Hybrid FS/PS SWIPT based Backscatter Communication for Internet of Things

In this paper, we propose a novel uplink backscatter communication scheme which exploits hybrid frequency-splitting and power-splitting (FS/PS) simultaneous wireless information and power transfer (SWIPT) signaling in the downlink for wireless-powered sensor networks. In the hybrid FS/PS SWIPT based backscatter communication, a tag reflects the unmodulated high-power continuous wave (CW) signal, which is intended for WPT in the downlink, to send sensory information back to the hybrid access point (H-AP). We formulate the problem to find the maximum distance coverage between the H-AP and tag by jointly adjusting the power-splitting ratio between the power signal and information signal at the H-AP and the reflection/absorption ratio at the tag. We then focus on the uplink communication scenario which aims to maximize the received signal-to-noise ratio (SNR) at the H-AP while meeting the energy-causality constraint for self-powering a battery-free tag. To show its superiority, we compare the hybrid FS/PS SWIPT based backscatter communication with the purely PS SWIPT based one, in terms of the coverage and spectral efficiency.