In realistic cellular communication systems, multiple service providers will operate within different frequency ranges. Each serving cell, which is managed by a distinct service provider, is designed individually due to the orthogonal frequencies. However, when a reconfigurable intelligent surface (RIS) is deployed for a certain cell, the RIS still incurs reflective channels for the overall system since the RIS reflects signals across all frequency ranges. This may cause severe undesired performance degradation for the other cells unless the reflection coefficients are properly designed. To tackle this issue, by utilizing the Riemannian manifold optimization method, an RIS reflection coefficients design is proposed in this paper to maximize the performance improvements of the cell that deploys the RIS while minimizing the undesired performance degradation for the other cells simultaneously. Numerical results demonstrate that the proposed design can effectively balance the two objectives for practical scenarios.

翻译：在实际的蜂窝通信系统中，多个服务提供商将在不同的频段范围内运营。由于频率正交，每个由不同服务提供商管理的服务小区都是独立设计的。然而，当为某个小区部署可重构智能表面（RIS）时，由于RIS会反射所有频段的信号，它仍会对整个系统产生反射信道。除非反射系数经过恰当设计，否则这可能对其他小区造成严重的非期望性能下降。为解决此问题，本文利用黎曼流形优化方法，提出了一种RIS反射系数设计方案，旨在最大化部署RIS的小区的性能提升，同时最小化对其他小区的非期望性能下降。数值结果表明，所提出的设计能够有效平衡实际场景中的这两个目标。