Partial-response-channel precoding

Apparatus for use in a data communication system in which a sequence of transmit symbols selected from a predetermined transmit constellation in response to binary input data is transmitted over a communication channel having a predetermined partial-response characteristic, said binary input data having a predetermined number of different values which is substantially equal to the number of symbols of said transmit constellations, said channel providing, in response to said transmitted symbols, a sequence of receiver symbols of an expanded receiver constellation, each of said transmit and receiver symbols having at least first and second coordinates, each transmit symbol being selected for a respective binary word of said data in such a way that that binary word can be recovered from a respective one of said receiver symbols independent if any other one of said receiver symbols,

• said apparatus comprising
• means for receiving said sequence of receiver symbols, and
• means for recovering said data from the sequence of receiver symbols received by said means for receiving in response to stored information which associates each different receiver symbol with a different binary word value, the values of the bits of each said binary word value interdependently identifying the values of the first and second coordinates of the associated receiver symbol.

A method comprising the steps of

• selecting, in response to input data, a sequence of signal points from a predetermined base constellation,
• combining each selected signal point with a feedback signal to provide a sequence of combined signal points, said feedback signal being a predetermined function of at least one previously provided one of the signal points, said base constellation and said function being such that ones of said combined signal points are signal points of said base constellation and the others are signal points of minimally non-overlapping lattice translates of said base constellation, and
• providing a transmit signal which represents said combined signal points, all of the combined signal points which are minimally non-overlapping lattice translates of one another being represented identically.

A method for use in a data communication system in which a sequence of transmit symbols selected from a predetermined transmit constellation in response to binary input data is transmitted over a communication channel having a predetermined partial-response characteristic, said channel providing, in response to said transmitted symbols, a sequence of receiver symbols of an expanded receiver constellation, each transmit symbol being selected for a respective binary word of said data in such a way that that binary word can be recovered from a respective one of said receiver symbols independent of any other one of said receiver symbols, there being a number of different binary word values, that number being substantially equal to the number of symbols of said transmit constellation,

• said method comprising the steps of
• receiving said sequence of receiver symbols, and
• recovering said data from the sequence of received receiver symbols in response to stored information which associates each different receiver symbol with a different stored binary word value, said transmit constellation and said expanded receiver constellation being other than M-PAM or M.sup.2 -ary quadrature amplitude modulation constellations.