  Data collection in massive Internet of Things networks requires novel and
flexible methods. Unmanned aerial vehicles (UAVs) are foreseen as a means to
collect data rapidly even in remote areas without static telecommunication
infrastructure. To this direction, UAV-mounted reconfigurable intelligent
surfaces (RISs) aid in reducing the hardware requirements and signal processing
complexity at the UAV side, while increasing the energy efficiency and
reliabilityof the network. Hence, in this paper, we propose the utilization of
a UAV-mounted RIS for data collection and study the coverage probability in
such networks. Additionally, we propose a novel medium access control protocol
based on slotted ALOHA and Code Combining to handle the communication of
multiple sensors. To account for the crucial energy issue in UAVs, we devise an
energy model that considers both the UAV and the RIS weight, as well as the
environmental conditions and the UAV velocity. Finally, we characterize the
performance of the proposed data collection scheme by analyzing the average
throughput and the average data per flight, while providing useful insights for
the design of such networks.
