ANÁLISIS DE DESEMPEÑO DEL NIVEL FÍSICO DE UN SISTEMA MIMO PUNTO A PUNTO

Los sistemas de comunicaciones de múltiples entradas y múltiples salidas son la base de las altas capacidades de los sistemas de comunicaciones de tercera y cuarta generación, es importante analizar las características de nivel físico de dichos sistemas y como la variación de sus parámetros influyen en el desempeño. En el entorno universitario, es necesario disponer de herramientas que permitan analizar el desempeño de los sistemas MIMO, en este trabajo se presenta el análisis y diseño a nivel físico de un sistema MIMO 2x2 y 4x4 con canal Rayleigh, con variaciones en el esquema de modulación y en los algoritmos de detección. El trabajo se desarrolla de acuerdo a una metodología específica para la simulación de sistemas de telecomunicaciones. El sistema se implementó en Matlab y se validó de acuerdo a trabajos previamente realizados, se configuraron diferentes escenarios sobre los cuales se comprobó que el desempeño del sistema MIMO depende del número de antenas en transmisión y en recepción, la modulación y el algoritmo de detección, consiguiéndose el mejor desempeño para el sistema MIMO 4x4 con modulación QPSK, con algoritmo de detección de máxima verosimilitud, pero con elevada complejidad computacional, seguido por el algoritmo esférico y finalmente los algoritmos suboptimos MMSE y ZF.PALABRAS CLAVES: Sistemas MIMO, Desempeño del Nivel Físico, Algoritmos de detecciónEsquemas de multiplexación, Matlab.ABSTRACTCommunications systems of multiple inputs and multiple outputs are the basis of high capacity communications systems of third and fourth generation, it is important to analyze the physical characteristics of these systems and how the variation of the parameters affecting performance . In the university environment, it is necessary to have tools to analyze the performance of MIMO systems, this paper presents the analysis and design at the physical level of a 2x2 and 4x4 MIMO Rayleigh channel with variations in the modulation scheme and detection algorithms. The work is carried out according to a specific methodology for the simulation of telecommunication systems. The system was implemented in Matlab and validated according to work already performed, different scenarios were configured on which it was found that the MIMO system performance depends on the number of antennas in transmission and reception, modulation and detection algorithm achieving the best performance for the 4x4 MIMO system with QPSK modulation, detection algorithm with maximum likelihood, but with high computational complexity, followed by the algorithm and finally spherical suboptimal MMSE and ZF algorithms.KEYWORDS: MIMO Systems, Physical Layer Performance, Detection Algorithms, Multiplexing schemes, Matlab

ANÁLISIS DE DESEMPEÑO DEL NIVEL FÍSICO DE UN SISTEMA MIMO PUNTO A PUNTO

Los sistemas de comunicaciones de múltiples entradas y múltiples salidas son la base de las altas capacidades de los sistemas de comunicaciones de tercera y cuarta generación, es importante analizar las características de nivel físico de dichos sistemas y como la variación de sus parámetros influyen en el desempeño. En el entorno universitario, es necesario disponer de herramientas que permitan analizar el desempeño de los sistemas MIMO, en este trabajo se presenta el análisis y diseño a nivel físico de un sistema MIMO 2x2 y 4x4 con canal Rayleigh, con variaciones en el esquema de modulación y en los algoritmos de detección. El trabajo se desarrolla de acuerdo a una metodología específica para la simulación de sistemas de telecomunicaciones. El sistema se implementó en Matlab y se validó de acuerdo a trabajos previamente realizados, se configuraron diferentes escenarios sobre los cuales se comprobó que el desempeño del sistema MIMO depende del número de antenas en transmisión y en recepción, la modulación y el algoritmo de detección, consiguiéndose el mejor desempeño para el sistema MIMO 4x4 con modulación QPSK, con algoritmo de detección de máxima verosimilitud, pero con elevada complejidad computacional, seguido por el algoritmo esférico y finalmente los algoritmos suboptimos MMSE y ZF.PALABRAS CLAVES: Sistemas MIMO, Desempeño del Nivel Físico, Algoritmos de detecciónEsquemas de multiplexación, Matlab.ABSTRACTCommunications systems of multiple inputs and multiple outputs are the basis of high capacity communications systems of third and fourth generation, it is important to analyze the physical characteristics of these systems and how the variation of the parameters affecting performance . In the university environment, it is necessary to have tools to analyze the performance of MIMO systems, this paper presents the analysis and design at the physical level of a 2x2 and 4x4 MIMO Rayleigh channel with variations in the modulation scheme and detection algorithms. The work is carried out according to a specific methodology for the simulation of telecommunication systems. The system was implemented in Matlab and validated according to work already performed, different scenarios were configured on which it was found that the MIMO system performance depends on the number of antennas in transmission and reception, modulation and detection algorithm achieving the best performance for the 4x4 MIMO system with QPSK modulation, detection algorithm with maximum likelihood, but with high computational complexity, followed by the algorithm and finally spherical suboptimal MMSE and ZF algorithms.KEYWORDS: MIMO Systems, Physical Layer Performance, Detection Algorithms, Multiplexing schemes, Matlab

