A Survey on Mobile Charging Techniques in Wireless Rechargeable Sensor Networks

The recent breakthrough in wireless power transfer (WPT) technology has empowered wireless rechargeable sensor networks (WRSNs) by facilitating stable and continuous energy supply to sensors through mobile chargers (MCs). A plethora of studies have been carried out over the last decade in this regard. However, no comprehensive survey exists to compile the state-of-the-art literature and provide insight into future research directions. To fill this gap, we put forward a detailed survey on mobile charging techniques (MCTs) in WRSNs. In particular, we first describe the network model, various WPT techniques with empirical models, system design issues and performance metrics concerning the MCTs. Next, we introduce an exhaustive taxonomy of the MCTs based on various design attributes and then review the literature by categorizing it into periodic and on-demand charging techniques. In addition, we compare the state-of-the-art MCTs in terms of objectives, constraints, solution approaches, charging options, design issues, performance metrics, evaluation methods, and limitations. Finally, we highlight some potential directions for future research

Integrated Data and Energy Communication Network: A Comprehensive Survey

OAPA In order to satisfy the power thirsty of communication devices in the imminent 5G era, wireless charging techniques have attracted much attention both from the academic and industrial communities. Although the inductive coupling and magnetic resonance based charging techniques are indeed capable of supplying energy in a wireless manner, they tend to restrict the freedom of movement. By contrast, RF signals are capable of supplying energy over distances, which are gradually inclining closer to our ultimate goal – charging anytime and anywhere. Furthermore, transmitters capable of emitting RF signals have been widely deployed, such as TV towers, cellular base stations and Wi-Fi access points. This communication infrastructure may indeed be employed also for wireless energy transfer (WET). Therefore, no extra investment in dedicated WET infrastructure is required. However, allowing RF signal based WET may impair the wireless information transfer (WIT) operating in the same spectrum. Hence, it is crucial to coordinate and balance WET and WIT for simultaneous wireless information and power transfer (SWIPT), which evolves to Integrated Data and Energy communication Networks (IDENs). To this end, a ubiquitous IDEN architecture is introduced by summarising its natural heterogeneity and by synthesising a diverse range of integrated WET and WIT scenarios. Then the inherent relationship between WET and WIT is revealed from an information theoretical perspective, which is followed by the critical appraisal of the hardware enabling techniques extracting energy from RF signals. Furthermore, the transceiver design, resource allocation and user scheduling as well as networking aspects are elaborated on. In a nutshell, this treatise can be used as a handbook for researchers and engineers, who are interested in enriching their knowledge base of IDENs and in putting this vision into practice

Mathematical optimization techniques for demand management in smart grids

The electricity supply industry has been facing significant challenges in terms of meeting the projected demand for energy, environmental issues, security, reliability and integration of renewable energy. Currently, most of the power grids are based on many decades old vertical hierarchical infrastructures where the electric power flows in one direction from the power generators to the consumer side and the grid monitoring information is handled only at the operation side. It is generally believed that a fundamental evolution in electric power generation and supply system is required to make the grids more reliable, secure and efficient. This is generally recognised as the development of smart grids. Demand management is the key to the operational efficiency and reliability of smart grids. Facilitated by the two-way information flow and various optimization mechanisms, operators benefit from real time dynamic load monitoring and control while consumers benefit from optimised use of energy. In this thesis, various mathematical optimization techniques and game theoretic frameworks have been proposed for demand management in order to achieve efficient home energy consumption scheduling and optimal electric vehicle (EV) charging. A consumption scheduling technique is proposed to minimise the peak consumption load. The proposed technique is able to schedule the optimal operation time for appliances according to the power consumption patterns of the individual appliances. A game theoretic consumption optimization framework is proposed to manage the scheduling of appliances of multiple residential consumers in a decentralised manner, with the aim of achieving minimum cost of energy for consumers. The optimization incorporates integration of locally generated and stored renewable energy in order to minimise dependency on conventional energy. In addition to the appliance scheduling, a mean field game theoretic optimization framework is proposed for electric vehicles to manage their charging. In particular, the optimization considers a charging station where a large number of EVs are charged simultaneously during a flexible period of time. The proposed technique provides the EVs an optimal charging strategy in order to minimise the cost of charging. The performances of all these new proposed techniques have been demonstrated using Matlab based simulation studies

