Dynamic User Pairing and Power Allocation for NOMA with Deep Reinforcement Learning

In this paper, we investigate the user pairing and power allocation scheme for multiple cellular users (CUs) under the downlink non-orthogonal multiple access (NOMA) system. To maximize the sum-rate of all CUs, we formulate the resource allocation issue through optimizing the user pairing relationship and power allocation method. However, due to the nonconvex property of the formulated problem, the original problem is decoupled into two subproblems. First, the optimal power allocation scheme with a given subchannel assignment is obtained via a closed-form solution. Furthermore, based on the obtained optimal allocation scheme, a classical deep reinforcement learning (DRL) method called Deep Q-Network (DQN) algorithm is adopted to find the optimal user pairing scheme, where the DQN algorithm is characterized by higher learning efficiency and better performance of the features extraction ability compared with traditional reinforcement learning (RL) schemes. Simulation results validate the effectiveness of our proposed resource allocation, as compared against the RL based scheme and conventional orthogonal multiple access (OMA) method.