Abstract: An echo canceller comprising a digital filter having adaptive coefficients which are updated to simulate an echo response, a temporary register for storing default coefficients, and a controller for monitoring ERLE and in the event the ERLE is greater than a first predetermined threshold then enabling the digital filter and replacing the default coefficients in the temporary register with the adaptive coefficients, and in the event the ERLE is less than a second predetermined threshold then disabling the digital filter and replacing the adaptive coefficients with said the default coefficients from the temporary register.

Abstract: Methods and systems pertaining to estimating and compensating for a round-trip or flat delay portion of an echo channel characteristic in an echo canceller are provided. According to a particular method, a filter coefficient vector of an adaptive filter that models the echo channel characteristic is updated. An instant flat delay is estimated by analyzing the filter coefficient vector after each update, and periodic averages of the instant flat delay estimate are performed. A final flat delay estimate average is determined when the flat delay estimate average has converged. The length of the adaptive filter is adjusted in response to the final flat delay estimate average. Further, an improved echo canceller apparatus that compensates for a flat delay portion of an echo channel characteristic is provided. The improved echo canceller includes an adaptive filter, a position detector, a periodic averager, and a level detector. The adaptive filter has an initial length N.

Abstract: The present invention provides an adaptive filter and a learning method therefor to eliminate real output signals generated by input signals and an environment signal response. The adaptive filter receives the input signals from an input signal source and generates estimated output signals according to an filter coefficients and the input signals. The first step of the learning method is storing the input signals and the real output signals within a past time period. Then, a predictive input signal and a predictive output signal are generated according to the input signals and the real output signals in the memories, respectively. Finally, the filter coefficients is updated according to the predictive input signal, the predictive output signal, one of the input, signals and one of the real output signals, causing the estimated signals to approximate the real output signals.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) receiver that compensates for FFT window drift by extracting pilots from a fast Fourier transformed and equalized OFDM signal, and processing the extracted pilots to derive an FFT window adjustment factor and an associated equalizer tap adjustment value. The OFDM receiver simultaneously controls the position of an FFT window and the phase of equalizer taps using the derived FFT adjustment factor and equalizer tap adjustment value.

Abstract: A communication circuitry for providing effective detection of tones in a communication network. The communication circuitry comprises filtration circuitry, summation circuitry, detection circuitry, and interface circuitry. The filtration circuitry is coupled to the summation circuitry and is configured to receive a communication, process the communication to estimate an echo return in the communication, and provide the estimated echo return to the summation circuitry. The summation circuitry is coupled to the detection circuitry and configured to receive the estimated echo return from the filtration circuitry, receive a tone transmission and echo return from the interface circuitry, subtract the estimated echo return from the tone transmission to generate a substantially pure tone, and provide the substantially pure tone to the detection circuitry. The detection circuitry is configured to receive the substantially pure tone and process the substantially pure tone to perform a programmed operation.

Abstract: Disclosed is an echo path delay estimating apparatus and method for estimating the echo path delay using decimators and an adaptive filter, so that a short computation time is used by the echo canceller.

Abstract: A wireless device is provided with at least one wireless transceiver and at least one controller manager to transmit and receive signals wirelessly to and from network devices of a first and second wireless network, in a coordinated manner, in accordance with a first and a second protocol respectively. The wireless device is further provided with a network manager to coordinate the network devices of the first and second wireless networks to reduce interference between the network devices of the two wireless networks. In various embodiments, the reduction is effectuated through proactive avoidance of interference with dominant devices by dominated devices, whenever an interference is predicted to occur. In other embodiments, the reduction is effectuated through corresponding application of appropriate filtering to correspondingly cancel the respective interfering signals, whenever an interference is predicted to occur.

