Energy-Efficient Non-Orthogonal Multicast and Unicast Transmission of Cell-Free Massive MIMO Systems with SWIPT

TL;DR

This paper proposes energy-efficient resource allocation strategies for layered-division multiplexing in cell-free massive MIMO systems, enabling simultaneous multicast and unicast transmission with wireless power transfer, and introduces algorithms that balance performance and computational complexity.

Contribution

It develops a novel optimization framework and algorithms for maximizing energy efficiency in non-orthogonal multicast and unicast transmission in cell-free massive MIMO systems.

Findings

First-order algorithms achieve near second-order performance.

Proposed algorithms significantly reduce computational complexity.

Numerical results confirm improved energy efficiency in large-scale systems.

Abstract

This work investigates the energy-efficient resource allocation for layered-division multiplexing (LDM) based non-orthogonal multicast and unicast transmission in cell-free massive multiple-input multiple-output (MIMO) systems, where each user equipment (UE) performs wireless information and power transfer simultaneously. To begin with, the achievable data rates for multicast and unicast services are derived in closed form, as well as the received radio frequency (RF) power at each UE. Based on the analytical results, a nonsmooth and nonconvex optimization problem for energy efficiency (EE) maximization is formulated, which is however a challenging fractional programming problem with complex constraints. To suit the massive access setting, a first-order algorithm is developed to find both initial feasible point and the nearly optimal solution. Moreover, an accelerated algorithm is designed to improve the convergence speed. Numerical results demonstrate that the proposed first-order algorithms can achieve almost the same EE as that of second-order approaches yet with much lower computational complexity, which provides insight into the superiority of the proposed algorithms for massive access in cell-free massive MIMO systems.