A Practical GDFE Precoder for Multiuser MIMO Systems

Generalized decision feedback equalizer (GDFE) achieves MIMO broadcast channel (BC) capacity but suffers from huge computational complexity and feedback overhead making it unsuitable for practical systems. Much of the complexity is due to the computation of the covariance matrix corresponding to the least favorable noise. Additionally GDFE implementation requires the base stations (BS) to feedback filter coefficients to the users thus increasing overhead. In this paper, we address both the aspects - computational complexity and feedback overhead. We first propose an alternative framework for realizing the GDFE precoder, which avoids the explicit computation of the least favorable noise. We show that, while maintaining capacity optimality of the GDFE precoder, the proposed algorithm has significantly lower complexity. Next, we propose another algorithm which does not require the feedback of filter coefficients from BS to users with minimal loss in achievable capacity. Thus our algorithms are a step towards adopting GDFE precoders in future wireless systems.