Energy-Efficient Solutions For Green Mobile Networks

This thesis focuses on the emerging research topic "green (energy-efficient) mobile networks" that has drawn huge attention recently from both academia and industry. This topic is highly motivated due to important environmental, financial and quality-of-experience (QoE) considerations. The term "green" emphasizes the environmental dimension of the proposed solutions. Hence, it is not sufficient to present a cost-effective solution unless it is eco-friendly. As base stations (BS) are responsible for the large amount of energy consumed in cellular networks, energy efficient BS sleep mode techniques have the potential to save a significant amount of energy. However, assuming that BSs are able to alternate between sleeping and active states as frequently as possible may have a negative impact on network reliability, shortening BS lifetime. In this thesis a multiobjective optimization framework which is aimed at minimizing the power consumption and the number of BS sleep mode switchings in typical and heterogeneous cellular networks (HetNet) is proposed, by jointly considering Quality of Service (QoS) requirements. Both the optimization procedure and the network planning complexity considerably increases when heterogeneous networks with a mix of cell sizes are considered. With the introduction of small cell overlays, the macro cell network becomes over-provisioned due to the offload of traffic by means of small cells. The proposed sleep mode solution aims at reducing the energy consumption of the network by jointly optimizing the amount of management operations related to the addition of low-power base stations. The trade-off between power consumption, sleep mode switchings and performance of the network is shown for different energy saving solutions and traffic load cases. Moreover, the concern about energy efficiency has been growing rapidly also for manufacturers and researchers of Professional Mobile Radio (PMR) systems, like Terrestrial Trunked Radio (TETRA), which have been designed to provide voice and data services to professional users. The future convergence of PMR to the LTE system introduces a new topic in the research discussion about the energy efficiency of wireless systems. In this thesis the feasibility of energy efficient solutions for current and potentially future PMR networks is discussed, by providing a mathematical formulation of power consumption in TETRA base stations and assessing possible business models and energy saving solutions for enhanced mission-critical operations. The final part of the thesis addresses green approaches for weather monitoring. Nowadays, the air quality is getting worse in highly anthropized environments: this phenomenon stimulates a high level of interest within the scientific community and public opinion because of the known strong relationship between exposure to many air pollutants and increased adverse effects on the human health. Developments in communication technologies allow more remote, real-time weather monitoring and access. The use of plants as biosensors represents a new reliable approach for ozone monitoring. In comparison with the traditional monitoring systems, the use of biosensors has the advantage to show us the real impact of pollutants on living organisms, thus providing additional data to the electronic instruments. In this thesis an automatic method of analysis of plant electrical signals for ozone critical levels detection is introduced, based on the fundamentals of correlation theory. The proposed detection algorithm represents a novel monitoring method for detecting critical levels of ozone concentrations.