal, the digital input signal including a plurality of digital input signal values;

a detector for determining whether the signal power level of the digital input signal exceeds a threshold value;

a buffer for temporarily storing the digital input signal values and for outputting digital input signal values when the detector determines that the signal power level of the digital input signal exceeds the threshold value;

a digital-to-analog converter for receiving the digital input signal values from the buffer and for converting the digital input signal values into a second RF input signal corresponding to the first RF input signal; and

an output for providing the second RF input signal to a second portion of the communication network,

whereby the second RF input signal is provided to the second portion of the communication network only when the detector determines that the signal power level of the digital input signal exceeds the threshold value.

6. In a cable television network including a forward path for transmitting signals from a headend to subscriber equipment and a reverse path for transmitting signal from the subscriber equipment to the headend, a dynamic switch for reducing the amount of reverse ingress noise in the reverse path of the cable television network, comprising:

an input for receiving a first analog reverse signal from a downstream portion of the cable television network, the first analog reverse signal including at least one of a desirable input signal and an ingress noise signal;

an analog-to-digital converter for converting the first analog reverse signal to a digital reverse signal, the digital reverse signal including a plurality of digital reverse signal values;

a detector for determining whether the signal power level of the digital reverse signal exceeds a threshold value;

a buffer for temporarily storing the digital reverse signal values and for outputting digital reverse signal values when the detector determines that the signal power level of the digital reverse signal exceeds the threshold value;

a digital-to-analog converter for receiving the digital reverse signal values from the buffer and for converting the digital reverse signal values into a second analog reverse signal corresponding to the first analog reverse signal; and

an output for providing the second analog reverse signal to an upstream portion of the cable television network,

whereby the second analog reverse signal is provided to the upstream portion of the cable television network only when the detector determines that the signal power level of the digital reverse signal exceeds the threshold value.

7. In a broadband communications network having forward and reverse paths for transmitting forward and reverse RF signals, respectively, the reverse RF signals including ingress signals, the broadband communications network including an intelligent dynamic switch (IDS), the IDS comprising:

an A/D converter for digitizing the reverse RF signals and for providing the digital signals to the data buffer and the carrier detect circuit;

a data buffer for delaying the digital signals by a predetermined timeframe;

a carrier detect circuit coupled to the A/D converter for receiving the digital signals and for detecting the presence of at least one RF carrier signal within the predetermined timeframe; and

an enable switch that is controlled by the carrier detect circuit for allowing the delayed digital signals to be transmitted along with the at least one RF carrier signal; and

a D/A converter coupled to the enable switch for converting the digital signals back to reverse RF signals,

whereby controlling the transmission of the reverse RF signals reduces the amount of ingress noise signals in the reverse path of the broadband communications network.

8. The broadband communications network of claim 7, wherein the carrier detect circuit detects the presence of the at least one RF carrier signal by determining when power level values associated with the reverse RF signals is above a threshold value for the predetermined timeframe.

9. The broadband communications network of claim 7, wherein the IDS further comprises:

a first filter having a high pass filter and a low pass filter, the high pass filter for isolating forward RF signals, and the low pass filter for receiving the reverse RF signals provided by the enable switch; and

a second filter having a high pass filter and a low pass filter, the high pass filter coupled to the high pass filter of the first filter for providing the forward RF signals to the forward path, and the low pass filter for isolating the reverse RF signals and for providing the reverse RF signals to the IDS.

10. In a broadband communications network having forward and reverse paths for transmitting forward and reverse signals, respectively, the reverse signals including power level values and ingress signals, the broadband communications network including a distribution tap, the distribution tap including:

a first diplex filter having a high pass filter and a low pass filter, the high pass filter for isolating the forward signals, and the low pass filter for isolating the reverse signals;

forward path elements coupled to the high pass filter of the first diplex filter for processing;

a second diplex filter having a high pass filter and a low pass filter, the high pass filter coupled to the forward path elements for providing the processed forward signals to the forward path, and the low pass filter for receiving reverse signals;

an intelligent dynamic switch (IDS) coupled to the low pass filter of the second diplex filter, the intelligent dynamic switch comprising;

detecting means for detecting when at least one reverse carrier signal is present in the reverse signals;

delaying means for delaying the reverse signals; and

a switch controlled by the detecting means for releasing the delayed signals upon detection of the at least one reverse carrier signal; and

reverse path elements coupled to the IDS for processing and for providing the processed reverse RF signals to the low pass filter of the first filter,

wherein upon detection of the at least one RF carrier signal, the reverse RF signals are provided to the reverse path elements.

11. The distribution tap of claim 10, wherein the IDS further comprises:

digitizing means for converting the reverse signals to digital signals, and for providing the digital signals to the detecting means and the delaying means; and

converting means coupled to the switch for converting the digital signals back to the reverse signals.

12. The distribution tap of claim 11, wherein the detecting means is a digital carrier detect circuit.

13. The distribution tap of claim 12, wherein the digital carrier detect circuit detects the presence of the at least one reverse carrier signal by determining whether the power level values exceed a threshold value within a predetermined period of time.

14. A broadband communications network having forward and reverse paths for transmitting forward and reverse signals, respectively, the reverse signals having power level values and ingress signals, the broadband communications network comprising:

a plurality of intelligent dynamic switches (IDSs), each IDS comprising;

detecting means for detecting when at least one reverse carrier signal is present in the reverse signals;

delaying means for delaying the reverse signals; and

a switch controlled by the detecting means for releasing the delayed signals upon detection of the at least one reverse carrier signal,

wherein the plurality of intelligent dynamic switches blocks the ingress signals from further transmission upstream in the reverse path, thereby significantly reduces the ingress signals that are transmitted to a headend facility.

15. The broadband communications network of claim 14, wherein each IDS further comprises:

an A/D converter for digitizing the reverse signals prior to the detecting means; and

a D/A converter coupled to the switch for providing reverse signals in accordance with the received delayed digital signals.

16. The broadband communications system of claim 15, wherein the detecting means is a digital carrier detect circuit.

17. The broadband communications system of claim 14, wherein the digital carrier detect circuit detects the presence of the at least one reverse carrier signal by determining whether the power level values exceed a threshold value.

18. The broadband communications network of claim 14, wherein the plurality of IDSs are located in various locations in the reverse paths.

19. The broadband communications network of claim 14, wherein a number of the plurality of IDSs is located in a communications device, wherein the communication device is one of a distribution tap and one of an RF amplifier.