Abstract: A circuit able to attenuate echo and side tones in a switching system connecting the first and second subscribers, comprises a first linear converter for converting pulse code modulated data generated by the first subscriber into an analog signal in the read message mode of the time switch, a side tone canceling filter for eliminating the side tones from the analog signal produced by the first linear converter, a clipper for clipping the analog signal rid of the side tones, a first PCM converter for converting the output signal of the clipper into a refined PCM data written into the time switch in the write message mode of the time switch and transferred to the second subscriber, a second linear converter for converting the PCM data generated by the second subscriber into an analog signal, an echo canceling filter for eliminating the echo from the analog signal produced by the second linear converter, and a second PCM converter for converting the analog signal rid of the echo into a refined PCM data written i

Abstract: An echo canceller having an adaptive algorithm for canceling an echo signal comprises an adaptive filter, a renewal controller and an initial operation controller. The adaptive filter generates a pseudo echo signal by renewing tap coefficients based on a far-end input signal, a near-end input signal and a residual signal, the renewal controller determines a time average of a renewal amount for each tap coefficients and estimates an initial delay of the echo signal by detecting the time average indicating a maximum renewal amount. The initial operation controller operates the adaptive filter to perform an initial operation to eliminate the tap coefficients corresponding to the initial delay of the echo signal and to renew the remaining tap coefficients corresponding to the echo signal.

Abstract: A mixed-mode crosstalk canceller is disclosed that performs crosstalk cancellation in the continuous time domain. The disclosed mixed-mode crosstalk canceller processes the pulse amplitude modulated (PAM) digital signal to be transmitted as well as the received signal to compensate for the crosstalk between the transmit and receive signals. The output of the crosstalk canceller is subtracted from the received signal in the continuous time domain. Thus, the transmit symbol clock and the receive symbol clock can be asynchronous. The tap weights for the crosstalk cancellation are illustratively obtained using a modified version of the least mean square (LMS) algorithm for discrete time signals. The modified least mean square (LMS) algorithm is applied for continuous time signals that are derived from different clocks.

Abstract: The present invention relates to an echo canceling method and apparatus for simultaneously erasing echoes produced on a plurality of transmission paths.

Abstract: The present invention relates to a system and method for canceling echoes from telecommunications networks by providing a multi-adaptation echo canceller. Unlike conventional TDM echo cancellers, the present invention uses at least two echo cancellers arranged in a novel manner to cancel echoes generated by a voice packet associated with an IP network or the like. The present invention further provides a double adaptation echo canceller that transfers coefficients from a first echo canceller to a second echo canceller. The present system compares the single and double adaptation echo error signals and selects the echo canceller with the smaller error signal. This process is continuously repeated so that the system can select the optimal echo canceller for canceling echoes for each voice block/packet. The present invention can be implemented with any number of echo cancellers so long as the each block or packet can be processed within a specified time frame.

Abstract: There is disclosed an echo cancelling apparatus in a digital mobile communication system and method thereof, which is incorporated in a single chip together with a speech coder, and can improve convergence rate by using an excited signal as an input to n adaptive filter and also obtain a stabilized convergence characteristic while using a NLMS algorithm. The echo canceller according to the present invention uses the excited signal obtained at the speech coder as an input signal to an adaptive filter thereby to lower the Eigenvalues distribution rate of the speech signal, thus providing an improved performance compared to the conventional echo canceller.

Abstract: To remove the echo of a received signal from a local input signal, an echo canceler adaptively estimates the transfer characteristics of the echo path. When a double-talk condition is detected, the echo canceler reverses the adaptation process and returns to a set of estimated transfer characteristics that were in use before the double-talk condition began. Imperfect echo cancellation due to incorrect estimation caused by double-talk is thus prevented inexpensively.

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 nonlinear echo compensator for an L-level message signal includes a plurality of groups of coefficient memories, wherein each group is assigned to at least one tupel of N successive symbols of the message signal. A selection circuit is connected to a transmit channel in order to receive an outgoing message signal. The selection circuit uses a value, which is currently received, and N−1 preceding symbols of the message signal to select the group associated with the tupel formed by these symbols. A superposition circuit superposes the coefficients of the group, successively and according to a symbol clock, onto a message signal arriving on a receive channel. The echo compensator is particularly suitable for use in a data transmission system in which the symbol pulse duration of the message signal is limited to N*T, where T is the symbol period of the message signal.

Abstract: A laminated LC filter includes inductors of a low-pass filter and an inductor of a trap circuit, which are disposed in different layers in the lamination direction of the insulator sheets. Inductor via-holes are connected to each other in the lamination direction of the insulator sheets to define columnar inductors. The inductor via-holes are electrically connected in series with coil-shaped conductor patterns to define inductors, respectively. The others of the inductor via-holes are electrically connected in series with a coil-shaped conductor pattern to define an inductor. Moreover, an inductor via-hole singly defines a columnar inductor.

