  In this manuscript, we propose an alternating optimization framework to
maximize the energy efficiency of a backscatter-enabled cooperative
Non-orthogonal multiple access (NOMA) system by optimizing the transmit power
of the source, power allocation coefficients (PAC), and power of the relay node
under imperfect successive interference cancellation (SIC) decoding. A
three-stage low-complexity energy-efficient alternating optimization algorithm
is introduced which optimizes the transmit power, PAC, and relay power by
considering the quality of service (QoS), power budget, and cooperation
constraints. Subsequently, a joint channel coding framework is introduced to
enhance the performance of far user which has no direct communication link with
the base station (BS) and has bad channel conditions. In the destination node,
the far user data is jointly decoded using a Sum-product algorithm (SPA) based
joint iterative decoder realized by jointly-designed Quasi-cyclic Low-density
parity-check (QC-LDPC) codes. Simulation results evince that the proposed
backscatter-enabled cooperative NOMA system outperforms its counterpart by
providing an efficient performance in terms of energy efficiency. Also,
proposed jointly-designed QC-LDPC codes provide an excellent bit-error-rate
(BER) performance by jointly decoding the far user data for considered BSC
cooperative NOMA system with only a few decoding iterations.
