Finite-length equalization over multi-input multi-output (MIMO) channels
View Patent ↗A Multiple-Input Multiple Output (MIMO) Decision Feedback Equalizer improves operation of a receiver by canceling the spatio-temporal interference effects caused by the MIMO channel memory with a set of (Finite Impulse Response (FIR) filters in both the feed-forward and the feedback MIMO filters. The coefficients of these FIR filters can be fashioned to provide a variety of controls by the designer.
1. A method executed in a receiver comprising the steps of:
receiving n o signals, each of which containing blocks of N f symbols;
applying the n o signals to a feed-forward filter structure having an n o ×n i plurality of Finite Impulse Response (FIR) filters where n i is an integer greater than 1 and is not restricted to equal n o , each responsive to a signal from one of said n o entry points and each developing an output signal that contributes to one of n i feed-forward filter structure outputs, with each of said FIR filters in said feed-forward filter structure having N f filter taps;
applying the signals of said n i feed-forward filter structure outputs to a subtractor structure comprising n i subtractor elements, which structure develops n i output signal;
applying the n i output signals of the subtractor structure to a decision logic block that develops n i receiver output signals;
applying the n i receiver output signals to a feedback filter structure that develops n i feedback signals, the feedback filter structure having an n o ×n i plurality of FIR filters, each being responsive to one of said n i receiver output signals; and
applying the n i feedback signals to said subtractor structure.
2. The method of claim 1 further comprising the step of the received signals at rate
T
S
=
T
l
,
where I is an integer greater than 1, and T is symbol rate of a transmitter whose signals said receiver receives.
3. The method of claim 1 further comprising the steps of
computing coefficients for said feed-forward filter structure and for said feedback filter structure based on a block of said received signals; and
applying the computed coefficients to said feed-forward filter structure and for said feedback filter structure.
4. The receiver of claim 3 where said coefficients are computed in a non-iterative manner.
5. The receiver of claim 3 where said coefficients are computed once every time interval that is related to rapidity of change in characteristics of transmission medium preceding said entry points.