Modems, methods, and computer program products for falling back to a lower data rate protocol upon detecting abnormal line conditions during startup

• US 6,381,267 B1
• Filed: 03/08/1999
• Issued: 04/30/2002
• Est. Priority Date: 03/08/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Ye, Hua, Ware, Malcolm Scott, Neeser, Fredy D., Dholakia, Ajay, Davis, Gordon Taylor, Hwang, Dongming, Eleftheriou, Evangelos Stavros, Abdelilah, Youssef, Derby, Jeffrey Haskell
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US09/264,421
• Time in Patent Office: 1,149 Days
• Field of Search: 375/222, 375/219, 375/224, 379/93.1, 379/27
• US Class Current: 375/222
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Modems, methods, and computer program products for falling back to a low speed mode of operation upon detection of abnormal line conditions during startup perform a first phase of a multiphase startup procedure in accordance with a high speed mode of operation. A determination is then made whether the line conditions will support high speed communication. If a high speed connection cannot be established, then subsequent phases of the startup procedure will be performed in accordance with the low speed mode of operation. Otherwise, subsequent phases of the startup procedure will be performed in accordance with the high speed mode of operation. By detecting abnormal line conditions, such as digital discontinuity, severe attenuation, or a local loop having a non-linear frequency response, early in the startup protocol, the remainder of the startup protocol can be performed in accordance with a low speed more of operation as the detected abnormalities in the communication path will prevent the establishment of a higher data rate connection. Accordingly, the reliability and efficiency of the startup protocol are improved.

Claims

1. A method of falling back from a high speed mode to a lower speed mode in a modem using a startup procedure having multiple phases for startup in the high speed mode and corresponding multiple phases for startup in the low speed mode, the method comprising the steps of:

performing a first phase of the multiple phases for startup in the high speed mode;

determining, responsive to the performing step, if a connection to the modem is capable of supporting high speed mode operation;

performing a second phase of the multiple phases for startup in the high speed mode if the connection is capable of supporting high speed mode operation; and

performing a phase of the multiple phases for startup in the low speed mode if the connection is incapable of supporting high speed mode operation, wherein the phase of the multiple phases for startup in the low speed mode corresponds to the second phase of the multiple phases for startup in the high speed mode.

2. A method as recited in claim 1, wherein the determining step comprises the step of comparing a mean square error at a first symbol rate with a first threshold.

3. A method as recited in claim 1, wherein the determining step comprises the step of comparing a ratio of a mean square error at a first symbol rate and a mean square error at a second symbol rate with a first threshold.

4. A method as recited in claim 3, wherein the determining step further comprises the step of comparing the mean square error at the first symbol rate with a second threshold prior to the comparing the ratio step.

5. A method as recited in claim 1, wherein the determining step comprises the steps of:

measuring harmonic distortion at a plurality of frequencies;

calculating a total harmonic measurement; and

comparing the total harmonic measurement with a first threshold.

6. A method as recited in claim 1, wherein the step of performing a first phase comprises the step of receiving a plurality of line probing signals.

7. A method of falling back from a high speed mode to a lower speed mode in a modem using a startup procedure having multiple phases for startup in the high speed mode and corresponding multiple phases for startup in the low speed mode, the method comprising the steps of:

performing a first phase of the multiple phases for startup in the high speed mode;

then

comparing a mean square error at a first symbol rate with a first threshold to determine if the modem is capable of supporting high speed mode operation;

comparing the mean square error at the first symbol rate with a second threshold;

comparing a ratio of the mean square error at the first symbol rate and a mean square error at a second symbol rate with a third threshold to determine if the modem is capable of supporting high speed mode operation if the mean square error at the first symbol rate surpasses the second threshold;

measuring harmonic distortion at a plurality of frequencies;

calculating a total harmonic measurement;

comparing the total harmonic measurement with a fourth threshold to determine if the modem is capable of supporting high speed mode operation;

performing a second phase of the multiple phases for startup in the high speed mode if all of the comparing steps determine that the connection is capable of supporting high speed mode operation; and

performing a phase of the multiple phases for startup in the low speed mode if less than all of the comparing steps determines that the connection is incapable of supporting high speed mode operation, wherein the phase of the multiple phases for startup in the low speed mode corresponds to the second phase of the multiple phases for startup in the high speed mode.

8. A modem having multiple phases for startup in a high speed mode and corresponding multiple phases for startup in a low speed mode, comprising:

first means for performing a first phase of the multiple phases for startup in the high speed mode;

means for determining, responsive to the first means for performing, if a connection to the modem is capable of supporting high speed mode operation;

second means for performing, responsive to the means for determining, a second phase of the multiple phases for startup in the high speed mode; and

third means for performing, responsive to the means for determining, a phase of the multiple phases for startup in the low speed mode, wherein the phase of the multiple phases for startup in the low speed mode corresponds to the second phase of the multiple phases for startup in the high speed mode.

9. A modem as recited in claim 8, wherein the means for determining comprises means for comparing a mean square error at a first symbol rate with a first threshold.

10. A modem as recited in claim 8, wherein the means for determining comprises first means for comparing a ratio of a mean square error at a first symbol rate and a mean square error at a second symbol rate with a first threshold.

