An Efficient MMSE Equalizer Implementation for 4Ã\x974 MIMO-OFDM Systems in Frequency Selective Fast Varying Channels

In this paper a FPGA implementation of a 4 times 4 MIMO MMSE Equalizer based on the QR factorization technique is presented. Considering fast varying channels a new filter is computed at each new channel realization thanks to an efficient architecture of matrix triangularization. The QR decomposition is performed with only 6 unrolled coordinate rotation digital computer (CORDIC) operators, which are efficiently exploited to minimize the latency of computation. Soft LLR obtained in output of the equalizer are validated on an FPGA hardware bench including a 4 times 4 Rayleigh fading channel and turbo- coding.