Abstract: A receiving apparatus receives a digital broadcast signal having been modulated in an orthogonal frequency multiplexing method of which data of each frame is composed of a synchronous reference signal and transmission data and of which data is assigned to a plurality of carriers that are orthogonal to each other. A synchronous TFPR signal is transmitted every frame. An AFC (automatic frequency control) circuit receives the synchronous TFPR signal, and obtains a frequency error and a timing error of the received signal to control the frequency and the timing. To remove an influence of a multi-path to the synchronous TFPR signal, an equalizer is disposed. The influence of the multi-path to the synchronous TFPR signal is removed by the equalizer. Thus, the frequency and the timing of a carrier of the receiver side can be exactly controlled.

Abstract: Using a known or later developed time domain equalizer coefficient training algorithm, a least square solution for the time domain equalizer coefficients is taken at a starting point and iteratively improved on. In particular, the improvement is directed towards maximizing number of bits per frame loaded over the time domain equalizer coefficient choice. This can be accomplished by maximizing capacity directly rather than setting a goal to shorten the channel and hoping that the capacity will be maximized as a result.

Abstract: Channel estimation is performed by receiving a received training sequence portion of a radio signal, and estimating a number of channel model structures based on the received training sequence and a predetermined training sequence. For each of the channel model structures, corresponding coefficients are determined by using all of a set of one or more taps associated with the corresponding channel model structure and no others. For each of the channel model structures, a variance measure is generated that represents an amount of variance between an estimated value generated by the channel model structure and a received signal value. An optimum channel model structure is selected from the channel model structures, based on the variance measures, and a number of states associated with the optimum channel model structure is generated. Equalization techniques are then used to generate the decided symbol from the received signal, the optimum channel model structure and the number of states.

Abstract: A method and apparatus for allowing a modem transmitting data in the data mode to initiate retraining mode due to changing line conditions. The modem inserts a test signal within the data received from a computer system. The data and test signal are encoded and sent over a network to a second modem. The second modem compares the test signal with a standard test signal, and if the test signal received is different from the standard test signal, the second modem initiates retraining of the modems to adjust for the varying line conditions.

Abstract: An adaptive CAP filter includes a clock-controlled A/D converter for converting an input signal, a digital level-control circuit, an adaptive controlled reception filtering system with two parallel filters and a downstream decision maker for outputting reconstructed signal coordinates. The digital level-control circuit and the adaptive reception filtering system are decoupled by virtue of the fact that either an adjustment of the digital level-control circuit or a coefficient adjustment of the adaptive reception filtering system is active. A method for controlling a cap receiver is also provided.

Abstract: The invention relates to a method and a base station for transmitting data in a downlink direction over a radio interface in a mobile radio communications system. The base station transmits the data in the downlink direction to a radio station in radio blocks that are organized in a time division multiplex method. Recurring training sequences are inserted between the radio blocks without decreasing the transmission power used for transmitting the data. The radio station carries out a channel estimation by means of the training sequences.

Abstract: The method is for the parameterization of at least one reception apparatus for a radio station, whereby the reception apparatus contains an adaptive pre-filter. The filter coefficients of the pre-filter for suppression of received noise quantities and the channel coefficients for the detector for compensating the transit time differences of different signal components of a reception signal are simultaneously determined. During a training sequence, test data present in the reception apparatus is evaluated with channel coefficients in a channel model, and received test data is evaluated with filter coefficients of the pre-filter and superposed to form antenna data or, respectively, model quantities. The minimization of the deviation of antenna data and model quantities is undertaken upon exclusion of the trivial solution. The method is especially suited for base stations and mobile parts in mobile radiotelephone systems.

Abstract: A method and apparatus for controlling an equalizer using a sync signal in a digital VSB system is provided, in which the sync signal is accurately separated even though a ghost having a short delay time and a large size is generated, and thus the equalizer is controlled with the separated sync signal. For this purpose, a switching unit is provided between a matched filter and an equalizer, which selects one of two input signals according to a NTSC rejection filter (NRF) on/off control signals and separates a data segment sync signal and a data field sync signal from the selected signal. A control signal is produced via the separated sync signal to control the equalizer to operate at one mode of a blind mode and a training sequence mode.

