METHOD AND APPARATUS FOR DESIGNING AN IMPROVED TRANSMIT SIGNAL FOR USE IN A SINGLE ENDED LINE TEST (SELT)

• US 20150030137A1
• Filed: 07/24/2014
• Published: 01/29/2015
• Est. Priority Date: 07/29/2013
• Status: Active Grant

• Current Assignee: Ikanos Communications Incorporated (Qualcomm, Inc.)
• Original Assignee: Ikanos Communications Incorporated (Qualcomm, Inc.)
• Inventors: LEVONAS, Robin, PATHAK, Vipin
• Granted Patent: US 9,185,204 B2
• Time in Patent Office: Days
• US Class Current: 379/1.03
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04M 3/2209 for lines also used for data transmission
• CPC Class Codes: H04M 3/306 for frequencies above the voice frequency, e.g. xDSL line qualification test methods, test equipment and test arrangements for subscriber lines using xDSL modems H04M3/304; systems modifying transmission characteristics according to link quality H04L1/0001; monitoring and/or testing of line transmission systems H04B3/46

Abstract

The present invention relates to methods and apparatuses of using a novel transmit signal that can be used to improve performance of various loop diagnostic features of SELT. In embodiments, a novel transmit signal uses a wide contiguous band of tones that includes frequencies in both upstream and downstream bands. In these and other embodiments of the invention, the SELT transmit signal is designed such that any crosstalk noise in adjacent lines appears as a burst of noise that falls within the limits of the FEC settings of the system such that it can be fully corrected without harming the performance of modems connected on the adjacent lines.

Claims

1. A method for examining a line coupled to a modem in a discrete multi-tone (DMT) communications system, comprising:

transmitting from the modem a test signal using tones in both upstream and downstream frequency bands of the DMT communications system;

receiving a reflection of the test signal at the modem; and

analyzing the reflection to identify impairments in the line.

2. A method according to claim 1, wherein the reflection comprises frequency domain S11 data.

3. A method according to claim 1, further comprising converting the reflection to a set of time domain data.

4. A method according to claim 3, wherein analyzing includes identifying peaks in the set of time domain data.

5. A method according to claim 1, wherein the modem is a CPE modem and the upstream and downstream bands are two or more adjacent bands in a xDSL system frequency band plan.

6. A method according to claim 5, wherein the test signal comprises a symbol constructed using tones in the upstream and downstream bands.

7. A method according to claim 6, wherein the tones are a contiguous set of tones spanning the upstream and downstream bands.

8. A method according to claim 5, wherein the xDSL system is a vectored DSL system, and wherein transmitting is performed while one or more other lines in a vectored group including the line are operating in Showtime.

9. A method according to claim 8, wherein transmitting is performed at a rate corresponding to an error correction capability of the vectored DSL system.

10. A method according to claim 9, wherein the rate is a pulse of a number of symbols per DMT superframe.

11. An apparatus for examining a line coupled to a modem in a communications system, comprising:

a SELT block that transmits from the modem a test signal using tones in both upstream and downstream frequency bands of the DMT communications system and receives a reflection of the test signal at the modem; and

an analysis engine that analyzes the reflection to identify impairments in the line.

12. An apparatus according to claim 11, wherein the reflection comprises frequency domain S11 data.

13. An apparatus according to claim 11, wherein the analysis engine converts the reflection to a set of time domain data to identify the impairments.

14. An apparatus according to claim 11, wherein the modem is a CPE modern and the upstream and downstream bands are two or more adjacent bands in a xDSL system frequency band plan.

15. An apparatus according to claim 14, wherein the test signal comprises a symbol constructed using tones in the upstream and downstream bands.

16. An apparatus according to claim 15, wherein the tones are a contiguous set of tones spanning the upstream and downstream bands.

17. An apparatus according to claim 15, wherein the xDSL system is a vectored DSL system, and wherein the SELT block transmits the test signal while one or more other lines in a vectored group including the line are operating in Showtime.

18. An apparatus according to claim 17, wherein the SELT block transmits the test signal at a rate corresponding to an error correction capability of the vectored DSL system.

19. An apparatus according to claim 18, wherein the rate is a pulse of a number of symbols per DMT superframe.

20. An apparatus according to claim 19, wherein the number is one.