Joint Association and Phase Shifts Design for UAV-mounted Stacked Intelligent Metasurfaces-assisted Communications

2025-08-01

AI Summary

This paper addresses the joint optimization of user association, three-dimensional UAV positioning, and intelligent metasurface (SIM) phase shifts in UAV-mounted stacked intelligent metasurfaces (UAV-SIMs)-assisted wireless communication systems, aiming to maximize network capacity. The underlying problem is non-convex, NP-hard, and highly coupled. To tackle it, we propose an alternating optimization-based decomposition framework that decouples the problem into three subproblems—user association, UAV placement, and SIM phase control—and solves them respectively via the Hungarian algorithm, convex approximation, and layer-wise phase iteration, efficiently implemented using CVX. Our key contribution lies in the first holistic modeling and co-optimization of all multidimensional degrees of freedom in UAV-SIM systems. Simulation results demonstrate significant improvements in both network capacity and link reliability across diverse scenarios, achieving an average gain of 28.5% over benchmark schemes.

Technology Category

• Search and Optimization: Sampling/Simulation-based Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems
• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Web Mining and Content Analysis: Web data generation and simulation

Abstract

Stacked intelligent metasurfaces (SIMs) have emerged as a promising technology for realizing wave-domain signal processing, while the fixed SIMs will limit the communication performance of the system compared to the mobile SIMs. In this work, we consider a UAV-mounted SIMs (UAV-SIMs) assisted communication system, where UAVs as base stations (BSs) can cache the data processed by SIMs, and also as mobile vehicles flexibly deploy SIMs to enhance the communication performance. To this end, we formulate a UAV-SIM-based joint optimization problem (USBJOP) to comprehensively consider the association between UAV-SIMs and users, the locations of UAV-SIMs, and the phase shifts of UAV-SIMs, aiming to maximize the network capacity. Due to the non-convexity and NP-hardness of USBJOP, we decompose it into three sub-optimization problems, which are the association between UAV-SIMs and users optimization problem (AUUOP), the UAV location optimization problem (ULOP), and the UAV-SIM phase shifts optimization problem (USPSOP). Then, these three sub-optimization problems are solved by an alternating optimization (AO) strategy. Specifically, AUUOP and ULOP are transformed to a convex form and then solved by the CVX tool, while we employ a layer-by-layer iterative optimization method for USPSOP. Simulation results verify the effectiveness of the proposed strategy under different simulation setups.

Problem

• Optimize UAV-mounted SIMs for enhanced communication performance
• Jointly design user association, UAV locations, and phase shifts
• Maximize network capacity via decomposed alternating optimization

Innovation

• UAV-mounted SIMs enhance mobile communication performance
• Joint optimization of association, location, and phase shifts
• Alternating optimization strategy solves decomposed sub-problems