Abstract: In frequency equalization, a received signals goes through frequency transform, the transformed signal is divided by a frequency transform of a channel response a method for equalization. The method comprises the step of: adjusting a quotient of the division by a weight function, wherein the function varies under a set of conditions; whereby for a frequency selective channel, deep fades are adjusted, and noise or interference are reduced.

Abstract: Systems and methods for a wireless communication system are provided. The method includes estimating a time-variation of a channel through which the wireless communication system transmits. This also includes decreasing the estimated time-variation of the channel from a signal transmitted by the wireless communications system.

Abstract: Channel equalization in a 1000BASE-T receiver is performed by a fixed mode analog filter 2 suitable for the longest possible cable length, by a FFE (3), and by a digital filter 4. The digital filter (4) has two sets of taps. One set is optimal for shorter cable lengths and so cancels adaptation for long cable lengths and assists operation of the analog filter. A decision block (5) selects an appropriate set of taps.

Abstract: A continuous time electronic dispersion compensation architecture using feed forward equalization and a non-linear decision feedback equalization forms an output signal by a linear combination of successively delayed versions of the input signal and the sliced output signal weighted by appropriate coefficients. A selected number of taps in the mixer used to generate a corresponding number of coefficients for use in the feed forward equalizer are held to a selected voltage to ensure that the coefficients associated with these two taps do not drift. This causes the other coefficients to converge to a unique minimum square error value. In one embodiment the selected voltage is the maximum system voltage.

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

Abstract: Adaptively analyzing an observed signal to estimate that part of the signal that best corresponds to a steering vector. Modifying the steering vector by convolution of the steering vector with a vector estimating the effect of multipath on the observed signal.

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

Abstract: A sampling rate conversion system reduces the signal processing burdens carried by cellular phones, headsets, and other electronic devices. Because the system consumes fewer resources to convert between signal sampling rates, the system may significantly reduce processing time and resource requirements in the device. As a result, the device may instead devote resources to performing other useful tasks, such as interacting with the user through a graphical user interface and performing selected processing tasks.

Abstract: In at least some embodiments, a receiver for a wireless communication system is provided. The receiver includes an equalizer that provides an equalized channel matrix. The receiver also includes scaling logic coupled to the equalizer, the scaling logic selectively scales coefficients of the equalized channel matrix. The receiver also includes a decoder coupled to the scaling logic. The decoder decodes a signal based on the equalized channel matrix with scaled coefficients.

Abstract: In one aspect, the present invention is directed to a technique of, and system for enhancing the performance of high-speed digital communications through a communications channel, for example a backplane. In this aspect of the present invention, a transmitter includes equalization circuitry to compensate for bandwidth limitations and reflections in high-speed digital communication systems. In one embodiment, the equalization circuitry is designed, programmed and/or configured to introduce intersymbol interference in order to improve the signal integrity in high-speed communications and enhance the operation and performance of such systems. In this regard, the equalization circuitry includes temporally overlapping leading and/or trailing taps (relative to the data (symbol) signal) to reduce, minimize, mitigate or effectively eliminate pre-cursor and/or post-cursor intersymbol interference due to, for example, bandwidth limitations and reflections in high-speed digital communication systems.

Abstract: Receiving a transmission line estimation sequence, a wireless communication apparatus generates a transmission line characteristic estimation value for each of a plurality of sub-carriers and smoothes the transmission line characteristic estimation value of a target sub-carrier to be processed and the transmission line characteristic estimation value of its adjacent sub-carrier. The apparatus includes a determination unit for determining whether or not the adjacent sub-carrier, is a null sub-carrier and a smoothing unit for smoothing the transmission line characteristic estimation value of the target sub-carrier by excluding the transmission line characteristic estimation value of the adjacent sub-carrier determined as a null carrier by the determination unit.

Abstract: A method and device for determining at least one traffic parameter in a data transmission system including at least one transmitter and one receiver, wherein the receiver includes a modem with equalizer. The method includes determining at least one piece of data given by the equalizer, wherein the piece of data includes the equalization error Ei; and determining one or more traffic parameters in taking account of the data provided, the fixed quality of service QoS and a relationship linking the quality of service and the equalization error Ei.

