Two-Ways Transmission Time Allocation Algorithm for Trapped User Based on SWIPT-TS

‍ ‍This paper proposes a relay cooperative transmission method for trapped user based on SWIPT energy harvesting to solve the problem of communication interruption between trapped user and the outside world due to mobile terminal cannot be charged in disaster scenarios. In the relay system， the trapped user is the source node， and the neighboring user terminals are randomly distributed between it and the base station and serve as relay nodes to assist the trapped user to communicate with the base station. In addition， SWIPT-TS method is adopted to charge the trapped users. Under the constraints of harvested energy by trapped user and system downlink rate， the optimization problem of maximum uplink available rate is established. By analyzing the duality of two-hop transmission and using Lambert W function， a relay selection and time allocation algorithm based on maximum uplink available rate is proposed. The solution of the algorithm proposed in this paper is closed-form， so the complexity is low. Simulation results show that the proposed relay selection and time allocation algorithm in this paper can provide energy for trapped user and improve data transmission rate.