Introduction
Multi-antenna technology with the associated multiple-input multiple-output (MIMO) techniques has been at the heart of modern communication and radar sensing systems. However, research and implementations over the past two decades always consider antenna arrays with fixed antenna positions and orientations, which fundamentally restrict the performance achievable with the multi-antenna technology. Since 2023, we have been studying a novel technique, which is now widely known as the rotatable antenna array (RAA), to transcend conventional multi-antenna approaches by intelligently adjusting the antenna orientations and exploiting the resulting favorable channel conditions in the angular domain to improve communication and sensing.
RAA bears some similarity with an earlier idea, namely the movable antenna (MA), in the sense that both rely on (electro-)mechanical movements of the antennas to reconfigure channel conditions. The difference lies in that MAs were initially proposed to adjust the positions, rather than orientations, of the antenna elements in the array. Recently, there are also interests in combining the ideas behind RAA and MA into the so-called 6D MAs. However, I personally consider it a crucial challenge to come up with practical hardware designs for e.g. antenna feeder of MAs. Moreover, how to address the side effects like mutual coupling and grating lobes associated with changing positions of antenna elements poses another challenge. In contrast, RAA naturally avoids these obstacles by design.
RAA for Communication
1) Joint Beamforming and Rotation Optimization
L. Xiang, F. Pei, and A. Klein, "Joint Optimization of Beamforming and 3D Array Steering for Multi-antenna UAV Communications", in Proc. IEEE WCNC, Dubai, United Arab Emirates, Apr. 2024.
2) Energy Consumption Modeling and Energy Efficiency Maximization
L. Xiang, X. Zhu, F. Pei, and D. W. K. Ng, "Energy-Efficient Dynamic Array-Steering and Beamforming for UAV-Aided Communications", in Proc. IEEE Globecom, Cape Town, South Africa, Dec. 2024.
3) Discrete Rotation Trajectory and User Scheduling Optimization
B. Yilmaz, A. Klein, and L. Xiang, "Completion Time Minimization for UAV-aided Communications with Rotatable Dipole Array", in Proc. IEEE ICC, Montreal, Canada, Jun. 2025.
4) RAA-Enabled Massive MIMO
X. Zhang, L. Xiang, J. Wang, X. Gao, D. W. K. Ng, and R. Schober, "Rotatable Antenna Array Enabled UAV mmWave Massive MIMO Communication", accepted for publication in IEEE Transactions on Communications, Sep. 2025.
RAA for Mono- and Bi-Static ISAC
F. Pei, L. Xiang, and A. Klein, "Joint Optimization of Beamforming and 3D Array-Steering for UAV-Aided ISAC", in Proc. IEEE ICC, Denver, Colorado, Jun. 2024.
F. Pei, L. Xiang, and A. Klein, "Transmit Beamforming and Array Steering Optimization for UAV-Aided Bistatic ISAC", in Proc. IEEE Globecom, Cape Town, South Africa, Dec. 2024.
F. Pei, A. Klein, and L. Xiang, "UAV-Aided ISAC with A Rotatable Dipole Array: Joint Beamforming and Steering Optimization", in Proc. ITG SCC, Karsruhe, Germany, Mar. 2025.