Accuracy evaluation of probabilistic location methods in UWB-RFID systems

The present project is focused on investigating the achievable accuracy of classical location methods commonly used in wireless and proposing an alternative location method based on combining two of them. The first part of the project studies the advantages and disadvantages of extending Ultra Wideband and Radiofrequency Identification technologies on some classical location methods. As a result of the study and with the goal of improving accuracy in indoor radio propagation channels, the Received Strength Signal-based location method and the Time Difference Of Arrival-based location method are selected to be combined in the alternative location method, including the proper channel models. This combined location method takes advantage of the virtues of each location method and combines information in order to improve the estimation of one target's position when locating in indoor channel. The second part of the project is devoted to analyse and simulate the modified RSS, TDOA and Combined location methods, considering the randomness of a real multipath fading channel. Results show that the Combined location method performs always the best accuracy. Specifically in analytical study, the combined location method provides a deterministic error of 24 cm which represents an improvement of 54% and 15% of the RSS and TDOA accuracies respectively. In the simulated study, results show that it is able to improve the accuracy up to 46% and 85% of the RSS and TDOA respectively in specific evaluated points

Accuracy evaluation of probabilistic location methods in UWB-RFID systems

The present project is focused on investigating the achievable accuracy of classical location methods commonly used in wireless and proposing an alternative location method based on combining two of them. The first part of the project studies the advantages and disadvantages of extending Ultra Wideband and Radiofrequency Identification technologies on some classical location methods. As a result of the study and with the goal of improving accuracy in indoor radio propagation channels, the Received Strength Signal-based location method and the Time Difference Of Arrival-based location method are selected to be combined in the alternative location method, including the proper channel models. This combined location method takes advantage of the virtues of each location method and combines information in order to improve the estimation of one target's position when locating in indoor channel. The second part of the project is devoted to analyse and simulate the modified RSS, TDOA and Combined location methods, considering the randomness of a real multipath fading channel. Results show that the Combined location method performs always the best accuracy. Specifically in analytical study, the combined location method provides a deterministic error of 24 cm which represents an improvement of 54% and 15% of the RSS and TDOA accuracies respectively. In the simulated study, results show that it is able to improve the accuracy up to 46% and 85% of the RSS and TDOA respectively in specific evaluated points

Integración de protocolos de acceso avanzados en redes WLAN IEEE 802.11

Las redes móviles ad hoc (MANETs) son redes inalámbricas distribuidas sin infraestructura formadas por un conjunto de dispositivos inalámbricos móviles. La ausencia de una entidad centralizada encargada de la gestión de la red implica que los dispositivos deben cooperar entre sí para establecer las comunicaciones. En la actualidad, estas redes se utilizan en situaciones muy diversas como conferencias, zonas rurales con dificultades de comunicación u operaciones de rescate en zonas donde la infraestructura no existe o ha quedado destruida. La mayoría de dispositivos inalámbricos que operan en estas redes implementan la función básica de coordinación DCF definida en el estándar IEEE 802.11 como protocolo de acceso al medio (MAC). Este protocolo ofrece un buen rendimiento para bajas cargas de tráfico y para un número de usuarios no muy elevado. Sin embargo, a medida que el número de usuarios con dispositivos inalámbricos aumenta y proliferan nuevas aplicaciones multimedia con grandes requisitos de recursos de red, el rendimiento de este protocolo empieza a ser insuficiente. Por ello, resulta necesario diseñar nuevos protocolos MAC que ofrezcan buen rendimiento para cualquier número de usuarios y para elevadas cargas de tráfico. En este trabajo se ha diseñado un nuevo protocolo MAC para redes inalámbricas de tipo ad hoc llamado Distributed Point Coordination Function (DPCF). El objetivo principal de diseño de este protocolo es el de aumentar el rendimiento de este tipo de redes en términos de throughput y retardo de transmisión. Asimismo, el DPCF se ha diseñado de manera que sea posible la coexistencia con los dispositivos estándar actuales, que llevan implementado el protocolo MAC del estándar 802.11. El rendimiento de DPCF se ha evaluado mediante simulación por ordenador, usando el simulador de redes inalámbricas MACSWIN. Se han implementado tres tipos de móviles MAC en este simulador. Uno de ellos implementa el nuevo protocolo MAC y los otros las funciones PCF y DCF del estándar 802.11. Los resultados muestran que DPCF es capaz de aumentar el throughput total de una red ad hoc comercial, y mejorar notablemente el retardo de transmisión. Además, se ha comprobado que en un entorno real, el DPCF es compatible con dispositivos WLAN 802.11 y que es capaz de ofrecer altas velocidades de transmisión a los usuarios que lo lleven implementado

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AimThe SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery.MethodsThis was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin.ResultsOverall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P ConclusionOne in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery