A Coalitional Model Predictive Control for the Energy Efficiency of Next-Generation Cellular Networks

Next-generation cellular networks are large-scale systems composed of numerous base stations interacting with many diverse users. One of the main challenges with these networks is their high energy consumption due to the expected number of connected devices. We handle this issue with a coalitional Model Predictive Control (MPC) technique for the case of next-generation cellular networks powered by renewable energy sources. The proposed coalitional MPC approach is applied to two simulated scenarios and compared with other control methods: the traditional best-signal level mechanism, a heuristic algorithm, and decentralized and centralized MPC schemes. The success of the coalitional strategy is considered from an energy efficiency perspective, which means reducing on-grid consumption and improving network performance (e.g., number of users served and transmission rates)

A Coalitional Model Predictive Control Approach for Heterogeneous Cellular Networks

Heterogeneous cellular networks (HetNets) are large-scale systems that comprise numerous base stations interacting with a significant number of users of diverse types. Finding a trade-off between energy consumption and quality of service is one of the major challenges in these networks. To deal with this issue, a coalitional model predictive control (MPC) approach is proposed for a HetNet powered by renewable power sources, and compared in simulation with the traditional best-signal level mechanism and the centralized MPC method. Furthermore, other key performance indicators associated with grid consumption such as the number of served users and transmission rates are also evaluated

User Association in 5G Networks: A Survey and an Outlook

26 pages; accepted to appear in IEEE Communications Surveys and Tutorial

Resource Allocation in Energy Cooperation Enabled 5G Cellular Networks

PhD thesisIn fifth generation (5G) networks, more base stations (BSs) and antennas have been deployed to meet the high data rate and spectrum efficiency requirements. Heterogeneous and ultra dense networks not only pose substantial challenges to the resource allocation design, but also lead to unprecedented surge in energy consumption. Supplying BSs with renewable energy by utilising energy harvesting technology has became a favourable solution for cellular network operators to reduce the grid energy consumption. However, the harvested renewable energy is fluctuating in both time and space domains. The available energy for a particular BS at a particular time might be insufficient to meet the traffic demand which will lead to renewable energy waste or increased outage probability. To solve this problem, the concept of energy cooperation was introduced by Sennur Ulukus in 2012 as a means for transferring and sharing energy between the transmitter and the receiver. Nevertheless, resource allocation in energy cooperation enabled cellular networks is not fully investigated. This thesis investigates resource allocation schemes and resource allocation optimisation in energy cooperation enabled cellular networks that employed advanced 5G techniques, aiming at maximising the energy efficiency of the cellular network while ensuring the network performance. First, a power control algorithm is proposed for energy cooperation enabled millimetre wave (mmWave) HetNets. The aim is to maximise the time average network data rate while keeping the network stable such that the network backlog is bounded and the required battery capacity is finite. Simulation results show that the proposed power control scheme can reduce the required battery capacity and improve the network throughput. Second, resource allocation in energy cooperation enabled heterogeneous networks (Het- Nets) is investigated. User association and power control schemes are proposed to maximise the energy efficiency of the whole network respectively. The simulation results reveal that the implementation of energy cooperation in HetNets can improve the energy efficiency and the improvement is apparent when the energy transfer efficiency is high. Following on that, a novel resource allocation for energy cooperation enabled nonorthogonal multiple access (NOMA) HetNets is presented. Two user association schemes which have different complexities and performances are proposed and compared. Following on that, a joint user association and power control algorithm is proposed to maximise the energy efficiency of the network. It is confirmed from the simulation results that the proposed resource allocation schemes efficiently coordinate the intra-cell and inter-cell interference in NOMA HetNets with energy cooperation while exploiting the multiuser diversity and BS densification. Last but not least, a joint user association and power control scheme that considers the different content requirements of users is proposed for energy cooperation enabled caching HetNets. It shows that the proposed scheme significantly enhances the energy efficiency performance of caching HetNets

Energy and throughput efficient strategies for heterogeneous future communication networks

