Energy Efficient Multiple Access Designs for Wireless-Powered Backscatter Communication: WPT-OMA or BAC-NOMA?

This paper investigates energy efficient multiple access designs for a wireless-powered backscatter communication (BackCom) system. Specifically, two energy and spectrally transmission strategies, namely wireless power transfer aided orthogonal multiple access (WPT-OMA) and backscatter communication aided non-orthogonal multiple access (BAC-NOMA), are proposed to encourage energy and spectrum cooperation among devices for overall energy minimization. A unified resource allocation problem of jointly optimizing time allocation, beamforming vectors, BackCom reflection coefficients, and device transmit power is formulated and solved by an efficient optimization algorithm. Simulation results are provided to compare the performance of the proposed schemes and demonstrate their advantage in terms of overall energy minimization over the benchmark schemes.