Abstract: A receiving apparatus comprises a receiver receiving signals via multiple propagation paths having different propagation delays and converting the signals to digital samples for processing. A channel estimator is operatively coupled to the receiver for correlating periodically selected groups of the digital samples corresponding to known symbols and periodically producing numerical estimates related to amplitudes and phases of the delayed propagation paths. A filter system filters the numerical estimates using filters periodically adapted to center frequencies of variations of the numerical estimates. A data decoder is operatively coupled to the receiver and the filter system for decoding data using the filtered estimates and the digital data.

Abstract: A compander circuit (20) for echo cancellation in telecommunications apparatus with an estimator module (21) for estimating an echo coupling and a delay of a line echo and a characteristic module (23) with an associated multiplier (24) for controlling the short-time output level of zout(k) as a function of the short-time input level of zin(k) is characterized in that at all inputs and outputs of the compander circuit (20), a plurality of N communications channels are applied and outputted, respectively, at an N-fold clock rate as compared with a single communications channel; that all memory units in the compander circuit (20) are designed as multiplexer-buffer-demultiplexer (MBD) units (30); and that a modulo-N counter (26) is provided which controls all MBD units (30) so that in each of the MBD units (30), always the same memory cell (351, 352, 35N) assigned to a particular communications channel is addressed.

Abstract: A communication integrated circuit, such as a full-duplex speakerphone circuit, includes a double-talk detector that operates in combination with an echo canceller. The echo canceller includes an adaptive filter with filter coefficients that are regularly adjusted to train to a received echo. The double-talk detector includes an ERLE detector for measuring the current ERLE of the echo canceller and a logic circuit for determining a best ERLE value over a plurality of measurements. The double-talk detector also includes a power estimator and noise estimator for determining a noise level. The noise level attained when the ERLE value is the best ERLE value is saved as a benchmark noise level. Filter coefficients of the echo canceller are updated or updating is blocked based on several considerations including a comparison of ERLE value to best ERLE value, the noise level in comparison to the benchmark noise level, whether the circuit is operating in half-duplex or full-duplex mode, and detection of a tone.

Abstract: The present invention generally relates to echo cancellation over an asymmetric transmission and receiving spectra. An apparatus is provided having a transmit path and a receive path, with an adaptive echo canceler disposed therebetween, for communicating data within a first bandwidth and a second bandwidth respectively. A first decimator is disposed between the transmit path and the echo canceler circuit and filters an incoming signal having a first sampling rate and emits a signal output at a second, reduced sampling rate. A second decimator is disposed along said receive path and filters an incoming signal and emits a signal output at a reduced sampling rate. An adder is disposed to subtract the output of the adaptive echo canceler from output of the second decimator to generate a received signal that is substantially free of echo.

Abstract: A system identification device is provided capable of performing a sequential updating process and preventing the quantity of operation from becoming too complex. The system identification device includes a first delay for delay of y2 (n), a matrix generator, a plurality of matrix calculators, a second delay, a third delay and a matrix separator for identifying an unknown system.

Abstract: At first, adaptive filters 601, 602, . . . , 60K are operated by the initial numbers of taps memorized in the memory circuit 25, secondly operated by the approximate number of taps calculated in the calculation circuit of approximate numbers of taps 20 using respective coefficient values, the numbers of taps and the input signal obtained from adaptive filters 601, 602, . . . , 60K, and subsequently operated by the optimum number of taps calculated in the tap assignment control circuit 10 using respective coefficient values, the numbers of taps, the input signals and the reference signals obtained from adaptive filters 601, 602, . . . , 60K.

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: For identifying an unknown system such as a transmission line or a spatial acoustical coupling, tap coefficients are arranged at taps of an adaptive filter which correspond to a part of an impulse response waveform other than a flat delay part of the impulse response, thus attaining reduction of the convergence time and residual errors without resulting in errors of tap coefficients and tap positions even when a highly nonstationary signal is received. A tap control circuit 91 includes an input signal evaluation circuit 170, which evaluates input signal samples received from delay elements 201 to 20N, sets step sizes to zero and generate a signal for stopping tap position control according to the result of evaluation.