As a result of the proliferation of wireless-enabled user equipment and data-hungry applications, mobile data traffic has exponentially increased in recent years.This in-crease has not only forced mobile networks to compete on the scarce wireless spectrum but also to intensify their power consumption to serve an ever-increasing number of user devices. The Heterogeneous Network (HetNet) concept, where mixed types of low-power base stations coexist with large macro base stations, has emerged as a potential solution to address power consumption and spectrum scarcity challenges. However, as a consequence of their inflexible, constrained, and hardware-based configurations, HetNets have major limitations in adapting to fluctuating traffic patterns. Moreover, for large mobile networks, the number of low-power base stations (BSs) may increase dramatically leading to sever power consumption. This can easily overwhelm the benefits of the HetNet concept. This thesis exploits the adaptive nature of Software-defined Radio (SDR) technology to design novel and optimal communication strategies. These strategies have been designed to leverage the spectrum-based cell zooming technique, the long-term evolution licensed assisted access (LTE-LAA) concept, and green energy, in order to introduce a novel communication framework that endeavors to minimize overall network on-grid power consumption and to maximize aggregated throughput, which brings significant benefits for both network operators and their customers. The proposed strategies take into consideration user data demands, BS loads, BS power consumption, and available spectrum to model the research questions as optimization problems. In addition, this thesis leverages the opportunistic nature of the cognitive radio (CR) technique and the adaptive nature of the SDR to introduce a CR-based communication strategy. This proposed CR-based strategy alleviates the power consumption of the CR technique and enhances its security measures according to the confidentiality level of the data being sent. Furthermore, the introduced strategy takes into account user-related factors, such as user battery levels and user data types, and network-related factors, such as the number of unutilized bands and vulnerability level, and then models the research question as a constrained optimization problem. Considering the time complexity of the optimum solutions for the above-mentioned strategies, heuristic solutions were proposed and examined against existing solutions. The obtained results show that the proposed strategies can save energy consumption up to 18%, increase user throughput up to 23%, and achieve better spectrum utilization. Therefore, the proposed strategies offer substantial benefits for both network operators and users

Joint Deployment and Mobility Management of Energy Harvesting Small Cells in Heterogeneous Networks

Small heterogeneous cells have been introduced to improve the system capacity and provide the ubiquitous service requirements. In order to make flexible deployment and management of massive small cells, the utilization of self-powered small cell base stations with energy harvesting (EH-SCBSs) is becoming a promising solution due to low-cost expenditure. However, the deployment of static EH-SCBSs entails several intractable challenges in terms of the randomness of renewable energy arrival and dynamics of traffic load with spatio-temporal fluctuation. To tackle these challenges, we develop a tractable framework of the location deployment and mobility management of EH-SCBSs with various traffic load distributions an environmental energy models. In this paper, the joint optimization problem for location deployment and mobile management is investigated for maximizing the total system utility of both users and network operators. Since the formulated problem is a NP-hard problem, we propose a low-complex algorithm that decouples the joint optimization into the location updating approach and the association matching approach. A suboptimal solution for the optimization problem can be guaranteed using the iteration of two stage approaches. Performance evaluation shows that the proposed schemes can efficiently solve the target problems while striking a better overall system utility, compared with other traditional deployment and management strategies

Self-Sustaining Caching Stations: Towards Cost-Effective 5G-Enabled Vehicular Networks

In this article, we investigate the cost-effective 5G-enabled vehicular networks to support emerging vehicular applications, such as autonomous driving, in-car infotainment and location-based road services. To this end, self-sustaining caching stations (SCSs) are introduced to liberate on-road base stations from the constraints of power lines and wired backhauls. Specifically, the cache-enabled SCSs are powered by renewable energy and connected to core networks through wireless backhauls, which can realize "drop-and-play" deployment, green operation, and low-latency services. With SCSs integrated, a 5G-enabled heterogeneous vehicular networking architecture is further proposed, where SCSs are deployed along roadside for traffic offloading while conventional macro base stations (MBSs) provide ubiquitous coverage to vehicles. In addition, a hierarchical network management framework is designed to deal with high dynamics in vehicular traffic and renewable energy, where content caching, energy management and traffic steering are jointly investigated to optimize the service capability of SCSs with balanced power demand and supply in different time scales. Case studies are provided to illustrate SCS deployment and operation designs, and some open research issues are also discussed.Comment: IEEE Communications Magazine, to appea

Energy and cost management in shared heterogeneous network deployments

During 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

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

Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks

Soaring capacity and coverage demands dictate that future cellular networks need to soon migrate towards ultra-dense networks. However, network densification comes with a host of challenges that include compromised energy efficiency, complex interference management, cumbersome mobility management, burdensome signaling overheads and higher backhaul costs. Interestingly, most of the problems, that beleaguer network densification, stem from legacy networks' one common feature i.e., tight coupling between the control and data planes regardless of their degree of heterogeneity and cell density. Consequently, in wake of 5G, control and data planes separation architecture (SARC) has recently been conceived as a promising paradigm that has potential to address most of aforementioned challenges. In this article, we review various proposals that have been presented in literature so far to enable SARC. More specifically, we analyze how and to what degree various SARC proposals address the four main challenges in network densification namely: energy efficiency, system level capacity maximization, interference management and mobility management. We then focus on two salient features of future cellular networks that have not yet been adapted in legacy networks at wide scale and thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and device-to-device (D2D) communications. After providing necessary background on CoMP and D2D, we analyze how SARC can particularly act as a major enabler for CoMP and D2D in context of 5G. This article thus serves as both a tutorial as well as an up to date survey on SARC, CoMP and D2D. Most importantly, the article provides an extensive outlook of challenges and opportunities that lie at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201