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

User-Centric Networking for Dense C-RANs: High-SNR Capacity Analysis and Antenna Selection

IEEE Ultra-dense cloud radio access networks (C-RANs) is one of the architectures that will be critical components of the next-generation wireless systems. In a C-RAN architecture, an amorphous cellular framework, where each user connects to a few nearby remote radio heads (RRHs) to form its own cell, appears to be promising. In this paper, we study the ergodic capacity of such amorphous cellular networks at high signal-tonoise ratios (SNRs) where we model the distribution of the RRHs by a Poisson point process. We derive tractable approximations of the ergodic capacity at high-SNRs for arbitrary antenna configurations, and tight lower bounds for the ergodic capacity when the numbers of antennas are the same at both ends of the link. In contrast to prior works on distributed antenna systems, our results are derived based on random matrix theory and involve only standard functions which can be much more easier evaluated. The impact of the system parameters on the ergodic capacity is investigated. By leveraging our analytical results, we propose two efficient scheduling algorithms for RRH selection for energy-efficient transmission. Our algorithms offer a substantial improvement in energy efficiency compared to the strategy of connecting a fixed number of RRHs to each user

Lights and Shadows: A Comprehensive Survey on Cooperative and Precoding Schemes to Overcome LOS Blockage and Interference in Indoor VLC

Visible light communications (VLC) have received significant attention as a way of moving part of the saturated indoor wireless traffic to the wide and unregulated visible optical spectrum. Nowadays, VLC are considered as a suitable technology, for several applications such as high-rate data transmission, supporting internet of things communications or positioning. The signal processing originally derived from radio-frequency (RF) systems such as cooperative or precoding schemes can be applied to VLC. However, its implementation is not straightforward. Furthermore, unlike RF transmission, VLC present a predominant line-of-sight link, although a weak non-LoS component may appear due to the reflection of the light on walls, floor, ceiling and nearby objects. Blocking effects may compromise the performance of the aforementioned transmission schemes. There exist several surveys in the literature focused on VLC and its applications, but the management of the shadowing and interference in VLC requires a comprehensive study. To fill this gap, this work introduces the implementation of cooperative and precoding schemes to VLC, while remarking their benefits and drawbacks for overcoming the shadowing effects. After that, the combination of both cooperative and precoding schemes is analyzed as a way of providing resilient VLC networks. Finally, we propose several open issues that the cooperative and precoding schemes must face in order to provide satisfactory VLC performance in indoor scenarios.This work has been supported partially by Spanish National Project TERESA-ADA(TEC2017-90093-C3-2-R) (MINECO/AEI/FEDER, UE), the research project GEOVEOLUZ-CM-UC3Mfunded by the call “Programa de apoyo a la realización de proyectos interdisciplinares de I+D parajóvenes investigadores de la Universidad Carlos III de Madrid 2019-2020” under the frame ofthe Convenio Plurianual Comunidad de Madrid-Universidad Carlos III de Madrid and projectMadrid Flight on Chip (Innovation Cooperative Projects Comunidad of Madrid - HUBS 2018/MadridFlightOnChip). Additionally, it has been supported partially by the Juan de la CiervaIncorporación grant IJC2019-040317-I and Juan de la Cierva Formación grant (FJC2019-039541-I/AEI/10.13039/501100011033)

Synthesis of bio-functional nanomaterials in reactive plasma discharges

Plasma processing technologies have been extensively used as surface modification platforms in many biomedical applications. Particularly, plasma polymerization (PP) is a versatile deposition technology which has the potential to deliver biocompatible interfaces for a myriad of medical devices. To successfully translate new materials for specific clinical applications, the plasma process needs to be scalable and incorporate appropriate control feedback strategies. However, the plasma medium in PP is exceptionally complex and identifying the main physical quantities that allow a suitable formulation and description of the interface growth mechanisms is challenging. The first part of the thesis reports the design and optimization of a single step ion assisted PP process to create plasma-activated coatings (PAC) that meet the extreme mechanical demands for cardiovascular implants and in particular stents. An ideal working window in the parameter space is identified, and found suitable for the synthesis of PAC interfaces that are mechanically robust, hemocompatibility and allow one step covalent protein immobilization without the need for chemical processes. This window is identified by combining plasma optical emission spectroscopy (OES) with a comprehensive macroscopic process description that isolates key coating growth mechanisms. During process scalability, OES diagnostics revealed the formation of plasma polymer nanoparticles (nanoP3), usually known as plasma dust, in parallel with the deposition of PAC coatings. The second part of the thesis reports the demonstration of carbonaceous plasma nanoparticles for nanomedicine applications. By controlling nanoparticle formation and collection, nanoP3 were engineered with unique immobilization capabilities facilitating multifunctional nanocarriers. The unique surface chemistry of nanoP3, allowing a robust immobilization of the cargo without the need for intermediate functionalization strategies, has great potential to overcome major limitations of currently proposed platforms. As many of the favorable characteristics of nanoP3 are inherent to the fabrication process, this work proposes PP as a nanoparticle synthesis route with valuable potential for broad clinical and commercial applications