Energy and cost management in shared heterogeneous network deployments

Pla de Doctorat industrial de la Generalitat de CatalunyaDuring the recent years, a huge augmentation of the data traffic volume has been noticed, while a further steep increase is expected in the following years. As a result, questions have been raised over the years about the energy consumption needs of the wireless telecommunication networks, their carbon dioxide emissions and their operational expenses. Aiming at meeting the high traffic demands with flat energy consumption and flat incurred expenses, mobile network operators (MNOs) have opted to improve their position (i) by deploying heterogeneous networks (HetNets), which are consisted of macrocell base stations (MBSs) and small cell base stations (SBSs) and (ii) by sharing their infrastructure. However, questions could be raised about the extend to which HetNet densification is of aid. Given that network planning is executed according to high traffic load volumes, BS underutilisation during low-traffic hours cannot be neglected. Similarly, the aggregated energy needs of multiple SBSs equals the ones of an energy hungry MBS, having thus a respectable share of the net energy consumption. In this context, a set of research opportunities have been identified. This thesis provides contribution toward the achievement of a greener and more cost efficient operation of HetNet deployments, where multiple stakeholders develop their activity and where energy support can have the form of various alternate schemes, including renewable energy (RE) sources. Depending on the network energy support, i.e., whether RE sources are used in the network or not, the main body of this thesis is divided in two research directions. The first part of the thesis uses the technology of switching off strategies in order to explore their efficiency in terms of both energy and costs in a HetNet. The HetNet is assumed to be a roaming-based cooperative activity of multiple MNOs that is powered exclusively by grid energy. A switching off and a cost allocation scheme are proposed, using as criteria the BS type, the BS load and the roaming cost for traffic offloading. The performance of the proposed schemes is evaluated with respect to energy efficiency, cost savings and fairness, using computer-based simulations. The second part of the thesis explores energy and cost management issues in energy harvesting (EH) HetNet deployments where EH-BSs use an EH system (EHS), an energy storage system (ESS) and the smart grid (SG) as energy procurement sources. The EH-HetNet is assumed a two-tier network deployment of EH-MBSs that are passively shared among an MNO set and EH-SBSs that are provided to MNOs by an infrastructure provider. Taking into consideration the infrastructure location and the variety of stakeholders involved in the network deployment, approaches of RE exchange (REE) are proposed as a cooperative RE sharing for the shared EH-MBSs, based on bankruptcy theory, and a non-cooperative, aggregator-assisted RE trading, based on double auctions, for the EH-SBSs. The performance of the proposed schemes is evaluated in terms of the hours of independence of the studied system from the SG, the fairness regulated by the provided solution and the economical payoffs extracted for the stakeholdersDurante los últimos años, se ha notado un aumento enorme del volumen de tráfico de datos, mientras que se espera un nuevo aumento en los próximos años. Como resultado, se han planteado preguntas sobre las necesidades de consumo de energía de las redes inalámbricas de telecomunicaciones, sus emisiones de dióxido de carbono y sus gastos operativos. Con el objetivo de satisfacer las altas demandas de tráfico con consumo de energía constante y con gastos incurridos constantes, además de utilizar soluciones basadas en la nube, los operadores de redes móviles (MNOs) han optado por mejorar su posición (i) desplegando redes heterogéneas (HetNets), que consisten en estaciones base de macro-células (MBSs) y estaciones base de células pequeñas (SBSs), y (ii) compartiendo su infraestructura. Sin embargo, podrían plantearse preguntas sobre hasta qué punto la densificación de una HetNet es de ayuda. Dado que la planificación de la red se ejecuta de acuerdo con los volúmenes de carga de tráfico más elevados, no se puede descuidar la subutilización de las estaciones base (BS) durante las horas de poco tráfico. De manera similar, las necesidades de energía agregadas de múltiples SBSs son iguales a las de una MBS que consume mucha energía, teniendo así una parte respetable del consumo neto de energía. En este contexto, se ha identificado un conjunto de oportunidades de investigación. Esta tesis contribuye al logro de una operación más ecológica y rentable de las implementaciones de HetNet, donde múltiples partes interesadas desarrollan su actividad y donde el apoyo energético puede tener la forma de varios esquemas alternativos, incluidas las fuentes de energía renovables (RE). Dependiendo del soporte de energía de red, es decir, si las fuentes de RE se usan en la red o no, el cuerpo principal de esta tesis se divide en dos direcciones de investigación. La primera parte de la tesis utiliza la tecnología de las estrategias de apagado con el objetivo de explorar su eficiencia en términos de energía y gastos en una HetNet. Se asume que la HetNet es una actividad cooperativa basada en la itinerancia de múltiples MNO que se alimenta exclusivamente de energía de la red. Se propone un esquema de desconexión y de asignación de costes, que utiliza como criterios el tipo de BS, la carga de BS y el coste de la itinerancia para la descarga de tráfico. El rendimiento de los esquemas propuestos se evalúa con respecto a la eficiencia energética, el ahorro de costes y la equidad, usando simulaciones en computadora. La segunda parte de la tesis explora los problemas de gestión de energía y de costes en las implementaciones de HetNet donde las estaciones base recolectan energía usando un sistema EH (EHS), un sistema de almacenamiento de energía (ESS) y la red eléctrica inteligente (SG) como sistemas de adquisición de energía. Se asume que el EH-HetNet es una implementación de redes de dos niveles donde los EH-MBSs se comparten pasivamente entre un conjunto de MNOs y EH-SBSs se proporcionan a los MNOs de un proveedor de infraestructura. Teniendo en cuenta la ubicación de la infraestructura y la variedad de partes interesadas e involucradas en el despliegue de la red, se proponen enfoques de intercambio de RE (REE) como un intercambio cooperativo de RE para los EH-MBS compartidos, basado en la teoría de bancarrota, y un no cooperativo comercio de RE para los EH-SBSs, que es asistido por un agregador y basado en las subastas dobles. El rendimiento de los esquemas propuestos se evalúa en términos de las horas de independencia del sistema estudiado con respecto al SG, la imparcialidad regulada por la solución proporcionada y los beneficios económicos extraídos para las interesadas.Postprint (published version