Texas Instruments Corporation

Broadcom Corporation

Amati Communications Corporation

2wire, Inc.

Brian Robert Wiese

Krista S Jacobsen

John A C Bingham

James T Schley-May

Michael Eugene Locke

Philip Desjardins

Jayasuryan Iyer

Hossein Sedarat

Andrew L Norrell

Kevin Dean Fisher

Jacky S Chow

John A Bingham

Nicholas Philip Sands

Celite Milbrandt

Thomas N Zogakis

Kevin Du

Michael D Agah

Richard Glentworth Greenfield

Douglas J Artman

A method of synchronizing a time division duplex (TDD) multi-line, multi-carrier data communication system is provided. Synchronization is established using unique pseudo-random bit sequences (PRBS) from a common generator polynomial having different seed values. Due to low correlation of PRBS generated with different seed values, a remote unit can only synchronize to its intended signal effectively mitigating far-end and near-end crosstalk impact of large bandwidth very high speed digital subscriber lines (VDSL).

Method of synchronizing a communication system

A method and apparatus to align data blocks in a data signal and a reference signal to increase cross-correlation between the data signal and the reference signal as compared to the unaligned data and reference signals and cancel interference in the data signal in the frequency-domain under changing conditions and in the presence of the data signal.

Adaptive frequency-domain reference noise canceller for multicarrier communications systems

A noise cancellation system has a first transformer with an input side and an output side, the input side having first and second taps coupled to a signal provider, and a center tap providing a first common-mode voltage signal. A first digital subscriber line (xDSL) modem has an input coupled to the output side of the first transformer and an output coupled to customer premises equipment (CPE) for providing an xDSL signal to the CPE. A second transformer has an input side and an output side, the input side having first and second taps coupled to a signal provider, and a center tap providing a second common-mode voltage signal. A second xDSL modem is coupled to the output side of the second transformer. The difference between the first and second common-mode voltage signals is provided to at least one of the first and second xDSL modems to filter out noise from the xDSL signal provided by that modem.

Reduced-complexity common-mode noise cancellation system for DSL

Methods and apparatuses for reducing effects of impulse noise in a DSL transmitter receiver device are described. According to certain embodiment, the method includes using a periodicity associated with the impulse noise affecting a DSL transmitter receiver device to determine data frames that are affected by the impulse noise, and sending a reduced data rate during those frames. In certain embodiments, no data is sent during those frames. The method further includes using a high margin bits and gain table, instead of a normal bits and gain table.

Various methods and apparatuses for impulse noise mitigation

A method and apparatus for channel equalization in a multi-carrier communication system. The method may include receiving a symbol having multiple sub-carriers and reducing an error on at least one of the sub-carriers of the symbol by adding to it, one or more weighted multiples of other sub-carriers. The added weighted multiples may be from neighboring sub-carriers in the same symbol and/or from other symbols in a tone, for example, a previous or next symbol. The apparatus may include a reduced-complexity block linear equalizer.

Block linear equalization in a multicarrier communication system

In an embodiment, a DSL communication device comprising a line interface circuit is disclosed. The line interface circuit includes a hybrid circuit to interface the communication device to a communication line, a lowpass transmit filter to pass signals in a first frequency band, and a highpass transmit filter to pass signals in a second frequency band, where the second frequency band is higher in frequency than the first frequency band. The outputs of the highpass and lowpass filters are coupled in parallel to the communication line. The lowpass and highpass filters as well as the low and highpass transformers are optimized for their frequency bands. Further, the edges of the low and high frequency bands are sufficiently separated to reduce interference from the other frequency band. These factors, in part, allow a multiple tone communication device to be capable of operating in multiple modes of operation with multiple DSL varieties.

Dual-band line interface circuit capable of multi-band communication

The present invention provides for a method and apparatus for allocating data to subchannels used for ADSL transmission over a communication link which supports further system transmissions. An expected interference impact from the further system transmissions is estimated for the ADSL subchannels. Signal-to-noise ratios (SNRs) for the subchannels are determined for bit loading by an estimator (). In one embodiment, actual noise associated with the communication link is used at initialization to determine a SNR which is subsequently modified by an adjusting unit () prior to bit loading responsive to the estimated interference impact. In another embodiment, a virtual noise signal, indicative of the estimated interference impact and generated by a noise signal generator (), is summed with the actual noise prior to determining a SNR for bit loading. Prior to transmitting, the data is allocated to the subchannels by a bit loader () based on respective SNRs modified responsive the estimated interference impact.

