In this letter, we investigate the tradeoff between energy efficiency (EE) and spectral efficiency (SE) while ensuring proportional rate fairness in massive multiple-input multiple-output enabled heterogenous networks, where user association and power coordination are jointly considered. It is first formulated as a multi-objective optimization problem, and then transformed into a single-objective optimization problem. To solve this mixed-integer non-convex problem, an effective algorithm is developed, where the original problem is separated into  lower level  power coordination problem and  master  user association problem. Simulation results verify that our proposed algorithm can significantly improve the performance of EE–SE tradeoff and obtain higher rate fairness compared with other algorithms.
['Yuanyuan Hao', 'Qiang Ni', 'Hai Li', 'Shujuan Hou']
Energy and Spectral Efficiency Tradeoff With User Association and Power Coordination in Massive MIMO Enabled HetNets