Sub-Femto-g free fall for space-based gravitational wave observatories : LISA Pathfinder results

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 +/- 0.1 fm s(-2)/root Hz, or (0.54 +/- 0.01) x 10(-15) g/root Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 +/- 0.3) fm/root Hz, about 2 orders of magnitude better than requirements. At f <= 0.5 mHz we observe a low-frequency tail that stays below 12 fm s(-2)/root Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.Peer ReviewedPostprint (published version

Exoskeleton for ankle joint flexion/extension rehabilitation

Este trabajo presenta el modelado, diseño, construcción, y control de un exoesqueleto para rehabilitación de la flexión/extensión de la articulación del tobillo. El modelo dinámico de la flexión/extensión del tobillo es obtenido por medio de la formulación de Euler-Lagrange y es construido en Simulink de MATLAB usando la ecuación diferencial no-lineal derivada del análisis dinámico. Un controlador PID de realimentación del desplazamiento angular, representando el control neuromusculoesquelético humano, es implementado en el modelo dinámico para estimar el torque articular requerido durante los movimientos del tobillo. Se realizan simulaciones en el modelo para el rango de movimiento (ROM) de la flexión/extensión del tobillo, y los resultados son usados para seleccionar el actuador más adecuado para el exoesqueleto. El exoesqueleto para rehabilitación del tobillo es diseñado en el software CAD SolidWorks, construido por impresión 3D en ácido poliláctico (PLA), accionado por dos servomotores que entregan juntos un torque continuo máximo de 22 [kg cm], y controlado por una placa Arduino que establece comunicación Bluetooth con un aplicativo móvil desarrollado en MIT App Inventor para la programación de los parámetros de las terapias de rehabilitation. El resultado de este trabajo es un exoesqueleto liviano de tobillo, con una masa total de 0.85[kg] incluyendo actuadores (servomotores) y electrónica (microcontrolador y baterías), el cual puede ser usado en prácticas de telerehabilitación garantizando errores de seguimiento del desplazamiento angular por debajo del 10%.This work presents the modelling, design, construction, and control of an exoskeleton for ankle joint flexion/extension rehabilitation. The dynamic model of the ankle flexion/extension is obtained through Euler-Lagrange formulation and is built in Simulink of MATLAB using the non-linear differential equation derived from the dynamic analysis. An angular displacement feedback PID controller, representing the human neuromusculoskeletal control, is implemented in the dynamic model to estimate the joint torque required during ankle movements. Simulations are carried out in the model for the ankle flexion/extension range of motion (ROM), and the results are used to select the most suitable actuators for the exoskeleton. The ankle rehabilitation exoskeleton is designed in SolidWorks CAD software, built through 3D printing in polylactic acid (PLA), powered by two on-board servomotors that deliver together a maximum continuous torque of 22 [kg cm], and controlled by an Arduino board that establishes Bluetooth communication with a mobile app developed in MIT App Inventor for programming the parameters of the rehabilitation therapies. The result of this work is a lightweight ankle exoskeleton, with a total mass of 0.85 [kg] including actuators (servomotors) and electronics (microcontroller and batteries), which can be used in telerehabilitation practices guaranteeing angular displacement tracking errors under 10%

Backhaul-Aware Dimensioning and Planning of Millimeter-Wave Small Cell Networks

The massive deployment of Small Cells (SCs) is increasingly being adopted by mobile operators to face the exponentially growing traffic demand. Using the millimeter-wave (mmWave) band in the access and backhaul networks will be key to provide the capacity that meets such demand. However, dimensioning and planning have become complex tasks, because the capacity requirements for mmWave links can significantly vary with the SC location. In this work, we address the problem of SC planning considering the backhaul constraints, assuming that a line-of-sight (LOS) between the nodes is required to reliably support the traffic demand. Such a LOS condition reduces the set of potential site locations. Simulation results show that, under certain conditions, the proposed algorithm is effective in finding solutions and strongly efficient in computational cost when compared to exhaustive search approaches.H2020 research and innovation project 5G-CLARITY 871428Spanish Ministry of Science, Innovation and Universities PID2019-108713RB-C5

