Técnicas OCDMA con códigos ópticos aleatorios para redes de telecontrol / telemetría en entornos cerrados

Los sistemas ópticos inalámbricos presentan numerosas ventajas que los hacen interesantes candidatos para las comunicaciones en entornos cerrados. En estos entornos la implantación de redes de telecontrol y telemetría impone requisitos particulares que permitan la comunicación de todos los nodos sin afectar la velocidad de transmisión y las condiciones de trabajo. Los sistemas basados en OCDMA suponen una buena alternativa para estos entornos por sus especiales características. En este trabajo se ha realizado una validación experimental de un sistema de comunicaciones ópticas inalámbricas para entornos cerrados, utilizando técnicas OCDMA para permitir la comuncación de un elevado número de terminales autónomos. Se presenta un estudio de diferentes familias de códigos para codificación, con especial énfasis sobre las familias de códigos ópticos aleatorios (ROC) y algorítmicos (AOC) recientemente propuestas. Se ha implementado un sistema que simula el funcionamiento de este sistema, consistente en diferentes nodos sensores y actuadores autónomos, y un nodo central que gestiona las comunicaciones del sistema y procesa los datos recogidos. Los nodos han sido diseñados de forma modular para facilitar su reconfiguración y reprogramación, permitiendo su utilización para probar diferentes técnicas de codificación y/o diferentes entornos. A partir de los datos obtenidos del funcionamiento del sistema se realiza la validación conforme a las simulaciones obtenidas en trabajos previos, confirmando el buen comportamiento del sistema y su adecuación para entornos con un elevado número de usuarios simultáneos. Abstract Optical wireless systems feature interesting characteristics which make them good candidates for communicating in closed environments. Usage of telecontrol/telemetry networks in such environments present particular constraints to allow communication between all nodes without limiting the data rate nor the work conditions. OCDMA based systems are a good choice for these environments because of their behaviour. In this work an experimental validation of an optical wireless system for closed environ¬ment is presented. OCDMA techniques have been used to communicate a large number of autonomous terminals. An study of different code families is presented, with particular interest on recently proposed families like random optical codes (ROC) or algorithmic optical codes (AOC). A test system consisting on a number of node with sensosing and actuating capabilities have been implemented to validate the overall behaviour, as well as a master node to manage the communication scheme and process the incoming data. Nodes have been designed using a modular approach to improve the reconfigurability and ease reprogramming tasks, allowing multiple coding techniques to be tested. A validation is presented comparing the data acquired with that coming from previous simulations, asserting the system’s functionalities and its good behaviour for closed environments with a large number of simultaneous users

Comparison between the Performance of Algorithmic Optical Codes and Orthogonal Optical Codes in OCDMA Systems

A novel method to be used in OCDMA systems is exhaustively described in this paper. It uses Algorithmic Optical Codes (AOCs). They are based on the signature sequence idea. However patterns are constantly changing. A common seed for pseudo-random sequence is the signature element. In this paper a derivation of the probability of error due to the multiple-access interference is provided. An other contribution of this work is also the comparison between the AOCs and the Orthogonal Optical Codes (OOCs) with (auto- and cross-) correlation equal to one. Attending to the cardinality limitation problem observed in OOCs, the comparison is focused on the number of users allowed by the two different systems aforementioned. As result we state that a system using AOCs allows more users than one using OOCs when the codes are long enough

Wireless Sensor Network based on OCDMA for closed environments

An infrared optical wireless system is presented, consisting on autonomous remote nodes communicating with a central node. The network is designed for telecommand/telemetry purposes, comprising a large number of nodes at a low data rate. Simultaneous access is granted by using CDMA techniques, and an appropriate selection of the code family can also keep power consumption to a minimu

LED Jitter-Induced Limitation Effects in the Baud Rate of VLC

In this paper we show that the effect of jitter due to driver and LED is the limiting factor in the baud rate in L-PPM formats for VLC systems

Towards energy neutral wireless communications : photovoltaic cells to connect remote areas

In this work, we have designed, developed and deployed the world's first optical wireless communication (OWC) system using off-the-shelf lasers and solar photovoltaics. Four bidirectional OWC prototypes have been installed on the Orkney Islands of Scotland at a 30 m link distance for the provision of high-speed internet access to two residential properties. The silicon-made solar panels can harvest power up to 5 W from sunlight and they offer data rates as high as 8 Mb/s. Using additional analogue processing, data rates higher than the existing landline broadband connection are achieved. This breakthrough opens the development path to low cost, self-powered and plug-and-play free-space optical (FSO) systems

