Method and apparatus for adaptively compensating channel or system variations in precoded communications system

An apparatus for communicating data from a transmitter over a communications channel to a receiver comprising:

• means for generating a precoded sequence of data symbols at a precoder at said transmitter, said precoded sequence being generated based on input data symbol values and previous values of said precoded sequence, said precoded sequence being transmitted to said receiver via said communications channel as a transmitted precoded sequence;
• means for determining adaptive compensation of a received signal of said transmitted precoded sequence by using a feedback filter in said receiver, feedback filter output of said feedback filter being generated based on previous values of modified estimates of said transmitted precoded sequence, said means for determining adaptive compensation comprises an adaptive feedforward filter at said receivers, with modified previous values of a sum of output of said feedforward filter and said feedback filter output being used as input to said feedback filter;
• and
• means for updating precoder coefficients of said precoder by periodically forwarding to said transmitter feedback filter coefficients of said feedback filter and generating new precoder coefficients based on previous values of said precoder coefficients and said feedback filter coefficients.

A method for communicating data from a transmitter over a communications channel to a receiver comprising generating a precoded sequence of data symbols at a precoder at said transmitter;

• transmitting said precoded sequence of data symbols to said receiver as a transmitted precoded sequence;
• and
• determining adaptive compensation for a received signal of said transmitted precoded sequence by using a feedback filter in said receiver, said feedback filter output being generated based on previous values of modified estimates of said transmitted precoded sequence, wherein a response function of said precoder is represented by the z transform
• P(z)=p1z−1+p2z−2+ . . . +pNpz−Np
• where p1 . . . Pnp represent said precoder filter coefficients from 1 to an integer represented by Np;
• a response function of said feedback filter is
• W(z)=w1z−1+w2z−2+ . . . +wNbz−Nb
• where w1 . . . wnb represent said feedback filter coefficients;
• and
• said means for updating said output of said precoder is equal to
• Pnew(z)=Pold(z)+W(z)−Pold(z)W(z)
• wherein Pold(z) represents the response function before application of said means for updating and pnew(z) represents the response function determined by said means for updating.

An apparatus for communicating data from a transmitter over a communications channel to a receiver comprising:

• means for generating a precoded sequence of data symbols at a precoder at said transmitter, said precoded sequence being generated based on input data symbol values and previous values of said precoded sequence, said precoded sequence being transmitted to said receiver via said communications channel as a transmitted precoded sequence;
• means for determining adaptive compensation of a received signal of said transmitted precoded sequence by using a feedback filter in said receiver, feedback filter output of said feedback filter being generated based on previous values of modified estimates of said transmitted precoded sequence, said means for determining adaptive compensation comprises an adaptive feedforward filter at said receiver, with modified previous values of a sum of output of said feedforward filter and said feedback filter output being used as input to said feedback filter;
• and
• means for updating said precoder coefficients of said precoder by forwarding to said transmitter feedback filter coefficients of said feedback filter after said determined adaptive compensation exceeds a predetermined threshold and generating new precoder coefficients based on previous values of said precoder coefficients and said feedback filter coefficients.

A method for communicating data from a transmitter over a communications channel to a receiver comprising generating a precoded sequence of data symbols at a precoder at said transmitter;

• transmitting said precoded sequence of data symbols to said receiver as a transmitted precoded sequence;
• determining adaptive compensation for a received signal of said transmitted precoded sequence by using a feedback filter in said receiver, feedback filter output being generated based on previous values of modified estimates of said transmitted precoded sequence and an adaptive feedforward filter at said receiver, with modified previous values of a sum of output of said feedforward filter and said feedback filter output being used as input to said feedback filter;
• updating precoder coefficients of said precoder by forwarding feedback filter coefficients of said feedback filter to said transmitter;
• and
• generating new precoded coefficients based on previous values of said precoder coefficients and said feedback filter coefficients.