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Wireless Communication with Cross-Linked Rotatable Antenna Array: Architecture Design and Rotation Optimization

Ailing Zheng, Qingqing Wu, Ziyuan Zheng, Qiaoyan Peng, Yanze Zhu, Honghao Wang, Wen Chen, Guoying Zhang

TL;DR

Addressing the need for extra spatial degrees of freedom with manageable hardware cost, this paper proposes a cross-linked rotatable antenna (CL-RA) architecture and analyzes uplink multi-user performance under two rotation schemes. A joint optimization framework over receive beamforming and rotation angles is developed, using MMSE for beamforming, feasible-direction updates for continuous rotations, and a genetic algorithm for discrete angles. In the single-user case, an analytic solution shows CL-RA on a uniform linear array can match fully flexible orientation, while in the multi-user case an alternating-optimization approach yields near-ideal performance with a significant cost/save trade-off; element-level rotation outperforms panel-level rotation. Simulation results confirm the proposed schemes achieve substantial gains over fixed-direction antennas, with GA-based discrete angles offering practical near-optimal performance and providing design insights for scalable 6G-era deployments.

Abstract

Rotatable antenna (RA) technology can harness additional spatial degrees of freedom by enabling the dynamic three-dimensional orientation control of each antenna. Unfortunately, the hardware cost and control complexity of traditional RA systems is proportional to the number of RAs. To address the issue, we consider a cross-linked (CL) RA structure, which enables the coordinated rotation of multiple antennas, thereby offering a cost-effective solution. To evaluate the performance of the CL-RA array, we investigate a CL-RA-aided uplink system. Specifically, we first establish system models for both antenna element-level and antenna panel-level rotation. Then, we formulate a sum rate maximization problem by jointly optimizing the receive beamforming at the base station and the rotation angles. For the antenna element-level rotation, we derive the optimal solution of the CL-RA array under the single-user case. Subsequently, for two rotation schemes, we propose an alternating optimization algorithm to solve the formulated problem in the multi-user case, where the receive beamforming and the antenna rotation angles are obtained by applying the minimum mean square error method and feasible direction method, respectively. In addition, considering the hardware limitations, we apply the genetic algorithm to address the discrete rotation angles selection problem. Simulation results show that by carefully designing the row-column partition scheme, the performance of the CL-RA architecture is quite close to that of the flexible antenna orientation scheme. Moreover, the CL antenna element-level scheme surpasses the CL antenna panel-level scheme by 25% and delivers a 128% performance improvement over conventional fixed-direction antennas.

Wireless Communication with Cross-Linked Rotatable Antenna Array: Architecture Design and Rotation Optimization

TL;DR

Addressing the need for extra spatial degrees of freedom with manageable hardware cost, this paper proposes a cross-linked rotatable antenna (CL-RA) architecture and analyzes uplink multi-user performance under two rotation schemes. A joint optimization framework over receive beamforming and rotation angles is developed, using MMSE for beamforming, feasible-direction updates for continuous rotations, and a genetic algorithm for discrete angles. In the single-user case, an analytic solution shows CL-RA on a uniform linear array can match fully flexible orientation, while in the multi-user case an alternating-optimization approach yields near-ideal performance with a significant cost/save trade-off; element-level rotation outperforms panel-level rotation. Simulation results confirm the proposed schemes achieve substantial gains over fixed-direction antennas, with GA-based discrete angles offering practical near-optimal performance and providing design insights for scalable 6G-era deployments.

Abstract

Rotatable antenna (RA) technology can harness additional spatial degrees of freedom by enabling the dynamic three-dimensional orientation control of each antenna. Unfortunately, the hardware cost and control complexity of traditional RA systems is proportional to the number of RAs. To address the issue, we consider a cross-linked (CL) RA structure, which enables the coordinated rotation of multiple antennas, thereby offering a cost-effective solution. To evaluate the performance of the CL-RA array, we investigate a CL-RA-aided uplink system. Specifically, we first establish system models for both antenna element-level and antenna panel-level rotation. Then, we formulate a sum rate maximization problem by jointly optimizing the receive beamforming at the base station and the rotation angles. For the antenna element-level rotation, we derive the optimal solution of the CL-RA array under the single-user case. Subsequently, for two rotation schemes, we propose an alternating optimization algorithm to solve the formulated problem in the multi-user case, where the receive beamforming and the antenna rotation angles are obtained by applying the minimum mean square error method and feasible direction method, respectively. In addition, considering the hardware limitations, we apply the genetic algorithm to address the discrete rotation angles selection problem. Simulation results show that by carefully designing the row-column partition scheme, the performance of the CL-RA architecture is quite close to that of the flexible antenna orientation scheme. Moreover, the CL antenna element-level scheme surpasses the CL antenna panel-level scheme by 25% and delivers a 128% performance improvement over conventional fixed-direction antennas.
Paper Structure (27 sections, 2 theorems, 64 equations, 10 figures, 1 table, 2 algorithms)

This paper contains 27 sections, 2 theorems, 64 equations, 10 figures, 1 table, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model and Problem Formulation
  3. CL-RA Architecture
  4. Antenna Element Rotation-based System
  5. Channel Model
  6. Signal Model
  7. Problem Formulation
  8. Antenna Panel Rotation-based System
  9. Channel Model
  10. Signal Model
  11. Problem Formulation
  12. Feasible Rotation Angle Range Analysis
  13. Single-User Case
  14. Multi-User Case
  15. Proposed Algorithm for Antenna Optimization
  16. ...and 12 more sections

Key Result

Proposition 1

To meet the physical constraints, the panel $b$ should ensure: where $\forall j \neq b, j \in \mathcal{B}$ and $j = (m_j-1)N+n_j$ and $b=(m-1)N+n$.

Figures (10)

  • Figure 1: The considered CL-RA architecture.
  • Figure 2: An RA-enabled uplink system.
  • Figure 3: Illustration of directional gain and rotation angles of antenna panel. If there is only one antenna on the panel, then the normal vector is replaced by the main lobe boresight of the antenna.
  • Figure 4: Convergence behavior of the proposed algorithms.
  • Figure 5: Sum rate vs. the maximum transmit power of each user.
  • ...and 5 more figures

Theorems & Definitions (5)

  • Proposition 1
  • proof
  • Remark 1
  • Proposition 2
  • proof