A novel approach to fairness-aware energy efficiency in multi-RAT heterogeneous networks

Abstract

Heterogeneous cellular networks are a viable solution in response to the growing demand for broadband services in the new-generation wireless networks. It is more challenging to manage resources (e.g., user association and power control) in multi-radio access technology (multi-RAT) HetNets than in conventional single-tier cellular networks due to the higher computational complexity and energy efficiency constraints. In addition, given the novel services and resource limitation of the user layer, energy efficiency and fairness assurance are critical issues in the uplink. Considering the uplink fairness criterion, this paper proposes a dynamic optimization model which maximizes the total uplink/downlink energy efficiency in addition to providing the essential coverage and capacity of heterogeneous cellular networks. Based on the non-convex characteristics of the energy efficiency maximization model, the mathematical model can be formulated into two subproblems, i.e., resource optimization and user association. In this approach, a subgradient method is applied for fair resource management and also successive convex approximation and dual decomposition methods are adopted to solve the proportional fairness problem. The simulation results exhibit a considerable throughput increase of 25% and 18% on average for random and hotspot user distributions, respectively. Based on the numerical results, the adaptive radio resource management method reduces the rate of vertical handoffs between RATs, which leads to more stable communications for the users. It also proved that the proposed approach managed to significantly improve the total network energy efficiency by up to 40%.