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 and method facilitating acoustic echo cancellation convergence detection is provided. The invention includes an acoustic echo cancellation convergence detector having a center clipping component, a convergence calculator, a convergence filter and a convergence statistic component. The invention provides for the acoustic echo cancellation convergence detector to provide an output regarding convergence of an adaptive filter based, at least in part, upon a filtered convergence statistic. Optionally, the acoustic echo cancellation convergence detector can provide an output associated with convergence history.

Abstract: Selected data (LSP1, LSP2) is monitored among other data passing through label switched paths (LSPs) of a communications network of interconnected label switching routers (LSR–LSR4). The method comprises designating at least one of the routers (LSR3) as a monitoring station and at least one of the routers (here LSR3 also) as a probe interface station, and connecting a probe apparatus to that interface station. The monitoring station (LSR3) is configured to multicast forward the selected data for monitoring additionally to the probe apparatus via the probe interface (506). Also disclosed is a probe apparatus including means for configuring the router to perform multicast forwarding of selected data to the interface.

Abstract: A method and apparatus for detecting whether a remote party has added a secondary telephone destination to a telephone call, for example through the activation of three-way calling service, conference calling or two lining bridging, by identifying an echo characteristic to the telephone connection between the local and the remote telephone and monitoring the echo characteristic to determine whether there is a significant change. The addition of a secondary telephone destination can be verified by continuing to monitor the echo characteristic to determine whether it has returned to its original value.

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: The present invention provides methods and systems for providing efficient use of available CPU cycles that may be achieved by reducing the length of the echo canceller filter. An echo canceller's adaptive algorithm may be implemented to reach a lower mean squared error due to the increased training time allowed by cycle reduction. Total power consumption of a processor may be reduced by reducing the number of multiplications (and/or other operations) that may be performed by an echo canceller filter for each time iteration. This may be achieved by not performing multiplications on taps that are not being used. For higher rates, a shorter echo canceller filter may be implemented by transmitting less energy in low frequencies. As a result, the temporal length of the echo channel may be shortened thereby reducing the total number of taps needed to model the channel. The present invention may further enhance performance by reducing CPU cycles and allowing for more echo canceller training time.

Abstract: A digital subscriber line transmission system comprising an IFFT circuit generating successive outgoing time domain symbols on a subscriber line from respective groups of digital frequency domain coefficients; an FFT circuit generating groups of digital frequency domain coefficients from respective incoming time domain symbols received on the subscriber line, a current incoming symbol being delayed with respect to a current outgoing symbol by a predetermined time interval; and circuitry for, during an end portion of a current incoming symbol, subtracting from the signal received on the subscriber line an estimated echo obtained by a filter from a signal portion following the end of the current outgoing symbol, and adding thereto, through said filter, a beginning portion of the current outgoing symbol, wherein said portions have a duration at least equal to said predetermined time interval.

Abstract: A method and apparatus for canceling a near-end echo of a far-end signal for each channel of a voice over packet multi-channel communications gateway. The invention applies “off-the-shelf” coding mechanisms as well as novel coding schemes to provide fixed compression rate and with options to maintain perfect speech integrity on certain processing components, such as network echo canceller, acoustic echo canceller, Voice Activity Detector, Comfort Noise Generation, etc. The off-the-shelf compression algorithm includes LPC-10, G.723.1, G.729A. The alternatives are Wavelet transform, DPCM, and ADPCM, etc.

Abstract: A circuit for transmitting and receiving communications. The circuit includes a transmit block, a receive block, and an echo canceller, coupled to the transmit block and to the receive block, for determining an echo signal and subtracting it from the received signal, the determination of the echo signal involving a predetermined number N of coefficients calculated at the beginning of each of the communications in an initialization phase. The circuit periodically updates during communication a restricted group of coefficients chosen from among the most significant coefficients. The present invention also relates to an echo cancellation method.

Abstract: A repetitive burst-mode input signal that has a dark time portion, a preamble portion, and a payload portion is converted into a limited output signal in accordance with a decision threshold level, which is controlled by selectively coupling an averaged value of the burst-mode data amplitude to the decision threshold level. The timing sequence for selectively coupling the averaged signal value is controlled such that the average value of the burst-mode signal acquired during the preamble portion of the burst-mode signal is applied to the decision threshold level during substantially all of the payload portion. The control circuit may incorporate a phase-locked loop, which locks onto the repetitive dark time frequency and in response synthesizes a switchable track enable signal that controls the timing sequence of the decision threshold level. The phase-locked loop can employ all-digital, analog, and/or hybrid digital/analog circuitry.

