Energy-Efficient Resource Allocation for Multicarrier NOMA Systems with Imperfect CSI

User power allocation and subcarriers assignment solution to maximize the minimum energy efficiency (EE) in a downlink transmission multi-carrier non-orthogonal multiple access (MC-NOMA) systems with imperfect channel state information (CSI) is investigated. We concentrate on EE resource allocation for a multiple user and MC system with imperfect CSI, which is a non-convex nonlinear fraction programming. We convert the problem into a convex one with the help of an auxiliary variable. For the transformed convex problem, Lagrange method is used to solve the power allocation and subcarriers assignment problem iteratively. A closed-form solution to allocate power and assign subcarriers to each user is found using the Karush–Kuhn– Tucker (KKT) conditions. Simulation illustrates that the offered scheme can substantially enhance the system EE while guaranteeing the quality of service (QoS) of total access users compared with the existing algorithm.