Abstract: The present invention provides an equalizer capable of accurately compensating for non-linearity of an input signal due to the asymmetry phenomenon, etc., during the disk production process. Two tap coefficients are provided in a coefficient unit. A comparator compares the value of a middle tap signal, which is a reference signal, and a threshold, so as to produce a selection signal based on the comparison result. The coefficient unit selects one of the two tap coefficients as the selected tap coefficient based on the selection signal, and a tap signal is multiplied with the selected tap coefficient. Thus, it is possible to adaptively switch the tap coefficients of the equalizer as a whole based on the value of the middle tap signal, which is the reference signal. Therefore, it is possible to accurately compensate for the non-linearity of the input signal.

Abstract: An equalization circuit is provided. The equalization circuit includes an input adapted to receive signals from a communications channel. The equalization circuit further includes a plurality of equalizer circuits coupled to the input and operable to generate a plurality of intermediate signals. A selector circuit is also included. The selector circuit is responsive to the plurality of equalizer circuits and selects one of the intermediate signals. The equalization circuit also includes an output coupled to the selector circuit that receives the selected intermediate signal.

Abstract: Disclosed is a channel equalizing apparatus and method for a digital television receiver that performs channel equalization using equalizing algorithms. The channel equalizing apparatus includes a channel equalizing section for compensating for channel distortion using a blind algorithm and a decision directed algorithm among equalizing algorithms, and a equalizing control section for calculating error values for compensating for the channel distortion from the blind algorithm and the decision directed algorithm and controlling the channel equalizing section to compensate for the channel distortion according to the calculated error values.

Abstract: A method and apparatus are disclosed for equalizing a channel using improved channel estimates. The present invention assumes that fading will follow a statistical model and obtains an improved channel estimate using one or more basis functions to describe the channel based on known channel statistics. A Karhunen-Loeve expansion can be used for channel estimation to describe the channel. Waveforms are selected that are matched to characteristics of the channel, such as transmission waveforms whose energy is largely restricted to a bandwidth assigned to the channel. Coefficients are estimated for the basis functions using real-time data.

Abstract: A method for compensating for attenuation in an input signal includes receiving an input signal, communicating a first portion of the input signal on a first path, communicating a second portion of the input signal on a second path, and communicating a third portion of the input signal on a third path. The method also includes applying a first gain to the first portion of the input signal, applying a first-order mathematical operation and a second gain to the second portion of the input signal, and applying a second-order mathematical operation and a third gain to the portion of the input signal. The method further includes recombining the first portion, the second portion, and the third portion into an output signal.

Abstract: A block-iterative equalizer is adapted for use in contemporary digital communication system receivers. In a preferred embodiment, data received over a communication channel is processed by a linear feed-forward filter and the resulting filtered signal is provided to a slicer which makes a first set of tentative symbol decisions. During later iterations, the same received data is processed by the linear feed-forward filter, the feed-forward filter parameters being modified at each iteration based on the received data and the tentative decisions are themselves filtered by a second, “feed-back” filter and used to improve the tentative decisions.

Abstract: Briefly, in accordance with one embodiment of the invention, a wireless network may include transmitters that may transmit information over a channel. the transmitter may also transmit channel side information over the channel. Further, the transmitters may adjust when channel side information is transmitted in accordance with the channel coherence time.

Abstract: In a training operation for optimizing a multiplication coefficient for each tap of an FIR equalizer equalizing a read signal read from a recording medium, as a restricted coefficient updating vector applied for updating the multiplication coefficient for each tap of an FIR filter, a vector is utilized which is obtained by projecting, onto a plane perpendicular to a predetermined restricting conditioning vector, a coefficient updating vector determined based on an equalizer error between the output of the FIR equalizer and a reproduction output determined therefrom and a delayed input value for each tap of the FIR equalizer.

Abstract: A method used in equalization processing is provided, in which a reference signal is received and a change point of transmission line characteristics is detected. A basic frequency signal of fluctuation period of the transmission line characteristics is extracted, and vectorized. The vector is adjusted such that vectors corresponding to two change points become symmetrical with respect to X axis. Then, fluctuation interval of transmission line characteristics is judged by comparing X component of the vector with a reference value. As a result, equalization processing is performed in accordance with the fluctuation.

