Multigroup Multicast Precoding in Massive MIMO

TL;DR

This paper proposes computationally efficient multicast precoders for massive MIMO systems that consider practical CSI acquisition, deriving spectral efficiency and optimal power control policies, verified through numerical simulations.

Contribution

It introduces new precoders accounting for CSI acquisition overhead and derives closed-form solutions for power control in massive MIMO multicast scenarios.

Findings

Proposed precoders outperform existing schemes in simulations.

Derived spectral efficiency expressions for practical precoding.

Closed-form solutions for uplink and downlink power control.

Abstract

Optimal physical layer multicasting (PLM) is an NP-hard problem that for simplicity has been studied under idealistic assumptions, e.g., availability of perfect channel state information (CSI), both at the base station (BS) and at the user terminals (UTs). With the advent of massive multiple-input-multiple-output (MIMO), PLM has become more challenging, as the computational complexity of the precoder design is proportional to the number of BS antennas. In this paper, we address these issues by introducing computationally efficient precoders that account for practical CSI acquisition. We derive achievable spectral efficiency expressions for the proposed precoders. Then we introduce a novel problem formulation for the max-min fairness power control that accounts the CSI acquisition overhead, uplink training and downlink transmission powers. We solve this problem and find the optimal uplink and downlink power control policies in closed form. Using numerical simulations, we verify the effectiveness of our proposed schemes compared to the-state-of-the-art PLM schemes for massive MIMO systems.