Estimación de canal y desplazamiento de frecuencia en sistemas MIMO-OFDM con prefijo cíclico insuficiente

La presente Tesis aborda el análisis de la estimación de canal y desplazamiento de frecuencia en sistemas MIMO-OFDM (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing) en condiciones de prefijo cíclico insuficiente. La motivación fundamental es estudiar uno de los sistemas más utilizados actualmente, como es MIMO-OFDM, pero con la intención de mejorar una de las características intrínsecas que le proporciona mayores ventajas, como es el uso del prefijo cíclico. Dicho prefijo cíclico permite mantener la ortogonalidad entre subportadoras y evita la aparición de interferencias entre símbolos y entre portadoras, facilitando también la ecualización en entornos multitrayecto, siempre que su longitud sea mayor que la del canal. Sin embargo, produce un decremento de la capacidad del sistema, al no llevar información por ser una réplica de las últimas muestras de cada símbolo OFDM, y disminuye la eficiencia de la estimación de parámetros. La Tesis se centra, por tanto, en analizar un sistema MIMO-OFDM con prefijo cíclico insuficiente, menor a la longitud del canal, que puede ser debido a una supresión intencionada para incrementar la capacidad, a canales largos altamente dispersivos o para eliminar patrones repetitivos de la señal que facilitan la interceptabilidad de la señal OFDM. Por consiguiente, para abordar el objetivo principal de esta Tesis es necesario analizar aquellos inconvenientes que surgen de la existencia de un prefijo cíclico insuficiente. Por un lado, se analiza el impacto sobre las comunicaciones MIMO-OFDM en términos de interferencias en la parte de datos de la estructura de trama así como sobre la estimación de canal y desplazamiento de frecuencia. También se evalúan las secuencias utilizadas como preámbulo para dichas estimaciones tanto desde el punto de vista de sus características y utilización como desde el punto de vista de rango de adquisición del desplazamiento de frecuencia. Se demuestra claramente que los estimadores propuestos convergen a sus límites teóricos y que las secuencias seleccionadas tienen el mayor rango de adquisición posible. Por otro lado, una vez analizado el efecto sobre la parte de datos de la trama, también se analiza el impacto sobre el propio preámbulo que se utiliza para labores de estimación y se presentan los resultados correspondientes a la tasa de error, demostrando que el rendimiento obtenido se equipara al de aquellos sistemas con prefijo cíclico suficiente. Debido a que las estrategias propuestas incrementan la complejidad del sistema, se analiza con detalle el coste computacional de la implementación del esquema de receptor propuesto concluyéndose que el coste que supone es muy inferior comparado con el ahorro que propicia en términos de capacidad y energía. Finalmente, se propone la implementación de algunas de las estrategias definidas anteriormente en un sistema real como es el enlace descendente del estándar LTE (Long Term Evolution). En primer lugar, se propone una estructura de trama y receptor aplicados a una aproximación simplificada del estándar. Posteriormente, se adaptan las estrategias propuestas a una versión más fidedigna de dicho estándar. Los resultados obtenidos en ambos casos ponen de manifiesto las notables mejoras que implica la utilización de los receptores propuestos dando lugar a rendimientos del sistema similares a los obtenidos en el caso de haber utilizado un prefijo cíclico suficiente.This Thesis tackles the analysis of channel and frequency offset estimation in MIMOOFDM (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing) systems in conditions of insufficient cyclic prefix. The main motivation is to study one of the most currently used systems, as is MIMO-OFDM, but with the intention of improving one of its intrinsic characteristics that provides more advantages, as the use of the cyclic prefix is. This cyclic prefix allows to keep the orthogonality between subcarriers and avoid the appearance of inter symbol and inter carrier interferences, making easier the equalization in multi-path environments provided that its length is longer than the channel length. However, it produces a decrease in the system capacity, since it does not bear any information because it is a replica of some last samples in every OFDM symbol, and decrease the efficiency of parameters estimation. Therefore, this Thesis is focused on analyzing a MIMO-OFDM system with insufficient cyclic prefix, shorter than the channel length, which can arise due to an intentional suppression to increase the system capacity, to highly dispersive long channels or to eliminate repetitive patterns in the OFDM signal that ease the signal interception. Consequently, to tackle the main objective of this Thesis it is necessary to analyze those inconveniences arisen from the existence of an insufficient cyclic prefix. On the one hand, the impact in MIMO-OFDM communications is analyzed in terms of interferences in the data part of the frame structure and in terms of channel and frequency offset estimation. In addition, those sequences used as preamble are assessed in relation with these estimations both concerning their characteristics and handling and considering which is the acquisition range of the frequency offset. It is clearly demonstrated that the proposed estimators converge to their theoretical limits and that the selected sequences have the highest possible acquisition range. On the other hand, once the effect over the data part of the frame has been analyzed, it is also evaluated the impact over the own preamble used for estimation tasks and the results corresponding to the error rate are presented, showing that the performance is similar to that one obtained in systems with insufficient cyclic prefix. Due to the fact that the proposed strategies increase the system complexity, the computational cost of the proposed receiver has been analyzed with detail to conclude that the implicit cost is much lower compared with the saving in terms of capacity or energy. Finally, the implementation of some of the previously defined schemes has been proposed for a real system, such as the down link in the LTE (Long Term Evolution) standard. In first place, it is proposed a frame structure and receiver for a simplified version of the standard. Later, these proposed strategies are adapted to a more similar version of the standard. The results in both cases prove the dramatic improvements of the utilization of these two proposed receivers giving rise to system performances comparable to those obtained in the case of having used a insufficient cyclic prefix.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Ana García Armada.- Secretario: Iván Alejandro Pérez Álvarez.- Vocal: María del Carmen Aguayo Torre

