Energy-Efficient Resource Allocation for Adaptive Modulated MIMO–OFDM Heterogeneous Cloud Radio Access Networks

In this paper, an optimal resource allocation method in multiple-input multiple-output-orthogonal frequency division multiplexing heterogeneous cloud radio access network is proposed for downlink transmission. Our problem formulation takes into account inter-tier interference and quality of service requirement for RRH/HPN association policy. We formulate two non-convex optimization problems for resource block (RB) assignment and power allocation, and then solve both problems using their equivalent convex feasibility problems. By considering Lagrange dual decomposition technique, a closed form expression for joint power and RB allocation in order to improve energy efficiency (EE) is derived. In addition, the adaptive modulation is investigated to realize practical scenario. Finally, the efficiency of the proposed algorithms in enhancing EE is confirmed through Monte Carlo simulations.