Abstract: An apparatus and method for echo cancellation is presented. The echo canceller comprises an adaptive filter that tracks the impulse response of the echo path and produces an estimate of the echo. Filter adaptation is controlled by a controller based on the rate of the far-end speech signal, the rate of the near-end signal, an acoustic loss measure, and a double talk hangover indicator. The controller may also comprise a step size adaptation unit for determining the adaptation step size of the adaptive filter. In addition, the controller may comprise a noise replacement unit, which controls replacement of the echo residual signal with comfort noise to ensure echo is completely rejected when only the far-end speaker is talking.

Abstract: A cancellation system comprises a channel circuit (11) for each noise source, such as echo in a particular cable pair. There are only eighty taps per channel, in two blocks (n_echo_a, f_echo_a). Each block is preceded by a variable delay line comprising blocks of registers cascaded so that a delay value of 0 to 40 clock cycles can be chosen. The delay value is determined by determining an optimum position for each tap block. This is achieved by determining a maximum coefficient sum for a number of windows. Taps from other channels are used during training, so that there is a total of 160 taps for each channel during training to enable the optimum positions to be determined.

Abstract: A digital echo cancellation device is provided. The digital echo cancellation device used for a high speed bidirectional communication system includes an adaptive beamformer in the form of a plurality of finite impulse response (FIR) filters for estimating an input receiving signal, the adaptive beamformer for estimating a front part, which rapidly changes in an echo path impulse response, by adaptively estimating the input receiving signal and an orthogonalized infinite impulse response (IIR) filter for receiving the estimated signal output from the adaptive beamformer and estimating a hind part of the echo path impulse response on the basis of an IIR. According to the digital echo cancellation device, the amount of calculation and the amount of required memory is significantly reduced, convergence speed is high, and the stability of the output of the filter is improved since the impulse response of the echo path is estimated by only several tens of taps.

Abstract: A method and system receives a far-end signal and determines whether the far-end signal is representative of a modulated signal. The method and system also receives a near-end signal and determines whether the near-end signal is representative of a modulated signal. Predetermined characteristics of the near and far-end signals are determined as is whether the echo canceller will converge for the far-end signal. The operation of the echo canceller is controlled in response to the determination of the predetermined conditions and in response the determination of whether the far-end and near-end signals are modulated signals.

Abstract: A method and apparatus for reducing crosstalk in a multi-channel communication system is disclosed. In one embodiment, outgoing signals in a multi-channel environment are manipulated into a transform domain, such as the frequency domain. Thereafter, the signals may be combined and modified based on a weighting variable to create a cancellation signal. Combined processing greatly reduces system complexity and increases processing speed. After processing in the transform domain, the cancellation signal undergoes further processing to return the cancellation signal into the time domain. The cancellation signal may then be combined with received signals to cancel crosstalk or echo. A method and apparatus for crosstalk cancellation in the analog domain and digital domain is also disclosed.

Abstract: A signal processing system which discriminates between voice signal and data signals modulated by a voiceband carrier. The signal processing system includes a voice exchange, a data exchange and a call discriminator. The voice exchange is capable of exchanging voice signals between a switched circuit network and a packet based network. The signal processing system also includes a data exchange capable of exchanging data signals modulated by a voiceband carrier on the switched circuit network with unmodulated data signal packets on the packet based network. The data exchange is performed by demodulating data signals from the switched circuit network for transmission on the packet based network, and modulating data signal packets from the packet based network for transmission on the switched circuit network. The call discriminator is used to selectively enable the voice exchange and data exchange.

