Backscatter-Enabled NOMA for Future 6G Systems: A New Optimization Framework under Imperfect SIC

This paper proposes a new optimization framework for power-domain non-orthogonal multiple access (PD-NOMA) ambient backscatter communication (AmBC) system with imperfect successive interference cancellation (SIC) decoding. In particular, we jointly optimize the transmit power of the source and the reflection coefficient of the backscatter tag to enhance the sum-rate of the system. Closed-form solutions are derived for the considered joint optimization problem via iteratively computing the Lagrange multipliers by the sub-gradient method. Simulation results validate the superiority of the proposed joint optimization framework over other benchmark frameworks, namely suboptimal PD-NOMA AmBC, optimal pure PD-NOMA, and orthogonal multiple access.