Abstract: The present invention proposes a signal processing device for processing received signals having been transmitted via a transmission channel, wherein said received signals (y) are supplied to an estimation means (2) adapted to estimated a channel impulse response function (h) of said transmission channel (1), with said estimation means being adapted to perform a Linear-Minimum-Mean-Square-Error-(LMMSE-) processing based on a training sequence (TR_SEQ) transmitted together with received samples contained in said received signals (y), and a noise and interference energy estimate represented by a noise and interference variance (&dgr;2) as well as an impulse response energy distribution estimate represented by an estimated parameter covariance matrix (Chh) for said channel (1). The present invention also proposes a corresponding method for signal processing.

Abstract: A broadband radio communication system and method therefore that conducts communication on a plurality of narrowband channels obtained by dividing a broadband channel into a plurality of narrowband channels. The invention provides a first radio communication terminal which sets transmission conditions of at least part of the narrowband channels and transmits a wireless packet on the narrowband channels of which the transmission conditions have been set, and a second radio communication terminal which receives the wireless packet from the first radio communication terminal, measures the line qualities of the narrowband channels and transmits measured line quality information to said first radio communication terminal. The first radio communication terminal receives the line quality information, sets new transmission conditions based on the line quality information, and transmits a wireless packet to the second radio communication terminal through the narrowband channels under the new transmission conditions.

Abstract: A receiver is described, for instance for GSM systems, wherein a plurality of digital signals each comprising a training sequence (xp(t)) usable to generate an estimation of the transmission channel are received in diversity (A.1 . . . A.N) in the form of a plurality of replicas (10.1 . . . 10.N) each comprising a respective replica of the training sequence. The received digital signal is subjected to a delaying action thereby obtaining a plurality of versions of such signal, each comprising a respective set of signal replicas. Each version is subjected to a respective filtering action (23.1 . . . 23.N) independently from the other versions, by employing a respective first set of filtering coefficients (w*11 . . . w*N1 . . . w*Nj) obtained starting from a respective initial set of filtering coefficients.

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 method of calculating TEQ and FEQ coefficients in a discrete multi-tone (DMT) system includes determining an estimated channel impulse response. A frame delay is determined based upon the estimated channel impulse response. Using these parameters and a known training sequence, the method generates the TEQ coefficients. The method then generates the FEQ coefficients based upon the TEQ coefficients and a version of the estimated channel impulse response.

Abstract: A system and method for user information transfer before modem connection. The invention makes high-speed modems more efficient, particularly for transaction and Internet applications, by providing for transmission of pre-connection user data during modem training. A training sequence for a modem in accordance with the invention may be summarized as follows: beginning training of the modem at a first data rate using a defined training sequence; after a selected amount of training, transmitting pre-connection user data from the modem at up to the first data rate while continuing training of the modem; ending training; and enabling transmission of user data at a full connected data rate of the modem.

Abstract: A digital multilevel signal receiver circuit which can sufficiently improve transmission efficiency while suppressing a data transmission error, and an automatic equalization circuit for use in the digital multilevel signal receiver circuit. An equalization training automatic equalizer is provided separately from a data reproducing equalizer having equalization characteristics which can be set up. A received training signal is once stored in a memory, read out from the memory and supplied to the equalization training automatic equalizer so as to update tap coefficients of the equalizer. The updated tap coefficients are given to the data reproducing equalizer so as to update equalization characteristics of the equalizer. A received data signal is equalized with the updated equalization characteristics.

Abstract: The subject invention improves tracking performance of an adaptive equalizing operation while reducing the calculation volume. A frame including a training sequence and a mixed data sequence in which at least one symbol of a whitened sequence is dispersively inserted into a data sequence is generated. The frame is converted into a wireless signal, which is then transmitted. The wireless signal of the frame is received. Tap coefficients of an equalization filter are set by using the training sequence in the frame. During reception of the mixed data sequence, an adaptive operation is performed by using the respective symbols of the whitened sequence in the frame and the tap coefficients of the equalization filter are updated.

Abstract: A method and apparatus for reducing convergence time in a digital filter. When the digital filter is initially run, the coefficients in the digital filter are adjusted to reduce error in the output of the digital filter. When the adjusted coefficients meet a selected error level, these coefficients are stored in a memory and the digital filter filters data. The next time the digital filter is run, the stored coefficients are loaded into the digital filter and a number of iterations are run in which the coefficients are adjusted. Then, a determination is made as to whether the error level meets a threshold that may be the same as the selected error level. If the coefficients meet the threshold, the coefficients are stored in the memory and the filter is then used to filter data.

