Method and apparatus for determining micro-reflections in a network

• US 8,537,972 B2
• Filed: 12/07/2006
• Issued: 09/17/2013
• Est. Priority Date: 12/07/2006
• Status: Active Grant

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Thompson, Robert J., Cooper, Michael J., Moore, Charles S., Moran, John L. III
• Primary Examiner(s): Ramakrishnaiah, Melur
• Application Number:
  US11/608,028
• Publication Number:
  US 20080140823A1
• Time in Patent Office: 2,476 Days
• Field of Search: 379/10.01, 379/29.01, 370/248, 370/249, 370251-252, 370/329, 370/330, 370/332, 370/431, 370/432, 370/437, 370/253, 370/9, 370/241, 370/242, 370/247, 725/111, 725/112, 725/118, 725/124, 725/138, 725/144, 375/224, 455/67.1, 455/62, 455/423, 455/425, 455/450, 455/461
• US Class Current: 379/10.01
• CPC Class Codes: H04L 43/50 Testing arrangements
• CPC Class Codes: H04M 1/24 Arrangements for testing

Abstract

The presence of micro-reflections is determined in a network by determining micro-reflections from amplifier and diplex filter impedance mismatches and micro-reflections from drop cable impedance mismatches. The micro-reflections from impedance mismatches are determined by instructing network element to transmit a test signal at a first symbol rate and a first resolution for amplifier and diplex filter impedance mismatches and a second frequency with a second symbol rate and second resolution for micro-reflections from drop cable impedance mismatches. The tests are performed with several frequencies and the channels with the least micro-reflections are identified.

Claims

1. An apparatus for monitoring a network comprising:

a microprocessor configured to provide instructions to a network element within a cable modem termination system (CMTS) serving group to tune to a test frequency and to transmit a test signal at a test symbol rate;

a receiver configured to receive the test signal from a network element; and

an equalizer which is configured to measure micro-reflections contained in the received test signal,

wherein the microprocessor is configured to determine an optimal communication channel to communicate with the network element based on the measured micro-reflections, further wherein the microprocessor is configured to assign the determined optimal communication channel to the CMTS serving group.

2. The apparatus of claim 1, wherein the test signal is instructed to be transmitted with a predetermined resolution.

3. The apparatus of claim 2, wherein the test symbol rate is about 2,560 ksym/s and the predetermined resolution is about 390 ns.

4. The apparatus of claim 2, wherein the test symbol rate is about 5,120 ksym/s and the predetermined resolution is about 195 ns.

5. The apparatus of claim 2, wherein the microprocessor repeatedly instructs the network element to tune to another frequency and transmit the test signal until all of the usable upstream frequencies have been tested.

6. The apparatus of claim 1, wherein the microprocessor is further configured to instruct the network element to transmit a second test signal having a second symbol rate, whereby the second test signal has a higher symbol rate than the first test signal.

7. The apparatus of claim 1, wherein the microprocessor is further configured to determine a distance from a source of the measured micro-reflections.

8. A method for monitoring a network comprising the steps of:

selecting a network element within a cable modem termination system (CMTS) serving group as a test network element;

instructing the test network element to transmit a test signal at a first frequency f1 as a test frequecy and a test symbol rate;

measuring micro-reflections on the test frequency by measuring micro-reflections in the test signals transmitted by the test network element;

instructing the test network element to transmit the test signal on a second frequency as the test frequency;

repeating the step of measuring micro-reflections on the test frequency as the second frequency by measuring micro-reflections in the test signal transmitted by the test network element;

determining optimum frequency channels for communications based on the micro-reflections in the test frequency as the first frequency and the second frequency; and

assigning the determined optimal frequency channels to the CMTS serving group.

9. The method of claim 8, wherein the step of measuring micro-reflections includes measuring micro-reflections caused by impedance mismatches in amplifiers and diplex filters in the network.

10. The method of claim 9, wherein the test signal is transmitted at a test symbol rate of approximately 2,560 kysm/s at a resolution of approximately 390 ns.

11. The method of claim 8, wherein the step of measuring micro-reflections includes measuring micro-reflections caused by impedance mismatches in drop cables in the network.

12. The method of claim 11, wherein the test signal is transmitted at a test symbol rate of approximately 5,120 kysm/s at a resolution of approximately 195 ns.

13. The method of claim 8, further including repeating the steps of instructing the test network element to transmit the test signal on another frequency selected as the test frequency;

and measuring micro-reflections until a plurality of usable upstream frequency channels have been tested as the test frequency.

14. The method of claim 8, further including the step of selecting another network element as the test network element and repeating the steps of instructing the test network element to transmit the test signal on a second frequency as the test frequency;

and

measuring micro-reflections until a plurality of network elements on a network port of a cable modem termination system and a plurality of usable upstream frequency channels have been tested.

15. The method of claim 8, further comprising the step of estimating a location of a source of micro-reflections in a network based on delay times between a signal and a corresponding micro-reflections and a propagation velocity factor of cables in the network.

16. The method of claim 8, further including the step of selecting another CMTS serving group and repeating the steps of instructing the test network element to transmit the test signal on a second frequency as the test frequency;

and measuring micro-reflections until a plurality of network elements on a network port of a cable modem termination system, a plurality of usable upstream frequency channels, and a plurality of CMTS serving groups have been tested.

17. A non-transitory computer readable medium carrying instructions for a computer to perform a method for monitoring a network, the method comprising the steps of:

selecting a network element within a cable modem termination system (CMTS) serving group as a test network element;

instructing the test network element to transmit a test signal at a first frequency f1 as a test frequecy and a test symbol rate;

measuring micro-reflections on the test frequency by measuring micro-reflections in the test signals transmitted by the test network element;

instructing the test network element to transmit the test signal on a second frequency as the test frequency;

repeating the step of measuring micro-reflections on the test frequency as the second frequency by measuring micro-reflections in the test signal transmitted by the test network element;

determining optimum frequency channels for communications based on the micro-reflections in the test frequency as the first frequency and the second frequency; and

assigning the determined optimal frequency channels to the CMTS serving group.

18. The non-transitory computer readable medium of claim 17, wherein the step of measuring micro-reflections includes measuring micro-reflections caused by impedance mismatches in amplifiers and diplex filters in the network.

19. The non-transitory computer readable medium of claim 18, wherein the test signal is transmitted at a test symbol rate of approximately 2,560 kysm/s at a resolution of approximately 390 ns.

20. The non-transitory computer readable medium of claim 17, wherein the step of measuring micro-reflections includes measuring micro-reflections caused by impedance mismatches in drop cables in the network.

21. The non-transitory computer readable medium of claim 20, wherein the test signal is transmitted at a test symbol rate of approximately 5,120 kysm/s at a resolution of approximately 195 ns.

22. The non-transitory computer readable medium of claim 17, further including repeating the steps of instructing the test network element to transmit the test signal on another frequency selected as the test frequency;

and measuring micro-reflections until a plurality of usable upstream frequency channels have been tested as the test frequency.

23. The non-transitory computer readable medium of claim 17, further comprising the step of selecting another network element as the test network element and repeating the steps of instructing the test network element to transmit the test signal on a second frequency as the test frequency;

and measuring micro-reflections until a plurality of network elements on a network port of a cable modem termination system and a plurality of usable upstream frequency channels have been tested.

24. The non-transitory computer readable medium of claim 17, wherein the instructions further comprise performing the step of estimating a location of a source of micro-reflections in a network based on delay times between a signal and a corresponding micro-reflections and a propagation velocity factor of cables in the network.