Abstract: An adaptive signal equalizer with a feedforward filter in which the feedback error signal and corresponding incoming data signal are dynamically aligned in time using signal interpolation, and further, to control the precursor/postcursor filter taps configuration, thereby producing more adaptive filter tap coefficient signals for significantly improved and robust signal equalization.

Abstract: A method and apparatus is disclosed to overcome the effects of intersymbol interference during data transmission. Overcoming the effects of intersymbol interference makes possible higher data transmission rates for a given error rate. In one embodiment a receiver processing system a first, second and third filter, such that the second and third filter comprise feedback filters. Filter coefficients are calculated to reduce the undesirable effects of the channel, such as intersymbol interference. A training process occurs to establish the first filter as a mixed phase filter and the third filter as minimum phase filter. The second filter is configured based on the transfer function of the channel and one or more coefficients may be set to a predetermined value.

Abstract: The present invention provides a method for initialization and stepsize control of a time-domain equalizer (TEQ) in a receiver of a multi-carrier communication system to upgrade the performance of adaptive TEQ algorithms. As to TEQ initialization, the Time-domain Window Mask method generates a modified channel impulse response (CIR) by performing a locate maximum energy algorithm and then applies a time-domain window mask to adjust the modified CIR to obtain an initial value of a target impulse response. Then, a dividing operation is performed on the frequency-domain initial target impulse response and the modified CIR to determine an initial value of the frequency-domain TEQ impulse response. The Head-tail Equalizing method also performs the locate maximum energy algorithm, and the remaining points other than the consecutive points with maximum energy are combined and padded zero to the last few points to generate a modified CIR.

Abstract: Equalisation of a communication channel is achieved through use of a Wiener filter frequency response mechanism that operates to transform at least a portion of a data stream generated from a plurality of space time coded (STC) symbol streams received from a plurality of transmit antenna elements into a packet spectrum. A training sequence for a channel through which the symbol streams have been sent is also transformed to a channel impulse response spectrum in order to assess the channel impulse response for the channel. The packet spectrum is equalised with the channel impulse response spectrum to produce an equalised packet spectrum in the transform domain. This is then converted into a time domain equalised data stream for recovery of originally transmitted information.

Abstract: A method for identifying and modeling nonlinearities in communications channels, particularly optical communication channels. A channel in general is modeled as a summation of linear and non linear terms having memory. The terms are functions of the input to the channel with respect to time, such as a sequence of input bits to the channel. In one embodiment the most recent input bits are used to access a value in a look up table. The value accessed is compared to an actual value received from the channel. The difference between the value in the table and the actual channel value may be used to correct the value in the table. When the look up table and the channel converge the look up table contains a model of the channel with memory that can model nonlinearities. A nonlinear channel having memory may also be modeled in terms of Volterra Kernels.

Abstract: A linear/non-linear adaptive filter for transforming an input signal to an output signal. The present invention also includes a novel GSPT LMS algorithm for significantly reducing complexity. The adaptive filter includes a coefficient updater that can execute a Carry-in operation or a Borrow-in operation to adaptively adjust a filtering coefficient according to whether an updating term signal is a Carry-in signal or a Borrow-in signal.

Abstract: A system for, and method of recovering primary channel operation in a facsimile (fax) receiver and a fax machine that incorporates the system, the method or both. In one embodiment, the system includes: (1) a signal receiver that receives a signal containing first and second points located at first and second angles and (2) angle determination circuitry that determines an offset angle by which the signal has been rotated based on the first and second angles.

Abstract: A physical layer transceiver, configured for retrieving signal samples from a prescribed network medium having an undetermined length, includes a digital feedforward equalizer, configured for generating equalized signal samples from the retrieved signal samples and based on supplied equalizer settings, and an equalizer controller. The equalizer controller is configured for supplying selected equalizer settings that overcome intersymbol interference encountered by transmission of the signal samples across the prescribed network medium. The equalizer controller is configured for supplying prescribed initial equalizer settings to the digital feedforward equalizer, receiving equalized signal samples from the digital feedforward equalizer, and selectively changing the prescribed initial equalizer settings based on comparing the equalized signal samples to a prescribed equalization threshold.

Abstract: A data communication transceiver, such as a PCM or xDSL modem, is operable in a training-while-working mode in which it both trains and communicates user data. In some embodiments, upon initiation of a data communication session, the transceiver operates in a startup training mode in which partial training occurs that is sufficient to enable low rate data communication; the transceiver then enters the training-while-working mode in which it communicates user data and completes training. When training is completed, the transceiver enters a data mode in which it communicates user data but does not train. In some embodiments, if in the data mode conditions arise requiring retraining or making retraining desirable, the transceiver enters the training-while-working mode and retrains while continuing to communicate user data.