Abstract: An echo canceller has an adaptive filter with an input coupled to a digitized audio input producing samples at a first rate. The adaptive filter also produces an estimated digitized audio feedback signal at the first rate based upon a set of tap values. A controller is coupled to the adaptive filter and determines the values of the set of tap values. A shared processor is coupled to the adaptive filter and the controller. The shared processor services tasks of the adaptive filter and the controller as well as other devices. When the adaptive filter has converged upon an unknown echo channel response, the controller determines the set of tap values at a rate lower than the first rate.

Abstract: An echo canceller circuit for use in an echo canceller system is set forth. The echo canceller circuit comprises a first digital filter having non-adaptive tap coefficients to simulate an echo response occurring during a call. A second digital filter having adaptive tap coefficients to simulate an echo response occurring during the call is also used. The adaptive tap coefficients of the second digital filter are updated over the duration of the call. A coefficient transfer controller is disposed in the echo canceller circuit to transfer the adaptive tap coefficients of the second digital filter to replace the tap coefficients of the first digital filter when a value, Ê, is greater than a value, {overscore (E)}, and, concurrently, when Ê is greater than a value, Emax. The value of {overscore (E)} corresponds to the ratio between a signal-plus-echo signal and a first echo compensated signal using the first digital filter.

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 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 digital/analog TV common-use receiver having a single ghost canceler, and a ghost cancellation method are provided. The single ghost canceler includes a first filter coefficient generator for generating first filter coefficients using a first reference signal included in the analog TV signal, a second filter coefficient generator for generating second filter coefficients using a second reference signal included in the digital TV signal, and a digital filter for filtering the analog TV signal using the first filter coefficients if the analog TV signal is received, and the digital TV signal using the second filter coefficients if the digital TV signal is received. Since an equalizer used when receiving a terrestrial digital TV broadcast is also used upon receiving a terrestrial analog TV broadcast, the single equalizer can correspond to both digital and analog TV signals.

Abstract: In an echo canceler, a first adaptive filter circuit calculates first tap coefficients using a first convergence coefficient, and generates a first pseudo echo signal, and a first subtracter subtracts the first pseudo echo signal from a transmitting signal to generate a first error signal. A second adaptive filter circuit calculates second tap coefficients using a second convergence coefficient, and generates a second pseudo echo signal, and a second substrate subtracts the second pseudo echo signal from the transmitting signal to generate a second error signal. A control circuit selects one set of the first tap coefficients and the second tap coefficients in accordance with a received signal, the transmitting signal, and the first and second error signals.

Abstract: An echo canceler in which effective transfer function coefficients of an adaptive echo-canceling filter are adjusted periodically to track changing system conditions. Periodic adjustment of the effective coefficients is accomplished using a set of more frequently adjusted update coefficients and an update gain which is varied based on a strategic and novel combination of system parameter measurements. By updating filtering coefficients periodically rather than continuously, and by making soft, fuzzy-logic-type decisions with respect to the magnitude of the update gain, exemplary embodiments optimize system speed and adaptability without sacrificing stability. Generally, relatively large update gains are applied in situations where only a far-end user is speaking and a near-end signal is relatively noise-free.

Abstract: An echo canceller circuit for use in an echo canceller system is set forth. The echo canceller circuit comprises a first digital filter having non-adaptive tap coefficients to simulate an echo response occurring during a call. A second digital filter having adaptive tap coefficients to simulate an echo response occurring during the call is also used. The adaptive tap coefficients of the second digital filter are updated over the duration of the call. A coefficient transfer controller is disposed in the echo canceller circuit to transfer the adaptive tap coefficients of the second digital filter to replace the tap coefficients of the first digital filter when a value, {circumflex over (E)}, is greater than a value, {overscore (E)}, and, concurrently, when {circumflex over (E)} is greater than a value, Emax. The value of {overscore (E)} corresponds to the ratio between a signal-plus-echo signal and a first echo compensated signal using the first digital filter.

Abstract: A filter device filters a speech signal that has a frequency spectrum featuring slopes separated by valleys. The filter device amplifies the slopes and attenuates the valleys for improving the intelligibility of the signal. The filter device includes a predictive speech signal analysis circuit for determining a polynomial whose coefficients are Linear Predictive Coding (LPC) parameters. The filter device further includes a calculator for synthesizing a digital post filter of the zeroes/poles type based on this polynomial. An extraction circuit of the filter device taps values of poles by extracting roots of the polynomial, and an interpolation circuit between the values of poles derives therefrom the zero values of the post filter.

