Future Wei Technologies, Inc.

Centillium Communications, Inc.

Huawei Technologies Co., Limited

Chin Ngek Hung

Guozhu Long

Yaron Bar-Ness

Haixiang Liang

Liming Fang

Xiang Wang

Jie Liu

Raphael Jean Cendrillon

Jianping Tu

Yuchen Jia

Xiao Liang

Jinxiong Lu

A method of far-end crosstalk (FEXT) channel estimation in a digital subscriber line (DSL) system, wherein the DSL system comprises a first subscriber line and a second subscriber line, the method comprising allocating a plurality of time slots, wherein the plurality of time slots comprises a first period and a second period, wherein the first period precedes the second period, and wherein each of the first and second periods comprises at least one time slot, transmitting at least one training symbol in the first period onto the second subscriber line in a downstream direction while no transmission is made on the first subscriber line, receiving at least one feedback symbol in the second period from the first subscriber line in an upstream direction, and estimating a level of downstream FEXT from the second subscriber line into the first subscriber line based on the at least one feedback symbol.

Time division multiple access far end crosstalk channel estimation

An apparatus configured to couple to a plurality of subscriber lines comprising a plurality of transmitters configured to couple to a plurality of physical channels and at least one virtual channel. The number of physical channels equals the number of subscriber lines. A processor is configured to compute a precoder matrix to minimize an error value. The error value accounts for an error on each channel subject to a constraint on power for each channel. A precoder is coupled to the processor and configured to use the precoder matrix to jointly process a plurality of data signals to generate a plurality transmit signals for the plurality of physical channels and the at least one virtual channel.

Power control in linear precoder design for MIMO DSL transmission

An apparatus for synchronizing a plurality of digital subscriber line access multiplexers (DSLAMs) comprising a reference clock configured to generate a reference clock signal, and an interface configured to transmit the reference clock signal to the DSLAMs, wherein each of the DSLAMs is configured to align its system clock with the reference clock.

Node level vectoring synchronization

A processing method and a transceiver for channel changing in a joint transceiving mode are provided. The method includes: performing fault detection for one or more direct channels; after a fault is detected on a direct channel, stopping sending signals on the direct channel; detecting whether the direct channel with fault has been recovered; and when recovery of the direct channel with fault is detected, resuming sending signals on the direct channel.

Processing method and transceiver for channel changing in joint transceiving mode

A system used to synchronize the clock frequency of a receiver with that of a transmitter, where both the receiver and transmitter communicate using the ADSL Annex C standard. The transmitter continuously transmits pilot tones to the receiver. The receiver determines the phase error between sequential pilot tone symbols to determine a phase error. The receiver uses the phase error to adjust the receiver clock frequency. However, if the most recently received symbol is subject to near end crosstalk or is subject to far end crosstalk and is a boundary symbol, the receiver ignores the phase error and does not adjust the receiver clock frequency.

Method and apparatus for timing recovery in ADSL transceivers under a TCM-ISDN crosstalk environment

A system used to synchronize the clock frequency of a receiver with that of a transmitter, where both the receiver and transmitter communicate using the ADSL Annex C standard. The transmitter continuously transmits pilot tones to the receiver. The receiver determines the phase error between sequential pilot tone symbols to determine a phase error. The receiver uses the phase error to adjust the receiver clock frequency. However, if the most recently received symbol is subject to near end cross talk or is subject to far end cross talk and is a boundary symbol, the receiver ignores the phase error and does not adjust the receiver clock frequency.

A technique for training an equalizer of an ADSL Annex C transceiver is provided. The technique defines the points in the transmission sequence at which equalizer training should take place, and what symbols comprising the transmission should be used for training. The technique avoids the effect of strong TCM-ISDN cross-talk noise. The equalizer is trained so as to achieve optimal communication channel performance. During the TEQ training phase, the cyclic prefix is not introduced. The TEQ is trained only on FEXT symbols except the FEXT symbols adjacent to NEXT symbols. In the early phase of FEQ training, the cyclic prefix is not introduced. The FEQ is trained on FEXT symbols only except the FEXT symbols adjacent to NEXT symbols. During a late training phase after the cyclic prefix is introduced, the training of the FEQ is continued by using signals received on all FEXT symbols only. Due to the introduction of the cyclic prefix and the time-domain equalizer, the inter-symbol interference is basically eliminated. Therefore, the FEXT symbols adjacent to NEXT symbols are not affected by the TCM-ISDN noise that exists in NEXT symbols only. As a result, the received signal on those symbols can also be used to train FEQ. In a show-time phase, the FEQ is updated on FEXT and NEXT symbols for bins where the number of bits per symbol is non-zero.

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San Jose, CA, United States of America

Chin Ngek Hung