Texas Instruments Corporation

Walter Y Chen

Michael Oliver Polley

Xiaolin Lu

Donald Phillip Shaver

Yaqi Cheng

Douglas B Weiner

Paul E Schurr

Alan Gatherer

Gene A Frantz

Song Wu

Domingo G Garcia

Dennis G Mannering

William C Timm

Adam M Chellali

Terence J Riley

Warren L Franz

A splitterless DSL modem (,) with an integrated off-hook detector (,) prevents data loss and/or disconnections as a voiceband device (,) coupled to the same transmission line (,) transition between steady states. The splitterless DSL modem (,) include a DSP (,), an interface (,) to a twisted pair wire line (,), signal converters (,), and various filters (,). The off-hook detector circuit (,) can be coupled to the interface (,) on the analog side of the DSL modem (,) or on the digital side of the signal converters (,).

Splitterless modem with integrated off-hook detector

A system for digitizing voiceband signals at the remote terminal (,) of a Digital Subscriber Line (DSL) connection and embedding the digitized voiceband component into an active DSL data stream using a DSL modem (,). Voiceband transmissions between the remote terminal (,) and the central office call switching equipment (,) occur in the analog domain when the DSL modem (,) is OFF and in the digital domain when the DSL modem (,) is ON with the digital voiceband signals transmitted over a DSL link. Preferably, the remote terminal (,) can drive a real analog telephone (,) by providing battery feed, ring-trip detection, off-hook detection and ringing generation (,) In-house 4-wire lines pairs (,) are configured between the modem, telephones and computer or home network to permit all digital transmission from the subscriber to the central office.

System and method of transmitting voice over digital subscriber line

Baud rates for Rate Adaptive Digital Subscriber Line (RADSL) are provided. Optimal baud rates are about 200 KHz apart for loops with an 1 kft length difference. By adapting a set of baud rates with 200 KHz spacing a performance within 0.5 dB of the optimal performance may be maintained.

Method for selecting baud rates for a rate adaptive digital subscriber line modem

A modem communication system with receiving and transmission paths includes a direct equalizer system having an adaptive filter (1532) in the transmission path to compensate for frequency distortion of the communication channel. The transmitter filter coefficients are adapted by a filter coefficient calculator (1528), under control of a data detector (1526) which detects incoming data in the receiving path. A switch (1534) is controlled by status of a transmit output data buffer to multiplex either the training sequence or output data into the transmission path. When the buffer is idle, the training sequence generator (1540) is linked to a digital-to-analog (D/A) converter (1536) and line driver (1538). The receiving path includes an isolation switch (1520), a receiver amplifier (1522) and a slicer (1524). The receiver correlates the received training sequence with a known training sequence and updates the equalizer filter coefficients using an adaptation algorithm, such as a least mean squared algorithm. A first embodiment utilizes a high speed digital programmable filter (1532). Another embodiment utilizes a data buffer (1533) which is periodically filled with data filtered by a digital signal processor (DSP).

Multimode digital modem

Direct equalization method

A modem that operates selectively in the voice-band frequency band and at higher frequency bands is provided. This modem supports multiple line codes, like DMT and CAP. The modem uses a Digital Signal Processor (DSP), so that different existing ADSL line codes, such as Discrete MultiTone (DMT) and Carrierless AM/PM (CAP), can be implemented on the same hardware platform. The modem negotiates in real-time, for a desired line transmission rate to accommodate line condition and service-cost requirement. The line code and rate negotiation process may be implemented at the beginning of each communication session through the exchange of tones between the modems. A four-step MDSL modem initialization process is provided for line code and rate compatibility.

Hybrid wireless wire-line network integration and management

Rate negotiation for variable-rate digital subscriber line signaling

Modem initialization process for line code and rate selection in DSL

A central office xDSL modem pool has N logical xDSL modems. Each modem consists of a transmitter part and a receiver part and is connected to a twisted pair subscriber loop. A central office clock synchronizes the modem transmitters. A reverse channel near-end crosstalk (NEXT) canceller bank is implemented within the modem pool. The NEXT canceller bank has N NEXT cancellers corresponding to the N MDSL modems. Each canceller has N adaptive filters of size M. Outputs of all N adaptive filters are combined to form the NEXT cancellation signal for the corresponding modem. Each adaptive filter is adapted according to the error signal between the received signal and the NEXT cancellation signal and the corresponding transmit signal as the correlation vector.

Reverse channel next cancellation for MDSL modem pool

A cable television system employs noise cancellation in order to reduce radio frequency noise for upstream signals. The noise cancellation can be located at the headend or located at the juncture between the cable distribution system and the subscriber distribution system. The system employing noise cancellation at the headend has an antenna at a central distribution point on the cable system, such as a fiber node. The system employing noise cancellation at the juncture between the cable distribution system and the subscriber distribution system employs a local antenna. The noise received by the antenna is correlated with noise on the line in an adaptive filter for cancelling or reducing the noise on the line.

Ingress noise cancellation for upstream signals on a cable television

A frequency-domain CAP receiver is provided that reduces the number of operations required to demodulate a CAP signal. The frequency-domain CAP receiver provides computational advantages over an equivalent time-domain version as the filter length required in the receiver increases.

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Plano, TX, United States of America

Walter Y Chen