Power-Constrained and Quantized MIMO-RSMA Systems with Imperfect CSIT: Joint Precoding, Antenna Selection, and Power Control

TL;DR

This paper introduces a joint optimization algorithm for power, precoding, and antenna selection in MIMO-RSMA systems with imperfect CSIT, demonstrating improved spectral efficiency and power efficiency with medium-resolution DACs.

Contribution

It proposes a novel joint optimization framework for precoding, antenna selection, and power control in power-constrained MIMO-RSMA systems with imperfect CSIT, including a complexity-reduction method for massive MIMO.

Findings

Medium-resolution DACs (8-11 bits) can be more power-efficient than low-resolution DACs.

The proposed algorithm effectively maximizes spectral efficiency under power constraints.

Simulation results validate the effectiveness of the joint optimization approach.

Abstract

To utilize the full potential of the available power at a base station (BS), we propose a joint precoding, antenna selection, and transmit power control algorithm for a total power budget at the BS. We formulate a sum spectral efficiency (SE) maximization problem for downlink multi-user multiple-input multiple-output (MIMO) rate-splitting multiple access (RSMA) systems with arbitrary-resolution digital-to-analog converters (DACs). We reformulate the problem by defining the ergodic sum SE using the conditional average rate approach to handle imperfect channel state information at the transmitter (CSIT), and by using approximation techniques to make the problem more tractable. Then, we decompose the problem into precoding direction and power control subproblems. We solve the precoding direction subproblem by identifying a superior Lagrangian stationary point, and the power control subproblem using gradient descent. We also propose a complexity-reduction approach that is more suitable for massive MIMO systems. Simulation results not only validate the proposed algorithm but also reveal that when utilizing the full potential of the power budget at the BS, medium-resolution DACs with 8-11 bits may actually be more power-efficient than low-resolution DACs.