11. A modem as recited in claim 10, wherein the means for determining further comprises second means for comparing the mean square error at the first symbol rate with a second threshold, the first means for comparing being responsive to the second means for comparing.

12. A modem as recited in claim 8, wherein the means for determining comprises:

means for measuring harmonic distortion at a plurality of frequencies;

means for calculating a total harmonic measurement; and

means for comparing the total harmonic measurement with a first threshold.

13. A modem as recited in claim 8, wherein the first means for performing comprises means for receiving a plurality of line probing signals.

14. A modem having multiple phases for startup in a high speed mode and corresponding multiple phases for startup in a low speed mode, comprising:

first means for performing a first phase of the multiple phases for startup in the high speed mode;

first means for comparing, responsive to the first means for performing, a mean square error at a first symbol rate with a first threshold to determine if the modem is capable of supporting high speed mode operation;

second means for comparing, responsive to the first means for performing, the mean square error at the first symbol rate with a second threshold;

third means for comparing, responsive to the first means for performing and the second means for comparing, a ratio of the mean square error at the first symbol rate and a mean square error at a second symbol rate with a third threshold to determine if the modem is capable of supporting high speed mode operation;

means for measuring, responsive to the first means for performing, harmonic distortion at a plurality of frequencies;

means for calculating, responsive to the means for measuring, a total harmonic measurement;

fourth means for comparing the total harmonic measurement with a fourth threshold to determine if the modem is capable of supporting high speed mode operation;

second means for performing, responsive to the first, third, and fourth means for comparing, a second phase of the multiple phases for startup in the high speed mode; and

third means for performing, responsive to the first, third, and fourth means for comparing, a phase of the multiple phases for startup in the low speed mode, wherein the phase of the multiple phases for startup in the low speed mode corresponds to the second phase of the multiple phases for startup in the high speed mode.

15. A computer program product for detecting abnormal conditions on a communication medium and used in a modem having multiple phases for startup in a high speed mode and corresponding multiple phases for startup in a low speed mode, comprising:

a computer readable storage medium having computer readable program code means embodied therein, the computer readable program code means comprising;

first logic configured to perform a first phase of the multiple phases for startup in the high speed mode;

logic configured to determine, responsive to the first logic configured to perform, if a connection to the modem is capable of supporting high speed mode operation;

second logic configured to perform, responsive to the logic configured to determine, a second phase of the multiple phases for startup in the high speed mode; and

third logic configured to perform, responsive to the logic configured to determine, a phase of the multiple phases for startup in the low speed mode, wherein the phase of the multiple phases for startup in the low speed mode corresponds to the second phase of the multiple phases for startup in the high speed mode.

16. A computer program product as recited in claim 15, wherein the logic configured to determine comprises logic configured to compare a mean square error at a first symbol rate with a first threshold.

17. A computer program product as recited in claim 15, wherein the logic configured to determine comprises first logic configured to compare a ratio of a mean square error at a first symbol rate and a mean square error at a second symbol rate with a first threshold.

18. A computer program product as recited in claim 17, wherein the logic configured to determine further comprises second logic configured to compare the mean square error at the first symbol rate with a second threshold, the first logic configured to compare being responsive to the second logic configured to compare.

19. A computer program product as recited in claim 15, wherein the logic configured to determine comprises:

logic configured to measure harmonic distortion at a plurality of frequencies;

logic configured to calculate a total harmonic measurement; and

logic configured to comparing the total harmonic measurement with a first threshold.

20. A computer program product as recited in claim 15, wherein the first logic configured to perform comprises logic configured to receive a plurality of line probing signals.

21. A computer program product for detecting abnormal conditions on a communication medium and used in a modem having multiple phases for startup in a high speed mode and corresponding multiple phases for startup in a low speed mode, comprising:

a computer readable storage medium having computer readable program code means embodied therein, the computer readable program code means comprising;

first logic configured to perform a first phase of the multiple phases for startup in the high speed mode;

first logic configured to compare, responsive to the first logic configured to perform, a mean square error at a first symbol rate with a first threshold to determine if the modem is capable of supporting high speed mode operation;

second logic configured to compare, responsive to the first logic configured to perform, the mean square error at the first symbol rate with a second threshold;

third logic configured to compare, responsive to the first logic configured to perform and the second logic configured to compare, a ratio of the mean square error at the first symbol rate and a mean square error at a second symbol rate with a second threshold to determine if the modem is capable of supporting high speed mode operation;

logic configured to measure, responsive to the first logic configured to perform, harmonic distortion at a plurality of frequencies;

logic configured to calculate, responsive to the logic configured to measure, a total harmonic measurement;

fourth logic configured to compare the total harmonic measurement with a third threshold to determine if the modem is capable of supporting high speed mode operation;

second logic configured to perform, responsive to the first, third, and fourth logic configured to compare, a second phase of the multiple phases for startup in the high speed mode; and

third logic configured to perform, responsive to the first, third, and fourth logic configured to compare, a phase of the multiple phases for startup in the low speed mode, wherein the phase of the multiple phases for startup in the low speed mode corresponds to the second phase of the multiple phases for startup in the high speed mode.