A device generates a symbol sequence by performing adaptive equalization by an estimation inverse transfer function of a transmission line on a reception signal sequence extracted from the transmission line, and performing provisional determination on the symbol sequence generated; generates a plurality of the symbol sequences indicating transmission line states in a range of a provisional determination symbol provisionally determined and nearby symbols of the provisional determination symbol; generates, based on the plurality of the symbol sequences indicating the transmission line states generated and an estimation transfer function of the transmission line, an estimation reception symbol sequence for each of the transmission line states; calculates a metric between the symbol sequence obtained from the reception signal sequence and each of a plurality of the estimation reception symbol sequences; selects a most likelihood estimation reception symbol sequence of the plurality of the estimation reception symbol sequences, based on the calculated metric, the provisional determination symbol, and the nearby symbols of the provisional determination symbol; and determines a transmission symbol sequence.

A feed forward equalizer including a first set of filter taps having a first set of filter tap coefficients to be adapted and a second set of one or more filter taps having one or more filter tap coefficients to be constrained. The feed forward equalizer includes an adaptation component to determine a set of adapted filter tap coefficient values corresponding to the first set of filter tap coefficients and a constraint function component to determine a constrained filter tap coefficient value for the second set of the one or more filter taps having the one or more filter tap coefficients to be constrained using a constraint function based on at least a portion of the set of adapted filter tap coefficient values. The feed forward equalizer generates, based at least in part on the constrained filter tap coefficient value, an equalized signal including a set of estimated symbol values.

A method of equalizing a communication link includes setting a number of coefficients equal to a required number of coefficients, determining a number of pulse responses for a waveform, the number of pulse responses being greater than the number of coefficients, setting all values in a set of values to zero, the set of values having a number of values equal to the number of coefficients, repeating, until all values in the set of values have been assigned, determining a current lowest parameter in a set of given parameters, using a position of the current lowest parameter in the set of given parameters as an index, determining a minimum value between a first term in the set of given parameters multiplied by a main pulse response minus a summation of each parameter in the set of parameters multiplied by each value in the set of values, divided by the current lowest parameter, and a corresponding pulse response, and assigning the minimum value to the value in the set of values having a position equal to position of the current lowest parameter, and determining a value of each coefficient in a set of coefficients by multiplying each value in the set of values with the sign of a corresponding pulse response in the number of pulse responses; defining an equalizer having a number of taps equal to the number of coefficients, each tap having a value based on the corresponding coefficient; and applying the equalizer to a waveform received through the communication link to produce an equalized waveform. A test and measurement device is also disclosed.

A feed forward equalizer including a first set of filter taps having a first set of filter tap coefficients to be adapted and a second set of one or more filter taps having one or more filter tap coefficients to be constrained. The feed forward equalizer includes an adaptation component to determine a set of adapted filter tap coefficient values corresponding to the first set of filter tap coefficients and a constraint function component to determine a constrained filter tap coefficient value for the second set of the one or more filter taps having the one or more filter tap coefficients to be constrained using a constraint function based on at least a portion of the set of adapted filter tap coefficient values. The feed forward equalizer generates, based at least in part on the constrained filter tap coefficient value, an equalized signal including a set of estimated symbol values.

Sampling circuitry for receiving an analog signal from photodetector circuitry and generating a sample analog signal. Equalization circuitry for generating an equalized signal comprising first and second sample values corresponding with a cursor tap and a first postcursor tap, and one or more third sample values corresponding with taps other than the cursor tap and the first postcursor tap. In the equalized signal, amplitudes of the first and second sample values are substantially equal while the third sample values are attenuated relative to the first and second sample values. The first and second sample values correspond with two or more first symbols of a first alphabet. Data slicer and modulo circuitry to generate a data signal based on the equalized signal and perform a modulo operation on the two or more first symbols and to generate one or more second symbols. The second symbols are according to a second alphabet.

Provided are a method and an apparatus for canceling interference, to resolve a problem that performance of interference cancellation is poor because accuracy of equalizer coefficients obtained by a CMTS through calculation is not sufficiently high. A specific solution is as follows: (101) A CMTS calculates L equalizer coefficients of an L-tap filter according to a preamble sequence by using an adaptive algorithm, and performs adaptive equalization on a received signal by using the L equalizer coefficients, where L is a positive integer greater than 24; and (102) the CMTS selects K equalizer coefficients from the L equalizer coefficients, and sends a ranging response message carrying the K equalizer coefficients to a cable modem CM, so that the CM performs pre-equalization on a to-be-sent signal according to the received K equalizer coefficients, where K is a positive integer less than or equal to L.

A reception device for receiving a data signal representing a data value 0 or 1. The reception device includes an equalizer circuit and a control circuit. The equalizer circuit outputs an output value representing a result obtained by comparing a voltage based on the received data signal and a first voltage as a reference, at each clock timing corresponding to the data signal. The control circuit is connected to the equalizer circuit. The control circuit changes, before the data signal is received, a tap coefficient related to a characteristic of the equalizer circuit in a state in which a second voltage different from the first voltage, instead of the voltage of the data signal, is supplied to the equalizer circuit, to detect an inverted tap coefficient that is the tap coefficient at a boundary where a data value of the output value is inverted. The control circuit sets the inverted tap coefficient to the equalizer circuit at a time of receiving the data signal.

A method of equalizing a communication link includes setting a number of coefficients to a required number, determining a number of pulse responses for a waveform, setting all values in a set of values to zero, repeating, until all values have been assigned, determining a current lowest parameter, using a position of the current lowest parameter as an index, determining a minimum value between a first term multiplied by a main pulse response minus a summation of each parameter multiplied by each value, divided by the current lowest parameter, and a corresponding pulse response, and assigning the minimum value to the value having a position equal to the position of the current lowest parameter, and determining a value of each coefficient in a set of coefficients by multiplying each value with the sign of a corresponding pulse response; defining an equalizer having a number of taps having a value based on the corresponding coefficient; and applying the equalizer to a waveform.

A feed forward equalizer includes a plurality of delay circuits connected to each other in series and configured to delay input signals. A plurality of filters respectively correspond to outputs of the plurality of delay circuits, except for a reference output which is an output of a first delay circuit among the plurality of delay circuits, and the input signals. A calculator configured to sum the reference output and outputs of the plurality of filters. Each of the plurality of filters is configured to receive an output of a delay circuit corresponding thereto, among the plurality of filters, and the reference output.

A device generates a symbol sequence by performing adaptive equalization by an estimation inverse transfer function of a transmission line on a reception signal sequence extracted from the transmission line, and performing provisional determination on the symbol sequence generated; generates a plurality of the symbol sequences indicating transmission line states in a range of a provisional determination symbol provisionally determined and nearby symbols of the provisional determination symbol; generates, based on the plurality of the symbol sequences indicating the transmission line states generated and an estimation transfer function of the transmission line, an estimation reception symbol sequence for each of the transmission line states; calculates a metric between the symbol sequence obtained from the reception signal sequence and each of a plurality of the estimation reception symbol sequences; selects a most likelihood estimation reception symbol sequence of the plurality of the estimation reception symbol sequences, based on the calculated metric, the provisional determination symbol, and the nearby symbols of the provisional determination symbol; and determines a transmission symbol sequence.