Compared to traditional intelligent reflecting surfaces(IRS), aerial IRS (AIRS) has unique advantages, such as more flexible deployment and wider service coverage. However, modeling AIRS in the channel presents new challenges due to their mobility. In this paper, a three-dimensional (3D) wideband channel model for AIRS and IRS joint-assisted multiple-input multiple-output (MIMO) communication system is proposed, where considering the rotational degrees of freedom in three directions and the motion angles of AIRS in space. Based on the proposed model, the channel impulse response (CIR), correlation function, and channel capacity are derived, and several feasible joint phase shifts schemes for AIRS and IRS units are proposed. Simulation results show that the proposed model can capture the channel characteristics accurately, and the proposed phase shifts methods can effectively improve the channel statistical characteristics and increase the system capacity. Additionally, we observe that in certain scenarios, the paths involving the IRS and the line-of-sight (LoS) paths exhibit similar characteristics. These findings provide valuable insights for the future development of intelligent communication systems.

翻译：与传统智能反射面（IRS）相比，空中智能反射面（AIRS）具有部署更灵活、服务覆盖范围更广等独特优势。然而，由于AIRS具备移动性，为其建立信道模型带来了新挑战。本文针对AIRS与IRS联合辅助的多输入多输出（MIMO）通信系统，提出了一种三维（3D）宽带信道模型，其中考虑了AIRS在空间中三个方向的旋转自由度及运动角度。基于所提模型，推导了信道冲激响应（CIR）、相关函数及信道容量，并提出了若干可行的AIRS与IRS单元联合相移方案。仿真结果表明，所提模型能准确捕获信道特性，且所提相移方法可有效改善信道统计特性并提升系统容量。此外，我们观察到在某些场景中，涉及IRS的路径与视距（LoS）路径呈现相似特征。这些发现为未来智能通信系统的发展提供了重要见解。