Method to mitigate effects of ISDN off/on transitions in ADSL

A receiver architecture featuring a decimation filter and a bypass around said decimation filter is disclosed along with a method for optimizing said receiver's sampling phase and programmable gain amplifier. Said method utilizes said receiver architecture to modify said receiver's receive path to simplify optimizations.

Communications receiver architectures and algorithms permitting hardware adjustments for optimizing performance

The present invention provides a system and method of an upstream power back-off in a very high rate Digital Subscriber Line (VDSL) system. The method is based on a global desired receive PSD (GDR PSD), which is used to determine an upstream power back-off algorithm. The GDR PSD is transmitted from the transceiver at the LT to the NT during initialization. The NT determines an upstream transmit power spectral density for data transmission using the received GDR PSD and a determined insertion loss of the loop on which it resides.

Upstream power back-off

Disclosed are radio frequency (RF) interference cancellation techniques that effectively estimate RF interference to the data signals being received using a frequency domain model, and then remove the estimated RF interference from the received data signals. Improved techniques for digitally filtering multicarrier modulation samples to reduce sidelobe interference due to the RF interference are also disclosed.

Digital radio frequency interference canceller

A variety of methods of initializing a connection between a remote modem and a central unit in a communication system that utilizes a multi-carrier modulation scheme are described. In one aspect of the invention, a relatively long duration single frequency activation signal that ramps up and ramps down in intensity is utilized. In a preferred embodiment, the activation signal is transmitted on a sub-carrier that is outside a range of sub-channels used for data transmission in the multi-carrier modulation scheme. In a separate aspect of the invention, an initialization sequence that includes central synchronization signal, a remote synchronization signal, a central setup signal, a remote setup signal, a central setup complete signal a remote message and a central message. The central unit transmits a central setup complete signal when it has completed a central setup procedure. However, the remote message is only sent after the remote unit has both completed the remote setup procedure and received the central setup complete signal. In one preferred embodiment, during a first superframe of each of the described signals, the transmitting unit sends only header symbols which constitute a first predetermined pattern in order to help clearly define a transition in signals. In some embodiments, in the event that an error is detected, the unit that detects the error transmits designated error symbols which constitute a second predetermined pattern. In another aspect of the invention, a plurality of header symbols having a first predetermined pattern are transmitted during a first superframe of the central setup signal. A sequence of training symbol sets are then transmitted during a plurality of following superframes of the central setup signal. Further, during the transmission of the central setup complete signal, the sequence of training symbol sets continue to be retransmitted and a designated symbol in each superframe that is not to be used by the remote unit to obtain training information is set to a state indicative of the completion of the central setup procedure. With this arrangement a synchronous setup of the central unit and the remote unit is facilitated since the remote unit may continue to receive the training symbol set even after the central setup procedure has been completed.

Initializing communications in systems using multi-carrier modulation

The present invention provides methods and apparatuses for reducing near-far cross-talk interference between channels in a communication system. Channels of different lengths that are disposed adjacent to each other and carrying signals at the same frequencies often time create cross-talk interference in their neighboring channels. By spectrally shaping the signals carried on shorter lines the amount of cross-talk interference generated by these lines to longer lines may be significantly reduced, resulting in a better overall performance. In one embodiment of the present invention, a method of reducing the generation of near-far cross-talk interference includes spectrally shaping a signal carried on a first channel to reduce the amount of cross-talk coupling a neighboring second channel. In further embodiments, the shaping of the signal carried on the first channel is based in part on characteristics of the second and/or first channel. The characteristics include, but are not limited to, the length of the channels and the transfer functions of the channels. The present invention, in alternative embodiments, may also be embodied in a communication system, a central unit and a transceiver (or remote unit) or other suitable types of communication devices that are capable of shaping transmissions to reduce cross-talk interference generated by the transmissions.

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San Francisco, CA, United States of America

Brian Robert Wiese