Energy Buffer-Aided Wireless-Powered Relaying System for Self-Sustainable 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. The proposed system is composed of an off-body access point (AP) and many users, where an implant device is placed in body while a dual-mode wearable device with an energy buffer is attached on body for each user. In the downlink, the dual-mode wearable device simultaneously 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 adopts the stored energy to decode and forward the data to the AP in an orthogonal multiple access way. 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. Furthermore, the outage probability and average throughput of the proposed system with both the BEP and OOP are analyzed. Simulation results are presented to validate the analytical expressions and provide some useful insights.