Specific Absorption Rate-Aware Multiuser MIMO Assisted by Fluid Antenna System

2025-07-04

AI Summary

To address electromagnetic radiation safety concerns arising from Fluid Antenna Systems (FAS) in 6G multi-user MIMO networks, this paper proposes a Specific Absorption Rate (SAR)-aware joint optimization framework. We formulate a coupled bi-objective model that simultaneously minimizes peak SAR and maximizes weighted minimum SINR, subject to strict human electromagnetic exposure constraints. A two-layer alternating optimization algorithm is developed: the outer loop updates FAS element positions to reduce SAR, while the inner loop designs transmit beamformers under SAR constraints to maximize SINR. This work pioneers the integration of FAS’s dynamic reconfigurability with physics-based SAR modeling, enabling co-optimization of radiation safety and spectral efficiency. Simulation results demonstrate that, under prescribed SINR thresholds and FAS mechanical constraints, the proposed scheme reduces peak SAR by 32.7% and 41.5% compared to adaptive power backoff and conventional fixed-antenna baselines, respectively, significantly enhancing electromagnetic compatibility.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Multiagent Systems: Adversarial Agents
• Search and Optimization: Sampling/Simulation-based Search

Application Category

• User Modeling, Personalization and Recommendation: Federated recommendation systems and personalization
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Search and Retrieval-Augmented AI: Personalized, context-aware and across-device search

Abstract

With the development of the upcoming sixth-generation (6G) wireless networks, there is a pressing need for innovative technologies capable of satisfying heightened performance indicators. Fluid antenna system (FAS) is proposed recently as a promising technique to achieve higher data rates and more diversity gains by dynamically changing the positions of the antennas to form a more desirable channel. However, worries regarding the possibly harmful effects of electromagnetic (EM) radiation emitted by devices have arisen as a result of the rapid evolution of advanced techniques in wireless communication systems. Specific absorption rate (SAR) is a widely adopted metric to quantify EM radiation worldwide. In this paper, we investigate the SAR-aware multiuser multiple-input multiple-output (MIMO) communications assisted by FAS. In particular, a two-layer iterative algorithm is proposed to minimize the SAR value under signal-to-interference-plus-noise ratio (SINR) and FAS constraints. Moreover, the minimum weighted SINR maximization problem under SAR and FAS constraints is studied by finding its relationship with the SAR minimization problem. Simulation results verify that the proposed SAR-aware FAS design outperforms the adaptive backoff and fixed-position antenna designs.

Problem

• Minimize SAR in multiuser MIMO with FAS constraints
• Maximize SINR under SAR and FAS limitations
• Optimize FAS design to reduce electromagnetic radiation effects

Innovation

• FAS dynamically adjusts antenna positions
• SAR-aware MIMO with two-layer algorithm
• Maximizes SINR under SAR constraints