Joint Waveform Design and Detection in Symbiotic Ambient Backscatter NOMA Systems

Nonorthogonal multiple access (NOMA) and symbiotic ambient backscatter communications (AmBCs) are both considered promising technologies for beyond 5G mobile communication technology by enabling low-powered and spectrum-efficient access in large-scale Internet of Things. In this article, we investigate the uplink symbiotic communication in AmBC enabled NOMA system. In contrast with existing works, we assume the carrier transmitter (CT) transmits information while providing energy to the backscatter devices (BDs), which improves the energy efficiency. However, the signal power transmitted by the CT to integrated receiver (IR) through the direct link is much larger than the signal reflected by the BD, which can seriously affect the detection of the reflected signal by BD. Therefore, we jointly design the signal waveforms of CT and BDs, and propose a multiuser blind detection algorithm based on interference cancellation at IR. The simulation results demonstrate that the proposed multiuser detection algorithm achieves improved performance even the active BD number is unknown or without direct link.