Abstract: An adaptive equalizer includes a channel memory length estimator (41) for estimating a channel memory length of a received signal, an adaptive equalizer (42) for reducing effect of intersymbol interference on the received signal using a technique suitable for a channel with a fast time-varying characteristic, an adaptive equalizer (43) for reducing effect of intersymbol interference on the received signal using a technique suitable for a channel with a large delay spread, and a selector for switching, in response to the channel memory length supplied from the channel memory length estimator (41), between the adaptive equalizer (42) suitable for the channel with the fast time-varying characteristic and the adaptive equalizer (43) suitable for the channel with the large delay spread, thereby implementing good bit error rate performance.

Abstract: In a training method in a time domain equalizer provided in a digital data transmission system for updating tap coefficients in the time domain equalizer so that an error between the tap coefficients and channel target characteristic becomes zero, the training method includes steps of: obtaining a first sum of the tap coefficients of the channel target characteristic before a rectangular window is provided to the tap coefficients, and storing the first sum in a memory; obtaining a second sum of the tap coefficients of the channel target characteristic after the rectangular window was provided to the tap coefficients; subtracting the second sum from the first sum, and dividing a resultant value of subtraction by the numbers of the tap coefficients existing within the rectangular window; and obtaining each of tap coefficients of the channel target characteristic by adding a divided value to each tap coefficient existing within the rectangular window.

Abstract: For training tap coefficients of an adaptive equalizer of L taps to be used for equalizing an impulse response of a transmission channel (200) to be shorter than v taps, stably and speedily, a training circuit comprises: a transmitter (100) for transmitting a transmission signal (x(D)) produced by converting a frequency-domain transmission vector (X) encoded with a PRBS into a time-domain; a target-impulse-response update means (1300) for producing an updated target impulse response (Bu) making use of frequency-domain division method referring to windowed tap coefficients (ww(D)), a reception signal (y(D)), and a training vector (X) encoded with a replica of the PRBS; a target-impulse-response windowing means (1400) for outputting a windowed target impulse response (Bw) together wit a normalization coefficient (S) by windowing and normalizing the updated target impulse response (Bu) within L taps in a time-domain; a tap-coefficient update means (2500) for updating the windowed tap coefficients (ww(D)) making

Abstract: An xDSL communication system using Discrete Multi-tone (DMT) symbols sent over a channel. The magnitude of the channel's frequency-domain equalizing filter is normalized, leaving only phase information. The inverse discrete fourier transform of the normalized filter gives a peak at a position which corresponds to the group time delay of the transmitted DMT symbol. Identification of the symbol boundary facilitates synchronization of the receiver symbol sample phase to the transmitter symbol phase.

Abstract: A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

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: A method for training a high speed decoder. A communication system includes an encoder and a decoder. The encoder has a digital connection to a digital portion of a telephone network. The digital portion of the telephone network is connected by an analog loop to the decoder. The method includes the step of transmitting M repetitions of N codewords from the encoder to the decoder. M and N are integers that are known to the decoder. The codewords correspond to PCM codes utilized by the digital portion of the telephone network. At the decoder, a received sequence of analog voltage levels corresponding to the transmitted codewords is sampled. A value associated with each sample is stored and the stored values are analyzed. A parameter of the decoder is adjusted in accordance with the analysis.

Abstract: A method of initializing the operation of a remote modem (10) and central office modem (20k) for asymmetric subscriber line modem communications over a twisted pair wire facility (TWP), using discrete multi-tone technology, is disclosed. The initialization process begins with the remote modem (10) issuing an initialization request, in response to which the central office modem (20k) issues an acknowledgment. The remote modem (10) includes a low-cost analog filter (21) for separating upstream communication echoes from downstream data. This analog filter (21) increases the duration of impulse response over the channel, and thus requires time-domain equalization (TEQ) process (31) performed by the remote modem (10) to filter relatively long circular prefixes, so that intersymbol interference is eliminated.