Abstract: An equalizer for a VSB receiver, which enables equalizations using segment synchronization information, has an extraction unit extracting the segment synchronization information included in the VSB broadcast signal, a storage unit storing the extracted segment synchronization information, and an equalization unit equalizing the VSB broadcast signal based on the segment synchronization information stored in the storage unit. The storage unit stores the segment synchronization information extracted from the extraction unit by field unit or by unit of N data segments within the field according to a channel state. More stable equalizations can be carried out in channel environment changes by storing segment synchronization information by the predetermined number of data segments and equalizing data within a corresponding data segment in a training mode while using the segment synchronization information every matching number of data segments.

Abstract: A method for demodulating a received digitally modulated signal subjected to multipath propagation impairment includes estimating the multipath propagation impairment of the received digitally modulated signal using a channel estimator, and estimating at least one symbol of the received digitally modulated signal using a symbol estimator. The at least one estimated symbol is adjusted based upon the estimated multipath propagation impairment to generate an estimate of the at least one symbol as impaired by the multipath propagation. At least one error signal is generated by comparing the estimate of the at least one symbol as impaired by the multipath propagation to the received digitally modulated signal. The at least one error signal is used for estimating remaining symbols to be demodulated and for refining the estimated multipath propagation impairment.

Abstract: The present invention provides a system and method for implementing a new TEQ training approach that trains TEQ coefficients by exploiting both time-domain and frequency-domain information. An advantage of this technique is that it reduces memory usage due to the training process. In addition, the complexity of the training process is simplified, and the associated computational work is reduced. The reduction of memory usage and computational work in turn may lead to cost savings, power consumption savings and other advantages.

Abstract: A channel impulse response for a channel is determined by determining an initial channel impulse response estimate based upon a stored training sequence and a received signal, by thresholding the initial channel impulse response estimate, by estimating a noise variance for the channel based upon the stored training sequence, the thresholded initial channel impulse response estimate, and the received signal, by determining an inverse of a covariance matrix based on the estimated noise variance and the thresholded initial channel impulse response estimate, by updating the channel impulse response based on the inverse covariance matrix, the stored training sequence, and the received signal, and by thresholding the updated channel impulse response estimate.

Abstract: An apparatus and method for adjusting the filter tap length of an adaptive equalizer using a training sequence, determining a required filter tap length by using multipath information detected from correlation values of sync symbols of a segment for data synchronization, training sequence for field synchronization and input data, and auto correlation values of the training sequence. In the case of a VSB signal, the presence or absence of a multipath detector, and the position and size thereof, can be identified from the correlation value by using a 704-symbols field sync signal. Also, the-pre-/post-ghosts which are farthest from the main tap are detected using the position of a multipath detector, thereby determining the tap length of the adaptive equalizer in a variable manner. Thus, the performance of the adaptive equalizer can be improved, and the power consumption can also be reduced.

Abstract: A method and device to equalize a signal received by a receiver after having traveled through a transmission channel, the signal including one data block and several probes located on either side of the data block. The method includes a step in which the impulse response of the channel is estimated before and after a data block n in taking account of the probes (Probe n 1 and Probe n) located on either side of the data block n and also of the probes that precede and follow the Probes n?1 and Probe n, the probes being weighted and combined with one another.

Abstract: A method of operation of a receiver of a mobile station or a base station of a radio access network and corresponding equipment, the method for especial use in providing interference cancellation according to a single antenna interference cancellation (SAIC) algorithm. The method includes a step (22) in which a channel estimator (12) estimates channel impulse response components for use by a SAIC equalizer (14); in estimating the channel impulse response components, the channel estimator (12) minimizes a special cost function (Jch(h)) with respect to the components of the channel impulse response h. In some embodiments, the method uses an iterative least mean squares procedure to minimize the cost function (Jch(h)).

Abstract: An embedded pattern-based adaptive equalizer coefficient updating mechanism updates weighting coefficients of an adaptive equalizer in accordance with an error or differential signal obtained by processing the distorted version of a known signal pattern, that is repetitively distributed among information signals contained within the electrical communication signal output from the equalizer, with a copy of the known signal pattern. No dedicated ‘training sequence’ communication with the transmitter is required, so that the coefficient update mechanism does not impact the operation or bandwidth availability of the channel.

