Aerial Reconfigurable Intelligent Surface-Assisted Channel Modeling Incorporating the Effect of UAV Fluctuations

Aerial reconfigurable intelligent surface (ARIS) system refers to a novel transmission scheme, in which an RIS is mounted on aerial platforms, such as unmanned aerial vehicles (UAVs), to achieve intelligent signal reflection over the air. Compared to terrestrial RIS, ARIS extends the service area and enables panoramic signal reflections. Benefiting from its high altitude, the UAV is more likely to establish line-of-sight (LoS) connections with ground nodes. However, implementing ARIS systems is challenging. Owing to atmospheric turbulence or propeller rotations, the UAV can experience random fluctuations, which lead to misalignment of reflected signal phases. In this letter, a three-dimensional (3D) ARIS-assisted channel model is proposed, in which UAV fluctuations are described by random processes. Statistics including temporal correlation function (TCF), Doppler power spectral density (PSD), and ergodic achievable rate are obtained. Results show that even for a minor vibration, the UAV wobbling can introduce extra Doppler frequency components, and significantly reduce the temporal correlation and achievable rate of the ARIS-assisted channel when systems operating at high frequency bands.