Fundamental Tradeoff in Movable Antenna Systems: How Long to Move Before Transmission?

2026-04-22

AI Summary

This work addresses the fundamental trade-off between antenna mobility and effective throughput in multiuser downlink systems with reconfigurable mobile antennas, where antenna movement improves channel conditions but incurs time overhead and Doppler-induced distortion. To maximize throughput, the paper jointly optimizes the duration and trajectory of antenna motion, proposing a fitting method based on a small number of sampled channel realizations to derive a closed-form expression for achievable rates. A closed-form threshold on the maximum antenna velocity is further established: below this threshold, the optimal strategy is to remain stationary. The proposed approach combines one-dimensional search with non-convex optimization and is validated in a two-antenna, two-user scenario, demonstrating significant throughput gains and substantially reduced computational complexity.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Intelligent Robots: Motion and Path Planning

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

The movable antenna (MA) technology enables flexible reconfiguration of wireless channels through adaptive antenna deployment, offering significant potential for enhancing communication performance. However, antenna movement requires a certain duration within which communication may be compromised due to factors such as channel fluctuation and Doppler effect. This leads to a fundamental tradeoff: A longer movement duration allows antennas to reach more favorable positions for better channel conditions, but it inevitably reduces the time available for data transmission. To characterize the aforementioned tradeoff, we focus on the MAs-enabled multiuser downlink scenario, and jointly optimize the movement duration and antenna deployment at the base station to maximize the effective throughput. The formulated problem is highly non-convex. The general solutions require an one-dimensional search over movement durations, each with optimized antenna deployment. To reduce complexity, we propose a fitting method that samples only a few rate-duration pairs, yielding a closed-form expression that captures the rate trend and enables a favorable solution immediately. We further derive a closed-form condition on the maximum antenna movement speed: When the speed is below a certain threshold, the optimal strategy is to keep antennas stationary throughout the transmission period. The fundamental tradeoff and the effectiveness of the proposed solutions are examined in a special case with two MAs and two users. Finally, numerical simulations validate the efficacy of the proposed schemes.

Problem

• movable antenna
• movement duration
• throughput tradeoff
• channel reconfiguration
• communication performance

Innovation

• movable antenna
• fundamental tradeoff
• effective throughput
• non-convex optimization
• closed-form solution