US 7,443,914 B2 · DFE to FFE equalization coefficient conversion process for DOCSIS 2.0

Abstract

A method and appartus for converting FFE and FBE coefficients from a DOCSIS compatible cable modem termination system upstream equalizer into FFE only coefficients to be sent down to the cable modem which transmitted the training burst which resulted in convergence on the FFE and FBE coefficients. The method involves programming an FBE like conversion structure comprised of an FFE filter and an FBE filter whose outputs are summed with the FFE and FBE coefficients from the CMTS equalizer. The FFE coefficients are stored in the FFE filter of the conversion structure. The FBE coefficients are stored in an FBE filter of the conversion structure. Then, an input vector which simulates the Dirac function (an impulse) is input to the conversion structure to derive coefficients at its output which define the impulse response and transfer function of the conversion structure. These coefficients are the FFE only coefficients which may be used to select a subset of 24 for sending to the cable modem.

Claims10

Dependent claims

A process for converting feed forward and feedback filter coefficients generated by a cable modem termination system to only feed forward coefficients for use by a cable modem, comprising:

accessing feed forward, hereafter FFE, and feedback, hereafter FBE, coefficients generated by a cable modem termination system upstream equalizer after processing a training burst from a cable modem, and storing said FFE coefficients in coefficient memories of a conversion filter structure having an feed forward filter, a feedback filter and a means for summing the results of each of said feed forward and feedback filters every symbol time, and storing said FBE coefficients in coefficient memories of said feedback filter of said conversion filter structure;
calculating an impulse response of said conversion filter structure, as defined by a plurality of FFE only coefficients output by said conversion filter structure;
and
providing only FFE coefficients from said coefficients output by said conversion filter structure which define said impulse response, thereby converting FFE coefficients and FBE coefficients to only FFE coefficients.

1 more element

A process for converting feed forward and feedback filter coefficients generated by a Data Over Cable Service Interface Specifications, hereafter DOCSIS compatible cable modem termination system to only feed forward coefficients for use by a cable modem, comprising:

A) receiving feed forward, hereafter FFE coefficients generated by a DOCSIS compatible cable modem termination system upstream equalizer and storing them in coefficient memories of an FFE filter of a conversion filter structure;
B) receiving feedback, hereafter FBE filter coefficients generated by a DOCSIS compatible cable modem termination system (CMTS) upstream equalizer and storing them in coefficient memories of an FBE filter of a conversion filter structure;
C) generating an input vector comprised of a plurality of elements which simulates an impulse and inputting said vector, one element at a time, into a first delay stage of said FFE filter of said conversion filter structure;
D) as said elements propagate through a plurality of delay stages of said FFE filter, multiplying said elements times said FFE coefficients in said coefficient memories of said FFE filter of said conversion filter structure and summing the results;
E) summing the results calculated in step D during each symbol time and inputting said results, one result at a time, into a first delay stage of said FBE filter of said conversion filter structure;
F) as said results propagate through a plurality of delay stages of said FBE filter, multiplying said results times the coefficients stored in said coefficient memories of said FBE filter of said conversion filter structure and inverting and summing the results;
G) summing the results generated in step F with the results generated in step E to generate a plurality of FFE only coefficients.

4 more elements

An apparatus comprising:

a feed forward digital filter having an input and a plurality of coefficient memories programmed with feed forward, hereafter FFE coefficients from a feedback, hereafter FFE filter of a cable modem termination system decision feedback equalization, hereafter DFE equalizer after said equalizer has converged upon said FFE coefficients after processing a training burst from a cable modem and having an output at which appears results of processing signals appearing at said input;
a feedback digital filter having an input and having an output and having a plurality of coefficient memories each storing an FBE coefficient from a feedback filter of said cable modem termination system DFE equalizer after said equalizer has converged upon said FFE coefficients after processing a training burst from a cable modem and having an output at which appears inverted results of processing signals appearing at said input
a summer coupled to receive output results from said feed forward digital filter and said feedback digital filter, for summing said results during every symbol time and outputting the sum as FFE coefficients only, thereby converting FFE coefficients and FBE coefficients to only FFE coefficients.

Dependencies are inferred from the claim text.

DFE to FFE equalization coefficient conversion process for DOCSIS 2.0

Life of this patent

DFE to FFE equalization coefficient conversion process for DOCSIS 2.0

Life of this patent

Abstract

Claims10