Abstract: In a distributed control system in which a plurality of nodes are connected to a transmission line, each node controlling components connected to this node and transmitting a message to other nodes, a message sent by each node includes at least two message-sending condition-identifying portions, one of the condition-identifying portions including data indicating a message-receiving node or non-designation of a message-receiving node; and a comparison-selection circuit provided in each node includes registration parts for registering data of message-receiving conditions, at least two registration parts for comparing contents of the condition-identifying portion in the taken-in message with the data of message-receiving conditions registered in the registration parts, a received-message storing part for storing a message to be received in this node, a control part for determining whether or not the taken-in message is to be received in this node based on a result of comparison-processing performed in the compar

Abstract: An echo cancellation system for detecting and canceling echo from a network speech path, comprising a pool of echo locators for detecting pure echo delay and dispersion of time, a pool of echo cancellers, a pool of line watchdogs for detecting presence or absence of echo in the network speech path, and a control system for (i) locating and applying an echo locator from the pool of echo locators to the network speech path for detecting the pure echo delay and dispersion of time of any echo in the network speech path, and thereafter returning the echo locator to the pool of echo locators; (ii) locating and applying an echo canceller from the pool of echo cancellers to the network speech path for canceling the echo using the pure delay and dispersion time, and thereafter returning the echo canceller to the pool of echo cancellers; and (iii) locating and applying a line watchdog from the pool of line watchdogs to the network speech path for detecting said presence or absence of echo, and in the event the presence

Abstract: An echo cancelling system for cancelling echoes in a communication path includes an echo locator and an echo canceller. The echo locator is coupled to the communication path and locates the positions of echo signals received from the communication path. The echo canceller is also coupled to the communication path and cancels echo signals received therefrom. During echo cancellation, the echo canceller becomes active in regions corresponding to the positions of echo signals in response to the echo locator.

Abstract: A training circuit for training a tap coefficient of an adaptive equalizer that performs error calculations in a training process and updating of the tap coefficient in a time area and thereby makes the tap coefficient converge stably in a short time.

Abstract: A network gateway is configured to facilitate on line and off line bi-directional communication between a number of near end data and telephony devices with far end data termination devices via a hybrid fiber coaxial network and a cable modem termination system. The described network gateway combines a QAM receiver, a transmitter, a DOCSIS MAC, a CPU, a voice and audio processor, an Ethernet MAC, and a USB controller to provide high performance and robust operation. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.

Abstract: A separation circuit, method of determining a residual level of an echo, and an echo canceling system, bit pump and transceiver employing the circuit and method. The echo canceling system employing the separation circuit is couplable between a transmit and receive path of the bit pump and generates an echo canceling signal. In one embodiment, the separation circuit includes a symbol determination circuit that accepts a receive signal, propagating along the receive path, substantially free of an echo and determines a symbol associated with the receive signal. The separation circuit also includes an estimator stage, coupled to the symbol determination circuit, that receives the symbol and provides an estimated receive signal. The separation circuit generates data representing a residual level of the echo as a function of the estimated receive signal and the echo canceling signal.

Abstract: An echo canceler for canceling echo components having a plurality of cascade-connected adaptive filters and a plurality of update control means. The echo canceler may further include an update control selective circuit for generating selective signals which enable or disable the update control means. Power values of opposite speech signals generated from the adaptive filters are used to control the updating of filter coefficients of the adaptive filters.

Abstract: A filter cell, method of deriving an echo component and an echo canceling system, bit pump and transceiver employing the same. In one embodiment, the filter cell includes a first summing node that receives a first input based on a signal sample that contains an echo component of an echo. The filter cell also includes a second summing node that receives a second input based on the signal sample. The filter cell still further includes a multiplier that employs outputs from the first and second summing nodes and a scaling factor to derive first and second outputs containing a remnant of the echo component.

Abstract: A method and an apparatus for echo cancellation in a digital data transmission system in which system the end of a transmission link to which sound returns as an echo is the far end and the end of the transmission link from which an echo is reflected back is the near end, and in which a speech coding method is used on the echo path at least for a far-end signal transmitted from the far end to the near end, the method comprising the following steps: the echo originating from the near end is estimated with an adaptive linear filter on the basis of the far-end signal, and the echo estimate is subtracted from the near-end signal transmitted from the near end to the far end, whereby the speech-encoded far-end signal is decoded in an echo canceller, and the echo originating from the near end is estimated on the basis of said decoded far-end signal.

Abstract: A method for dynamically regulating the power consumption of a high-speed integrated circuit which includes a multiplicity of processing blocks. A first metric and a second metric, which are respectively related to a first performance parameter and a second performance parameter of the integrated circuit, are defined. The first metric is set at a pre-defined value. Selected blocks of the multiplicity of processing blocks are disabled in accordance with a set of pre-determined patterns. The second metric is evaluated, while the disabling operation is being performed, to generate a range of values of the second metric. Each of the values corresponds to the pre-defined value of the first metric. A most desirable value of the second metric is determined from the range of values and is matched to a corresponding pre-determined pattern. The integrated circuit is subsequently operated with selected processing blocks disabled in accordance with the matching pre-determined pattern.