Suppression of cyclic prefix in down-link LTE like systems to increase capacity

The proceeding at : 77th Vehicular Technology Conference (VTC Spring), took place 2013, June 02-05, in Dresden (Germany).In this paper it is presented a proposal to increase the capacity of Down-Link (DL) transmissions in Long Term Evolution (LTE) like systems based on Multiple-Input Multiple-Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM). The augment of the data rate is achieved with the total or partial suppression of the Cyclic Prefix (CP), which requires the use of a variable number of samples without conveying any information. The proposal is based on an iterative cancellation of the main impairments that the CP suppression supposes, the Inter Symbol and Inter Carrier Interferences. The interference mitigation procedure demands adequate channel estimations obtained in two different stages. Firstly, this new scheme requires the utilization of a preamble symbol appended to the beginning of the data transmission, which enables an initial Maximum Likelihood channel estimation. Secondly, time-variant channels will be estimated using a Least Squares estimator by the use of scattered pilots within the LTE frame structure. Through simulations it has been demonstrated that, despite the interferences arisen due to the CP suppression, our proposal attains adequate channel estimations which converge to theoretical bounds and the overall system obtains values of Bit Error Rate similar to the ideal situation of not suppressing the CP. It is also presented that considering the typical values of CP in the LTE standard the increment of the capacity employing this strategy can range between 7% and 25%.This work has been partly funded by the Spanish national projects GRE3NSYST (TEC2011-29006-C03-03) and COMONSENS (CSD2008-00010).Publicad

Iterative Joint Estimation Procedure for Channel and Frequency Offset in Multi-Antenna OFDM Systems With an Insufficient Cyclic Prefix

This paper addresses a strategy to improve the joint channel and frequency offset (FO) estimation in multi-antenna systems, widely known as multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM), in the presence of intersymbol interference (ISI) and intercarrier interference (ICI) occasioned by an insufficient cyclic prefix (CP). The enhancement is attained by the use of an iterative joint estimation procedure (IJEP) that successively cancels the interferences located in the preamble of the OFDM frame, which is used for the joint estimation and initially contains the interferences due to a CP shorter than the channel length. The IJEP requires at certain steps a proper iterative interference cancellation algorithm, which makes use of an initial FO compensation and channel estimation obtained due to the use of a symmetric sequence in the preamble. After the iterative cancellation of interferences, the procedure performs an additional joint channel and FO estimation whose mean square error converges to the Cramer-Rao bound (CRB). Later on, this subsequent joint estimation permits the removal of the interferences in the data part of the frame, which are also due to an insufficient CP, in the same iterative fashion but saving iterations compared with the use of other estimation strategies. The appraisal of the procedure has been performed by assessing the convergence of the simulated estimators to the CRB as a function of the number of iterations. Additionally, simulations for the evaluation of the bit error rate (BER) have been carried out to probe how the utilization of the proposed IJEP clearly improves the performance of the system. It is concluded that, with a reduced number of iterations in the preamble, the IJEP converges to the theoretical bounds, thus reducing the disturbances caused by a hard wireless channel or a deliberately insufficient CP.This work was supported in part by the Spanish na-tional projects GRE3N-SYST (TEC2011-29006-C03-03) and COMONSENS (CSD2008-00010).Publicad