Abstract: A channel estimator is configured for determining a gain adjustment for a received wireless signal having a prescribed plurality of tones. The channel estimator is configured for generating, for each of the tones, a corresponding pseudo power value representing a detected power level for the corresponding tone. An accumulated pseudo power value is obtained based on accumulating the respective pseudo power values of the prescribed plurality of tones. Each of the pseudo power values is selectively adjusted by an adjustment factor based on a determined difference between the accumulated pseudo power value relative to an expected accumulated power level relative to a prescribed dynamic range. The pseudo power values are then output for decoding of data modulated at the respective tones.

Abstract: A decision feedback equalizer (DFE) architecture uses feedback samples that are over-sampled with respect to the symbol rate. On-baud feedback samples are quantized with a slicer, while off-baud samples are linear, IIR samples. Both forward and feedback filters are fractionally-spaced, but adapted only at the baud instances.

Abstract: In order to generate a signal for canceling a chirped signal, a transmitter generates a cancellation signal along with the transmitted signal, using a single term variable complex gain multiplier adapted to cancel the chirped signal only at its instantaneous frequency, rather than attempting to cancel it with a complex FIR filter that works over the entire bandwidth of the chirped signal. The cancellation signal is varied in amplitude and phase as a function of the frequency of the chirped transmit signal for which it is intended to compensate. Since the signal that is to be cancelled is essentially sinusoidal but swept through a frequency range, the cancellation signal for the instantaneous transmit signal needs to be swept in both amplitude and phase in unison with the change in frequency of the transmit signal in order to accommodate gain and phase changes in the transmitted signal as a function of frequency.

Abstract: A method for use in an equalization of a channel by means of an equalizer 22, 23 is shown, wherein the channel uses a certain frequency band for a transfer of signals. In order to enable a channel equalization which requires a low complexity and which provides at the same time a good performance, the method determines a channel response for at least one frequency point within the frequency band used by the channel. The method further sets at least one adjustable coefficient (?0k, bck, brk, a0k, a1k, a2k of the equalizer such that an equalizer response compensates optimally the determined channel response at the at least one selected frequency point. Also shown is a corresponding signal processing device 2, a corresponding signal processing system and a corresponding software program product.

Abstract: Demodulation apparatus includes a transversal filter characterized by coefficients adjusted by a coefficient determiner responsive to a constant modulus error signal and variable mode error signal related to the output of a spectral mean frequency detector having its input coupled to the output of the transversal filter.

Abstract: The invention relates to a method for synchronizing a plurality of digital input signals which are formed by sampling with the aid of a dedicated operating clock in each case. In order to be able to carry out such a method reliably with a relatively low outlay, according to the invention digital auxiliary signals (xd(nk+j), (yd(nk+j)) are formed by sampling the digital input signals (x(k)) with the aid of a common postprocessing clock, use being made of a postprocessing clock which is at least twice as fast as the fastest operating clock; synchronized digital output signals (x(m), y(m)) which correspond to the digital input signals (x(k)) are formed by means of interpolating each digital auxiliary signal (xd(nk+j), yd(nk+j)).

Abstract: Certain embodiments of the present invention provide systems and methods for data communication. Certain embodiments provide a method including temporarily holding data being transmitted, determining a sequence of the data based at least on data priority and metering transmission of the data based on at least one user-specified metering criterion to provide a level of quality of service in transmitting the data. Certain embodiments provide a computer-readable medium having a set of instructions for execution on a processing device. The set of instructions includes a holding routine for temporarily holding data being transmitted, a sequencing routine for determining a sequence of the data based on at least one sequencing criterion, and a metering routine for metering a flow of the data based on at least one metering criterion to provide a level of quality of service in transmitting the data.

