Interference Exploitation for Ambient Backscatter Communication Networks via Symbol Level Precoding

Although ambient backscatter communications (AmBCs) are capable of achieving high spectrum- and energy-efficiency in numerous cutting-edge Internet-of-Things applications, the legacy user devices (UDs) will suffer from severe interference caused by the backscatter device (BD). In this letter, we leverage the symbol level precoding (SLP) technique to convert the harmful interference perceived at the UD into a useful signal, thereby improving the communication quality of the legacy users. Specifically, we consider an AmBC system where one access point (AP) simultaneously transmits information to all UDs and receives the BD’s reflected signal. To reduce the power consumption of the AP, we formulate a joint transmit SLP and receive beamforming optimization problem while guaranteeing the quality of service of all UDs and the BD. An efficient algorithm is proposed to solve the formulated non-convex problem. Simulation results show that the proposed SLP scheme can achieve superior performance over conventional beamforming schemes in the sense of saving power consumption.