Iterative soft interference cancellation and filtering for spectrally efficient high-speed transmission in MIMO systems

A method of canceling interference among multiple signals simultaneously transmitted from multiple transmitting antennae and received by multiple receiving antennae, the method comprising:

• (a) providing a received signal from each receiving antenna to each of a plurality of interference cancellers, at least one interference canceller corresponding to each said transmitted signal, and each interference canceller dedicated to canceling interference against its corresponding transmitted signal;
• (b) preparing an estimate of the transmitted signals from all transmitting antennae for use in each interference canceller,
• (c) multiplying each estimate by a channel coefficient matrix;
• (d) subtracting the resulting products of each estimate and the channel coefficient matrix from the received signals, resulting in a corresponding difference between each of the products and each of the received signals;
• (e) multiplying each corresponding difference by a filter weight vector;
• (f) decoding the received signal based upon the resulting products of said difference and said filter weight vector;
• g) if a predetermined interrupt criteria is not met, then using said decoded signal in the preparation of an estimate for a subsequent interference cancellation iteration;
• and
• (h) iteratively performing steps (b)-(g) if the predetermined interrupt criteria is not met.

An apparatus for canceling interference among multiple signals simultaneously transmitted from multiple transmitting antennae and received by multiple receiving antennae, the apparatus comprising:

• a plurality of interference cancellers, at least one interference canceller corresponding to each said transmitted signal, and each interference canceller dedicated to canceling interference against its respective transmitted signal;
• soft symbol estimator means for preparing an estimate of the transmitted symbols for use in each interference canceller, each estimate including a forced zero term for the transmitted signal corresponding to each interference canceller;
• means for multiplying each estimate by a channel coefficient matrix;
• means for subtracting the resulting products of each estimate and the channel coefficient matrix from the received signal;
• means for calculating a filter weight vector;
• means for multiplying the each difference between said product and the received signal by a filter weight vector;
• and
• means for decoding the signal based upon the resulting products of said difference and said filter weight vector.