NAPA: An algorithm to auto-tune unicast reliable communications over DDS

This paper proposes NAPA (Non-supervised Adaptative Publication Algorithm) a framework for a uto-tuning unicast reliable communications over DDS. We provide the NAPA design rationale, and some implementation details. After the experimental conducted evaluation, we demonstrate how using the subscriber's feedback, as NAPA does, the publisher can vary its sending rate in order to improve the overall performance in terms of end-to-end latency and throughput in DDS applications.Universidad de Granada. Departamento de Teoría de la Señal, Telemática y ComunicacionesThis research was partially founded by Spanish Ministry of Education (collaboration grant 2012-2013)

Modeling and Dimensioning of a Virtualized MME for 5G Mobile Networks

Network function virtualization is considered one of the key technologies for developing future mobile networks. In this paper, we propose a theoretical framework to evaluate the performance of a Long-Term Evolution (LTE) virtualized mobility management entity (vMME) hosted in a data center. This theoretical framework consists of 1) a queuing network to model the vMME in a data center and 2) analytic expressions to estimate the overall mean system delay and the signaling workload to be processed by the vMME. We validate our mathematical model by simulation. One direct use of the proposed model is vMME dimensioning, i.e., to compute the number of vMME processing instances to provide a target system delay given the number of users in the system. Additionally, the paper includes a scalability analysis of the system. In our study, we consider the billing model and a data center setup of Amazon Elastic Compute Cloud service and estimate the processing time of MME processing instances for different LTE control procedures experimentally. For the considered setup, our results show that the vMME is scalable for signaling workloads up to 37 000 LTE control procedures per second for a target mean system delay of 1 ms. The system design and database performance assumed imposes this limit in the system scalability.This work was supported in part by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (project TIN2013-46223-P) and in part by the Spanish Ministry of Education, Culture, and Sport under FPU Grant 13/04833

Reduced M2M Signaling Communications in 3GPP LTE and Future 5G Cellular Networks

The increase of machine-to-machine (M2M) communications over cellular networks imposes new requirements and challenges that current networks have to handle with. Many M2M UEs (User Equipment) may send small infrequent data, which suppose a challenge for cellular networks not optimized for such traffic, where signaling load could increase significantly and cause congestion over the network. This paper evaluates current proposals to manage small transmissions over the Long Term Evolution (LTE) cellular network. We also propose a new Random Access-based Small IP packet Transmission (RASIPT) procedure for M2M UEs small data transmissions. Its main feature is data transfer without establishment of Radio Resource Control (RRC) connection to reduce signaling overhead. In our design, we assume a Software Defined Networking-based architecture for 5G system. When compared with current LTE scheme, our procedure reduces significantly the signaling load generated by M2M UEs small transmissions.This work is partially supported by the Spanish Ministry of Economy and Competitiveness (project TIN2013- 46223-P), FEDER and the Spanish Ministry of Education, Culture and Sport (FPU grant 13/04833)

A LoRaWAN Architecture for Communications in Areas without Coverage: Design and Pilot Trials

This research was partially funded by the Andalusian Knowledge Agency (projects A-TIC-241-UGR18 and B-TIC-568-UGR20), the Spanish Ministry of Science and Innovation (project PID2019-108713RB-C53), the Spanish Ministry of Economic Affairs and Digital Transformation (project TSI-063000-2021-28) and the Spanish Ministry of Universities (FPU Grant Number: 20/02621).This article proposes a system based on a long-distance communications system with low economic and energy costs that allows connectivity to be carried out independently from the existing cellular coverage in the area. In addition, it describes the design, development, implementation and analysis of an Internet of Things (IoT) architecture based on Long-RangeWide-Area Network (LoRaWAN). Moreover, the system has been deployed as a prototype, and the behavior and scope of the system have been analyzed in various real environments: urban, rural and natural. The results obtained from the analysis show that the system is suitable for working in areas without coverage such as mountains.Andalusian Knowledge Agency A-TIC-241-UGR18 B-TIC-568-UGR20Spanish Government PID2019-108713RB-C53Spanish Ministry of Economic Affairs and Digital Transformation TSI-063000-2021-28Spanish Ministry of Universities (FPU) 20/0262

