Method and apparatus for testing network interfaces

• US 9,203,730 B1
• Filed: 03/13/2013
• Issued: 12/01/2015
• Est. Priority Date: 11/19/2012
• Status: Active Grant

• Current Assignee: Sifos Technologies
• Original Assignee: Sifos Technologies
• Inventors: Johnson, Peter G., Bennett, Kendrick R., Skinner, John H.
• Primary Examiner(s): LIU, JUNG
• Application Number:
  US13/798,422
• Time in Patent Office: 993 Days
• US Class Current: 1/1
• CPC Class Codes: H04L 43/08 Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
• CPC Class Codes: H04L 43/50 Testing arrangements

Abstract

Methods and apparatus provide for a system to measure transceiver parameters and test network interfaces at a physical layer without requiring specialized interface fixtures and excessive preparation and intervention.

Claims

1. A method to test electrical characteristics of a port-under-test, the method comprising:

establishing a communication link to the port-under-test using a test cable connected between the port-under-test and a test port, having a medium dependent interface (MDI) and an integrated transceiver having a diagnostic digital receiver;

configuring the diagnostic digital receiver;

probing at least one diagnostic digital receiver signal originating from the port-under test over at least one wire pair within the test cable while maintaining the communications link to the port-under test;

processing the at least one probed diagnostic digital receiver signal into a measurement;

adjusting the measurement to remove from the measurement at least one predetermined power characteristic associated with at least one of;

the test cable;

the MDI; and

the diagnostic digital receiver; and

comparing the adjusted measurement to a predetermined standard for the port-under-test.

2. The method of claim 1, wherein configuring the diagnostic digital receiver comprises establishing a predetermined receiver gain;

wherein probing the at least one diagnostic digital receiver signal comprises probing a received digital signal;

wherein processing the at least one probed diagnostic digital receiver signal into a measurement comprises computing signal power of the received digital signal averaged over a predetermined time interval;

wherein adjusting the measurement to remove from the measurement at least one predetermined power characteristic comprises removing from the computed signal power a predetermined power loss attributable to the test cable, to the medium dependent interface, and to the diagnostic digital receiver; and

wherein comparing the adjusted measurement comprises comparing the adjusted measurement of computed signal power to a predetermined power level.

3. The method of claim 2, wherein the port-under-test comprises an ideal transmitter transmitting nominal power signals on at least one wire pair;

and

further comprising retaining the measurement as a calibration of predetermined power loss attributable to the test cable, the medium dependent interface, and the diagnostic digital receiver.

4. The method of claim 1, wherein configuring the diagnostic digital receiver comprises establishing a predetermined receiver gain;

wherein probing the at least one diagnostic digital receiver signal comprises probing a received digital signal and a reproduced digital signal at a plurality of symbol interval offsets;

wherein processing the at least one probed diagnostic digital receiver signal into a measurement comprises;

computing correlation power averaged over a predetermined time interval for each of the plurality of symbol interval offsets to produce an inter-symbol interference measurement;

convolving the inter-symbol interference measurement with a plurality of constant amplitude sine waves to produce a power-frequency spectrum;

wherein adjusting the measurement to remove from the measurement at least on predetermined power characteristic comprises removing from the power-frequency spectrum a predetermined power-frequency spectrum attributable to the test cable, the medium dependent interface, and the diagnostic digital receiver; and

wherein comparing the adjusted measurement comprises comparing the adjusted measurement to a power frequency spectrum corresponding approximately to an ideal transmitted signal.

5. The method of claim 4, further comprising configuring a second different test port to be a calibration test port configured with a nominal power-frequency spectrum;

wherein the port-under-test comprises the calibration test port; and

further comprising retaining the inter-symbol interference measurement attributable to the test cable, to the medium dependent interface, and to the diagnostic digital receiver as a calibration.

6. The method of claim 1, wherein configuring the diagnostic digital receiver comprises establishing a predetermined receiver gain;

wherein probing the at least one diagnostic digital receiver signal comprises probing a corrected digital signal and a reproduced digital signal;

wherein processing the at least one probed diagnostic digital receiver signal into a measurement comprises computing power of the corrected digital signal and the reproduced digital signal averaged over a predetermined time interval;

wherein adjusting the measurement to remove from the measurement at least on predetermined power characteristic comprises removing a predetermined noise power level attributable to the diagnostic digital receiver from the corrected digital signal power; and

wherein comparing the adjusted measurement comprises computing a difference between the adjusted corrected digital signal power and the reproduced digital signal power and comparing that difference to the reproduced digital signal power.

7. The method of claim 1, wherein configuring the diagnostic digital receiver comprises:

establishing a predetermined receiver gain;

establishing a predetermined transmitter level;

wherein probing the at least one diagnostic digital receiver signal comprises probing at least one canceller filter coefficient for the at least one wire pair;

wherein processing the at least one probed diagnostic digital receiver signal into a measurement comprises computing power of the at least one canceller filter coefficient averaged over a predetermined time interval;

wherein adjusting the measurement to remove from the measurement at least on predetermined power characteristic comprises;

removing a predetermined canceller filter coefficient power attributable to the test cable, the medium dependent interface, and the diagnostic digital receiver from each probed canceller filter coefficient;

summing power levels from the at least one adjusted canceller filter coefficient; and

wherein comparing the adjusted measurement comprises comparing the adjusted measurement to a predetermined power transmitted to the port-under-test on the wire pair.

8. The method of claim 1 further comprising:

configuring a second different test port to be a calibration test port terminated with a nominal impedance;

connecting the calibration test port as the port-under-test; and

retaining the predetermined power characteristic measurement as a calibration.

