Frequency division duplexing system which accommodates symmetric and asymmetric channels

• US 6,333,920 B1
• Filed: 09/08/1997
• Issued: 12/25/2001
• Est. Priority Date: 09/09/1996
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Werner, Jean-Jacques, Nguyen, Mai-Huong
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US08/926,497
• Time in Patent Office: 1,569 Days
• Field of Search: 370/278, 370/280, 370/281, 370/286, 370/295, 370/296, 370/480, 370/481, 370/482, 370/485, 370/468, 370/498, 370/282, 370/478, 370/319, 370/330, 370/343, 370/345, 375/295, 375/296, 375/227, 375/226, 375/298, 375/222, 375/346, 375/349, 709/235, 348/6-15
• US Class Current: 370/281
• CPC Class Codes: H04L 5/143 for modulated signals H04L5/1469 takes precedence
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

A communications system employs frequency division duplexing to accommodate symmetric and asymmetric services, while substantially eliminating near-end cross talk. Upstream and downstream channels are separated by a guard band in order to insure that near-end cross talk is kept to a minimum. An asymmetric upstream channel is preferably located at a lower frequency range than that of the asymmetric downstream channel. The guard band between these asymmetric upstream and downstream channels shifts in frequency along with the shift in frequency of the respective upstream and downstream channels as a function of reach. This guard band shifting permits the communications systems to utilize a greater percentage of the frequencies available to it and to thereby substantially maximize the communications rate that it can support. Although the asymmetric guard band is allowed to shift in the manner described, it is not allowed to do so in a manner that would create a conflict with symmetric channels. Additionally, for symmetric services upstream channels are provided both above and below a downstream channel and are located so as not to interfere with asymmetric channels.

Claims

1. A frequency division duplexing telecommunications system which provides very high speed digital subscriber line symmetric and asymmetric services to a plurality of subscribers connected to said system by local subscriber loops comprising varying lengths of two wire pairs thereby defining local subscriber loops of varying reach, said system comprising:

an upstream transmitter which transmits over the local subscriber loops within a relatively low frequency upstream channel, and

a downstream transmitter which transmits within a downstream channel that is a higher frequency channel than said relatively low frequency upstream channel, wherein said frequency channels are separated by a guard band, the upstream and downstream channels are varied with the reach of a particular subscriber local loop, and the guard band varies along with the upstream and downstream channels, with the lowest frequency of the upstream channel remaining substantially the same while the lowest frequency of the downstream channel shifts to a lower frequency as the reach of the particular subscriber loop increases.

2. The system of claim 1, wherein transmissions are sent over local subscriber loops and all pairs of said frequency channels are shifted to lower frequencies to accommodate longer reaches, while maintaining guard bands between all of said frequency channels.

3. The system of claim 1, wherein said transmitters employ multilevel signalling.

4. The system of claim 3, wherein said transmitters employ a two-hundred and fifty six symbol constellation for upstream transmissions and a sixteen symbol constellation for downstream transmissions.

5. The system of claim 4, wherein said upstream channel ranges from approximately 1.03 MHz to approximately 2.00 MHz and supports a data rate of 6.48 Mb/s, and said downstream channel ranges from approximately 2.4 MHz to approximately 17.95 MHz and supports a data rate of 51.84 Mb/s for short reach asymmetric loops.

6. The system of claim 4, wherein said upstream channel ranges from approximately 0.97 MHz to approximately 1.46 MHz and supports a data rate of 3.24 Mb/S, and said downstream channel ranges from approximately 2.04 MHz to approximately 9.81 MHz and supports a data rate of 25.92 Mb/s for medium reach asymmetric loops.

7. The system of claim 4, wherein said upstream channel ranges from approximately 0.99 MHz to approximately 1.24 MHz and supports a data rate of 1.62 Mb/s, and said downstream channel ranges from approximately 2 MHz to approximately 5.89 MHz and supports a data rate of 12.96 Mb/s for long reach asymmetric loops.

8. The system of claim 4, wherein said upstream channels range from approximately 1.03 MHz to approximately 2.00 MHz and from approximately 11.3 MHz to approximately 19.08 MHz and support a data rate of 25.92 Mb/s, and said downstream channel ranges from approximately 2.49 MHz to approximately 10.27 MHz and supports a data rate of 25.92 Mb/s for short reach asymmetric loops.

9. The system of claim 4, wherein said upstream channels range from approximately 1.03 MHz to approximately 2.0 MHz and from approximately 10.36 MHz to approximately 15.19 MHz and support a data rate of 12.96 Mb/S, and said downstream channel ranges from approximately 2.46 MHz to approximately 6.35 MHz and supports a data rate of 12.96 Mb/s for medium reach asymmetric loops.