Abstract: A method for reducing interference in a desired signal in a GSM communication system uses a finite-impulse-response filter for alternate linear equalization. The method includes a first step (300) of inputting a burst of data of a received waveform including interference from a channel of the communication system. A next step (302) includes training the finite-impulse-response filter with a set of symbols of specific quadrature phase, known a priori, in the burst of data of the received waveform. For example known real only and imaginary only symbols are alternatively selected from a midamble of the data burst. A next step (304) includes operating on the received waveform with the finite-impulse-response filter to alternately linearly equalize the burst of data to provide an estimate of the desired signal.

Abstract: A method for demodulating a received digitally modulated signal subjected to multipath propagation impairment includes estimating the multipath propagation impairment of the received digitally modulated signal using a channel estimator, and estimating at least one symbol of the received digitally modulated signal using a symbol estimator. The at least one estimated symbol is adjusted based upon the estimated multipath propagation impairment to generate an estimate of the at least one symbol as impaired by the multipath propagation. At least one error signal is generated by comparing the estimate of the at least one symbol as impaired by the multipath propagation to the received digitally modulated signal. The at least one error signal is used for estimating remaining symbols to be demodulated and for refining the estimated multipath propagation impairment.

Abstract: Training signals can be chosen based on stored prior connection information to reduce the use of extra tones in transmitted training signals and thereby improve receiver performance. By choosing training signals based on the stored prior connection information, it is possible to make the training signals indirectly a function of the loop impairments. One advantage of this scheme is that we can choose to omit certain tones in the training signals, based on previous connection information, on a loop-by-loop basis. For example, in an ADSL Transceiver Unit-Central office end (ATU-C) device, per-local-loop prior connection information may be employed to select DMT tones to be included in downstream training signals. Similarly, in an ADSL Transceiver Unit-Remote terminal end (ATU-R) device, prior connection information may be employed to select DMT tones to be included in upstream training signals.

Abstract: This invention provides colored noise detection algorithm(s). This colored noise detection algorithm(s) may be implemented with a multi-branch equalizer processing module that enables interference cancellation when colored noise is associated with received radio frequency (RF) bursts. The noise discriminator identifies when the radio frequency (RF) bursts have white noise or colored noise associated with them. Alternatively the noise discriminator may be able to determine and enable interference cancellation in response to an interference-limited received RF burst as opposed to a noise-limited received RF burst. The multi-branch equalizer improves the signal-to-noise ratio by improving the equalization with a second branch operable to be trained based upon known training sequences and at least partially re-encoded data bits.

Abstract: The tap weights of an equalizer are initialized in response to a received relatively short training sequence, and new tap weights for the equalizer are thereafter successively calculated in response to relatively long sequences of received symbols and corresponding sequences of decoded symbols. These new tap weights are successively applied to the equalizer.

Abstract: Error contributions in a DMT system where a received DMT-signal is effected by intersymbol interference, intercarrier interference and additive noise are minimized. Intersymbol interference average power, intercarrier interference average power, and additive noise average power are calculated. A cost function is determined by adding the intersymbol interference average power, the intercarrier interference average power, and the additive noise average power. A constraint is introduced which avoids a trivial solution where a time domain equalizer (TEQ) vector is equal to zero. The cost function is minimized by optimizing the TEQ vector.

Abstract: An equalizer, consisting of a plurality of taps, each tap having a multiplier which is coupled to multiply a respective input sample by a respective coefficient, the taps being arranged in sequence so that the input sample to each of the taps, except to a first tap in the sequence, is delayed relative to a preceding tap in the sequence. The equalizer further includes an input selector, which is coupled to toggle the input sample to at least a selected tap among the plurality of taps, responsive to a state of the equalizer, so that the equalizer operates in a first state as a feed forward equalizer, and in a second state as a blind equalizer.

Abstract: A training sequence is created for space-time diversity arrangement, having any training sequence length, while limiting the training sequence to a standard constellation. Given a number of channel unknowns that need to be estimated, L, a training sequence can be creates that yields minimum means squared estimation error for lengths Nt=kNPRUS+L?1, for any positive integer k?1, where NPRUS is a selected perfect roots-of-unity sequence (PRUS) of length N. The training sequence is created by concatenating k of the length N perfect roots-of-unity sequences, followed by L?1 initial symbols of that same PRUS. Good training sequences can be created for lengths Nt that cannot be obtained through the above method by concatenating a requisite number of symbols found through an exhaustive search.

