Sum Rate Maximization for IRS-Assisted Cooperative NOMA Network with UAV

In this paper, we proposed an intelligent reflecting surface (IRS)-assisted cooperative non-orthogonal multiple access (NOMA) scheme for downlink transmission, with an unmanned aerial vehicle (UAV) acting as a base station. Our proposed scheme involves two users: one within the communication range of the UAV and the other outside that range (e.g., in a tunnel or subway). The key idea is that the user within the range of the UAV receives the signal from the UAV, decodes the outer user's information, and forwards it to that user. We formulated a sum rate maximization problem for our system model by optimizing ground users' power allocation, the IRS's reflection coefficients, and the relay node's transmit power. Due to the non-convexity of our problem, we employed an alternating optimization algorithm where the main problem is decomposed into four sub-problems and optimized the power allocation, reflection coefficient, and relay power by considering power budget, quality-of-service (QoS), and cooperation constraints. Simulation results show that the proposed IRS-assisted cooperative NOMA with UAV scheme achieves a higher sum rate than the benchmark schemes.