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2

Reduction of cardiac imaging tests during the COVID-19 pandemic: The case of Italy. Findings from the IAEA Non-invasive Cardiology Protocol Survey on COVID-19 (INCAPS COVID)

Background: In early 2020, COVID-19 massively hit Italy, earlier and harder than any other European country. This caused a series of strict containment measures, aimed at blocking the spread of the pandemic. Healthcare delivery was also affected when resources were diverted towards care of COVID-19 patients, including intensive care wards. Aim of the study: The aim is assessing the impact of COVID-19 on cardiac imaging in Italy, compare to the Rest of Europe (RoE) and the World (RoW). Methods: A global survey was conducted in May–June 2020 worldwide, through a questionnaire distributed online. The survey covered three periods: March and April 2020, and March 2019. Data from 52 Italian centres, a subset of the 909 participating centres from 108 countries, were analyzed. Results: In Italy, volumes decreased by 67% in March 2020, compared to March 2019, as opposed to a significantly lower decrease (p &lt; 0.001) in RoE and RoW (41% and 40%, respectively). A further decrease from March 2020 to April 2020 summed up to 76% for the North, 77% for the Centre and 86% for the South. When compared to the RoE and RoW, this further decrease from March 2020 to April 2020 in Italy was significantly less (p = 0.005), most likely reflecting the earlier effects of the containment measures in Italy, taken earlier than anywhere else in the West. Conclusions: The COVID-19 pandemic massively hit Italy and caused a disruption of healthcare services, including cardiac imaging studies. This raises concern about the medium- and long-term consequences for the high number of patients who were denied timely diagnoses and the subsequent lifesaving therapies and procedures

International Impact of COVID-19 on the Diagnosis of Heart Disease

Background: The coronavirus disease 2019 (COVID-19) pandemic has adversely affected diagnosis and treatment of noncommunicable diseases. Its effects on delivery of diagnostic care for cardiovascular disease, which remains the leading cause of death worldwide, have not been quantified. Objectives: The study sought to assess COVID-19's impact on global cardiovascular diagnostic procedural volumes and safety practices. Methods: The International Atomic Energy Agency conducted a worldwide survey assessing alterations in cardiovascular procedure volumes and safety practices resulting from COVID-19. Noninvasive and invasive cardiac testing volumes were obtained from participating sites for March and April 2020 and compared with those from March 2019. Availability of personal protective equipment and pandemic-related testing practice changes were ascertained. Results: Surveys were submitted from 909 inpatient and outpatient centers performing cardiac diagnostic procedures, in 108 countries. Procedure volumes decreased 42% from March 2019 to March 2020, and 64% from March 2019 to April 2020. Transthoracic echocardiography decreased by 59%, transesophageal echocardiography 76%, and stress tests 78%, which varied between stress modalities. Coronary angiography (invasive or computed tomography) decreased 55% (p &lt; 0.001 for each procedure). In multivariable regression, significantly greater reduction in procedures occurred for centers in countries with lower gross domestic product. Location in a low-income and lower–middle-income country was associated with an additional 22% reduction in cardiac procedures and less availability of personal protective equipment and telehealth. Conclusions: COVID-19 was associated with a significant and abrupt reduction in cardiovascular diagnostic testing across the globe, especially affecting the world's economically challenged. Further study of cardiovascular outcomes and COVID-19–related changes in care delivery is warranted

Impact of COVID-19 on Diagnostic Cardiac Procedural Volume in Oceania: The IAEA Non-Invasive Cardiology Protocol Survey on COVID-19 (INCAPS COVID)

Objectives: The INCAPS COVID Oceania study aimed to assess the impact caused by the COVID-19 pandemic on cardiac procedure volume provided in the Oceania region. Methods: A retrospective survey was performed comparing procedure volumes within March 2019 (pre-COVID-19) with April 2020 (during first wave of COVID-19 pandemic). Sixty-three (63) health care facilities within Oceania that perform cardiac diagnostic procedures were surveyed, including a mixture of metropolitan and regional, hospital and outpatient, public and private sites, and 846 facilities outside of Oceania. The percentage change in procedure volume was measured between March 2019 and April 2020, compared by test type and by facility. Results: In Oceania, the total cardiac diagnostic procedure volume was reduced by 52.2% from March 2019 to April 2020, compared to a reduction of 75.9% seen in the rest of the world (p&lt;0.001). Within Oceania sites, this reduction varied significantly between procedure types, but not between types of health care facility. All procedure types (other than stress cardiac magnetic resonance [CMR] and positron emission tomography [PET]) saw significant reductions in volume over this time period (p&lt;0.001). In Oceania, transthoracic echocardiography (TTE) decreased by 51.6%, transoesophageal echocardiography (TOE) by 74.0%, and stress tests by 65% overall, which was more pronounced for stress electrocardiograph (ECG) (81.8%) and stress echocardiography (76.7%) compared to stress single-photon emission computerised tomography (SPECT) (44.3%). Invasive coronary angiography decreased by 36.7% in Oceania. Conclusion: A significant reduction in cardiac diagnostic procedure volume was seen across all facility types in Oceania and was likely a function of recommendations from cardiac societies and directives from government to minimise spread of COVID-19 amongst patients and staff. Longer term evaluation is important to assess for negative patient outcomes which may relate to deferral of usual models of care within cardiology