Practical low complexity linear equalization for MIMO-CDMA systems

This article first reviews recently proposed techniques for adaptive and direct linear MIMO equalization in the context of MIMO-CDMA systems and in particular with application to a MIMO-extended UMTS-FDD downlink. The focus is thereby mainly on the complexity of the algorithms. The second part of the paper proposes frequency domain (FD) MIMO equalization using the overlap/add FFT method in conjunction with two different low-complexity FD-deconvolution techniques to obtain the equalizer coefficients based on explicit channel impulse response estimates. The effects of imperfect channel estimation are discussed. An architecture for the VLSI implementation of the proposed method is suggested and an estimate of the complexity of the proposed circuit is given in the conclusions.