In this paper, we study the performance of reconfigurable intelligent surfaces (RISs) in a multicell broadcast channel (BC) that employs improper Gaussian signaling (IGS) jointly with non-orthogonal multiple access (NOMA) to optimize either the minimum-weighted rate or the energy efficiency (EE) of the network. We show that although the RIS can significantly improve the system performance, it cannot mitigate interference completely, so we have to employ other interference-management techniques to further improve performance. We show that the proposed NOMA-based IGS scheme can substantially outperform proper Gaussian signaling (PGS) and IGS schemes that treat interference as noise (TIN) in particular when the number of users per cell is larger than the number of base station (BS) antennas (referred to as overloaded networks). In other words, IGS and NOMA complement to each other as interference management techniques in multicell RIS-assisted BCs. Furthermore, we consider three different feasibility sets for the RIS components showing that even a RIS with a small number of elements provides considerable gains for all the feasibility sets.

翻译：本文研究了在多小区广播信道中，可重构智能表面（RIS）与采用非正交多址接入（NOMA）的非适定高斯信号（IGS）联合使用时，如何优化网络的最小加权速率或能量效率（EE）性能。研究表明，尽管RIS能显著提升系统性能，但无法完全消除干扰，因此需采用其他干扰管理技术以进一步提高性能。我们证明，所提出的基于NOMA的IGS方案在性能上显著优于传统适定高斯信号（PGS）及将干扰视为噪声（TIN）的IGS方案，尤其当每小区用户数超过基站天线数（即过载网络）时更为明显。换言之，在RIS辅助的多小区广播信道中，IGS与NOMA作为干扰管理技术具有互补性。此外，我们考虑了三种不同的RIS组件可行集，结果表明即使仅有少量元件的RIS也能为所有可行集带来可观的性能增益。