Abstract: A speech communication system is provided that uses pitch information, pitch lags, pitch gains, energy and/or other speech characteristics about the outgoing speech and the unknown signal on a frame basis to determine if the unknown signal is an echo signal of the outgoing speech or if the unknown signal also contains speech from a second talker (double talk). Additionally, a plurality of frames of these characteristics of the outgoing speech signal and the unknown incoming signal may be buffered so that the analysis and comparison can be made more efficiently and quickly in the frame domain as opposed to a time domain. Multiple characteristics may be optionally weighted and then analyzed. The system and method may further determine a level of confidence, based on any criterion, in the determination that may then be used to adjust the gain of a filter.

Abstract: An apparatus of a digital echo canceller and method therefor, a designed selector is used values of receiving and input signals to estimate the length of a cable. The response values of an insignificant part of the echo signal can be selected. Multiplication and addition operations are carried out in a response region of a significant part of the echo signal. An estimated echo signal is produced to cancel the echo signal, unnecessary operations and the cost of a hardware can be reduced.

Abstract: A double-talk detector (109) for an acoustic echo canceler (104) of a VoIP terminal (101) converts (216,226) received far-end signals (212) and transmitted near-end signals (222) into the frequency domain and high-pass filters out (218,228) low-frequencies representing noise to obtain a complex reference signal and a complex error signal, respectively. It then correlates (230) the complex signals and computes (232) the instantaneous error energy (234) and smoothed (long-term average) error energy (235) of the complex error signal. If the convergence value is below 0.06 (300), the signals are converged and double-talk detection is enabled (306). If the convergence value is above 0.09 (312), the signals are diverged and double-talk detection is disabled (316). If double-talk detection is not enabled, an error threshold (236) is set (304,318) to the value of the smoothed error energy.

Abstract: Multiported register files used for storing coefficients in adaptive FIR are improved upon by implementing a split memory architecture that has the ability to separately control the least significant bits and the most significant bits of coefficient values that are stored in the filter. When the filter is operated to use so-called “burst mode” updating, the updating circuitry of the filter can be disabled and only the most significant bits of the coefficients are read out from the multiported register file while the least significant bits remain unchanged. This conserves power without sacrificing precision, since only certain ones of the bits of the coefficients are used in the multiplication of the sample.

Abstract: In an adaptive audio equalizer apparatus, a signal that is output from an adaptive filter 13 is fed to a speaker and to a delaying unit. The signal fed to the delaying unit is delayed for a predetermined time, and is multiplied by a scaling factor in a multiplying unit. A first calculation unit calculates a difference between an output of a microphone and a target response signal, and outputs the result as an error signal. A second calculation unit adds the output of the multiplying unit to the error signal, and outputs the result to a filter coefficient setting unit of the adaptive filter.

Abstract: A configurable adaptive filter that is used for echo cancellation is disclosed, which includes a method of detecting a voice or no-voice signal. The presence of a voice or no-voice signal is determined by calculating a histogram of signal amplitude value over a period of time. If this histogram has more than a predefined number of samples that are above a threshold then the signal is classified as no-voice or periodic otherwise the signal is classified as a voice signal. A variable maximum amplitude limit and lower amplitude thresholds are disclosed to detect a voice or no-voice from the histogram signal faster than traditional methods utilized in echo cancelers. A configurable hysteresis time is used to ensure the signal register primarily contains voice signal when the filter coefficients of the echo canceler are allowed to adapt.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) receiver that compensates for FFT window drift by extracting a training symbol from a fast Fourier transformed OFDM signal, and processing the extracted training symbol to derive an FFT window adjustment factor and an associated equalizer tap initialization value. The OFDM receiver controls the position of an FFT window and the initialization of equalizer taps using the FFT adjustment factor and equalizer tap initialization value. The OFDM receiver preferably filters the fast Fourier transformed OFDM signal to remove additive channel noise and increase the likelihood of reliable equalizer tap initialization in a low SNR environment.