A Survey on 5G Usage Scenarios and Traffic Models

The fifth-generation mobile initiative, 5G, is a tremendous and collective effort to specify, standardize, design, manufacture, and deploy the next cellular network generation. 5G networks will support demanding services such as enhanced Mobile Broadband, Ultra-Reliable and Low Latency Communications and massive Machine-Type Communications, which will require data rates of tens of Gbps, latencies of few milliseconds and connection densities of millions of devices per square kilometer. This survey presents the most significant use cases expected for 5G including their corresponding scenarios and traffic models. First, the paper analyzes the characteristics and requirements for 5G communications, considering aspects such as traffic volume, network deployments, and main performance targets. Secondly, emphasizing the definition of performance evaluation criteria for 5G technologies, the paper reviews related proposals from principal standards development organizations and industry alliances. Finally, well-defined and significant 5G use cases are provided. As a result, these guidelines will help and ease the performance evaluation of current and future 5G innovations, as well as the dimensioning of 5G future deployments.This work is partially funded by the Spanish Ministry of Economy and Competitiveness (project TEC2016-76795-C6-4-R)H2020 research and innovation project 5G-CLARITY (Grant No. 871428)Andalusian Knowledge Agency (project A-TIC-241-UGR18)

Link-Level Access Cloud Architecture Design Based on SDN for 5G Networks

The exponential growth of data traffic and connected devices, and the reduction of latency and costs, are considered major challenges for future mobile communication networks. The satisfaction of these challenges motivates revisiting the architecture of these networks. We propose an SDN-based design of a hierarchical architecture for the 5G packet core. In this article we focus on the design of its access cloud with the goal of providing low latency and scalable Ethernet-like support to terminals and MTC devices including mobility management. We examine and address its challenges in terms of network scalability and support for link-level mobility. We propose a link-level architecture that forwards frames from and to edge network elements (AP and routers) with a label that identifies the APs through which the terminal is reachable. An SDN local controller tracks and updates the users' location information at the edge network elements. Additionally, we propose to delegate in SDN local controllers the handling of non-scalable operations, such as broadcast and multicast messages, and network management procedures.This work is partially supported by the Spanish Ministry of Economy and Competitiveness (project TIN2013-46223-P), and the Granada Excellence Network of Innovation Laboratories (projects GENIL-PYR-2014-20 and GENIL-PYR-2014-18)

Network slicing for 5G with SDN/NFV: Concepts, architectures and challenges

The fifth generation of mobile communications is anticipated to open up innovation opportunities for new industries such as vertical markets. However, these verticals originate myriad use cases with diverging requirements that future 5G networks have to efficiently support. Network slicing may be a natural solution to simultaneously accommodate over a common network infrastructure the wide range of services that vertical-specific use cases will demand. In this article, we present the network slicing concept, with a particular focus on its application to 5G systems. We start by summarizing the key aspects that enable the realization of so-called network slices. Then, we give a brief overview on the SDN architecture proposed by the ONF and show that it provides tools to support slicing. We argue that although such architecture paves the way for network slicing implementation, it lacks some essential capabilities that can be supplied by NFV. Hence, we analyze a proposal from the ETSI to incorporate the capabilities of SDN into the NFV architecture. Additionally, we present an example scenario that combines SDN and NFV technologies to address the realization of network slices. Finally, we summarize the open research issues with the purpose of motivating new advances in this field