Author Identifier

Md Munjure Mowla

Date of Award


Document Type



Edith Cowan University

Degree Name

Doctor of Philosophy


School of Engineering

First Supervisor

Dr Iftekhar Ahmad

Second Supervisor

Professor Daryoush Habibi


The rapid growth in global mobile phone users has resulted in an ever-increasing demand for bandwidth and enhanced quality-of-service (QoS). Several consortia comprising major international mobile operators, infrastructure manufacturers, and academic institutions are working to develop the next generation wireless communication systems fifth generation (5G) - to support high data rates and increased QoS. 5G systems are also expected to represent a greener alternative for communication systems, which is important because power consumption from the information and communication technology (ICT) sector is forecast to increase significantly by 2030. The deployment of ultra-dense heterogeneous small cell networks (SCNs) is expected to play a major role in meeting the explosive growth of user traffic demand in 5G wireless communication systems. However, while the concept of small cells in heterogeneous networks (HetNets) largely addresses the bandwidth scarcity problem, unless otherwise carefully managed, a large number of uncoordinated and lightly loaded SCNs will significantly increase the access network power consumption, contrary to the green communication target of 5G systems. In addition, to cater for the huge volumes of traffic, the backhaul network power consumption will also increase.

This thesis addresses the research challenges facing 5G systems in regard to energy efficiency and QoS. The thesis examines ways to reduce power consumption in access networks, how to design green backhauling solutions, how to develop synergy between wired and wireless backhauling options, and how to increase energy efficiency in a weather-dependent backhaul network without hindering network QoS. Different system models and solution techniques are investigated in order to successfully minimize overall power consumption in 5G HetNets while maintaining network QoS.

The thesis contributes as follows: first, an energy-efficient resource management system is introduced to minimize access network power consumption; second, two green backhauling solutions, one for wired optical backhaul and the other for wireless millimeter wave (mmWave) backhaul, are presented; third, a synergy is developed between two energy-efficient backhauling solutions to reduce power consumption; fourth, the impacts of SCN topology and mmWave spectrum are presented; and finally, a hybrid free-space optics (FSO)/mmWave channel model is introduced to minimize power consumption for weather-dependent channels. Each phase of the research listed above also investigates the network QoS, i.e., average delay and jitter for 5G HetNets.

The research presented in this thesis therefore contributes new knowledge in energy efficiency and QoS for next generation wireless communication networks and makes important contributions to this field by investigating different system models and proposing solutions to significant issues.