System and method to test network performance with impairments

• US 7,451,472 B2
• Filed: 09/30/2002
• Issued: 11/11/2008
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Cable Television Laboratories Incorporated
• Original Assignee: Cable Television Laboratories Incorporated
• Inventors: Williams, Thomas H.
• Primary Examiner(s): Grant; Christopher
• Assistant Examiner(s): Ray; Amit K
• Application Number:
  US10/262,234
• Publication Number:
  US 20040073937A1
• Time in Patent Office: 2,234 Days
• Field of Search: 725/127, 725/107, 725/121, 725/124, 725/125
• US Class Current: 725/107
• CPC Class Codes: H04N 17/00 Diagnosis, testing or measuring for television systems or their details

Abstract

The upstream performance characteristics of a network are measured by looping a signal through both the downstream and upstream paths of the network. Test equipment may be located at a headend of the network and configured to transmit a signal downstream to a remotely located loopback device that redirects the signal in the upstream path to the test equipment. The upstream characteristics may be predominant in the analysis of the return signal because the downstream path may be relatively free from noise.

Claims

1. A method for testing a non-symmetrical network comprising:

providing said non-symmetrical network having a distribution point, a first direction of transmission operating at a first frequency, and a second direction of transmission operating at a second frequency, said first direction of transmission corresponding to a downstream direction of transmission operating at said first frequency that is a higher frequency than said second frequency, said second direction of transmission corresponding to an upstream direction of transmission operating at said second frequency that is a lower frequency than said first frequency, and said upstream direction of transmission having larger impairments than said downstream direction of transmission;

connecting a test apparatus having a cable modem termination system (CTMS), an input to said non-symmetrical network, an output to said non-symmetrical network, at least one cable modem, a diplex filter, and an upconverter having an input and an output at said distribution point of said non-symmetrical network such that said test apparatus output is connected to said first direction of transmission that corresponds to said downstream direction of transmission through a combiner device, said test apparatus input is connected to said second direction of transmission that corresponds to said upstream direction of transmission through a splitter device, said cable modem connects to said CTMS and said upconverter input through said diplex filter, said CTMS connects at said input of said test apparatus to said upstream direction of transmission, and said upconverter output connects at said output of said test apparatus to said downstream direction of transmission;

connecting a loopback device having an input and an output to said non-symmetrical network at a remote location from said distribution point such that said loopback device input is connected to said first direction of transmission operating at said first frequency and said loopback device output is connected to said second direction of transmission operating at said second frequency;

creating a test signal in said test apparatus;

transmitting said test signal from said test apparatus to said loopback device through said test apparatus output on said first direction of transmission operating at said first frequency;

receiving said test signal on said first direction of transmission at said loopback device input at said first frequency;

transforming said test signal from said first frequency operating at said higher frequency of said downstream direction of transmission to said second frequency operating at said lower frequency of said upstream direction of transmission in said loopback device operating as a downconverter device;

transmitting said test signal from said loopback device output to said distribution point on said second direction of transmission operating at said second frequency;

receiving said test signal on said second direction of transmission at said test apparatus input connected to said second direction of transmission and operating at said second frequency; and

performing at least one analysis measurement test on said test signal.

2. A method for testing a non-symmetrical network comprising:

providing said non-symmetrical network having a distribution point, a first direction of transmission operating at a first frequency, and a second direction of transmission operating at a second frequency, said first direction of transmission corresponding to an upstream direction of transmission operating at said first frequency that is a lower frequency than said second frequency, said second direction of transmission corresponding to a downstream direction of transmission operating at said second frequency that is a higher frequency than said first frequency, and said upstream direction of transmission has larger impairments than said downstream direction of transmission;

connecting a test apparatus having a cable modem termination system (CTMS), an input to said non-symmetrical network, an output to said non-symmetrical network, at least one cable modem, and a diplex filter at said distribution point of said non-symmetrical network such that said test apparatus output is connected to said first direction of transmission that corresponds to said upstream direction of transmission, said test apparatus input is connected to said second direction of transmission that corresponds to said downstream direction of transmission through a downconverter device, said cable modem is connected to said CTMS and said test apparatus output through said diplex filter;

connecting a loopback device having an input and an output to said non-symmetrical network at a remote location from said distribution point such that said loopback device input is connected to said first direction of transmission corresponding to said upstream direction of transmission operating at said first frequency through a splitter device and said loopback device output is connected to said second direction of transmission corresponding to said downstream direction of transmission operating at said second frequency through a combiner device;

creating a test signal in said test apparatus;

transmitting said test signal from said test apparatus to said loopback device through said test apparatus output on said first direction of transmission operating at said first frequency;

receiving said test signal on said first direction of transmission at said loopback device input at said first frequency;

transforming said test signal from said first frequency operating at said lower frequency of said upstream direction of transmission to said second frequency operating at said higher frequency of said downstream direction of transmission in said loopback device operating as an upconverter device;

transmitting said test signal from said loopback device output to said distribution point on said second direction of transmission operating at said second frequency;

receiving said test signal on said second direction of transmission at said test apparatus input connected to said second direction of transmission and operating at said second frequency; and

performing at least one analysis measurement test on said test signal.

