This work discusses the optimal placement of a reconfigurable intelligent surface (RIS) in a millimeter wave (mmWave) point-to-point link. In particular, we present a novel system model that takes into account the relationship between the transmission beam footprint size at the RIS plane and the RIS size. Moreover, we present the theoretical framework that quantifies the RIS gain loss in the case that the transmission beam footprint in the RIS plane is smaller than the RIS size, and the beam waste for the case in which the transmission beam footprint in the RIS plane is larger than the RIS size, by extracting closed-form expressions for the received power and the end-to-end signal-to-noise-ratio (SNR) for both cases. Subsequently, building upon the expressions, we provide SNR maximization policies for both cases. Finally, we perform a comparison, in terms end-to-end SNR, between the RIS-aided link and its relay-aided counterpart.

中文翻译：

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毫米波网络中的可重构智能表面优化布局

这项工作讨论了可重构智能表面 (RIS) 在毫米波 (mmWave) 点对点链路中的最佳放置。特别是，我们提出了一种新的系统模型，该模型考虑了 RIS 平面上的传输波束足迹大小与 RIS 大小之间的关系。此外，我们提出了在 RIS 平面中传输波束足迹小于 RIS 尺寸的情况下量化 RIS 增益损失的理论框架，以及在 RIS 平面中传输波束足迹为通过提取两种情况下接收功率和端到端信噪比 (SNR) 的封闭式表达式，比 RIS 大小更大。随后，在表达式的基础上，我们为这两种情况提供了 SNR 最大化策略。最后，我们进行比较，