An intelligent reflecting surface (IRS) is an emerging technology in the next-generation (B5G and 6G) wireless communications with the aim of improving the spectral/energy efficiency of the wireless networks. In this paper, we focus on multiple IRS-aided multiuser multiple-input single-output (MISO) downlink network, where each IRS is deployed near to the cell boundary of the cellular network in order to help the downlink transmission to the cell-edge users. To achieve the significant performance benefits provided by the rate-splitting (RS) transmission in multiuser scenario, two-layer hierarchical rate splitting (2L-HRS) technique is deployed at the base station (BS) to serve all the users. Furthermore, we propose an On-Off scheme for controlling the IRSs with practical phase shifts. In order to analyze the performance of the users, we derive the closed-form expressions of outage probability for both cell-edge users and near users. By extensive Monte Carlo simulations, we demonstrate that the proposed design framework outperforms the corresponding one-layer RS (1L-RS), the multiuser linear precoding (MU-LP) and 2L-HRS without IRS. In addition, we reveal the advantages of introducing RS-based IRS in improving the cell-users’ performance. The impact of channel estimation errors due to imperfect channel state information, and the various network’s parameters, such as the number of reflecting elements and the number of cell-users, on the network performance is demonstrated.

中文翻译：

---

智能反射面辅助下行多用户MISO通信的分层速率划分分析

智能反射面（IRS）是下一代（B5G和6G）无线通信中的新兴技术，旨在提高无线网络的频谱/能量效率。在本文中，我们专注于多个IRS辅助的多用户多输入单输出（MISO）下行链路网络，其中，每个IRS都部署在靠近蜂窝网络的小区边界处，以帮助下行链路传输到小区边缘用户。为了在多用户场景中实现速率拆分（R​​S）传输所提供的显着性能优势，在基站（BS）部署了两层分层速率拆分（2L-HRS）技术来为所有用户提供服务。此外，我们建议开关控制具有实际相移的IRS的方案。为了分析用户的性能，我们导出了小区边缘用户和附近用户的中断概率的封闭形式。通过广泛的蒙特卡洛模拟，我们证明了所提出的设计框架优于相应的单层RS（1L-RS），多用户线性预编码（MU-LP）和不带IRS的2L-HRS。此外，我们揭示了引入基于RS的IRS在改善小区用户性能方面的优势。演示了由于不完善的信道状态信息以及各种网络参数（如反射元素的数量和小区用户的数量）导致的信道估计错误对网络性能的影响。