Efficient fixed-point implementation of linear equalization for cooperative MIMO systems

We describe an efficient fixed-point calculation of the weight matrices for a linear MMSE equalizer in a MIMO-OFDM system intended for the large numbers of antennas typical for cooperative base stations. Our real-time implementation is numerically stable also in critical channels with reduced rank. Implementation loss due to the 16 bit fixed-point arithmetic is noticeable only in high SNR range above 30 dB. A speed optimization technique is proposed splitting the algorithm in several dot products which can be highly optimized. Using 3 parallel C64x+ DSP cores running at 1 GHz each, equalization of a 12 × 12 MIMO-OFDM system with 1200 subcarriers can be realized in less than 1 millisecond. Compared to a floating-point implementation, at the same performance power consumption can be reduced by a factor of 6.