Power Minimization Transmission Design for IRS-Assisted Uplink NOMA Systems

Combining intelligent reflecting surface (IRS), which can reconfigure the channel environment of wireless communication, with non-orthogonal multiple access (NOMA), which can enhance the spectrum and power efficiency, is a promising technique to satisfy the foreseeable applications. In this paper, we consider an IRS-assisted uplink NOMA system. The goal is to minimize the power consumption under the constraint of each user's minimum SINR. In order to solve the joint optimization problem of power control at users and phase shift at IRS, we develop the relationship between the transmit power of each user and the phase shift. Furthermore, the original optimization problem is transformed into the pure phase shift optimization problem but is still non-convex. We propose a method based on semi-definite relaxation to find a sub-optimal solution. It is shown by simulations that, compared to other benchmarking schemes, the method proposed in this paper can reduce the power consumption of uplink NOMA system obviously.