Throughput and backhaul energy efficiency analysis in two-tier HetNets: A multiobjective approach

Fifth Generation (5G) networks will compromise of heterogeneous networks (HetNets) with macrocell overlaid with lower power small cells to achieve higher throughput by offloading users with low signal-to-noise-ratio from macrocell to the small cells. In this paper, we proposed a multi-objective optimization problem (MOP) to jointly investigate the tradeoff between throughput and backhaul energy efficiency (BEE) using ω-fair utility function for two different backhauling technologies in downlink transmission scheme of a two-tier HetNets. We then transform the proposed MOP into a single objective optimization problem (SOP) employing the weighted sum method to obtain the complete Pareto Frontier solution set with minimum QoS requirements and rate fairness level ω. The transformed SOP is solved in an iterative manner using Lagrangian Dual Decomposition (LDD) with a subgradient method providing a near-optimal solution. Simulation results demonstrate the effectiveness of our proposed approach in reducing the total area power consumption irrespective of the backhauling technology by dynamically adjusting weighting coefficient α and rate fairness level ω. Our numerical results also demonstrate the fundamental tradeoff between throughput and BEE for different parameters such as weighting coefficient α and rate fairness level ω.