Distributed Deep Reinforcement Learning-Based Power Control and Device Access for High-Speed Railway Networks With Symbiotic Radios

In this paper, we investigate a novel symbiotic radio (SR)-aided high-speed railway (HSR) wireless network, in which the Internet of Things (IoT) device, operating as a secondary transmitter, transmits its own information to the mobile relay (MR) on the HSR by backscattering radio frequency (RF) signals from the base station (BS). With the assistance of SR, the designed network facilitates the transmission of locally collected environmental sensing messages from the IoT network to the HSR, simultaneously enhancing the primary communication between the BS and MRs. Aiming to maximize the sum transmission rate of the primary and the IoT network, we focus on a joint power control and device access (JPCDA) problem. Specifically, each IoT device accesses the network through appropriate time slot selection and appropriate power control, thereby achieving satisfactory overall network performance. However, since the fast channel variations arising from the high mobility of HSRs make it impractical to acquire accurate channel state information (CSI), it is challenging to achieve an optimal resource allocation scheme. To address this challenge, we develop a distributed deep reinforcement learning (DRL)-based algorithm that utilizes historical CSI to infer real-time CSI for decision making. In particular, each computing unit of the agent performs action selection for only one IoT device at one time based on the current local observation information. Numerical results illustrate that our proposed algorithm outperforms other baselines, and still works effectively when the environment changes.