Development of an Original Framework for Joint Optimization of Energy Efficiency and Throughput in Green 5G Heterogeneous Networks for Nigeria

The energy consumption of mobile network infrastructure constitutes a growing operational expenditure challenge for Nigerian operators, where diesel-based power dependence amplifies both cost and environmental impact, while simultaneously subscriber throughput demands continue escalating. Jointly optimizing energy efficiency and throughput in 5G heterogeneous networks requires resolving a fundamental trade-off that existing approaches address separately. This doctoral study develops an original mathematical framework for joint optimization of energy efficiency and throughput in green 5G heterogeneous networks contextualized to Nigerian operator environments. An original multi-objective optimization problem formulation is developed that simultaneously maximizes energy efficiency measured in bits per joule and sum network throughput subject to minimum quality of service constraints, base station power budgets, and practical deployment constraints representative of Nigerian heterogeneous network configurations. The multi-objective problem structure is analytically characterized, with Pareto optimality conditions derived and a novel successive convex approximation algorithm proposed for tractable computation of Pareto-optimal operating points. The algorithm's convergence to a Karush-Kuhn-Tucker optimal solution is proved. Simulation using a heterogeneous network topology derived from publicly available base station location data in Abuja evaluates the proposed framework against single-objective energy efficiency and throughput maximization baselines. The joint optimization framework achieves a 27% improvement in energy efficiency relative to throughput-only optimization while sacrificing only 9% of maximum throughput, representing a significantly improved operating point compared to baseline approaches. The original framework and convergence-guaranteed algorithm constitute doctoral-level contributions to green network optimization theory. Keywords: energy efficiency, 5G heterogeneous network, green communications, multi-objective optimization, Nigeria.