This work discusses the optimal reconfigurable intelligent surface placement in highly-directional millimeter wave links. In particular, we present a novel system model that takes into account the relationship between the transmission beam footprint at the RIS plane and the RIS size. Subsequently, based on the model we derive the end-to-end expression of the received signal power and, furthermore, provide approximate closed-form expressions in the case that the RIS size is either much smaller or at least equal to the transmission beam footprint. Moreover, building upon the expressions, we derive the optimal RIS placement that maximizes the end-to-end signal-to-noise ratio. Finally, we substantiate the analytical findings by means of simulations, which reveal important trends regarding the optimal RIS placement according to the system parameters.

中文翻译：

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毫米波网络中的可重构智能表面最佳布局

这项工作讨论了在高度方向性毫米波链接中的最佳可重构智能表面放置。特别是，我们提出了一种新颖的系统模型，该模型考虑了RIS平面处的传输束足迹与RIS大小之间的关系。随后，基于该模型，我们得出接收信号功率的端到端表达式，此外，在RIS大小小得多或至少等于传输波束足迹的情况下，提供近似的封闭式表达式。此外，基于这些表达式，我们得出了最佳的RIS位置，该位置可以最大化端到端的信噪比。最后，我们通过仿真证实分析结果，这些仿真结果揭示了根据系统参数优化RIS放置的重要趋势。