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: This invention deals with an adaptive echo cancelling system for communication networks. The system includes an adaptive filter for acoustic echo cancellation that uses a combination of echo cancelling and gain control techniques. The main advantages of the combination of these approaches are good communication quality during double talk and easier control of the output echo level.

Abstract: A method and apparatus for providing multi-channel telephony multimedia services. A multi-tasking DSP processes a plurality of multimedia services for a plurality of telephone channels. The DSP operates in conjunction with a host processor. The host processor indicates to the DSP, in real-time, the services required for a channel. The DSP in response allocates a portion of its fast memory in which a program is stored comprising the multimedia services routines required for the channel. The multimedia services program stored in the portion of fast memory allocated to a channel is then utilized to process the incoming channel signal data. The processed signal data is then output to memory shared between the DSP and the host processor. The portion of memory and the program for each channel can be dynamically reconfigured in real-time on a per channel basis.

Abstract: An echo detecting system includes data stores for storing signals from up and down channels respectively. The signals undergo pre-processing to identify signals forms characteristic of speech and instruct a measurement unit to carry out comparison using cross-correlation techniques between the signals stored in the stores only when such characteristics are detected. This reduces the processing power required and raises the accuracy of the correlations. Parallel processing techniques allow echoes with longer delay periods to be detected. The results of the measurement may be used to generate an echo-cancellation signal.

Abstract: A single two-ended echo canceller is provided that uses an adaptive FIR filter to model the impulse response of the echo path and cancel the echo originating from the PSTN side of the connection, and a non-linear processor controlled by input signal levels to cancel the echo originating from the mobile phone side of the connection. Since the linear processing function is not used for cancelling echoes of the mobile phone side, the algorithms directed to estimating and cancelling echoes on the two sides of the connection can be executed in a single DSP, with all of the attendant advantages.

Abstract: A device for the selection of address words each having n bit locations and serving for addressing m different receiving locations of a digital communication module, in at least one of the receiving locations, including a digital acceptance module through which address words can be selected. The device has an address word segmenting module through which each address word received by the receiving location can be subdivided into s address word segments with b segment bit locations each, wherein b=n/s and n is an integral multiple of s. The device further has z digital segment filters whose inputs can each be fed with an address word segment, with each segment filter having the function of examining one address word segment each with respect to conformity with a predetermined segment bit pattern, and a filter output signal being available at the output of the respective segment filter, which in accordance with the examination result is either a conformity signal or a non-conformity signal.

Abstract: An input signal is supplied to a tapped-delay line adaptive filter to produce tap signals which are equally divided into groups. The tap signals are selectively coupled on a per group basis through a switch to coefficient generators where tap-weight coefficients are produced. The selected tap signals are weighted respectively by the coefficients and summed together to produce a correction signal, which is combined with an output signal which is a replica of the input signal. The coefficients are updated with a residual error of the correction signal. Using the coefficients, the hopping order for selecting a tap group and the dwell time of the tap group are determined. Total power of the selected tap signals is monitored. When the monitored power is lower than a threshold value, the determination of the hopping order and dwell time is disabled, coefficient updating is disabled, and the residual error is nullified for fast convergence.

Abstract: Complex coding of speech signals, as this is used, for example, in the GSM half rate speech coder, requires the use of a signal processor. On the other hand, a hands-free facility requires an arithmetic unit which adaptively calculates filter coefficients. This is only effected during speech pauses in which the speech coder is switched to a mode in which it generates codes for background noise with only little processing circuitry and expense. According to the invention, the signal processor for the coding device is therefore used for calculating the coefficients for the echo cancelling filter during speech pauses. This requires the use of not more than a single signal processor which can thus be used twice.

Abstract: An echo cancelling system for communication systems. The system includes an adaptive filter that processes the speech signal re-constructed by a voice decoder to generate an echo estimate. The echo estimate is subtracted from the echo containing signal propagating in the communication link to remove or at least reduce the echo corruption. The tap coefficients of the adaptive filter are established on the basis of an error signal that is representative of difference between the echo estimate and the actual echo and on the basis of a signal element that is a component of the re-constructed speech signal. The signal element is highly decorrelated to enable the adaptive filter to converge faster and manifest an improved echo return loss enhancement.

