Digital and Hybrid Precoding and RF Chain Selection Designs for Energy Efficient Multi-User MIMO-OFDM ISAC Systems

TL;DR

This paper proposes joint precoding and RF chain selection strategies for energy-efficient multi-user MIMO-OFDM ISAC systems, optimizing power consumption while maintaining sensing performance, and demonstrates significant EE improvements through simulations.

Contribution

It introduces novel energy-efficient joint optimization algorithms for both digital and hybrid precoding architectures in MIMO-OFDM ISAC systems, addressing RF chain selection and power tradeoffs.

Findings

Significant EE improvements over existing schemes.

Effective joint optimization algorithms with proven convergence.

Enhanced EE-sensing performance tradeoff in simulations.

Abstract

Using multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) for integrated sensing and communication (ISAC) has attracted considerable attention in recent years. While most existing works focus on improving MIMO-OFDM ISAC performance, the impact of transmit power and radio-frequency (RF) circuit power consumption on energy efficiency (EE) remains relatively underexplored. To address this gap, this paper investigates joint precoding and RF chain selection for multi-user MIMO-OFDM ISAC systems, and develops energy-efficient designs for both fully digital and hybrid precoding architectures through the joint optimization of precoding and RF-chain activation. Specifically, we first formulate a novel EE maximization problem subject to sensing performance constraints. Then, efficient optimization algorithms are proposed for both architectures, together with analyses of their computational complexity and convergence behavior. Building on the proposed approaches, spectral efficiency-power consumption tradeoff designs are also provided. Simulation results demonstrate that, compared with existing schemes, the proposed approaches achieve significant improvements in the EE-sensing tradeoff for ISAC systems.