Proceso asistencial integrado de esclerosis lateral amiotrófica

O proceso asistencial integrado da esclerose lateral amiotrófica, elaborouse co obxectivo de crear un proceso de traballo común en todas as áreas para facilitar a asistencia sanitaria ás persoas diagnosticadas desta enfermidade. Establécense actuacións como o asesoramento continuo, as consultas en acto único, a coordinación asistencial, tanto entre especialidades como coa atención primaria e a coordinación administrativa do sistema socio sanitario. Neste proceso participaron profesionais das diferentes áreas sanitarias especialistas en neuroloxía, endocrinoloxía, neumoloxía, psicoloxía clínica, rehabilitación, traballo social e hospitalización a domicilioEl proceso asistencial integrado de la esclerosis lateral amiotrófica, se elaboró con el objetivo de crear un proceso de trabajo común en todas las áreas para facilitar la asistencia sanitaria a las personas diagnosticadas de esta enfermedad. Se establecen actuaciones como el asesoramiento continuo, las consultas en acto único, la coordinación asistencial, tanto entre especialidades como con la atención primaria y la coordinación administrativa del sistema socio sanitario. En este proceso participaron profesionales de las diferentes áreas sanitarias especialistas en neurología, endocrinología, neumología, psicología clínica, rehabilitación, trabajo social y hospitalización a domicili

Artistas sobre outras obras

A pós modernidade encerra a interrogação crítica do homem sobre o homem: a linguagem ameaça o que é significante, o que é corpo. O sujeito é falado, e assim constituído depois da linguagem (Althusser, 1976). O jovem Arthur Rimbaud sintetiza-o, aos dezassete anos, numa carta ao seu professor de retórica Georges Izambard, datada de 13 de maio 1871: «C’est faux de dire: je pense: on devrait dire on me pense. Pardon du jeu de mots. Je est un autre». (Rimbaud, 1999: 237) A identidade resiste à linguagem dos homens. A linguagem é transmitida entre as gerações e com ela transporta os sujeitos, ou, o que é dizer o mesmo, a possível interrogação: quem me fala? É esta também a perplexidade que motivou o tema desta revista Estúdio. Reuniram-se, nesta edição, 22 artigos, provenientes de diferentes autores da Argentina, Brasil, Portugal e Espanha, que se debruçam sobre artistas cuja identidade se mostra e merece ser interrogada: são espaços ‘ex-cêntricos,’ para se descobrir.info:eu-repo/semantics/publishedVersio

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Equipos docentes y nuevas identidades académicas : en educación superior

Resumen basado en el de la publicaciónLa noción de equipos docentes en Educación Superior define una práctica de coordinación docente, bien para el logro de determinados propósitos transversales, bien en un sentido mucho más estricto, en el despliegue coordinado de una Titulación. Se aborda la pregunta de por qué y sobre qué ha de coordinarse el profesorado universitario, como reto fundamental a la cultura organizativa docente, basada en el ejercicio individual del profesorado y en la fragmentación de tareas, de responsabilidades y del conocimiento. Los cambios apuntados en las diversas contribuciones obedecen a las transformaciones que se están dando en la universidad española como consecuencia de nuevas demandas socio-formativas, las cuales generan nuevas necesidades, funciones y estructuras. Ello da lugar a nuevas identidades académicas. Lo anterior, nos sitúa en un contexto interpretativo de calado más amplio, el de la reconstrucción de las identidades académicas en relación a las funciones ejercidas dentro de ella.MadridBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín 5 -3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]

Equipos docentes y nuevas identidades académicas : en educación superior

Resumen basado en el de la publicaciónLa noción de equipos docentes en Educación Superior define una práctica de coordinación docente, bien para el logro de determinados propósitos transversales, bien en un sentido mucho más estricto, en el despliegue coordinado de una Titulación. Se aborda la pregunta de por qué y sobre qué ha de coordinarse el profesorado universitario, como reto fundamental a la cultura organizativa docente, basada en el ejercicio individual del profesorado y en la fragmentación de tareas, de responsabilidades y del conocimiento. Los cambios apuntados en las diversas contribuciones obedecen a las transformaciones que se están dando en la universidad española como consecuencia de nuevas demandas socio-formativas, las cuales generan nuevas necesidades, funciones y estructuras. Ello da lugar a nuevas identidades académicas. Lo anterior, nos sitúa en un contexto interpretativo de calado más amplio, el de la reconstrucción de las identidades académicas en relación a las funciones ejercidas dentro de ella.MadridBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín 5 -3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]

Considerations and consequences of allowing DNA sequence data as types of fungal taxa

Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.Peer reviewe