The widespread adoption of Reconfigurable Intelligent Surfaces (RISs) in future practical wireless systems is critically dependent on the integration of the RIS into higher-layer protocols beyond the physical (PHY) one, an issue that has received minimal attention in the research literature. In light of this, we consider a classical random access (RA) problem, where uncoordinated users' equipment (UEs) transmit sporadically to an access point (AP). Differently from previous works, we ponder how a RIS can be integrated into the design of new medium access control (MAC) layer protocols to solve such a problem. We consider that the AP is able to control a RIS to change how its reflective elements are configured, namely, the RIS configurations. Thus, the RIS can be opportunistically controlled to favor the transmission of some of the UEs without the need to explicitly perform channel estimation (CHEST). We embrace this observation and propose a RIS-assisted RA protocol comprised of two modules: Channel Oracle and Access. During channel oracle, the UEs learn how the RIS configurations affect their channel conditions. During the access, the UEs tailor their access policies using the channel oracle knowledge. Our proposed RIS-assisted protocol is able to increase the expected throughput by approximately 60% in comparison to the slotted ALOHA (S-ALOHA) protocol.

翻译：可重构智能表面（RIS）在未来实际无线系统中的广泛应用关键取决于其与物理层（PHY）以上高层协议的集成，而这一议题在现有研究文献中受到的关注极少。基于此，我们考虑一个经典的随机接入（RA）问题，其中无协调的用户设备（UE）向接入点（AP）间歇性传输数据。与以往研究不同，我们探究如何将RIS融入新型媒体接入控制（MAC）层协议设计以解决该问题。我们认为AP能够控制RIS改变其反射元件配置（即RIS配置）。因此，RIS可以被机会性地控制以有利于某些UE的传输，而无需显式执行信道估计（CHEST）。基于这一观察，我们提出一种由信道先知和接入两个模块组成的RIS辅助RA协议。在信道先知阶段，UE学习RIS配置如何影响其信道条件；在接入阶段，UE利用信道先知知识调整其接入策略。与分隙ALOHA（S-ALOHA）协议相比，我们提出的RIS辅助协议能够将期望吞吐量提升约60%。