152 results about "DSL modem" patented technology

Controlling margins in a DSL modem pair is based on collected operational data. The operational data is analyzed and at least one of the modems in the modem pair is instructed to use a margin-related parameter value to assist the modem pair in meeting a margin target, such as a margin limit imposed by a DSL standard or the like. A controller, such as a DSM Center, a “smart” modem unit and/or a computer system can collect and analyze the operational data and generate one or more margin-related parameter values. The margin-related parameter value may be a PSD-related value, such as the MAXNOMPSD, MAXNOMATP or PSDMASK parameter used by various ADSL systems, and may be a shaped spectral mask and/or caps or limits on bit loading for use in transmissions between the modems. In some cases, preference bands can be imposed to direct modems to favor and/or avoid certain frequencies in the modem's usable band(s). The operational data may include historical data relating to prior performance of the modem pair and prior margin compliance. A distribution of margins also may be based on operational data and may be estimated as a function of data rate. Using the estimated margin distribution, a distribution of performance parameters also is calculated, including the probabilities of line outages and probabilities of one or more error parameters exceeding minimum levels. Data rates and/or performance-related parameters may be set on the basis of the estimated performance of the system using various margin settings and levels.

An apparatus includes a plurality of DSL modems. Each DSL modem is configured to be connected to a corresponding DSL subscriber line. A first of the DSL modems is configured to transmit a data stream to a DSL subscriber via inter-line cross-talk between the one of the DSL subscriber lines connected to the first of the DSL modems and the one of the DSL subscriber lines connected to a second of the DSL modems.

Methods and systems provide an efficient power save mode for multi carrier modems, such as DMT based ADSL and VDSL modems. Fast transitions from power save mode to full operational mode occur, without the overhead of transmitting large quantities of configuration information between the transmitter and receiver. Signal constellation size changes occurring while operating in power save mode to continue to apply once full operational mode is resumed. Multiple power save modes are enabled, each having a different level of power dissipation and crosstalk, both far end crosstalk and near end crosstalk. Power dissipation and crosstalk can thus be graduated on a line, according to a user-requested bit rate.

A method and apparatus for selectively terminating sealing current in an asymmetric digital subscriber line modem is provided. The technique comprises providing a mechanism (e.g., a resistor or suitable current sink) to a DSL modem (e.g. an ADSL modem or any XDSL modem used where POTS is underlying service). The mechanism is operable to be dynamically switched on and off and to operate under low current conditions. The system allows for provision of DSL (e.g., ADSL or XDSL where POTS is the underlying current) in the absence of plain old telephone service (POTS) and for improved performance.

Using DSL modems as data collectors, the modems processes the data to, for example, allow easier interpretation of the line characteristics. In particular, the modems postprocess the data including calibration, filter compensation, determination of the SNR medley from the bits and gains tables and rate conversion. The interpretation process uses the postprocessed data and determines loop characterization, interferer detection, a data reduction estimation and a data rate estimation. The outputs of these determinations least allow for the characterization of the line conditions between the two modems.

Method and modem for fast timing recovery of transmitted data between a master χDSL modem and a slave χDSL modem, over a noisy, high loss, high distortion wiring. Transmitted QAM symbols are received and sampled at the slave modem. The sampled data is split into in-phase and quadrature channel, each of which is filtered by matched filter. The filtered outputs are sampled at twice the symbol rate and the lower and upper band edge components are extracted by modulating each of the sampled sequences of outputs with two discrete time sequences: cos(0.5 π n)=. . . 1,0,−1,0 . . . and sin(0.5 π n)=. . . 0,1,0,−1 . . . . Each of the resulting products is filtered with a first order low-pass filters and re-sampled again at the symbol rate. The Bit Error Rate is computed, and the slave modem switches from blind timing recovery mode, to data directed timing recovery mode, after the Bit Error Rate has sufficiently decreased.

After establishing a connection between an ATU-C and an ATU-R and having a state where data communication is enabled, the ATU-R checks a packet that flows through a network at the user side. When there is no packet addressed to the ATU-R for a predetermined time period, the ATU-R transmits, to the ATU-C, a request to transition to an energy-save mode. The ATU-C and AUT-R determines a parameter to be used for the energy save mode, the parameter enabling a number of carriers and/or transmission power to be decreased compared to the ones in a normal mode. Using the determined parameter, a state in which data communication is enabled is maintained.

A digital subscriber line (DSL) modem that has a canceller digital filter for cancelling crosstalk and RF interference in a received DSL signal is disclosed. The modem includes common-mode sense circuitry and also differential-mode sense circuitry. Samples of the common-mode signal are acquired during a “quiet” period of initialization of the DSL modem, and samples of the differential-mode signal are acquired during live transmission of a DSL signal. An estimate of an autocorrelation function is obtained from the common-mode samples, and a cross-correlation of the common-mode samples and differential-mode samples is also estimated. Digital filter coefficients are derived from these estimates, based on the assumption that the common-mode samples acquired during the “quiet” phase represent crosstalk and RF interference present during differential-mode communications. The digital filter coefficients can also be updated during showtime of the DSL link, using an expanded number of samples of the common-mode and differential-mode signals.

A three-port TDR front end comprises numerous components. An exemplary three-port TDR front end is a DSL modem. Information-bearing TDR signals are distorted as they pass through these components. With a perfect model of the response of its front-end, a TDR system usually can compensate for the effects of its front-end. In reality, however, the electrical characteristics of each component vary from design-to-design, board-to-board, and slowly over time. The result is imperfect knowledge about the true response of the front-end, errors in the model of the front-end, and degraded TDR performance. At least for this reason it is important to precisely calibrate the response of the TDR front-end through the use of a TDR modeling system.

