Resource Allocation for Energy Efficiency in NOMA Enhanced Small Cell Networks

In this paper, we consider a downlink non-orthogonal multiple access (NOMA) heterogeneous small cell networks (HSCN), where the macro base station (MBS) simultaneously communicate with multiple small cell base stations (SBS) through the wireless backhauls. The goal is to investigate an energy-efficient power, and bandwidth allocation scheme aiming at maximizing the EE of the small cells in downlink NOMA-HSCN constrained by the maximum transmit power and the minimum required data rate simultaneously. The optimization problem is non-convex due to the fractional objective function and non-convex constraints and is challenging to obtain an exact solution efficiently. To deal with the problem, the joint optimization is first decomposed into two subproblems. Then, an iterative algorithm to solve the power optimization subproblem is proposed with guaranteed convergence. Furthermore, a closed-form solution for the bandwidth allocation subproblem is derived. Finally, an iterative power and bandwidth allocation algorithm are proposed for NOMA-HSCN. Simulation results reveal the effectiveness of the proposed schemes in terms of energy efficiency (EE) as compared to the existing NOMA schemes and the conventional orthogonal multiple access (OMA) baseline schemes.