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

Abstract: Described are methods and devices for processing a signal transmitting symbols which are temporally spaced on symbol intervals. The signal may be tapped at fractional symbol intervals to provide a plurality of signal taps at the fractional symbol intervals. Each of a plurality of coefficients may be applied to a corresponding one of the signal taps to generate an equalized signal. For at least one of the signal taps, the corresponding coefficient may be updated no more frequently than once per symbol interval.

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

Abstract: An adaptive equalizer finite impulse response (FIR) filter for high-speed communication channels with modest complexity, where the filter is iteratively updated during a training sequence by a circuit performing the update: h(t+1)= h(t)+?[sgn{d(t)}?sgn{z(t)?Kd(t)}]sgn{ x(t)}, where h(t) is the filter vector representing the filter taps of the FIR filter, x(t) is the data vector representing present and past samples of the received data x(t), d(t) is the desired data used for training, z(t) is the output of the FIR filter, ? determines the memory or window size of the adaptation, and K is a scale factor taking into account practical limitations of the communication channel, receiver, and equalizer. Furthermore, a procedure and circuit structure is provided for calibrating the scale factor K.

Abstract: A correlative error detection system (60) for a signal equalizer (10) that corrects a distorted communications signal. The detection system (60) correlates a sequence of bits in a signal from an FFE and/or a DFE processor (12, 14) with a predetermined sequence of correlation values. The detection system (60) includes a summing network (66) that sums the correlated signals. If the sequence of signal bits matches the sequence of correlation values, then the summed correlated signal will include a signal maxima. A peak detector (76) detects and holds the signal maxima so that a slow speed weight computer (40) can process the signal values to set weight values in the processors (12, 14). By knowing how often the sequence of bits that match the correlative values should occur in a random bit stream for an undistorted signal, the weight computer (40) can set the weight values to provide that magnitude of the bit sequence.

Abstract: A channel equalizer for a single-carrier receiver interacting with a Trellis decoder and a channel equalization method therefor. The channel equalizer includes a first equalizer having a first feed forward (FF) unit for eliminating a pre-ghost of an input signal and a first feedback (FB) unit for eliminating a post-ghost of the input signal, a Trellis decoder for Trellis-decoding an output signal of the first equalizer, and a second equalizer having a second FF unit for eliminating the pre-ghost of the input signal and a second FB unit for eliminating the post-ghost of the input signal based on a signal decoded by the Trellis decoder. The first and second equalizers, interacting with the Trellis decoder, enable the equalization performance and speed of the channel equalizer to be enhanced.

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

Abstract: A diversity receiver (60) has two diverse channels fed by the antennas, an adaptive equalizer (20,30) for each channel and a coefficient adapter (40) for adapting two sets of coefficients in a time shared manner for the equalizers. A combiner combines the equalized signals. By sharing one adapter for adapting the coefficients between two or more equalizers, the calculation load can be reduced. This is useful for small mobile terminals powered by battery, for use with GSM or UMTS or other radio networks. It can be applied to any type of equalizer, and using any manner of time sharing. The combiner can exploit any type of diversity between the equalized signals. The equalizers can output two equalized signal values in consecutive time slots, by reusing the same coefficients, while new coefficients are being calculated.

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

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

Abstract: New version packet data devices support a backwards-compatible signal format. New version devices operate within a first frequency band while old version devices operate within a second frequency band. The first frequency band differs from but overlaps with the second frequency band. The new version devices may operate on a first carrier frequency (within the first frequency band) while old version devices may operate at a second carrier frequency (within the second frequency band). The new version devices and/or the old version devices may also support carrier-less modulations. Preamble, header, and trailer portions of a new version signal include a plurality of spectral copies of a baseband modulated signal. One or more of these spectral copies of the baseband modulated signal is/are indistinguishable from corresponding components of an old version signal. The payload of the new version signal may be formed in the same manner or may be formed in have a wider bandwidth, higher data rate format.

