Mechanical Power Modeling and Energy Efficiency Maximization for Movable Antenna Systems

TL;DR

This paper addresses the energy efficiency (EE) of movable antenna (MA) systems where antenna movement incurs mechanical power. It develops a fundamental power consumption model for a stepper-motor-driven MA and formulates EE optimization over the MA destination $x_t$, moving speed $v$, and transmit power $P$, revealing that EE increases with moving speed and is maximized at $v_{\max}$. The solution combines a semi-closed-form transmit-power update via the Dinkelbach algorithm with a full enumeration over discrete MA positions, achieving a tractable approach with complexity $\mathcal{O}(J_x I_1)$. Numerical results show the MA can substantially outperform fixed-position antennas in EE, with gains dependent on array size, channel coherence time, and channel richness, thereby offering a hardware-aware pathway to improve EE in MA-enabled networks.

Abstract

Movable antennas (MAs) have recently garnered significant attention in wireless communications due to their capability to reshape wireless channels via local antenna movement within a confined region. However, to achieve accurate antenna movement, MA drivers introduce non-negligible mechanical power consumption, rendering energy efficiency (EE) optimization more critical compared to conventional fixed-position antenna (FPA) systems. To address this problem, we develop in this paper a fundamental power consumption model for stepper motor-driven MA systems by resorting to basic electric motor theory. Based on this model, we formulate an EE maximization problem by jointly optimizing an MA's position, moving speed, and transmit power. However, this problem is difficult to solve optimally due to the intricate relationship between the mechanical power consumption and the design variables. To tackle this issue, we first uncover a hidden monotonicity of the EE performance with respect to the MA's moving speed. Then, we apply the Dinkelbach algorithm to obtain the optimal transmit power in a semi-closed form for any given MA position, followed by an enumeration to determine the optimal MA position. Numerical results demonstrate that despite the additional mechanical power consumption, the MA system can outperform the conventional FPA system in terms of EE.

Figures (9)

• Figure 1: Stepper motor-driven MA system.
• Figure 2: Two-stage transmission protocol in MA systems.
• Figure 3: (a) Pull-out torque; (b) Output power versus the angular speed of the stepper motor.
• Figure 4: EE performance of the proposed algorithm versus the MA's moving speed.
• Figure 5: EE performance versus the normalized size of the transmit array.