A Novel 3D Non-Stationary Channel Model for Aerial Hybrid Reconfigurable Intelligent Surface-Assisted ISAC Systems

Aerial hybrid reconfigurable intelligent surface (AHRIS) -assisted integrated sensing and communication (ISAC) has recently emerged as a promising candidate for practical deployment in the sixth generation (6G) wireless networks. System design and gain rely heavily on accurately modeling of the underlying channel characteristics, which is challenging due to the high mobility of AHRIS and the unique properties of ISAC. This letter aims to propose a novel three-dimensional (3D) non-stationary geometry-based stochastic model (GBSM) for AHRIS-assisted ISAC systems. Firstly, a novel GBSM considering the non-stationarity caused by the unavoidable jitter of AHRIS and the correlations between sensing and communication channels is proposed. For the former, both the random jitter vector and the jitter factor are introduced to model the impacts of the jitter of AHRIS on its velocity vector. For the latter, the channel characteristics of sensing, including forward scattering and backward scattering, are introduced into the communication channel model, in which the non-line-of-sight (NLoS) transmission are divided into single-clusters scattering and twin-clusters scattering. Then, in order to create a favorable propagation environment and make full use of the channel information sensed by the AHRIS, two AHRIS phase-shift design methods based on sensing channels are proposed. Finally, the impacts of several factors, e.g., the AHRIS speed and jittery, AHRIS phase-shift design methods, AHRIS non-ideality and clusters distribution, on the statistical properties of the proposed channel model are studied, which include the spatial-temporal correlation function (STCF), Doppler power spectral density (PSD) and spectral efficiency. Numerical simulation results demonstrate that the proposed model can accurately capture the channel characteristics, thus providing valuable insights for the future deployment of AHRIS-assisted ISAC systems.