Green Internet of Things (IoT) aims to enable a sustainable smart world by making energy efficiency (EE) the main performance indicator for IoT hardware and software. With respect to network design, this implies in developing energy-efficient communication protocols and network architectures adapted to the ubiquitousness of the IoT machine-type devices (MTDs) and the sporadic traffic generated by them, keeping a low power consumption at the MTDs-side. In this sense, reconfigurable intelligent surfaces (RISs) have presented the capacity of significantly improving the network coverage using mostly passive reflecting elements, drastically reducing the power expenditure. In this paper, we develop a realistic power consumption model and an expression for the overall system EE for RIS-aided IoT networks that adopt a two time-scale random access (RA) protocol to handle the uplink transmissions. Specifically, during each time slot of the RA protocol, the RIS covers a specific area of interest in the communication cell with a predefined set of phase-shift configurations, changing the channel qualities of the contending MTDs. Numerical results comparing the RA protocol performance reveal that access policies that exploit information of the channel qualities are suitable for green IoT networks, simultaneously attaining competitive EE and throughput combined with low power consumption at the MTDs-side.

翻译：绿色事物互联网(IoT)的目标是通过将能源效率(EE)作为IoT硬件和软件的主要业绩指标,使可持续智能世界成为可持续智能世界。在网络设计方面,这意味着要开发适合IoT机器类型设备(MTDs)和它们产生的零星流量的节能通信协议和网络结构,使之适应IoT机器类型设备(MTDs)的无处不在,保持MTDs一侧的低电耗。从这个意义上讲,可重新配置的智能表面(RIS)展示了大幅改进网络覆盖的能力,主要使用被动反映要素,大幅度降低了电力支出。在本文中,我们开发了现实的电力消费模式和整个系统EEE用于RIS辅助IoT网络的表达方式,采用两种时间尺度随机访问协议来处理上传传输。具体地说,在RA协议的每个时间段,RIS覆盖通信单元的特定兴趣领域,预先界定了分阶段配置,改变了对MTD的频道质量,大大降低了电力开支。我们把RAD-TD联合的结果与RAPRO公司低电路段的竞争性业绩同时显示,获取政策利用了绿色消费。</s>