Reduced dimension equalizer and interference canceller for MIMO-OFDM

In this paper, an interference cancellation and equalization method is proposed for a multiple-input, multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. Standard equalization techniques such as zero-forcing (ZF) and adaptive array processing techniques such as per-tone or time-domain equalization may require large amounts of training and memory for storage of the weight coefficients. In a MIMO-OFDM system with N carriers, equalizers at each antenna are characterized by the solution space associated with an underdetermined system of linear equations. A structured per-tone technique is proposed that utilizes the extra degrees of freedom in order to cancel interfering signals; the resultant equalizers (weight vectors) have lengths significantly smaller than N, but at least as long as the channel impulse response.