LAUSR

Ambient backscatter is an intriguing technology that enables ultra-low-power devices to communicate with each other by reflecting and modulating the existing pervasive RF signals, e.g., TV signals, WIFI signals, cellular signals, etc. This paper works on the mathematical modeling and performance analysis of ambient backscatter communications (AmBackComs) underlying cellular networks for Internet of Things applications. Based on the time switching (TS) and power splitting (PS) receiver architectures, two operating schemes are employed to enable energy harvesting and ambient backscattering at the ambient backscatter (AB) transmitter. In order to maximize the outage capacity for the AB transmitters, we formulate two optimization problems optimizing the TS and PS ratios. Two schemes with low complexity are proposed to obtain the near-optimal outage performance. Considering the coexistence of the AmBackComs and cellular downlink transmissions, successful transmission probabilities for AB transmitters and cellular downlink transmissions are both derived for the TS and PS schemes and provide insights on how various system parameters, such as the TS ratio, the PS ratio, the density of base stations (BSs)/AB transmitters, etc., impact the system performance. Numerical results show that the outage capacity for AmBackComs can be significantly improved by selecting a proper TS/PS ratio and our proposed schemes can achieve near-optimal outage capacities. The study also shows that many more ultra-low-power devices users can be connected via the proposed scheme at a cost of a slightly reduced overall network capacity.