A Prospective Look: Key Enabling Technologies, Applications and Open Research Topics in 6G Networks

The fifth generation (5G) mobile networks are envisaged to enable a plethora of breakthrough advancements in wireless technologies, providing support of a diverse set of services over a single platform. While the deployment of 5G systems is scaling up globally, it is time to look ahead for beyond 5G systems. This is driven by the emerging societal trends, calling for fully automated systems and intelligent services supported by extended reality and haptics communications. To accommodate the stringent requirements of their prospective applications, which are data-driven and defined by extremely low-latency, ultra-reliable, fast and seamless wireless connectivity, research initiatives are currently focusing on a progressive roadmap towards the sixth generation (6G) networks. In this article, we shed light on some of the major enabling technologies for 6G, which are expected to revolutionize the fundamental architectures of cellular networks and provide multiple homogeneous artificial intelligence-empowered services, including distributed communications, control, computing, sensing, and energy, from its core to its end nodes. Particularly, this paper aims to answer several 6G framework related questions: What are the driving forces for the development of 6G? How will the enabling technologies of 6G differ from those in 5G? What kind of applications and interactions will they support which would not be supported by 5G? We address these questions by presenting a profound study of the 6G vision and outlining five of its disruptive technologies, i.e., terahertz communications, programmable metasurfaces, drone-based communications, backscatter communications and tactile internet, as well as their potential applications. Then, by leveraging the state-of-the-art literature surveyed for each technology, we discuss their requirements, key challenges, and open research problems

Enhancing the biocompatibility of coronary artery stents

Cardiovascular disease, in particular coronary artery disease is a leading cause of morbidity and mortality worldwide. Coronary artery disease occurs as a consequence of atherosclerosis. Impediment to coronary blood flow causes myocardial ischemia, manifesting clinically as angina. Plaque rupture can lead to rapid vessel occlusion and myocardial necrosis. Revascularization (restoration of normal blood flow) can be achieved percutaneously with balloon angioplasty and coronary stent placement. Coronary stents are the most commonly implanted medical prostheses. To date the majority of commercially available stents are constructed from metallic alloys. Implantation of stents in the vasculature has two main biocompatibility issues 1) metals are thrombogenic, 2) stent deployment injures the vessel wall. Stent thrombosis and in stent restenosis are clinical consequences of stent thrombogenicity and vessel injury, respectively. Potent anti‐platelet agents and use of anti‐proliferative drug eluting stents reduce thrombogenicity and restenosis at the cost of increased bleeding and retardation of stent strut endothelialization leading to very late stent thrombosis. The interaction of biological systems with biomaterials is highly dependent on surface properties. Modification of the physical and chemical properties of the surface offers a simple and effective meanings to modulate the biological response to stents without altering the mechanical benefits that metallic alloys offer. Recently, plasma polymer deposition of thin films has been adapted for metallic substrates and three dimensional structures. These films reduce thrombogenicity and can attach biomolecules. One such molecule, recombinant human tropoelastin (rhTE) when attached to the films has been shown to enhance endothelial activity. Increasingly endothelial progenitor cells (EPCs) have been implicated in the maintenance of vascular health. Of particular interest is the capacity of these cells to participate in the healing of injured endothelium. Animal models demonstrate the ability of these cells to home in to sites of iatrogenic vessel injury and contribute to re‐endothelialisation. The goal of this thesis is to design a reproducible and scalable biocompatible coating platform for coronary stents. We explored the capacity of rhTE to support EPC activity followed by a mechanistic study of the nature of this interaction. Following this, we purpose built a plasma polymer film deposition chamber, optimizing for consistent and predictable film production. Nitrogen content of the plasma polymer films were progressively increased. A detailed physical, chemical and biological characterization of these nitrogenized films was carried out. There were several key findings from this thesis. We found rhTE supported EPC attachment, spreading and proliferation via an integrin mediated process. Using truncated rhTE constructs we were able to narrow down the site of interaction on rhTE to a region between N‐terminal domains 10 and 18. By increasing the flow of nitrogen during plasma film deposition we successfully created films with increasing concentration of nitrogen. Physical and chemical analyses demonstrated an amorphous carbon structure with smooth topography, containing nanoscale p‐conjugated graphite‐ like clusters, independent of nitrogen content. In contrast, nitrogen doping increased surface wettability and the amount of polar functional groups. In thrombogenicity assays lower thrombus formation, platelet adhesion and activation correlated with higher nitrogen concentration. Surprisingly, highly nitrogenized films also enhanced endothelial cell and EPC attachment and proliferation independent of rhTE functionalization. Nitrogenization of the plasma polymers did not impact on the capacity to covalently attach proteins. Nitrogenized plasma films is a promising platform to improve the biocompatibility of existing coronary stents