A Plain Old Telephone System (POTS) connection is established between a Broadband modem and a remote server. A configuration request is then transmitted from the Broadband modem to the remote server using DTMF tones. Subsequently a domain name associated with a Broadband Service Node (BSN) and a user identifier, such as a telephone number, is received from the remote server via the POTS connection using Dual-Tone Multi-Frequency (DTMF) tones. A PPPoE session is then established using the domain name, by firstly authenticating the Broadband modem for the PPPoE session and then configuring the DSL modem. This configuration is accomplished by transmitting a request for configuration details from the Broadband modem to the BSN having the domain name and then receiving configuration details from the configuration server. The Broadband modem then automatically configures itself using the configuration details.

An algorithm for computing an efficient, reduced complexity, windowed optimal linear time domain equalizer for a dispersive channel comprises the steps of determining a window of maximum energy in the impulse response of length equal to or less than a number of cyclic prefix samples associated with a received digital data signal, computing the corresponding inside and outside matrices, performing an inverse Cholesky decomposition of the inside matrix, creating a resultant matrix as the product of the outer and the upper and lower square root inner matrix, followed by Householder reduction and QL transformation to thereby compute the time domain equalizer as the linear transformation of the eigenvector corresponding to the smallest eigenvalue at the receiver. The smallest eigenvalue is determined using the aforementioned orthogonal transformations without determining all the eigenvalues efficiently but without the loss accuracy associated with iterative methods like the conventional power method. The algorithm may be most conveniently implemented, for example, in the form of a thirty-two bit digital signal processor at a data receiver.

A noise determiner for use with a communications system, a method of determining noise in a communications system and a digital subscriber line (DSL) modem. In one embodiment, the noise determiner includes (1) a crosstalk identifier that detects directly a noise source in a frequency domain from observed noise associated with the communications system and (2) a crosstalk estimator coupled to the crosstalk identifier and that provides a corresponding level of the noise source.

A transceiver (100) such as used in Discrete Multitone (DMT) modulation of digital signals for communication, such as in a DSL modem communications system, is described. The transceiver (100) includes a function (119) by way of which unloaded subchannels are encoded with a clip prevention signal. The clip prevention signal is derived to avoid clipping by an amplifier (18) after modulation into the time domain, upsampling, and filtering. The effects of the upsampling and filtering are considered in deriving the clip prevention signal, by considering the upsampling and filtering as a polyphase combination, and using the filter response for each phase. Frequency domain and time domain update alternatives are disclosed.

A non-symmetrical half-duplex data communications apparatus and method provides for transmitting and receiving non-symmetrical half-duplex signals over a communications link. The non-symmetrical half-duplex data communications apparatus includes interface circuitry that is connectable to the communications link and modulation circuitry to transmit and receive the non-symmetrical half-duplex signals over the communications link. The modulation circuitry of the non-symmetrical half-duplex data communications apparatus includes the ability to transmit data signals with a transmission time that is different than the transmission time of receive signals. The modulation circuitry of the non-symmetrical half-duplex data communications apparatus also includes the ability to transmit data signals with a transmission data rate different than the transmission data rate of receive signals.

A method includes maintaining temporally parallel DSL data communication sessions with DSL modems of a group via a set of lines. The method includes, in response to substantially stopping to receive DSL communications from one of the DSL modems via one of the lines, transmitting a substantially reduced average power to the one of the lines and monitoring the one of the lines to determine whether DSL communications have restarted being received from the one of the DSL modems. The method also includes resuming the maintaining of the temporally parallel DSL communication sessions in response to the monitoring determining that DSL communications have restarted being received from the one of the DSL modems.

Operational data collected from a communication system, such as a DSL system, may include exclusionary data and/or indicative data that can be analyzed to determine the type of communication device, such as a DSL modem, that generated the operational data. Exclusionary data, if any, can be used to exclude one or more communication device types from consideration. Indicative data, if any, may be used to influence the selection of a communication device type, such as by assigning scores to communication device type features and/or to communication device types. Information pertaining to various communication devices may be maintained in a database or the like. In a DSL system, modem types may be evaluated and selected by a modem identification unit or identifier that collects and analyzes the operational data using collecting means and identifying means. The identifier may be part of a controller, such as a DSM Center or the like implemented in and/or with a computer and coupled to the DSL system. Information such as a modem type selection then can be used by the controller to generate modem and/or system operation signals to assist in operation of the DSL system.

A central office modem (50) that includes the capability of single-ended loop testing (SELT) is disclosed. The modem (50) includes a digital signal processor (54), a codec (56), line driver and receiver circuitry (58), and a hybrid circuit (60), by way of which a subscriber loop (LOOP) can be driven and sensed. The line driver and receiver circuitry (58) may include a transformer (74a, 74b) for driving the loop (LOOP), or the output may be capacitively coupled. The line driver and receiver circuitry (58) includes active termination, by way of operational amplifiers (80a, 80b). Switches (82a, 82b; 84a, 84b) are provided to selectively enable and disable the active termination function, and to selectively bypass or include the hybrid circuit (60). This control of the line driver and receiver circuitry (58) provides the ability to calibrate out its own characteristics, providing high precision SELT measurements of the load impedance type, and of frequency domain reflectometry, and time domain reflectometry. A third set of switches (86a, 86b) selectively bypass receive path filter circuitry (78), to permit upstream and downstream noise measurements.