Time Allocation for RIS-Aided Wireless Power Communication Networks in Disaster Sceneio

Wireless power communication networks(WPCN) can be used in disaster scenarios to provide reliable communication and power supply, helping to improve disaster response efforts. Using reconfigurable intelligent surface(RIS) to assist WPCN can improve signal quality and extend the transmission distance where traditional infrastructure is damaged or unavailable. However, it is important to transmit an emergency response in disaster scenarios as soon as possible, which is little consideration before. In this paper, we propose a time allocation scheme whose key idea is to find the minimum time for disaster scenario information dissemination while optimizing the time threshold for downlink energy harvest to confirm uplink information transmit requirements. We propose a new optimization problem of minimizing the transmit time duration by jointly optimizing the RIS shifts, downlink time for energy havest, uplink time and power for information transmission, subject to the constraints on harvesting power at user, the phase shift module 1, and the minimum Quality of Service(QoS) constraints. We find that our proposed optimization problem is multi variables and non-convex. To solve this, we apply alternating optimization to divide it into two sub-problems. Then Successive Convex Approximation and penalty-based algorithm are introduced to solve the sub-problems, respectively. Simulation results show that we can find the least time for information transmission in disaster scenarios.