Weighted autocorrelation method for downlink CDMA LMMSE equalizers

A system for receiving in a mobile terminal a wireless CDMA signal from a base station comprising:

• a transceiver for receiving at least one received signal grouped in blocks of chips, the blocks being further grouped in slides, on at least one receive antenna;
• an LMMSE equalizer for equalizing said received signal;
• a signal processor for updating said equalizer by estimating the auto-correlation matrix with the sample average of received signals over an update period;
• computation means for passing said auto-correlation matrix through a multidimensional matrix filter that weights a plurality of older data samples less than recent data samples, where the number of weighted older data samples depends from a detemined channel coherence interval;
• and
• signal processing means for processing the output of said equalizer to generate said wireless CDMA signal.

A method of dynamically adjusting a filter in a receiver for changing channel conditions, comprising:

• receiving a first block of signals over at least one channel;
• estimating a first correlation matrix for the first block of signals once in an update period P1, said first correlation matrix correlating data from a total of n1 blocks of signals;
• equalizing the first block of signals using the first correlation matrix;
• receiving a second block of signals over the at least one channel;
• determining that a coherence interval between the second block of signals and a block of signals received immediately prior to the second is shorter than a coherence interval between the first block of signals and a block of signals received immediately prior to the first;
• estimating a second correlation matrix for a second block of received signals once in an update period P2, said first correlation matrix correlating data from a total of n2 blocks of data, where P2 is shorter than P1 and n2 is greater than n1;
• and
• equalizing the second block of signals using the second correlation matrix.