Abstract: A system for ensuring optimum performance of a modem used in conjunction with a telephone system employing a digital PBX coupled with a two-wire analog trunk includes an echo cancellation circuit having an adaptive filter connected in series circuit with a linear codec between the digital PBX and a two-to-four wire hybrid converter coupled with the two-wire analog telephone trunk. The combination of the echo canceller and the linear codec allows accurate decoding of weak far end modem signals when such signals are summed with a strong near end modem signal echo. The DSP echo canceller removes the very strong near end modem echo and passes the far end modem signal with little distortion, while the linear codec permits accurate recovery of the weak far end signal in the presence of high noise levels.

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: Method and apparatus for an improved echo canceller provide for faster convergence in echo canceling, which also contribute to better voice quality and provide for an increase in the capacity (number of channels) of a multi-channel voice processing products. Whitening filters are used to flatten the spectrum of the signals that pass through the echo canceller. Higher convergence rate is achieved when flattened signals pass through the echo canceller. A reconstruction filter is used to introduce the spectral envelop back into the outbound signal.

Abstract: A system and method of Acoustic Echo Cancellation includes a digital filter used to estimate the echo path is split into 2 filters: one fixed infinite impulse response (IIR) filter and one adaptive finite impulse response (FIR) filter. The fixed filter models the composite frequency response of the loudspeaker, its cabinet enclosure and the direct coupling path between the loudspeaker and the microphone(s). The adaptive filter models the time varying characteristics of the indirect coupling path between the loudspeaker and microphone.

Abstract: An xDSL modem having an adaptively adjustable guard band comprising a finite number of spaced-apart frequency bins between the upstream and downstream frequencies. The guard band is adjusted by selecting one from among a plurality of filters belonging to a filter bank of the receiver circuitry. A weighted loss in data capacity is calculated when each of the candidate filters are used, and the filter which gives the lowest loss in data capacity, subject to certain criteria, is used. The adjustment is made pursuant to noise and signal characteristics measured during start or restart of an xDSL communications session.

Abstract: A network echo canceller for integrated telecommunications processing. The network echo canceller processes echoes in multiple communication channels over a packet network. The network echo canceller adapts a least means squared finite impulse response filter to each communication channel in order to estimate an echo therein. The echo estimation is subtracted from signals that are being sent over each communication channel. The echo canceller includes a residual error suppressor to suppress non-linear sources of echo when desired. The echo canceller includes a double talk detector to inhibit filter adaptation during double talk. The network echo canceller is programmable into a digital signal processor and can be flexibly controlled through messaging.

Abstract: The filtering coefficients of a frequency domain stereophonic echo canceller are adapted by a method which takes account of the cross-correlation between the input signals relating to the two channels. In particular, the adaptation process takes account of the coherence function, reducing the problems commonly encountered with stereophonic cancellation schemes when relatively correlated input signals occur.

Abstract: A wireless transceiver featuring a compensating filter circuit with a frequency and optionally an amplitude response which has the same function as the composite of filter effects from the transmit side as well as from the intermediate frequency (IF) stage of the receive side. The compensating filtering approximately duplicates the effects of the phase lock loop on the transmit side and the effects of IF filtering on the receive side, as well as amplitude distortion in the detector, which would delay or distort the audio. Then, the compensated audio is added or subtracted, depending on phase considerations, from the receive signal so that the receive signal is free of filter artifacts.

Abstract: This invention is generally concerned with the reception of high rate digital data, and more particularly with methods and apparatus for improved channel estimation in high rate digital data communications systems, particularly packet data communications systems.

Abstract: When an echo attenuation amount ACOM(i) is smaller than a desired echo attenuation amount ACOM, and an echo cancellation amount ACANC(i) is equal to or greater than a echo/noise ratio E/N(i), a block length computer increases the block length BL(i) and outputs that increased block length BL(i) to a block length controller. The echo canceler comprises such a block length computer and such a block length controller, wherefore the echo attenuation amount can ultimately be made to be equal to or greater than the desired echo attenuation amount.

