Reduction of interference in discrete multi-tone (DMT) based communications systems
First Claim
Patent Images
1. A method for use in multi-carrier equipment, the method comprising the steps of:
- receiving a multi-carrier signal from a far-end multi-carrier endpoint; and
synchronizing the transmitter of the multi-carrier equipment to the received multi-carrier signal by turning the transmitter on and off.
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Accused Products
Abstract
An Asymmetric Digital Subscriber Loop (ADSL) Discrete Multi-Tone system has disjoint and adjacent upstream and downstream channels. During the training phase of an ADSL connection, an ADSL DMT transmitter first determines a round trip propagation delay by transmitting a ranging signal to a far-end ADSL endpoint. During the subsequent communications phase, the ADSL transmitter synchronizes transmission of DMT symbols to a reference clock. In addition, the cyclic extensions of each DMT symbol are increased as a function of the propagation delay.
96 Citations
58 Claims
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1. A method for use in multi-carrier equipment, the method comprising the steps of:
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receiving a multi-carrier signal from a far-end multi-carrier endpoint; and
synchronizing the transmitter of the multi-carrier equipment to the received multi-carrier signal by turning the transmitter on and off. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
performing clock recovery on the received multi-carrier signal for recovery of a timing signal; and
using the recovered timing signal to synchronize transmission.
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10. The method of claim 9 wherein the recovered timing signal is an DMT symbol clock.
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11. The method of claim 1 wherein the multi-carrier equipment is asynchronous digital subscriber line (ADSL) equipment.
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12. A method for use in multi-carrier equipment, the method comprising the steps of:
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adjusting a value of a cyclic extension; and
synchronizing transmission of a multi-carrier signal with a transmission from a far-end multi-carrier equipment by turning the transmitter on and off, wherein the multi-carrier signal includes the adjusted cyclic extensions. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
measuring a propagation delay associated with multi-carrier communications with the far-end multi-carrier equipment; and
adjusting the value of the cyclic extension as a function of the measured propagation delay.
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14. The method of claim 13 wherein the measuring and adjusting steps are performed during a training phase of a multi-carrier connection and the synchronizing step is performed during a communications phase of the multi-carrier connection.
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15. The method of claim 13 wherein the propagation delay is a round trip propagation delay.
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16. The method of claim 12 wherein the multi-carrier signal is a sequence of extended discrete multi-tone (DMT) symbols, each extended DMT symbol comprising a DMT symbol and the adjusted cyclic extensions.
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17. The method of claim 16 wherein the synchronization step synchronizes the transmitter such that a received DMT symbol and a transmitted extended DMT symbol overlap one another in time.
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18. The method of claim 12 wherein the synchronizing step includes the steps of:
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performing clock recovery on a received multi-carrier signal resulting from the transmission of the far-end multi-carrier equipment for recovery of a timing signal; and
using the recovered timing signal to synchronize transmission.
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19. The method of claim 18 wherein the recovered timing signal is a DMT symbol clock.
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20. The method of claim 12 wherein the multi-carrier equipment is asynchronous digital subscriber line (ADSL) equipment.
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21. Apparatus for use in multi-carrier equipment, the apparatus comprising:
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means for receiving a multi-carrier signal from a far-end multi-carrier endpoint; and
means for synchronizing the transmitter of the multi-carrier equipment to the received multi-carrier signal by turning the transmitter on and off. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. An improved apparatus for use in multi-carrier equipment, the multi-carrier equipment comprising a discrete multi-tone (DMT) modulator and a DMT demodulator, the DMT modulator transmitting a sequence of extended DMT symbols and the DMT demodulator receiving a sequence of extended DMT symbols, each extended DMT symbol comprising a cyclic extender and a DMT symbol, the improvement comprising:
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processing circuitry for synchronizing the transmitted sequence of extended DMT symbols to the received extended DMT symbols by turning the DMT modulator on and off. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41)
clock recovery circuitry for recovery of a timing signal from the received sequence of extended DMT symbols; and
wherein the processing circuitry uses the recovered timing signal to synchronize transmission of the transmitted sequence of extended DMT symbols.
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39. The improvement of claim 38 wherein the recovered timing signal is a DMT symbol clock.
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40. The improvement of claim 33 further comprising a plurality of single tap echo cancelers for echo canceling the received multi-carrier signal.
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41. The improvement of claim 33 wherein the multi-carrier equipment is asynchronous digital subscriber line (ADSL) equipment.
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42. An improved apparatus for use in a multi-carrier system, the multi-carrier system comprising a far-end multi-carrier endpoint that provides a multi-carrier signal comprising a sequence extended discrete multi-tone (DMT) symbols, each extended DMT symbol comprising a cyclic extender and a DMT symbol, the multi-carrier endpoint including a modulator, the improvement comprising:
a multi-carrier endpoint for receiving the sequence of extended DMT symbols and for synchronizing transmission of its sequence of extended DMT symbols to the received sequence by turning on and off the multi-carrier endpoint modulator. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49, 50)
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51. Apparatus comprising:
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a discrete multi-tone (DMT) modulator for transmitting a sequence of extended DMT symbols to a far-end multi-carrier endpoint;
a DMT demodulator for receiving a sequence of extended DMT symbols from the far-end multi-carrier endpoint; and
a controller for synchronizing the DMT modulator to the received sequence of extended DMT symbols by turning the DMT modulator on and off. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58)
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Specification