10. A frequency division duplexing telecommunications system which provides very high speed digital subscriber line symmetric and asymmetric services, comprising:

an upstream transmitter which transmits over a two wire local loop within a relatively low frequency upstream channel,

a downstream transmitter which transmits within a downstream channel that is a higher frequency channel than said relatively low frequency upstream channel, wherein said frequency channels are separated by a guard band, the upstream and downstream channels are varied with the reach of the local loop, and the guard band varies along with the upstream and downstream channels, with the lowest frequency of the upstream channel remaining substantially the same while the lowest frequency of the downstream channel shifts to a lower frequency as the reach of the local loop increases, and

an upstream transmitter which transmits within an upstream channel that is a frequency channel higher than that of said downstream channel.

11. The system of claim 10, wherein transmissions are sent over local subscriber loops and all of said frequency channels are shifted to lower frequencies to accommodate longer reaches, while maintaining guard bands between all pairs of said frequency channels.

12. The system of claim 10, wherein said transmitters employ multilevel signalling.

13. The system of claim 12, wherein said transmitters employ a two-hundred and fifty six symbol constellation for upstream transmissions and a sixteen symbol constellation for downstream transmissions.

14. The system of claim 13, wherein said upstream channel ranges from approximately 1.03 MHz to approximately 2.00 MHz and supports a data rate of 6.48 Mb/s, and said downstream channel ranges from approximately 2.4 MHz to approximately 17.95 MHz and supports a data rate of 51.84 Mb/s for short reach asymmetric loops.

15. The system of claim 13, wherein said upstream channel ranges from approximately 0.97 MHz to approximately 1.46 MHz and supports a data rate of 3.24 Mb/S, and said downstream channel ranges from approximately 2.04 MHz to approximately 9.81 MHz and supports a data rate of 25.92 Mb/s for medium reach asymmetric loops.

16. The system of claim 13, wherein said upstream channel ranges from approximately 0.99 MHz to approximately 1.24 MHz and supports a data rate of 1.62 Mb/s, and said downstream channel ranges from approximately 2 MHz to approximately 5.89 MHz and supports a data rate of 12.96 Mb/s for long reach asymmetric loops.

17. The system of claim 13, wherein said upstream channels range from approximately 1.03 MHz to approximately 2.00 MHz and from approximately 11.3 MHz to approximately 19.08 MHz and support a data rate of 25.92 Mb/s, and said downstream channel ranges from approximately 2.49 MHz to approximately 10.27 MHz and supports a data rate of 25.92 Mb/s for short reach asymmetric loops.

18. The system of claim 13, wherein said upstream channels range from approximately 1.03 MHz to approximately 2.0 MHz and from approximately 10.36 MHz to approximately 15.19 MHz and support a data rate of 12.96 Mb/S, and said downstream channel ranges from approximately 2.46 MHz to approximately 6.35 MHz and supports a data rate of 12.96 Mb/s for medium reach asymmetric loops.

19. A method of providing very high speed digital subscriber line duplex telecommunications services, comprising the steps of:

a) assigning frequency channels for upstream and downstream communications whereby;

i) an upstream transmitter transmits over a local loop within a relatively low frequency upstream channel,

ii) a downstream transmitter transmits within a downstream channel that is a higher frequency channel than said relatively low frequency upstream channel,

iii) wherein said frequency channels are separated by a guard band,

iv) the frequency bands of the upstream and downstream channels are varied with the reach of the local loop,

v) and the guard band varies along with the upstream and downstream channels,

vi) with the lowest frequency of the upstream channel remaining substantially the same,

vii) while the lowest frequency of the downstream channel shifts to a lower frequency as the reach of the loop increases, and

viii) an upstream transmitter transmits within an upstream channel that is a frequency channel higher than that of said downstream channel;

b) transmitting the assignment information of step a to subscribers and central offices within a telecommunications system; and

c) transmitting data between a central office and a subscriber location employing the frequency channels assigned in step a.

20. The method of claim 19 further comprising the step storing the assignment information at a central office.

21. The method of claim 19 further comprising the step of storing information indicative of a local loop'"'"'s service type at a central office so that subscribers who are to receive symmetric services or asymmetric services are identified by such stored information.

22. The method of claim 19 wherein the step of assigning frequency channels comprises sending a test signal to a subscriber and determining the frequency profile according to the quality of the channel, as indicated by said test signal.