Abstract: A method and radio stations for transmitting signals between a first radio station (1) and a second radio station (2) are proposed, in which the influence of amplitude fluctuations or fading can be reduced. In a modulator (4) of the first radio station (1) a pre-equalization of the signals to be transmitted is performed. The pre-equalized signals are transmitted from the first radio station (1) to the second radio station (2) via a plurality of radio channels (20, 25).

Abstract: An adaptive interference suppression receiver for a DS/CDMA system includes: input signal generators outputting a part of received signals of receiver antennas that has a coding block's transfer code; adaptive filter blocks filtering a complex signal output from the input signal generators with a tap weight updated based on a constraint MMSE criterion and estimating phase and amplitude components of a specific user channel using the filtering output signal to generate a channel-estimated signal; a signal restorer combining the channel-estimated signal and the filtering output signal and restoring an original signal; a signal selector for selecting known training data signal or the restored signal; and error generators comparing the channel-estimated signal and the filtering output signal and calculating an error between the two signals.

Abstract: Rapid identification and modeling of transmission media channel characteristics of a communications system using a correlation based technique. The technique provides a known training sequence used to generate a known quantity that operates on an observed or measured received signal, which is a function of the training sequence and the channel's impulse response, to give an estimate of the model of the channel. The technique decouples the training sequence from the observed or measured output, leaving the estimated impulse response. The impulse response of the transmission media channel is rapidly computed and processed to set the initial values of filter coefficients, for example, an echo canceller and an equalizer, in the communications system. Once the coefficients are initialized, if needed, a standard technique, such as least mean square (LMS) correlation, can be used to fine-tune the coefficients to converge on or model the transmission media channel's characteristics.

Abstract: A system, device, and method for time-domain equalizer training uses a two-pass auto-regressive moving average model. A communication channel is first modeled using p1 poles and q1 zeros to form a first shortened channel impulse response having a first approximation H1(z)=B1(z)/1+A1(z), wherein q1, is greater than a predetermined cyclic prefix length. A time-mirrored image of the first shortened channel impulse response is then formed, and the resulting time-mirrored image of the first shortened channel impulse response is modeled using p2 poles and q2 zeros to form a second shortened channel impulse response having a second approximation H2(z)=B2(z)/1+A2(z), wherein q2 is less than or equal to the predetermined cyclic prefix length. The time-domain equalizer coefficients are determined by combining A1(z) and A2(1/z) with an appropriate amount of delay.

Abstract: A compensation circuit and method for reducing ISI products within an electrical data signal corresponding to a detected data signal received via a signal transmission medium introduces distinct compensation effects for individual ISI products within the electrical data signal. Distinct data signal components within the detected data signal and corresponding to such ISI products can be selectively and individually compensated, thereby producing a compensated data signal in which each selected one of such individual data signal components is substantially removed. Individual data signal components or selected combinations of data signal components can be compensated as desired.

Abstract: Method and apparatus that compensates for overestimation of channel SINR due to overfitting of an adaptive equalizer to the pilot portion of a received frame. The SINR of a wireless channel is estimated by adapting an adaptive equalizer using the pilot portion of the frame, applying the adaptive equalizer to a non-pilot portion of the frame, determining a parameter using the adaptive equalizer output, and estimating the SINR of the wireless channel using the parameter. The parameter can include, for example, the mean square error (MSE) or the bias of the equalizer output. The accuracy of the SINR estimate according to this aspect of the present invention is thereby improved (as compared to a SINR estimate based on parameters calculated during the pilot interval) because the adaptive equalizer is not overfit to the control or data portions of the frame.

Abstract: A communication system is disclosed that comprises first and second communication apparatus. The first communication apparatus is provided with a transmitter for each of the transmission paths, which are capable of sending at least part of a communication signal to the second communication apparatus. The first communication apparatus moreover comprises training mechanisms for generating a training code to be sent to the second communication apparatus enabling a receiver to match a received signal to a corresponding transmitted signal. According to the invention, a training code is used with at least nearly ideal cyclic auto-correlation properties such that its cyclic auto-correction function is at least nearly zero for all cyclic shifts. The transmitter concurrently sends a training code in a mutually shifted manner, while the receiver is capable of performing a cyclic auto-correlation with respect to a received training signal.

