Joint User Association and Sub-channel Assignment in Wireless Networks with Heterogeneous Multiple Access and Heterogeneous Base Stations

Abstract

This paper studies the joint problem of user association and sub-channel assignment in a wireless network, where orthogonal (OMA) and non-orthogonal multiple access (NOMA) techniques co-exist. We also assume the co-existence of millimeter wave and sub-6 GHz communications. Inspired by the fact that traditional resource allocation methods may not be effective in such heterogeneous multiple access networks (HetNets), a joint optimization problem of user association and sub-channel assignment is formulated where the objective is to maximize the number of associated users. The considered problem is proved to be $\mathcal{N}\mathcal{P}$-hard, and therefore an efficient heuristic algorithm is proposed to solve it in a polynomial time. Simulation results corroborate the effectiveness of the proposed algorithm and show that combining OMA and NOMA techniques outperforms single OMA or NOMA technique.