The impact of radiofrequency-assisted transection on local hepatic recurrence after resection of colorectal liver metastases

Resection is the gold standard in the treatment of liver metastases from colorectal cancer. An internal cooled radiofrequency electrode was described to achieve tissue coagulation to a greater margin width. The aim of this study is to determinate if a RFassisted transection device (RFAT) has any effect on local hepatic recurrence (LHER) compared to conventional technologies. A study population of 103 patients who had undergone a hepatic surgical resection was retrospectively analysed. Patients were classified into two groups according to the device used: a RF-assisted device (RFAT group; n=45) and standard conventional devices (control group; n=58). LHER was defined as any growing or enhancing tumour in the margin of hepatic resection during follow-up. Cox proportional models were constructed and variables were eliminated only if p>0.20 to protect against residual confounding. To assess the stability of Cox’s regression model and its internal validity, a bootstrap investigation was also performed. Baseline and operative characteristics were similar in both groups. With a mean followup of 28.5 months (range 2-106), in patients with positive margins, we demonstrated 0% of LHER in RFAT vs. 27% in control group (p=0.032). In the multivariate analysis five factors demonstrated significant influence on the final model of LHER: RFAT group, size of the largest metastases, number of resected metastases, positive margin and usage of Pringle-manoeuvre. This study suggests that parenchymal transection using a RFAT able to create deep thermal lesions may reduce LHER especially in case of margin invasion during transectionQuesada-Diez, R.; Moreno, A.; Poves, I.; Berjano, E.; Grande, L.; Burdío Pinilla, F. (2017). The impact of radiofrequency-assisted transection on local hepatic recurrence after resection of colorectal liver metastases. Surgical Oncology. 26(3):229-235. doi:10.1016/j.suronc.2017.04.004S22923526

Introduction to indoor networking concepts and challenges in LiFi

LiFi is networked, bidirectional wireless communication with light. It is used to connect fixed and mobile devices at very high data rates by harnessing the visible light and infrared spectrum. Combined, these spectral resources are 2600 times larger than the entire radio frequency (RF) spectrum. This paper provides the motivation behind why LiFi is a very timely technology, especially for 6th generation (6G) cellular communications. It discusses and reviews essential networking technologies, such as interference mitigation and hybrid LiFi/Wi-Fi networking topologies. We also consider the seamless integration of LiFi into existing wireless networks to form heterogeneous networks across the optical and RF domains and discuss implications and solutions in terms of load balancing. Finally, we provide the results of a real-world hybrid LiFi/Wi-Fi network deployment in a software defined networking testbed. In addition, results from a LiFi deployment in a school classroom are provided, which show that Wi-Fi network performance can be improved significantly by offloading traffic to the LiFi

Wireless Optical Communications for Intra-Spacecraft Networks Based on OCDMA with Random Optical Codes

In recent years, spacial agencies have shown a growing interest in optical wireless as an alternative to wired and radio-frequency communications. The use of these techniques for intra-spacecraft communications reduces the effect of take-off acceleration and vibrations on the systems by avoiding the need for rugged connectors and provides a significant mass reduction. Diffuse transmission also eases the design process as terminals can be placed almost anywhere without a tight planification to ensure the proper system behaviour. Previous studies have compared the performance of radio-frequency and infrared optical communications. In an intra-satellite environment optical techniques help reduce EMI related problems, and their main disadvantages - multipath dispersion and the need for line-of-sight - can be neglected due to the reduced cavity size. Channel studies demonstrate that the effect of the channel can be neglected in small environments if data bandwidth is lower than some hundreds of MHz

Radiofrequency-induced heating versus mechanical stapler for pancreatic stump closure: in vivo comparative study

