Rate adaptive XDSL communication system and method

• US 5,999,540 A
• Filed: 12/22/1998
• Issued: 12/07/1999
• Est. Priority Date: 12/22/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: McGhee, David Wesley
• Primary Examiner(s): Ton, Dang
• Assistant Examiner(s): HO, TUAN Q
• Application Number:
  US09/219,148
• Time in Patent Office: 350 Days
• Field of Search: 370/465, 370/466, 370/467, 370/468, 370/469, 370/391, 370/437, 375/222, 375/225, 375/232, 379/93.01, 379/93.05, 379/93.06, 379/93.31
• US Class Current: 370/465
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling

Abstract

A rate adaptive digital subscriber line (XDSL) communication system and method are disclosed. An XDSL link for XDSL equipment is trained at a data rate set by a baud rate and a constellation size. Actual operating characteristics of the XDSL equipment are then obtained from parameters for the trained XDSL link. One or more rate adaptive data tables storing empirical data for performance of the XDSL equipment are accessed. Then, it is determined whether the trained data rate will provide a desired bit error rate using the actual operating characteristics and the empirical data from the accessed one or more of the rate adaptive data tables. In one embodiment, if the trained data rate will not provide the desired bit error rate, a new data rate is selected using the empirical data and the actual operating characteristics. Then, the XDSL link is trained using the new data rate, and the process is repeated. Further, in one embodiment, the actual operating characteristics used comprise the actual receiver gain and signal-to-noise ratio, and the empirical data comprises specified receiver gains, signal-to-noise ratios, baud rates and constellation sizes used to achieve a desired bit error rate.

Claims

1. A method for rate adaptive digital subscriber line (XDSL) communication, comprising:

training an XDSL link for XDSL equipment at a data rate set by a baud rate and a constellation size;

obtaining actual operating characteristics of the XDSL equipment from parameters for the trained XDSL link;

accessing one or more rate adaptive data tables storing empirical data for performance of the XDSL equipment; and

determining whether the trained data rate will provide a desired bit error rate using the actual operating characteristics and the empirical data from the accessed one or more of the rate adaptive data tables.

2. The method of claim 1, further comprising, if the trained data rate will not provide the desired bit error rate:

selecting a new data rate using the empirical data and the actual operating characteristics;

repeating the step of training using the new data rate; and

repeating the steps of obtaining, accessing, determining and selecting based upon the newly trained XDSL link at the new data rate.

3. The method of claim 2, wherein the actual operating characteristics comprise an actual receiver gain and signal-to-noise ratio.

4. The method of claim 1, wherein obtaining comprises obtaining an actual receiver gain and signal-to-noise ratio.

5. The method of claim 4, wherein the empirical data stored by the one or more rate adaptive data tables comprises specified receiver gains, signal-to-noise ratios, baud rates and constellation sizes used to achieve a desired bit error rate.

6. The method of claim 5, wherein determining comprises using the empirical data and the actual receiver gain and signal-to-noise ratio.

7. The method of claim 6, wherein selecting a new data rate uses the empirical data and the actual receiver gain and signal-to-noise ratio.

8. The method of claim 1, wherein the XDSL equipment comprises an XDSL modem.

9. A rate adaptive digital subscriber line (XDSL) communication system, comprising:

an XDSL physical layer chip set;

data storage storing one or more rate adaptive data tables which hold empirical data for performance of the XDSL physical layer chip set; and

a processor operating to access the data storage and to control the physical layer chip set, the processor further operating;

to train an XDSL link at a data rate set by a baud rate and a constellation size;

to obtain actual operating characteristics from parameters for the trained XDSL link;

to access one or more of the rate adaptive data tables; and

to determine whether the trained data rate will provide a desired bit error rate using the actual operating characteristics and the empirical data from the accessed one or more of the rate adaptive data tables.

10. The system of claim 9, wherein, if the trained data rate will not provide the desired bit error rate, the processor further operating:

to select a new data rate using the empirical data and the actual operating characteristics;

to repeat the step of training using the new data rate; and

to repeat the steps of obtaining, accessing, determining and selecting based upon the newly trained XDSL link at the new data rate.

11. The system of claim 10, wherein the actual operating characteristics comprise an actual receiver gain and signal-to-noise ratio.

12. The system of claim 9, wherein obtaining comprises obtaining an actual receiver gain and signal-to-noise ratio.

13. The system of claim 12, wherein the empirical data held in the one or more rate adaptive data tables comprises specified receiver gains, signal-to-noise ratios, baud rates and constellation sizes used to achieve a desired bit error rate.

14. The system of claim 13, wherein the processor determines whether the trained data rate will provide a desired bit error rate using the actual receiver gain and signal-to-noise ratio and the empirical data.

15. The system of claim 14, wherein the processor selects a new data rate using the empirical data and the actual receiver gain and signal-to-noise ratio.

16. The system of claim 9, wherein the XDSL physical layer chip set, the data storage and the processor are components of an XDSL modem.