Coalitional game-based user pairing and power allocation in downlink non-orthogonal multiple access networks

This article studies the user pairing and power allocation in a downlink non-orthogonal multiple access (NOMA) network in which users form different pairs accessing orthogonal channels and NOMA is utilized in each channel. Existing studies mainly focused on throughput optimization, while throughput cannot completely reflect users' quality of experience. Therefore, we aim to maximize the network's sum of mean opinion scores rather than throughput to meet different traffic demands of users. The mixed integer nonlinear programming problem is decomposed into two subproblems. The first user pairing problem is modeled as a coalition formation game, and a Nash-stable suboptimal pairing scheme is obtained via proposed coalition formation algorithm. The second power allocation problem is modeled as a knapsack problem, and we obtain the optimal power allocation scheme through dynamic programming with bisection method. These two subproblems are solved alternately until converging to the final resource allocation strategy. Simulation results show that the proposed strategy outperforms existing NOMA resource allocation techniques and achieves near-optimal performance.