基于大规模可重构智能表面的近远场混合信道模型

近来，可重构智能表面(RIS)作为一种全新的革命性技术引起了学术界和工业界的广泛关注。随着通信频率的提高以及RIS孔径的增大，RIS辅助无线通信的工作条件逐渐靠近天线的近场辐射模式，而非仅仅存在传统意义中的远场辐射。单独考虑远场或者近场的信道模型均无法准确刻画RIS辅助无线通信的传输特性，造成性能损失。针对此问题，该文梳理了大规模RIS辅助通信近场和远场信道模型，通过引入权重因子，构建了大规模RIS辅助无线通信场景下近远场混合信道模型。在此基础上，推导了近远场混合信道模型下系统的增益与损耗，并进行鲁棒性分析，仿真结果表明该混合模型带来的系统增益与模型鲁棒性均显著提升。

Near-far Field Hybrid Channel Model Based on Massive Reconfigurable Intelligent Surface

Recently, Reconfigurable Intelligent Surface (RIS) has attracted a lot of attention from both academia and industry as a new revolutionary technology. With the increase of communication frequency and the RIS elements, the operating conditions of RIS-assisted wireless communication are gradually approaching the near field radiation pattern of antennas, not just the existence of far field radiation in the traditional sense. Considering either far field or near field, the transmission characteristics of RIS-assisted wireless communication can not be portrayed accurately by the channel model, which results in a loss in performance. In order to solve the problem, a hybrid near-far field channel model is established for massive RIS-assisted communication in this paper by introducing a weighting factor. The gain, the loss and the robustness analysis of the hybrid system are derived in this paper. It is indicated that the hybrid model brings significant improvement in the gain of system and the robustness of model according to the simulation results.