Joint Time Switching and Transmission Scheduling for Wireless-Powered Body Area Networks

Outfitting humans with on-body/in-body sensor nodes, wireless body area networks (WBANs) are positioned as the key technology to enhance future telehealth service. The newly emerged wireless power transfer (WPT) and energy harvesting (EH) technology provides a potential of continuous power supply for WBANs. Since the radio frequency (RF) signals can carry energy as well as information at the same time, the time switching between the WPT phase and the wireless information transfer (WIT) phase should be carefully scheduled. By considering a telehealth application scenario (in which multiple patients coexist in a ward and each of them is monitored by multiple sensor nodes), this paper proposes to allocate the duty cycles for the WPT and WIT phases and schedule the transmission time for the WIT links in a joint manner. First, a frame structure for simultaneous information and power transfer (SWIPT) is designed over the time-and-spectrum domain. With the aim to satisfy the minimum rate demands of all the sensor nodes, the optimal duty time for the WPT phase and the optimal transmission time for the WIT links are jointly found by using the convex optimization technique. Finally, a fast algorithm is developed to search the optimal solution by introducing an admission control. The simulation results show that the proposed algorithm can effectively exploit the broadcasting property of RF energy radiation. If the network load were controlled below a certain level, the rate demands of all the sensor nodes in the network can be satisfied.