Abstract: A system and method for enhancing the reception of a single carrier signal. The single carrier signal includes periodic training signal and data. The system includes a transmitter configured such that L symbols of either the beginning or end of the N symbols of the training signal, where L<N, are duplicated at either the end or the beginning of the training signal, respectively. The system further includes a receiver configured to receive the modified training signal for the calculation of FIR coefficients in a single pass and without the need for least mean square (LMS) methods or the like.

Abstract: Methods and Systems for Determining an Optimal Training Interval in a Communications System. A method is provided for determining an optimal training interval for a channel of a communications system. The method can include a step for receiving first channel estimations of a signal carried by a channel of a communications system, wherein the first channel estimations are generated by a first channel estimator. The communications system can include a normal mode for utilizing the channel to carry user data, a training mode for training the first channel estimator, and a failure mode for recovering channel communication after channel failure. The method can include a step for determining a time distribution of the channel transition from the normal mode to the failure mode, wherein channel failure occurs when error in the first channel estimations exceeds a first predetermined threshold.

Abstract: A digital equalizer comprises a matched filter that, in conjunction with an FIR filter, assures a single peak with substantially greater energy than other peaks caused by ghosts, thereby permitting synchronization even with multiple, arbitrarily strong ghosts caused by strong multipathing, multiple transmitters, or both.

Abstract: The present invention employs training sequence hopping in a cellular communications system to permit tight frequency reuse by minimizing or avoiding co-channel interference and/or other signal degrading phenomena. During a first portion of a transmission, e.g., a first burst, a first training sequence is used. During a second portion of that transmission, e.g., a second burst, a second different training sequence is used. Different training sequences are used for different portions of the transmission according to a predetermined training sequence hopping pattern and with a predetermined number of training sequences. The portion duration can extend for the length of a burst, for more than one burst, for a speech frame, or for some other time period.

Abstract: A digital and a multiplication method are described, which lead to an efficient architecture for a hardware implementation of digital FIR and IIR filters into FPGAs. The multiplications of input sample data and delayed sample data with filter coefficients are performed by addressing look-up tables in which corresponding multiplication results are prestored. The size of the look-up tables is reduced by storing only those multiplication results which cannot be obtained by a shifting operation performed on the other pre-stored multiplication results, the input sample data, or the delayed sample data. Thereby, the size of the look-up tables can be compressed significantly such that an implementation of large digital filters into FPGAs is possible.

Abstract: The present invention has many aspects. One aspect of the invention is to perform equalization using a sliding window approach. A second aspect reuses information derived for each window for use by a subsequent window. A third aspect utilizes a discrete Fourier transform based approach for the equalization. A fourth aspect relates to handling oversampling of the received signals and channel responses. A fifth aspect relates to handling multiple reception antennas. A sixth embodiment relates to handling both oversampling and multiple reception antennas.

Abstract: A decision feedback equalizer with dynamic feedback control for use in an adaptive signal equalizer. Timing within the decision feedback loop is dynamically controlled to optimize recovery of the data signal by the output signal slicer. The dynamic timing is controlled by a signal formed as a combination of feedback and feedforward signals. The feedback signal is an error signal related to a difference between pre-slicer and post-slicer signals. The feedforward signal is formed by differentiating and delaying the incoming data signal.

Abstract: A method and system for reducing the DC offset in a receiver in the presence of carrier frequency offset between the transmitter and the receiver. The present invention utilizes the knowledge of the carrier frequency offset to determine the phase difference between two (or more) snapshots of the same transmitted symbol. The receiver DC offset is solved for using a linear system solver which can be implemented outside the analog domain. The DC offset may be tracked in order to maintain a constant adjust of the DC offset, which in combination with the above DC offset estimation technique implements a complete solution for the DC offset cancellation problem.

Abstract: A pulse code modulation (PCM) modem system employs a relatively white training signal to optimize the adaptive filter coefficients in the receiver equalizers. During the training mode, any line coding or equivalent spectral shaping is disabled to provide a training signal sequence having a substantially even spectral content. The presence of DC within the training signal reduces the likelihood that the error function of the equalizers will settle at a local minimum. Following the training interval, the encoder enables the line coder to condition the digital input sequences, introduce DC nulls, and reduce the detrimental effects of baseline wander.