Energy Efficient Resource Allocation of Cooperative Non-Orthogonal Multiple Access with Hardware Impairments

In this paper, we investigate energy-efficient resource allocation for downlink cooperative non-orthogonal multiple access (C-NOMA) systems, where a source node communicates with two users via an amplify-and-forward (AF) relay with hardware impairment (HI) conditions. We first derive the energy efficiency (EE) of the system with HI under the power constraint of the source, relay and minimum signal to interference plus noise ratio (SINR) requirement of each user. Then, fractional programming is utilized to convert the energy efficient optimization problem into a subtractive form. Next, a joint power and amplification gain allocation algorithm is proposed to maximize the system energy efficiency (EE) based on Lagrangian dual and Dinkelbach method. Simulation results show that the proposed algorithm can improve the system EE compared with the orthogonal multiple access (OMA) scheme.