A Search-Free Algorithm for Precoder Selection in FD-MIMO Systems with DFT-Based Codebooks

In this paper, we propose a novel method for selecting the precoding matrix indicator (PMI) from a DFT-based codebook, such as the one specified for LTE full dimension (FD) MIMO. While conventional approaches are based on explicit codebook search, our method directly estimates the best PMI from the singular vectors of the channel matrix. The key idea is to exploit the DFT structure to formulate the PMI selection problem as the estimation of the linear phase ramping of a sequence. The main advantage of the proposed method is that its complexity does not scale with the number of PMI candidates, while achieving performance comparable or superior to that of state-of-the-art search-based approaches.