具有过时信道状态信息的可重构智能表面：集中式与分布式部署
Reconfigurable Intelligent Surfaces with Outdated Channel State Information: Centralized vs. Distributed Deployments
摘要：
在本文中，我们调查的性能的RIS辅助无线通信系统受到过时的信道状态信息，可能会在近场和远场区域。特别地，我们考虑两种RIS部署策略：（i）集中式部署，其中所有反射元件都安装在单个RIS上，以及（ii）分布式部署，其中相同数量的反射元件放置在多个RIS上。对于这两种部署策略，我们推导出精确的封闭形式近似的遍历容量，我们引入严格的上限和下限的遍历容量，以获得有用的设计见解。通过分析发现，增加发射功率、Rician-K因子、信道状态信息的准确性和反射单元的数量有助于提高系统性能。此外，我们证明了集中式RIS辅助部署可以实现更高的遍历容量相比，分布式RIS辅助部署时，RIS位于基站附近或附近的用户。在不同的设置，另一方面，我们证明了分布式部署优于集中式部署。最后，分析结果进行了验证，使用Monte Carlo模拟。
英文摘要：
In this paper, we investigate the performance of an RIS-aided wireless communication system subject to outdated channel state information that may operate in both the near- and far-field regions. In particular, we take two RIS deployment strategies into consideration: (i) the centralized deployment, where all the reflecting elements are installed on a single RIS and (ii) the distributed deployment, where the same number of reflecting elements are placed on multiple RISs. For both deployment strategies, we derive accurate closed-form approximations for the ergodic capacity, and we introduce tight upper and lower bounds for the ergodic capacity to obtain useful design insights. From this analysis, we unveil that an increase of the transmit power, the Rician-K factor, the accuracy of the channel state information and the number of reflecting elements help improve the system performance. Moreover, we prove that the centralized RIS-aided deployment may achieve a higher ergodic capacity as compared with the distributed RIS-aided deployment when the RIS is located near the base station or near the user. In different setups, on the other hand, we prove that the distributed deployment outperforms the centralized deployment. Finally, the analytical results are verified by using Monte Carlo simulations.
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