A Wireless-Powered Relaying System with Energy Buffer for Implant WBAN

Wireless body area networks (WBANs) can provide continuous monitoring of human biological signals. Due to the limited energy of the sensors, wireless powered system has been adopted to prolong network lifetime for implant WBANs. In this paper, we propose an energy buffer aided wireless-powered relaying system for self-sustainable implant WBAN, which includes an implant device, a wearable device with an energy buffer and an off-body access point (AP). In the downlink, the wearable device harvests energy that is stored in the energy buffer from a radio-frequency signal broadcasted by the AP and provides energy supply via wireless energy transfer to the implant device. In the uplink, the implant device uses harvested energy to transmit its collected data to the wearable device. Then the wearable device uses the stored energy to decode and forward the data to the AP. We investigate two transmission policies for the wearable device, namely best-effort policy (BEP) and on-off policy (OOP). We derive the limiting distribution of the energy for both the BEP and OOP, and the performance expressions in terms of the outage probability and average throughput. Simulation results are presented to validate the analytical expressions and provide some useful insights.