Purpose: To assess the capacity of two methods of surgical pancreatic stump closure in terms of reducing the risk of pancreatic fistula formation (POPF): radiofrequencyinduced heating versus mechanical stapler. Materials and Methods: Sixteen pigs underwent a laparoscopic transection of the neck of the pancreas. Pancreatic anastomosis was always avoided in order to work with an experimental model prone to pancreatic fistula formation (POPF). Pancreatic stump closure was conducted either by stapler (ST Group, n=8) or radiofrequency energy (RF Group, n=8). Both groups were compared for incidence of POPF and histopathologic alterations of the pancreatic remnant. Results: Six animals (75%) in the ST Group and one (14%) in the RF Group were diagnosed of POPF (p=0.019). One animal in the RF Group and three animals in the ST Group had a pseudocyst in close contact with both pancreas stumps. On day 30 postoperative, almost complete atrophy of the exocrine distal pancreas was observed when the main pancreatic duct was efficiently sealed. Conclusions: Our findings suggest that RF-induced heating is more effective at closing the pancreatic stump than mechanical stapler and leads to the complete atrophy of the distal remnant pancreas.This work was supported by the Spanish 'Programa Estatal de Investigacion, Desarrollo e Innovacion Orientada a los Retos de la Sociedad' under grant TEC2014-52383-C3-R (TEC2014-52383-C3-3-R). F.B., R.Q. and E.B. declare stock ownership in Apeiron Medical S.L., a company that has a license for the patent US 8.303.584.B2, on which the device tested in this study is based. The other authors report no conflict of interests or financial ties to disclose. The authors alone are responsible for the content and writing of the paper.Burdío Pinilla, F.; Dorcaratto, D.; Hernandez, L.; Andaluz, A.; Moll, X.; Quesada-Diez, R.; Poves, I.... (2016). Radiofrequency-induced heating versus mechanical stapler for pancreatic stump closure: in vivo comparative study. International Journal of Hyperthermia. 32(3):272-280. https://doi.org/10.3109/02656736.2015.113684527228032

El huerto didáctico de la facultad de educación: un espacio de formación y transferencia para mejorar las competencias profesionales de maestros de educación infantil y primaria

El huerto escolar es una herramienta pedagógica que ofrece importantes beneficios en Educación Infantil y Primaria, permitiendo trabajar de forma experimental y manipulativa contenidos de ciencias de la naturaleza, matemáticas, artes plásticas o tecnología. El huerto es un espacio donde también se trabaja el consumo responsable, el uso eficiente de los recursos naturales, la alimentación sana, y donde se generan nuevas formas de relación entre alumnado y profesorado, desarrollando valores como el trabajo en equipo, la responsabilidad, la solidaridad y el esfuerzo. Sin embargo, la sola existencia de un huerto en un centro escolar no implica que se obtenga de él un adecuado rendimiento didáctico. Desde las propias escuelas reconocen que el rendimiento del huerto es en ocasiones subóptimo, y los maestros manifiestan la necesidad de disponer de materiales oficiales para apoyar y dirigir el trabajo en el huerto escolar. Es, por tanto, fundamental que el huerto escolar se acompañe de una adecuada formación académica de los futuros maestros de Educación Infantil y Primaria. La Facultad de Educación de la UCM cuenta con un huerto didáctico que se creó en 2014 gracias a un Proyecto de Innovación, al que se dio continuidad en 2015 con otro Proyecto de Innovación. En estos años el huerto de la Facultad de Educación ha sido un recurso importante para la formación de más de 200 alumnos de diferentes asignaturas de los Grados de Maestro en Educación Infantil y Primaria. El curso 2016-2017 damos continuidad a este proyecto a través de la convocatoria Innova-Docencia, con el objetivo de diseñar e implementar actividades innovadoras entorno al huerto didáctico de la Facultad de Educación. Se plantean actividades orientadas a trabajar la conservación de la biodiversidad, los recursos naturales y el desarrollo sostenible. Algunas actividades han tenido conexión con la tecnología, como el uso de códigos QR para ampliar el conocimiento de diferentes especies vegetales. El trabajo en el huerto esta ligado de manera oficial a la formación académica de los estudiantes de la Facultad de Educación a través de las prácticas de diferentes asignaturas. En el proyecto participan 6 docentes del Departamento de Didáctica de las Ciencias Experimentales, un miembro del PAS y 19 alumnos. Las actividades planteadas en el huerto han tenido una ‘dimensión on-line’. El huerto didáctico de la Facultad de Educación cuenta con el apoyo del Equipo de Gobierno de la Facultad, de la Delegación Rectoral para Campus y Medio Ambiente de la UCM y de la Unidad Técnica de Mantenimiento de Zonas Verdes de la UCM. El objetivo a medio-largo plazo es continuar consolidándolo como herramienta docente oficial en la Facultad de Educación