Abstract: A startup protocol is provided for use in a communications system having a communications line with a master transceiver at a first end and a slave transceiver at a second end, each transceiver having a noise reduction system, a timing recovery system and at least one equalizer all converging at startup of the system. The operation of the startup protocol is partitioned into stages. The first stage includes the step of converging the equalizer and the timing recovery system of the slave while converging the noise reduction system of the master. Upon completion of the first stage the protocol enters a second stage which includes the step of converging the equalizer and the timing recovery system of the master, converging the noise reduction system of the slave, freezing the timing recovery system of the slave, and resetting the noise reduction system of the master.

Abstract: The present invention provides an optimal procedure for determining in the time domain equalizer coefficients for an equalizer, where the equalizer compensates for the effects of the communications channel on the transmitted signal. A unit pulse is transmitted over the communications channel, and a channel impulse response is estimated from the received signal. A cost function establishes a mean-square error associated with the estimated channel impulse response as compared to a desired impulse response signal. The value of the cost function varies based upon an offset value between the estimated channel impulse response and an equalized channel impulse response. Values of the cost function are determined for different offsets, and the offset that produces the smallest cost function value (corresponding to the minimum mean-square error) is selected. The optimal equalizer coefficients are then calculated using the selected offset and the established cost function.

Abstract: Analog modems are enabled to better learn the slicing levels employed at the interface to a digital transmission network by reducing the effects of the various noise sources. Initially a training sequence is received to preliminarily adjust the analog modem's equalizer. Thereafter, a special training sequence, protected against intersymbol interference, is employed to collect samples of each slicing level, to ascertain the least mean squared value of each slicing level from the received samples and to obtain the channel's impulse response at each slicing level. Thereafter, the analog modem's equalizer may be fine tuned in accordance with the channel impulse response ascertained at each slicing level.

Abstract: A cellular communication signal receiver receives a desired signal in the presence of at least one co-channel interference signal. The receiver comprises a channel estimator configured to receive a plurality of training signal samples to estimate the finite impulse response to the desired signal and the co-channel interference signal. The finite impulse response estimates having a predetermined number of channel taps defining the length of the desired channel and the length of co-channel interference channel. A Viterbi decoder is coupled to the channel estimator, and configured to receive the desired and co-channel interference signals. The channel estimator generates channel tap estimates. A power calculator is coupled to the channel estimator and configured to estimate the power of the estimated channel taps.

Abstract: A V.34 compliant modem uses a noise whitening filter to compensate for noise enhancement in an equalizer. The noise whitening filter uses a 3 tap FIR the response of which is determined by 3 coefficients. The coefficients are derived using a newly developed extension of the Levinson-Durbin algorithm to complex numbers. The coefficients thus derived are used to control the precoder as well as the noise whitening filter. The coefficients are also used to control precoding reconstruction after the decoder.

Abstract: In a communications arrangement, a first pulse code modulation (PCM) modem communicates data in the form of PCM words with a second PCM modem through a public switched telephone network (PSTN). The transmitted data may be affected by robbed bit signaling imposed by the PSTN such that the least significant bits (LSBs) of certain PCM words are "robbed" and substituted with signaling bits. In accordance with the invention, any imposed robbed bit signaling is detected during training of the second PCM modem. The would-be PCM words affected by such robbed bit signaling are identified to the first PCM modem. The latter then avoids transmitting data using the LSBs of those PCM words. In addition, through the training, a decision feed-back equalizer in the second PCM modem is properly adjusted, taking into account any robbed bit signaling affecting the transmitted training data.

Abstract: A device system and method of detecting impairments in a communication network, involving: receiving during a plurality of time intervals equalized training signals which are produced from training symbols that have been transmitted over the network and equalized; generating reference symbols corresponding to the training symbols and equalized training signals; indexing the equalized training signals by their time intervals and corresponding reference symbols; calculating errors due to impairments from the indexed, equalized training signals; and detecting impairments in the network from the calculated impairment errors.

Abstract: An adaptive equaliser particularly for equalising digital signals with analogue modulation, where use is made of a training sequence formed by a previously known sequence of symbols which is applied to said equaliser simultaneously with the demodulated signal present in the receiver. In this way a first estimate is made of the coefficients of the filter or filters of the equaliser that compensate the linear distortions in the transmission channel. The training sequence (TS), before being used in the equaliser (CEQ), is first applied to a lowpass filter whose transfer function is the same as that of the premodulation filter employed in the modulator. This transfer function also incorporates distortion effects, both linear and non-linear, to which the data are subjected in the receive side when they have been demodulated prior to their detection or regeneration.