3. A non-symmetrical network test system comprising:

a non-symmetrical network that has a distribution point, a first direction of transmission operating at a first frequency, and a second direction of transmission operating at a second frequency, said first direction of transmission corresponding to a downstream direction of transmission operating at said first frequency that is a higher frequency than said second frequency, said second direction of transmission corresponding to an upstream direction of transmission operating at said second frequency that is a lower frequency than said first frequency, and said upstream direction of transmission having larger impairments than said downstream direction of transmission, and further comprising;

a test apparatus located at said distribution point of said non-symmetrical network that has a cable modem termination system (CTMS), an input to said non-symmetrical network, an output to said non-symmetrical network, at least one cable modem, a diplex filter, and an upconverter that has an input and an output, such that said test apparatus output is connected to said first direction of transmission that corresponds to said downstream direction of transmission, said test apparatus input is connected to said second direction of transmission that corresponds to said upstream direction of transmission, said cable modem is connected to said CTMS and said upconverter input through said diplex filter, said CTMS is connected at said input of said test apparatus to said upstream direction of transmission, and said upconverter output is connected at said output of said test apparatus to said downstream direction of transmission;

a loopback device located at a remote location from said distribution point that has an input and an output to said non-symmetrical network, such that said loopback device input is connected to said first direction of transmission operating at said first frequency and said loopback device output is connected to said second direction of transmission operating at said second frequency;

a test signal creation subsystem that is part of said test apparatus that creates a test signal and transmits said test signal from said test apparatus to said loopback device through said test apparatus output on said first direction of transmission operating at said first frequency;

a signal transformation subsystem that is part of said loopback device that receives said test signal on said first direction of transmission at said loopback device input at said first frequency, transforms said test signal from said first frequency to said second frequency, and transmits said test signal from said loopback device output to said distribution point on said second direction of transmission operating at said second frequency;

a test signal reception subsystem that is part of said test apparatus that receives said test signal on said second direction of transmission at said test apparatus input connected to said second direction of transmission and operating at said second frequency; and

a test signal analysis system that performs at least one analysis measurement test on said test signal.

4. The non-symmetrical network test system of claim 3 further comprising:

a combiner device that connects said test apparatus output to said downstream direction of transmission;

a splitter device that connects said test apparatus input to said upstream direction of transmission; and

a downconverter subsystem that is part of said signal transformation subsystem of said loopback device that transforms said test signal from said higher frequency of said downstream direction of transmission to said lower frequency of said upstream direction of transmission.

5. A non-symmetrical network test system comprising:

a non-symmetrical network that has a distribution point, a first direction of transmission operating at a first frequency, and a second direction of transmission operating at a second frequency;

a test apparatus located at said distribution point of said non-symmetrical network that has a cable modem termination system (CTMS), an input to said non-symmetrical network, an output to said non-symmetrical network, at least one cable modem, and a diplex filter, such that said test apparatus output is connected to said first direction of transmission, said test apparatus input is connected to said second direction of transmission, and said cable modem is connected to said CTMS and said test apparatus output through said diplex filter;

a loopback device located at a remote location from said distribution point that has an input and an output to said non-symmetrical network, such that said loopback device input is connected to said first direction of transmission operating at said first frequency and said loopback device output is connected to said second direction of transmission operating at said second frequency;

a test signal creation subsystem that is part of said test apparatus that creates a test signal and transmits said test signal from said test apparatus to said loopback device through said test apparatus output on said first direction of transmission operating at said first frequency;

a signal transformation subsystem that is part of said loopback device that receives said test signal on said first direction of transmission at said loopback device input at said first frequency, transforms said test signal from said first frequency to said second frequency, and transmits said test signal from said loopback device output to said distribution point on said second direction of transmission operating at said second frequency;

a test signal reception subsystem that is part of said test apparatus that receives said test signal on said second direction of transmission at said test apparatus input connected to said second direction of transmission and operating at said second frequency; and

a test signal analysis system that performs at least one analysis measurement test on said test signal.

6. The non-symmetrical network test system of claim 5 wherein said first direction of transmission corresponds to an upstream direction of transmission operating at said first frequency that is a lower frequency than said second frequency, said second direction of transmission corresponds to a downstream direction of transmission operating at said second frequency that is a higher frequency than said first frequency, and said upstream direction of transmission has larger impairments than said downstream direction of transmission, and further comprising:

a downconverter device that connects said test apparatus input to said downstream direction of transmission;

a splitter device that connects said loopback device input to said upstream direction of transmission;

a combiner device that connects said loopback device output to said downstream direction of transmission; and

an upconverter subsystem that is part of said signal transformation subsystem of said loopback device that transforms said test signal from said lower frequency of said upstream direction of transmission to said higher frequency of said downstream direction of transmission.