9. The method of claim 1 further comprising:

configuring a second different test port to be a calibration test port terminated with a predetermined mismatch impedance;

connecting the calibration test port as the port-under-test;

computing transmit power from the adjusted measurement in combination with a predetermined return loss associated with the predetermined mismatch impedance;

retaining the transmit power as the power transmitted; and

wherein probing the at least one diagnostic digital receiver signal comprises probing at least one echo canceller filter coefficient for at least one wire pair.

10. The method of claim 1, wherein the at least one diagnostic digital receiver signal on the at least one wire pair is an Ethernet signal, the integrated transceiver comprises an Ethernet transceiver, the port-under-test comprises an Ethernet port and the test port and the port-under-test are coupled by an Ethernet patch cable;

and

wherein while measurements are performed the Ethernet port-under-test is in a state of one of;

idle transmission; and

transmitting arbitrary packet data.

11. A method to test electrical characteristics of a port-under-test, the method comprising:

establishing a communication link to the port-under-test using a test cable, the test cable connected between the port-under-test and a test port, the test port having an integrated transceiver, a physical layer impairment generator, and a medium dependent interface, the medium dependent interface having a wideband impairment coupler;

generating at least one pre-characterized physical layer impairment;

applying at least one pre-characterized physical layer impairment through the wideband impairment coupler to at least one wire pair of the test cable;

obtaining at least one status indication from the integrated transceiver while maintaining an idle communications link to the port-under-test;

obtaining at least one status indication from the integrated transceiver while transmitting arbitrary packet data to the port-under-test;

analyzing the at least one status indication from the integrated transceiver; and

determining disruption of integrity and stability of the communication link caused by at least one pre-characterized physical layer impairment from the at least one status indication.

12. The method of claim 11, wherein applying the at least one pre-characterized physical layer impairment to at least one wire pair comprises at least one of:

applying a predetermined passive line insertion loss replicating a worst case channel insertion loss;

applying an adjustable level of frequency contoured noise, to approximate a nominal power spectrum of transmission signals;

applying an adjustable random transmission symbol timing modulation having a predetermined modulation frequency spectrum; and

applying an adjustable symbol frequency offset from nominal symbol rate.

13. The method of claim 11, wherein obtaining the at least one status indication comprises at least one of:

sampling a remote receiver error status indicator; and

sampling a link status indicator.

14. The method of claim 11, wherein the integrated transceiver comprises an Ethernet transceiver, the port-under-test comprises an Ethernet port and the test port and the port-under-test are coupled by an Ethernet patch cable;

and

wherein while measurements are performed the Ethernet port-under-test is a state of

idle Ethernet signal transmission

transmitting arbitrary Ethernet packet data.

15. A system to measure transceiver parameters comprising:

a test port comprising

a microcontroller;

a medium dependent interface in communication with the microcontroller and including a wideband physical layer impairment coupler;

an integrated transceiver in communication with the microcontroller and the medium dependent interface, the integrated transceiver comprising;

a diagnostic digital receiver including a digital differential power detector; and

a transmitter; and

a memory including at least one predetermined power characteristic from at least one of;

a test cable;

the medium dependent interface; and

the diagnostic digital receiver.

16. The system of claim 15, wherein the diagnostic digital receiver further comprises:

an analog front end;

an analog to digital (A/D) converter coupled to the analog front end;

a digital signal correction logic coupled to the A/D converter;

a digital discriminator coupled to the digital signal correction logic; and

wherein the digital differential power detector is coupled to the A/D converter, the digital signal correction logic, and the digital discriminator.

17. The system of claim 15, wherein the test port further comprises at least one of:

a wideband impairment coupler including a passive insertion loss impairment circuit switchably coupled to at least one wire pair; and

a wideband impairment coupler including a wideband impedance mismatch circuit switchably coupled to at least one wire pair and wherein the test port functions as a calibration test port; and

a frequency contoured noise generator in communication with the microcontroller and coupled to the medium dependent interface; and

a timing generator in communication with the microcontroller and coupled to the integrated transceiver.

18. The system of claim 15 further comprising a plurality of test ports having a corresponding plurality of test cable connections linkable to a corresponding plurality of ports-under-test;

a backplane coupled to each of the plurality of test ports;

a controller blade interfacing the backplane to a host computer; and

a trigger bus communicating a trigger signal from the controller blade to the plurality of test ports.

19. The system of claim 15 wherein the test port further comprises a pass-through medium dependent interface switchably connectable to the medium dependent interface;

wherein the integrated transceiver is switchably connectable to the medium dependent interface; and

wherein the medium dependent interface with wideband impairment coupler is coupled to the pass-through medium dependent interface in place of

the integrated transceiver.

20. A computer readable storage medium for tangibly storing thereon computer readable instructions for a method comprising:

establishing a communication link to the port-under-test using a test cable connected between a port-under-test and a test port, having a medium dependent interface (MDI) and an integrated transceiver having a diagnostic digital receiver;

configuring the diagnostic digital receiver;

probing at least one diagnostic digital receiver signal originating from the port-under test over at least one wire pair within the test cable while maintaining the communications link to the port-under test;

processing the at least one probed diagnostic digital receiver signal into a measurement;

adjusting the measurement to remove from the measurement at least one predetermined power characteristic associated with at least one of;

the test cable;

the MDI; and

the diagnostic digital receiver; and

comparing the adjusted measurement to a predetermined standard for the port-under-test.