Abstract: The present invention relates to an arrangement and a process for the demodulation of a received signal to a form suitable for decoding. A first element (4) is adapted to correlate at least one first signal with a predetermined training sequence for a first type of signal routine and to make at least one first qualitative measurement of the first signal. A second element (5) is adapted to process the second signal according to a second type of signal routine by correlating the second signal with a predetermined training sequence for a second type of signal routine, thereby making a first qualitative measurement of the second signal. The qualitative measurements of the said first and second signal are compared in a first means (6), which is adapted to select at least one signal for which the best value is obtained in the said qualitative measurement and to establish the type of signal routine corresponding to the best qualitative measurement.

Abstract: This invention improves the success rate of rereception of a primary channel equalizer training signal, which is performed when, in a data communication apparatus having an ITU-T recommendation V.34 communication function, a control circuit performs control to receive a line probing signal, and thereafter, shift to reception of a primary channel equalizer training signal, and to control circuit performs control to, when the primary channel equalizer training signal is not detected within a predetermined time, send a tone A signal and receive a tone B signal, and thereafter, shift to transmission of a limited INFOh signal.

Abstract: A system and method for training a plurality of equalizers to recognize a plurality of symbols in a received signal, the plurality of equalizers deriving intermediate symbols from the received signal as a function of at least one filter coefficient, the system including 1) a phase detection circuit that determines a phase error between at least one intermediate symbol and at least one symbol in a predetermined constellation of symbols, and 2) a coefficient modification circuit that modifies at least one filter coefficient of the plurality of equalizers as a function of the phase error to cause the at least one intermediate symbol to converge toward a symbol in the predetermined constellation of symbols as the phase error approaches zero, the intermediate symbols being substantially equal to the predetermined constellation of symbols when the phase error is equal to zero.

Abstract: A reproduced signal of a test signal recorded together with data on a recording medium in each unit recording area thereof is equalized in waveform by an adaptive waveform equalizing means while tap coefficients thereof are being varied. The tap coefficients obtained when an equalized signal is as close to an ideally equalized dignal as possible are used as optimum tap coefficients, and the reproduced signals of the data in the unit recording areas are equalized in waveform using the optimum tap coefficients.The data can be equalized in waveform stably, reliably, and quickly by a small-scale circuit. There is provided an apparatus for reproducing data so as to be able to achieve high-density recording.

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

Abstract: A codec supports PCM modem communications (e.g., V.90, X2, or K56flex protocols) over a universal digital loop carrier (UDLC) having an analog interface to the central office (CO). The codec includes an analog-to-digital converter (ADC) that is synchronized to the CO clock, and an equalizer that has been trained to provide a transfer function to compensate for the distortion introduced by the CO line interface reconstruction filter and connecting circuits, to minimize resampling error. These features allow the codec to output a PCM stream that accurately reproduces the PCM data at the central office, at data rates sufficient to support PCM modem communications, as well as voice and conventional modem communications. The equalizer can be trained using a remote training unit that transmits a predetermined sequence of training signals to the equalizer.

Abstract: A technique for the blind equalization of digital communications channels relies on the iterative minimization of a cost function known as the J-divergence between a known or assumed probability density function (PDF) of the source data signal and an estimated PDF of a receiver decision output signal derived from the equalizer output signal by minimum-distance mapping. The J-divergence function is defined in terms of the Kullback-Leibler distance between the two PDFs. Minimization is achieved by continually updating both an equalizer tap coefficient vector and the estimated PDF of the decision output signal using a stochastic gradient algorithm applied to the J-divergence cost function.

Abstract: The invention relates to a digital transmission system having a receiver which includes an equalizer for estimating transmitted binary symbols, from a sequence of sample values (6) of a received signal distorted by a transmission channel, by a reduced-state sequence estimation method or a reduced-state single symbol estimation method (11). To provide a receiver featuring high reliability combined with a clear state reduction of the estimation method, a minimum-phase substitute system (14) distorts the sample values received after received after a known training sequence (27) in the sequence of sample values (6)in the received order, and a maximum-phase substitute system (14) distorts the sample values (6) received before a known training sequence (27) and to be processed in reverse order for forming an estimate (11) for a received signal. The number coefficients of the impulse response which are reduced by the state reduction and used for the estimation, render the estimation inaccurate.

