Beamforming Design for BackCom Assisted NOMA Systems

Backscatter communication (BackCom) assisted non-orthogonal multiple access (NOMA) has received significant attention recently and can be applied to Internet of Things (IoT). The BackCom system aims to realize energy cooperation among the devices. NOMA is a well-known technique to enable spectrum cooperation among the devices, which motivates the combination of the two techniques. This letter focuses on the beamforming design in BackCom NOMA networks, where an uplink data rate maximization problem is formulated with a constraint to guarantee the downlink user's quality of service requirements. As the formulated optimization problem is not concave, semidefinite relaxation (SDR) is applied to transform the considered problem into a concave form which can be solved efficiently. Simulation results are provided to demonstrate that the proposed algorithm can achieve superior performance over the considered benchmarking scheme.