Abstract: A method of NEXT cancellation in a modem pool having a plurality of modems, where each modem has at least one FIR filter, each FIR filter for filtering signals from a transmitting one of the modems, each modem transmitting a signal having a plurality of contiguous signal blocks, the method including providing a frequency response vector per FIR filter, for each corresponding one of the transmitted signal blocks for each of the modems adapting the length of the signal block to equal the length of the frequency response vector, transforming the adapted signal block into the frequency domain, thereby generating a frequency-domain signal vector, for each of the modems and its at least one FIR filter multiplying the frequency response vector of the FIR filter by a corresponding one of the frequency-domain signal vectors, thereby generating a filtered frequency-domain signal vector, adding the filtered frequency-domain signal vectors, thereby generating a combined filtered frequency-domain signal vector, transformi

Abstract: A method, apparatus and system employing such for adapting the Beta factor in a echo cancellation adaptive filter by using echo loss return enhancement (ERLE) as a metric to determine the setting of the Beta factor. In addition, a method and apparatus for determining the optimum number of filter taps used in an adaptive filter by dividing a filter array into blocks of taps, finding for each tap the sum of squares of the coefficients therein and then comparing the sum to an average block energy. Based on this comparison, a block is deemed to either contribute significantly to the operation of the filter or not. Starting with the tail end block of the array, the optimum filter order is found by determining when the first contributing block is found.

Abstract: An echo canceller is described with improved performance. The echo canceller is capable of maintaining audio quality with less consumption of processor cycles by initially segmenting coefficients corresponding to successive audio samples of a delay line into a predetermined number of segments. The coefficients are used in computing an echo estimate. Upon segmenting the coefficients, certain segments are assigned to a first segment group, where the coefficients of that group are updated more frequently than coefficients assigned to one or more of the remaining groups. In one embodiment, this grouping is achieved by periodically computing a cumulative magnitude of the coefficients of each segment for all coefficients of the segments and subsequently placing a lesser number of segments with the highest cumulative coefficient magnitudes into the first segment group. Of course, in lieu of cumulative magnitude calculations, the energy of the coefficients may be computed.

Abstract: A receiver, system, and method for performing equalization. The receiver includes a multi-channel chip equalizer for receiving a plurality of receive baseband signals and restoring chip pulse shapes of a plurality of transmit baseband signals transmitted by a plurality of transmit antenna to produce a plurality of equalized output streams and a correlator for correlating the plurality of equalized output streams with a correlation signal to reduce gradient noise in the plurality of equalized output streams. The method of equalizing includes receiving a plurality of receive baseband signals and restoring chip pulse shapes of a plurality of transmit baseband signals transmitted by a plurality of transmit antenna to produce a plurality of equalized output streams and correlating the plurality of equalized output streams with a correlation signal to reduce gradient noise in the plurality of equalized output streams.

Abstract: A communication system having an echo canceller is disclosed. One embodiment of the echo canceller includes an adaptive filter used to provide an estimate of reflected echo which is removed from the send signal. The echo canceller may also include a near-end talker signal detector which may be used to prevent the adaptive filter from adapting when a near-end talker signal is present. The echo canceller may also include a nonlinear processor used to further reduce any residual echo and to preserve background noise. The echo canceller may also include a monitor and control unit which may be used to monitor the filter coefficients and gain of the adaptive filter to maintain stability of the echo canceller, estimate pure delay, detect a tone, and inject a training signal. The echo canceller may also include a nonadaptive filter used to reduce the length of the adaptive filter.

Abstract: An adaptive filter for echo cancellation includes a segmented sparse transversal filter having an input, the filter having an adjustable length, adjustable lengths for the segments and adjustable tap weights. The adaptive filter further includes an adaptive tap weight control mechanism providing a tap weight vector including tap weights and a tap weight vector length to the taps of the transversal filter, the adaptive tap weight control mechanism setting the tap weights and the tap weight vector length in response to comparison of estimated truncation error to a target truncation value and in response to a magnitude of integrated cross correlation coefficients between a reference signal and an error signal from the adaptive filter.

Abstract: A communication system having an echo canceller is disclosed. One embodiment of the echo canceller includes an adaptive filter used to provide an estimate of reflected echo which is removed from the send signal. The echo canceller may also include a near-end talker signal detector which may be used to prevent the adaptive filter from adapting when a near-end talker signal is present. The echo canceller may also include a nonlinear processor used to further reduce any residual echo and to preserve background noise. The echo canceller may also include a monitor and control unit which may be used to monitor the filter coefficients and gain of the adaptive filter to maintain stability of the echo canceller, estimate pure delay, detect a tone, and inject a training signal. The echo canceller may also include a nonadaptive filter used to reduce the length of the adaptive filter.