Pilot-Data Superposition for Beam-Based FDD Massive MIMO Downlinks

In this letter, we propose a superposition signaling of pilots and data scheme (SPD) for beam-based frequency-division-duplex massive multiple-input multiple-output systems, which allows pilots and data to be transmitted simultaneously in the downlink. The proposed SPD scheme leverages spatial channel correlations to reduce the dimensionality loss, and more importantly, addresses the problem of uneven user channel correlations by superposition signaling of pilots and information bearing data symbols. Essentially, users with smaller dimensionality loss entail less pilots based on the SPD scheme. Simulations results reveal significant throughput gain by the SPD scheme over the state-of-the-art pilot-based approaches.