Hybrid Backscatter NOMA Under Imperfect CSI and Hardware Impairment

Abstract

Wireless-powered relaying with backscatter assistance is a promising technique to increase the coverage of self-sustainable energy-constrained devices with improved energy efficiency. In this letter, we propose a non-orthogonal multiple access (NOMA) based coordinated direct and relay transmission system, which utilizes a hybrid backscatter relay. The hybrid backscatter relay consists of passive information transmission via backscatter, energy harvesting (EH), and active information reception. We present a novel and simple hybrid protocol where the relay operates in EH mode and the active mode in the first phase, whereas in the second phase, the relay operates in passive mode. The paper investigates the outage probability of the backscatter NOMA systems, considering realistic assumptions of nonlinear EH, channel estimation errors, and residual hardware impairments. Moreover, to gain deeper insights into the considered system, asymptotic outage probability, system throughput, and energy efficiency are derived. Finally, the Monte Carlo simulations verifies correctness of the theoretical analysis. IEEE