Abstract: A novel system by which the utilization of a central processing unit (CPU) in performing filtering operations can be reduced by shortening the filter's length thus degrading the performance of the system down to a predetermined level or threshold. The present invention is applicable to such systems that incorporate filters whereby shortening their length decreases the performance of the system and to such systems where a reliable quality criteria exists that can be measured during run time. A method iteratively minimizes the filter's length so that the quality criteria does not fall below a predetemined threshold level. In addition, a signal to noise ratio (SN) criteria is suggested for estimating the quality of the reception of communication signals. An implementation is suggested for the method in the particular case of an echo cancellation adaptive filter. In addition, a method for determining an immediate approximation of the echo canceler filter's length as opposed to finding it iteratively.

Abstract: An echo canceller of the present invention and for packet signals includes a buffer (4) for converting the rate of a residual echo, and a buffer (1) for converting the rate of a received packet. An echo path estimator (2) generates, by referencing the outputs of the buffers (1, 4), filter coefficients for estimating an echo path. An adaptive FIR (Finite Impulse Response) filter (3) performs convolutional computation with the filter coefficients and the output of the buffer (1) for thereby outputting a false echo component. A buffer (5) packetizes the false echo component. A subtracter (6) subtracts the packetized false echo component from a packet to be transmitted so as to cancel an echo. Because a line assigned to the packet to be transmitted involves only subtraction, the echo canceller prevents packets from being delayed.

Abstract: A conventional computer is coupled to an analog telephone transmission link by means of an analog/digital conversion interface adapter. Modem transmission is accomplished by performing the modulation and demodulation functions digitally in the computer's existing processor which executes programs which transfer data between the computer's memory and the interface adapter. Using the same interface adapter and existing processor, the arrangement may be used to send and receive images in the form of standard V.29 format facsimile data, to send and receive data operating as a synchronous IBM 3270 compatible terminal device, or to record and play back conventional voice transmissions rather than data to implement a telephone answering, voice message handling, and telemarketing systems.

Abstract: A method of and an apparatus for unknown system identification with an adaptive filter of effective and inactive taps is disclosed. An adaptive tap position control is executed by active tap number update and effects coefficient update by using a first step size till completion of a predetermined number of times of active tap number update and by using a second step size in a second state held after the completion of the predetermined number of times of active tap number update. The adaptive tap position control without counting the number of times of coefficient update is executed as active tap number update in the first state when the ratio of an input power supplied to the minimum absolute value coefficient tap to the total input power supplied to the active taps is less than a predetermined ratio.

Abstract: A method for processing a signal in a CSD filter includes the steps of obtaining real coefficients optimized to desired filter characteristics, calculating scaling factors for each real coefficient which minimizes errors between the real coefficients and converted CSD codes, producing optimum CSD coefficients by using the calculated scaling factors, and filtering input data by using the optimum CSD coefficients. In the method of the present invention, conversion of the real coefficients into the CSD coefficients is performed in the time domain, thereby improving operating speed and increasing bit resolution with the number of non-zero digits fixed, as compared to conversion in the frequency domain. As a result, the present invention can be applied to an adaptive filter and a polyphase filter.

Abstract: A far-end modem transmits a "pilot tone" during the time that a near-end modem is training its echo canceler. Correspondingly, the near-end modem is modified to notch, or filter, out this pilot tone from the received signal. The filtered received signal is then used by the near-end modem to train its echo canceler.

Abstract: A fast response gain tracker operates to adjust the magnitude of an echo cancellation signal. The latter signal is developed from an echo canceler. The fast response gain tracker provides an adjusted echo cancellation signal that is subtracted from an echo-corrupted received signal to provide an echo-canceled signal. In particular, the fast response gain tracker correlates the echo-canceled signal with the echo cancellation signal from the echo canceler. If the gain of the gain tracker is correct the echo is canceled and there is zero correlation between the echo-canceled signal and the echo cancellation signal. However, if the echo level changes then a residual echo component appears in the echo-canceled signal, which now becomes correlated with the echo cancellation signal. In response, the magnitude of the gain tracker automatically adjusts the gain of the echo cancellation signal to match the change in echo level and thereby subsequently eliminates the residual echo.