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

Abstract: An equalizing circuit is provided for a playback apparatus not requiring tracking control. A playback signal is supplied to a plurality of unit delay devices which are connected in series, and the signals at the input ends and the output ends are supplied to weighting devices, respectively. Furthermore, the playback signal is supplied to a computation circuit, whereby weighting coefficients are determined. Weighting is performed on the signals from unit delay devices, and these signals are added together by an adder so that the equalization of the playback signal is performed, and the signal is extracted from an output terminal. Simultaneously, in the computation circuit, when the envelope value of the playback signal is within a range the phase lock for the playback signal is used so that the calculation of the weighting coefficients is done, and the coefficients of the weighting devices are changed.

Abstract: A receiver chain is provided for use in wireless data communication including a plurality of receive antennas and a vector Barker decoder or a CCK decoder. The vector Barker decoder operates on the plurality of received signals, preferably processed through a plurality of channel matched filters. The weightings of the plurality of channels can be done using a slicer variance, a PLL variance or another method.

Abstract: In a tap 1 in a shift register of a waveform equalizer, data of an input signal is stored in a data storing FF 111. A tap coefficient computing unit 114 calculates a tap coefficient, which is stored in a tap coefficient storing FF 112 and output to an absolute value computing unit 115. The unit 115 obtains the absolute value of the tap coefficient. A comparator 116 compares the absolute value to a threshold value. A masking unit 117 masks and outputs the data from the data storing FF 111 to a multiplier 113 if the absolute value is smaller than the threshold value, while outputting the data from the data storing FF 111 without change if the absolute value is no less than the threshold value. The multiplier 113 multiplies the data of the input signal by the tap coefficient and outputs a signal to an adder 108.

Abstract: A method for shared estimation of parameters (?, ?, |C1|, C0, ?, ??) is described, which together with an error vector e(k), describe the connection between a digitally modulated reference signal inputted to a transmission channel and a received receiver signal z(k) which is at an end of the transmission channel. The method includes the following steps: forming the error vector e(k) in dependence of the parameters (?, ?, |C1|, C0, ?, ??), a reference signal s(k), and the receiver signal z(k); linearizing the error vector e(k); substituting a real parameter of the linearized error vector through components of a estimation vector, wherein a substituted error vector is produced; inserting the substituted error vector into the cost function; and determining the estimation vector through gradient development of the cost function and subsequently setting the gradient to zero.

Abstract: The present invention is to provide a digital radio receiver using a carrier offset compensating circuit capable of compensating for carrier offsets even in a TDD communication system, and extending the range that can cope with offset frequencies to secure stable operation. The digital radio receiver is such that an initial phase correction part determines a phase shift from a known signal and corrects the phase shift, a multiplication part performs multiplication of a tap coefficient of the immediately preceding symbol from a first equalizer, and an equalizer performs waveform equalization while updating the coefficient based on an area-determination result.

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

Abstract: A method of signal equalization of a transmitted bit stream by means of a feed forward equalizer is provided, whereby the signal is decomposed into at least two components and the components are multiplied with equalization parameters to form equalized components, which are superposed to form an equalized signal, and whereby conditional bit error rates by counting faulty transmitted bits in dependence of preceding and succeeding bits are determined and the equalization parameters are tuned dependent on the determined conditional bit error rates.

Abstract: A decision feedback equalizer with dynamic feedback control for use in an adaptive signal equalizer. Timing within the decision feedback loop is dynamically controlled to optimize recovery of the data signal by the output signal slicer.

Abstract: A received communication signal in which input data has been differentially encoded using a number of nominal symbols is filtered according to variable filter coefficients. A symbol is predicted based on the filtered signal, as if the input data had been encoded non-differentially in the communication signal. The filter coefficients are updated in response to the predicted symbol. An example of the differential encoding is differential phase shift keying (DPSK) modulation.

Abstract: A system and method detect symbols of a modulated signal received via a plurality of channels of a wireless communications system. A symbol transmitted via the channels is initially estimated based on the channel estimate from either pilot symbol or previously estimated symbol, and then channel estimate is updated. The next estimate of the symbol is computed by using updated channel information and maximizing the expectation of the log likelihood function. The next estimate is then quantized according to the signal constellation. The quantized estimate of the symbol is compared with the previous estimate of the symbol to determine if the previous estimate of the symbol and the quantized next estimate of the symbol have converged. Otherwise, the quantized next estimate of the symbol is made as the input for the next iteration, and the updating, optimizing, quantizing, and comparing are repeated until the estimate converges.

