Abstract: The present invention relates to a method for estimating properties of a transmission line by means of features of a noise spectrum generated by noise entering said transmission line at an intermediate location between the ends of the line. The invention provides possibility to estimate a number of properties, e.g. length of a portion of the transmission line, line attenuation of said Sine portion and even line termination.

Abstract: A system and method for using loop topology identification to investigate a transmission line having a plurality of cable segments. At a measurement plane for each segment, a probing signal is transmitted into the cable. A reflected signal is detected, and an equivalent total input impedance is calculated. The system iteratively calculates the distance between the measurement planes as well as the length, characteristic impedance, and the propagation constant of each segment. A model is used to calculate the respective equivalent input impedance of each segment using the calculated characteristic impedance, propagation constant, and length of the preceding segment. The equivalent total input impedance is then calculated from the iteratively calculated segment values.

Abstract: The present invention concerns methods for estimating one or more transmission properties of a telecommunications transmission line. Estimates of the line input impedance, Zin at a frequency f, and the line capacitance ? are made. An estimate is then made in dependence of ?, the frequency f and a value ?, where ? satisfies the relationship ? coth (?)=Zin·j??, and ?=2?f. Accuracy may be improved by least squares fitting a curve to a set of intermediate values and then generating an estimate from the coefficients of the curve.

Abstract: A method and localization unit for localizing load coils within a transmission line. The load coil localization is achieved using a measurement of a Single-Ended Line Testing (SELT) parameter for the transmission line and an approximation of the SELT parameter obtained from a model of the transmission line. The model is based on a parameter vector ? including parameters describing the transmission properties of each load coil and cable section and the length of a plurality of individual cable sections as unknown independent parameters. The location of at least one load coil is determined by substantially minimizing a criterion function that represents a deviation between the measurement of the SELT parameter and the approximation of the SELT parameter obtained from the model. The load coil localization method and unit can be used for both symmetric and asymmetric transmission lines.

Abstract: A method and localization unit for localizing load coils within a transmission line. The load coil localization is achieved using a measurement of a Single-Ended Line Testing (SELT) parameter for the transmission line and an approximation of the SELT parameter obtained from a model of the transmission line. The model is based on a parameter vector ? including parameters describing the transmission properties of each load coil and cable section and the length of a plurality of individual cable sections as unknown independent parameters. The location of at least one load coil is determined by substantially minimizing a criterion function that represents a deviation between the measurement of the SELT parameter and the approximation of the SELT parameter obtained from the model. The load coil localization method and unit can be used for both symmetric and asymmetric transmission lines.

Abstract: An echo canceller reduces an echo signal produced when the transmitted signal leaks back into the receiver via a hybrid. The echo canceller estimates the echo signal from the transmitted signal, and then subtracting the estimated echo signal from the received signal. In practice, the echo path channel in a DMT-modem is much longer than the cyclic prefix, and therefore, the received echo signal will be subjected to both ISI (inter-symbol-interference) and ICI (inter-carrier-interference). A traditional echo canceller, designed for a xDSL-modem, uses either a time domain adaptive FIR-filter or a combined echo canceller implemented in both time and frequency domain. A matrix-based adaptive echo canceller is implemented in the frequency domain. Various example embodiments are disclosed.

Abstract: A method and device for estimating one or more transmission properties of a telecommunication transmission line. At least one signal is sent on the line, the at least one signal including at least two frequencies for which the absolute value of the line propagation constant times the line length is less than ?, and a resulting signal is received. An estimate of at least one transmission line property is then determined by examining the relationship between the sent and resulting signal or signals. The process may be repeated, if necessary. The estimate determination may also be repeated one or more times, with each successive estimate preferably using for the determination only those frequencies for which, as previously estimated, the absolute value of the line propagation constant times the line length is less than ?.

Abstract: A system and method for using loop topology identification to investigate a transmission line having a plurality of cable segments. At a measurement plane for each segment, a probing signal is transmitted into the cable. A reflected signal is detected, and an equivalent total input impedance is calculated. The system iteratively calculates the distance between the measurement planes as well as the length, characteristic impedance, and the propagation constant of each segment. A model is used to calculate the respective equivalent input impedance of each segment using the calculated characteristic impedance, propagation constant, and length of the preceding segment. The equivalent total input impedance is then calculated from the iteratively calculated segment values.

Abstract: A method is described herein that can be used to detect the presence of a load coil within a transmission line. The method can also be used to determine the number of load coil(s) present within the transmission line. In addition, the method can be used to determine the distance to the first load coil.

Abstract: A method is described herein that can be used to detect the presence of a load coil within a transmission line. The method can also be used to determine the number of load coil(s) present within the transmission line. In addition, the method can be used to determine the distance to the first load coil.

Abstract: The invention refers to single-ended test of a loop with the aid of a transceiver, wherein an input impedance (Zin(ƒ)) of the loop is generated. The transceiver has a digital part, a codec and an analog part and is connected to the loop. With the aid of a transmitted and a reflected broadband signal (vin, vout) an echo transfer function Hecho(ƒ)=V(f)out/Vin(f) is generated, which also can be expressed as H echo ? ( f ) = H ? ? ( f ) ? Z in ? ( f ) + Z h0 ? ( f ) Z in ? ( f ) + Z hyb ? ( f ) . Here Zh0(ƒ), Zhyb(ƒ) and H?(ƒ) are model values for the transceiver. In a calibration process a test transceiver, with the same type of hardware as the transceiver, is connected to known impedances, replacing the loop. Hecho(ƒ)=V(f)out/Vin(f) is generated for the known impedances and the model values are generated and are stored in a memory in the transceiver.

