Modeling and Optimization for Rotatable Antenna Enabled Wireless Communication

TL;DR

This work proposes a rotatable antenna (RA) architecture as a simplified six-dimensional movable antenna (6DMA) to leverage additional spatial degrees of freedom in uplink MIMO. For a single-user, free-space link, the authors derive closed-form deflection angles under maximum-ratio combining (MRC) and provide an SNR upper bound, illustrating orientation toward the user maximizes channel power. In the general multi-user, multi-path setting, they develop an alternating-optimization (AO) framework that jointly optimizes receive beamforming and RA deflections, casting the angle subproblem as a pointing-vector problem solved via successive convex approximation (SCA). Simulations show the RA-enabled system with optimized deflections significantly outperforms fixed-angle, isotropic, and randomly-oriented benchmarks, highlighting practical gains for 6G-like networks with enhanced spatial adaptability.

Abstract

Fluid antenna system (FAS)/movable antenna (MA) has emerged as a promising technology to fully exploit the spatial degrees of freedom (DoFs). In this paper, we propose a new rotatable antenna (RA) model, as a simplified implementation of six-dimensional movable antenna (6DMA), to improve the performance of wireless communication systems. Different from conventional fixed antenna, the proposed RA system can independently and flexibly change the three-dimensional (3D) orientation/boresight of each antenna by adjusting its deflection angles to achieve desired channel realizations. Specifically, we study an RA-enabled uplink communication system, where the receive beamforming and the deflection angles of all RAs are jointly optimized to maximize the minimum signal-to-interference-plus-noise ratio (SINR) among all the users. In the special single-user and free-space propagation setup, the optimal deflection angles are derived in closed form with the maximum-ratio combining (MRC) beamformer applied at the base station (BS). In the general multi-user and multi-path setup, we propose an alternating optimization (AO) algorithm to alternately optimize the receive beamforming and the deflection angles in an iterative manner. Simulation results are provided to demonstrate that the proposed RA-enabled system can significantly outperform other benchmark schemes.

Figures (6)

• Figure 1: An RA-enabled uplink communication system.
• Figure 2: Illustration of deflection angles and gain pattern of RA $n$.
• Figure 3: Receive SNRs obtained by different schemes versus the number of RAs $\bar{N} = N_y = N_z$ for the single-user system with $\varphi =$ 0.
• Figure 4: Receive SNRs obtained by different schemes versus the azimuth angle of the user $\psi$ for the single-user system with $N_y$ = $N_z$ = 501.
• Figure 5: Minimum receive SINRs obtained by different schemes versus the transmit SNR $\bar{P}$ for the multi-user system with $K =$ 4.