Abstract: Equalization for ports of a crosspoint switch at least partially offsets transmission losses such as skin loss. The equalization may be tailored on a port-by-port basis using adaptive equalization or adjustable equalization, but fixed equalization may be used. In some implementations, each input port or output port of a crosspoint switch has a dedicated equalization circuit that has filtering characteristics that are based on the signal characteristics (e.g., jitter) measured at the affected output port. For an adjustable equalization approach, the adjustable equalization circuitry includes various switched connections that are selectively coupled and decoupled to achieve the target level of equalization.

Abstract: A method for estimating the impulse response of an information transmission channel includes evaluating a useful number of coefficients of an impulse response of the information transmission channel as a function of actual characteristics of the information transmission channel. This evaluation is carried out, for example, by using a time domain spreading parameter of the channel.

Abstract: A method for a carrier phase recovery apparatus in a multiple-link hopping radio system includes hopping among a plurality of radio links to receive bursts of radio signals on the plurality of radio links and determining channel information for each radio link from a received burst on the radio link. Further, the method includes storing the determined channel information and using the determined channel information for the radio link to reliably recover the carrier phase of a next received burst on the radio link.

Abstract: A channel decoder employs a hybrid frequency-time domain equalizer for effectively combining a frequency domain equalizer with a time domain equalizer to achieve superior static and dynamic multi-path performance compared to conventional decision feedback equalizers. A frequency domain equalizer structure is included within the forward path of a time domain, decision feedback equalizer, with both the frequency domain and time domain portions employing a common error vector. Updates to the taps (frequency bins) may be adapted individually, or fully within the frequency domain without altering the feedback filter. Improved performance, including performance for noisy channels with deep notches, is achieved, and the frequency domain equalizer portion is relieved from equalizing minimum phase zeros of the channel.

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

Abstract: A method and system for equalizing a signal transmitted via a channel of a communications system stores an input signal received via the channel in a main buffer. A training signal portion of the received input signal is stored in a circular buffer as a circulating training signal. A mean square error of the training signal is minimized while estimating the transmitted signal, until the mean square error is less than a predetermine threshold. In this case, the input signal received via the channel is equalized directly to make decisions on symbols of the signal transmitted via the channel. During an initial stage of training, the mean square error is determined directly from the training signal, during subsequent stages of training the circulating training signal is used.

Abstract: An apparatus and method suitable for producing a set of filter coefficients are provided. Sequences of samples of first and second signals are received by the apparatus. Each received sample is processed to update a set of auto-correlation data elements and cross-correlation data elements. The set of auto-correlation data elements corresponds to a compressed version of a corresponding auto-correlation matrix data structure. A scheduling controller generates a scheduling signal including a succession of scheduling commands, the scheduling command indicating that a new set of filter coefficients is to be computed. A new scheduling command is issued when at least two samples of first and second signals are received subsequent to a previously issued scheduling command. In response to a scheduling command, the auto-correlation data elements are processed to generate the auto-correlation matrix data structure.

Abstract: A delay equalizing unit includes a delay time calculating unit for calculating a plurality of delay times which differ from each other by short time periods and which include the delay time of the delayed wave with respect to the direct wave, so that an OFDM-modulated signal input to path correlation detectors is delayed by the plurality of delay times. A feedback unit causes the amplitude and phase of the negatively fed back direct wave to coincide with the amplitude and phase of the delayed wave input to an adding unit based on the largest of the path correlations, so that the negatively fed back direct wave is delayed by a designated delay time based on which the largest path correlation is determined.

Abstract: Distortion due to transmission characteristics of a transmission medium is corrected by measuring leakage in a signal orthogonal to a received signal. The frequency response of an equalizer is adaptively adjusted until the measured leakage is at a local minimum.