Abstract: The invention refers to single-ended test of a loop with the aid of a transceiver, wherein an input impedance (Zm(ƒ)) of the loop is generated. The transceiver has a digital part, a codec and an analog part and is connected to the loop. With the aid of a transmitted and a reflected broadband signal (vin, vout) an echo transfer function Hecho(ƒ)=V(f)out/Vin(f) is generated, which also can be expressed as H echo ? ( f ) = H ? ? ( f ) ? Z in ? ( f ) + Z h0 ? ( f ) Z in ? ( f ) + Z hyb ? ( f ) Here Zh0(ƒ), Zhyb(ƒ) and H?(ƒ) are model values for the transceiver. In a calibration process a test transceiver, with the same type of hardware as the transceiver, is connected to known impedances, replacing the loop. Hecho(ƒ)=V(f)out/Vin(f) is generated for the known impedances and the model values are generated and are stored in a memory in the transceiver.

Abstract: Analysis of an electrical circuit is performed using a computer program product (60) and a method. In accordance with the program and the method, a electrical circuit analyzer generates an admittance matrix for an electrical circuit which is being analyzed. The admittance matrix includes symbolic expressions rather than numerical expressions for at least some components of the electrical circuit. The electrical circuit analyzer linearly and algebraically solves an equation system including the admittance matrix for analyzing at least a part of the electrical circuit. The electrical circuit analyzer uses symbolic computation to solve the equation system including the admittance matrix for analyzing at least a part of the electrical circuit. The equation system including the admittance matrix can be solved in various types of analyses, including (1) determining a transfer function between specified nodes of the electrical circuit; and (2) optimizing a component of the electrical circuit.

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 or other training sequence which allows determination of the impulse response 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.

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: The present invention significantly reduces the number of complex computations that must be performed to compute a DFT or IDFT when a pattern is identified in an original input data sequence and is used to modify the data sequence in order to reduce the size of the sequence to be transformed. A DFT (IDFT) is performed on the modified input data sequence to generate a transformed sequence. The transformed data sequence is then manipulated to generate an output sequence that corresponds to the DFT (IDFT) of the original input data sequence without having actually calculated the DFT (IDFT) of the entire, original input data sequence. Three symmetrical patterns are used in the invention to simplify and render more efficient DFT and IDFT computations: Hermite symmetry, index-reversed, complex-conjugate symmetry, and mirror symmetry.

Abstract: The present invention significantly reduces the number of complex computations that must be performed in computing the discrete Fourier transform (DFT) and inverse DFT (IDFT) operations. In particular, the DFT and IDFT operations are computed using the same computing device. The computation operations are substantially identical for both operations with the exception that for the IDFT operation, the data are complex conjugated before and after processing. Using the same computing device/operations, both DFT and IDFT computations are optimized for maximum efficiency. A common transform process is selectively connected to first and second data processing paths. A DFT operation is performed on an N-point sequence on the first data processing path, and an IDFT operation is performed on an N-point sequence on the second data processing path using the same N-point fast Fourier transform (FFT).

Abstract: In a digital communications system, a sampled signal is precisely reconstructed (rather than approximated) even in situations where the phase of the sampling signal is adjusted. More particularly, the sampled signal is compensated in the frequency domain for phase adjustments to the sampling instance in the time domain. In the context of echo cancellation, an echo transfer function is generated representing the echo channel impulse response. Aliased components present in the echo impulse response are specifically identified and compensated for in the frequency domain by treating each spectral filter coefficient of the echo transfer function as the sum of a baseband component and an aliased component. In addition to accurately compensating for sampling phase adjustments, this technique considerably relaxes traditional sampling constraints.

Abstract: A decision feedback equalizer (DFE) is controlled co equalize a current signal sample for intersymbol interference and/or other distortion caused by the communications channel. An incorrect symbol decision by the DFE is detected and corrected to prevent propagation of the error with possible adverse effects on subsequent DFE decisions. More specifically, an error threshold is determined based on an expected bit error rate and a first postcursor value h.sub.1 of the communications channel impulse response. The decision feedback equalizer determines an intersymbol interference (ISI) component in a first, current sample of the signal being processed. The ISI component is subtracted from the current sample to generate an equalized sample. A corresponding symbol value is detected using that equalized sample. A symbol error is calculated by subtracting the equalized sample from the detected symbol value. The symbol error is compared with the error threshold.

Abstract: The present invention provides accurate, unbiased adaptive gain control in high speed digital communications systems. The probability of receiving each of a plurality of symbols to be transmitted over a data communications channel is determined for the predetermined communications protocol used over that data communications channel. Based on the probability determined for each symbol, an adaptive gain control adjustment factor is established for each symbol. During active communications, symbols transmitted over the data communications channel are detected, and the adaptive gain control value is selectively adjusted using an adjustment factor established for the detected symbol. Accordingly, adaptive gain control updating in accordance with one embodiment of the invention employs different step sizes for incrementing and decrementing the adaptive gain control value depending on the magnitude of the symbol received.