Future Internet-of-Things (IoT) has high demand for energy-saving communications, especially in remote areas and smart cities. To meet this demand, we propose novel Unmanned Aerial Vehicle-assisted backscatter communications, where a UAV first collects data from multiple terrestrial backscattering tags via time division multiple access, and then flies into the coverage region of a terrestrial base station to upload its collected data to its associated base station.To determine the optimal UAV data collection location, we first analyze the system average outage probability, and then optimize the energy efficiency with the optimal backscattering location through Golden Section method under UAV energy constraint. Our analytical and simulation results illustrate that there is a trade-off between UAV data collection location and the outage probability, and the optimal UAV data collection location to achieve maximum energy efficiency needs to be closer to the tags for lower UAV transmit power.
Index TermsUAV, backscatter communications, energy efficiency, optimal UAV data collection location.
I. INTRODUCTIONBackscatter communication is a promising technology for future IoT networks to link a huge number of smart devices in various applications, including industrial automation, precision agriculture, and smart cities [1,2]. In ambient backscatter systems [3], ambient radio frequency (RF) energy, such as TV, WiFi and cellular signals, is harvested as the only power source for tag operations. Since the available ambient energy is limited, its communication range is commonly in the range of a few meters, hindering its extensive field applications [4]. In order to extend its communication range, bistatic architecture with dedicated RF power sources [4][5][6] is proposed, where a nearby signal generator is exploited to create a RF carrier that, after being modulated by the tags, is able to convey information to readers located hundreds or even thousands of meters away. Specifically, in [4], their Manuscript