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

Abstract: An apparatus and method for adaptively equalizing a signal received from a remote transmitter. The equalizer includes a filter having an output and a decision circuit coupled to the filter output. In addition, the equalizer has a reference coupled to the decision circuit. The reference includes a model of a non-linear characteristic of a remote transmitter. The method relates to adaptively equalizing a signal received from a remote transmitter. The method includes the step of receiving a signal corresponding to a predetermined reference level from the remote transmitter. Next, the received signal level is filtered to remove linear error terms. The next step of the method includes measuring a non-linear error term associated with the received and filtered signal. The measured non-linear error term may then be stored and used to make improved decisions on data signals transmitted from the remote transmitter.

Abstract: A system for equalization of two-way digital communications between a base and portable unit is described. Equalization is implemented in a manner so as to reduce the complexity of the portable unit. The reverse link (portable to base transmission) is equalized by a decision feedback equalizer (DFE). The forward link (base to portable) is equalized by an asymmetric decision feedback equalizer (ADFE), which consists of a forward filter located at the transmitter, and a decision feedback filter at the receiver.

Abstract: The invention provides a training method for a non-Nyquist transmission system and a training data transmission apparatus for a non-Nyquist transmission system by which initialization processing of a reception section can be performed with certainty even where a non-Nyquist transmission system is employed.

Abstract: A digital transmission system comprising a receiver, the receiver including a receiver input stage and a digital memory for storing a sequence of binary symbols of sample values, formed in the receiver input stage, of a signal distorted by a transmission channel, and an equalizer for forming a sequence of binary estimates from the sample values by an impulse response of a substitute system describing the transmission channel, the impulse response being determined by first correlations of coefficients of a known training sequence with the sample values of a part of the known training sequence extended by at least one binary symbol.

Abstract: The present invention discloses a timing phase control apparatus which is particularly suitable for use in a modem used for very high speed data transmission employing a metallic line. The timing phase control apparatus includes a timing phase extracting portion to extract timing phase information from an input signal, a timing phase control filter portion to make a timing phase control to the input signal depending upon the timing phase information from the timing phase extracting portion through filter processing using a coefficient operation having a preset impulse response characteristic, and a filter processing coefficient determining portion to determine a coefficient used for the filter processing in the timing phase control filter portion depending upon the timing phase information and information about an approximate expression of the impulse response characteristic.

Abstract: A transmission apparatus which can realize high demodulation efficiency even in the case where the channel characteristic is deteriorated. The same pattern data as those of the known pattern data contained in the transmitting data to be transmitted to the channel is generated on the receiving side and the correlation between said pattern data and the receiving data to be received through the channel is obtained. Then, the channel characteristic is successively estimated based on the correlation value and the receiving data will be demodulated depending upon said estimated result. Thus, since the channel characteristic can be estimated based on the receiving data, the data can be demodulated correctly even in the case where the receiving data is distorted due to the characteristic deterioration.

Abstract: The object of the invention is to provide an equalizer capable of generating an equalized output compensated in the non-linearity of the signal reproduced by an MR head and a reliable high-density magnetically recorded-signal reproducer. An equalizer of an FIR-type filter structure comprises a plurality of delay elements for delaying input signals by a certain period, a plurality of coefficient processing units provided to input or output taps of the delay elements, and an adder for obtaining the sum of the outputs of the coefficient processing units, in which the distortion of the reproduced waveform can be corrected by a relatively simple circuit structure by comparing the signal value inputted to the coefficient processing unit from each tap with a predetermined threshold level and changing the signal value and a coefficient value to be multiplied in accordance with the comparison result.

Abstract: A truncated maximum likelihood sequence estimator that provides a best estimate of a transmitted symbol sequence includes a lookup table and a comparator. The lookup table may be responsive to at least a next sample of a received RF signal, a first decision made on a first previous sample of the RF received signal and a second decision made on the second previous sample of the RF received signal. The lookup table provides at an output at least one threshold value stored in the lookup table that is addressed by the next sample of the received signal, the first decision made on the first previous sample and the second decision made on the second previous sample. The comparator is coupled to the output of a lookup table and is responsive to the at least one threshold value and a current sample of the received RF signal. The comparator compares the current sample of the received RF signal with at least one threshold value and provides a best estimate of the transmitted symbol sequence.