On power minimization for IRS-Aided downlink NOMA systems

Both intelligent reflecting surface (IRS) and non-orthogonal multiple access (NOMA) are the cutting-edge technologies for future wireless communications. In this letter, we examine the effectiveness of IRS in NOMA system with respect to transmit power consumption. Towards this end, the power minimization problem for IRS-aided downlink NOMA system is formulated, taking into consideration the constraint of each user's minimum signal-to-interference-ratio (SINR). To solve the joint power control and IRS phase shifts optimization problem, we first explore the relationship between individual user's transmit power and the variables of phase shifts. Then, we solve the phase shift determination problem via the sequential rotation algorithm. Numerical results show that our designed joint optimization algorithm can significantly reduce the required transmit power when compared with various benchmarking schemes.