Telecommunications is converging on the use of IP based networks. Due to the low cost of VoIP applications, they are being increasingly used instead of conventional telephony services. IEEE802.11 WLANs are already widely used both commercially and domestically. VoIP applications will also expand from usage over wired networks to voice communications over IEEE802.11 WLANs. This is known as VoWLAN. The use of VoWLAN may reach the maximum capacity of a wireless channel if there are many simultaneous VoIP calls operating close to each other. There is much published research based on a single IEEE802.11 infrastructure WLAN concluding that packet loss, transmission efficiency and latency issues are the major challenges limiting the VoWLAN capacity. The VoIP service quality will drop sharply when the demands exceed the WLAN’s capacity. This thesis demonstrates that these challenges also apply to distributed WLANs. To extend these findings from the existing research, the analysis in this thesis indicates that the capacity of a single IEEE802.11 WLAN channel is 12 VoIP calls. When the number of simultaneous VoIP calls is within the capacity, the WLAN can deliver more than 90% of the voice packets to the receiver within 150 ms (the lowest network performance for supporting acceptable VoIP service). However, as soon as the traffic loads are beyond the wireless channel capacity e.g. the number of simultaneous VoIP calls is greater than 13, the VoIP service quality catastrophically collapses. When the capacity is exceeded there are almost no voice packets that can be delivered to the receiver within 150 ms. Our research results indicate that the delay accumulation for voice packets in the transmitter’s outgoing buffer causes this problem. Our research also found that dropping ‘stale’ voice packets that are already late for delivery to the receiver can give more transmission opportunities to those voice packets that may still be delivered in time. This thesis presents a new strategy called Active Cleaning Queue (ACQ) which actively drops ‘stale’ voice packets from the outgoing buffer and prevents the accumulation of delay in congested conditions. When ACQ is applied in a saturated wireless channel the network performance for supporting VoIP traffic was found to gradually decrease proportional to the numbers of simultaneous VoIP calls rather than catastrophically collapse. There is also published research suggesting that the aggregation of packets can improve the efficiency of WLAN transmissions. An algorithm called Small Packet Aggregation for Wireless Networks (SPAWN) is also presented in this thesis to improve transmission efficiency of small voice packets in WLANs without introducing further delay to VoIP traffic. The evaluation result shows that after applying the SPAWN algorithm, the VoIP capacity of a single wireless channel can be extended up to 24 simultaneous calls.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-12T13:37:34Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Master_Dissertation___Performance_Measurements_and_Analysis_of_Bluetooth_Low_Energy (8).pdf: 8669109 bytes, checksum: cb0af886f0cdc7babced229049a33535 (MD5) / Made available in DSpace on 2017-07-12T13:37:34Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Master_Dissertation___Performance_Measurements_and_Analysis_of_Bluetooth_Low_Energy (8).pdf: 8669109 bytes, checksum: cb0af886f0cdc7babced229049a33535 (MD5) Previous issue date: 2016-05-17 / The Internet of Things (IoT) paradigm has been rapidly gaining ground in the academic and industry communities as one of the most important emerging technologies. Some wireless communication technologies such as Bluetooth Low Energy (BLE) have been pointed as key technologies that will drive IoT applications. In order to leverage the BLE technology in IoT applications and identify the niche of applications this technology is more suitable, it is essential we have a deep understanding regarding some features such as link capacity, data transfer delay, connection establishment latency, and power consumption. This work evaluates the networking capabilities from BLE in scenarios of data transfer and connection establishment. The metrics maximum throughput, one-way delay, round-trip time, and connection establishment latency are evaluated through experimental measurements and we investigate how some factors (e.g. connection interval, pairing, packet size) impact on these metrics. Finally, this work proposes analytical models for the metrics investigated. / O paradigma da Internet das Coisas (Internet of Things - IoT) tem recebido grande destaque tanto das comunidades científicas como da indústria nos últimos anos. Algumas tecnologias de comunicação sem fio como Bluetooth Low Energy (BLE) tem sido apontadas como tecnologias que terão um papel fundamental na concepção de aplicativos de IoT. Um entendimento profundo de algumas características da tecnologia, como vazão e atraso na transmissão de dados, latência no estabelecimento de conexão e consumo de energia, é essencial para explorar ao máximo a tecnologia em cenários de IoT e identificar o nicho de aplicação onde esta tecnologia é mais aplicável. Este trabalho apresenta uma avaliação de desempenho da tecnologia BLE em cenários de transmissão de dados e estabelecimento de conexão. As métricas vazão máxima, atraso fim-a-fim, atraso ida-e-volta (Round-Trip Time - RTT) e latência de estabelecimento de conexão são avaliadas através de experimentos. Este trabalho também investiga como alguns fatores, como intervalo de conexão, encriptação de link e tamanho de pacote, impactam nas métricas avaliadas. Por fim, este trabalho apresenta modelos analíticos para as métricas investigadas.

Esta tesis estudia la aplicación a la World Wide Web (WWW) de las técnicas de prebúsqueda desde un punto de vista realista y práctico. La prebúsqueda se aplica a la web para reducir la latencia percibida por los usuarios ya que, básicamente, consiste en predecir y preprocesar los siguientes accesos de los usuarios. Hasta ahora, la literatura disponible acerca de la prebúsqueda web se ha concentrado en cuestiones teóricas y no ha considerado algunos de los problemas que aparecen al implementar la técnica en condiciones reales. Por otra parte, los trabajos de investigación existentes usan para la evaluación modelos simplificados que no consideran cómo los aspectos prácticos afectan realmente a la implementación de una técnica de prebúsqueda. Además, apenas unos pocos trabajos han usado índices de prestaciones que sean relevantes para los usuarios en la evaluación de los beneficios que la prebúsqueda puede lograr. Con objeto de superar estas tres restricciones se ha desarrollado Delfos, un entorno de prebúsqueda web que implementa predicción y prebúsqueda en un sistema real, puede integrarse en la arquitectura web sin realizar modificaciones en los protocolos web estándar, y es compatible con los programas existentes. Delfos también puede usarse para evaluar y comparar técnicas de prebúsqueda y algoritmos de predicción así como ayudar en el diseño de otros nuevos ya que proporciona información estadística detallada de los experimentos llevados a cabo. A modo de ejemplo, Delfos se ha usado para proponer, probar y evaluar una nueva técnica (Predecir en la Prebúsqueda, PAP) que es capaz de reducir considerablemente la latencia percibida por el usuario sin costes adicionales respecto al mecanismo de prebúsqueda básico. Los algoritmos de predicción propuestos en la literatura de investigación que alcanzan la mayor precisión incurren en un alto coste computacional, y esto representa un problema para incluirlos en sistemas reales. Para aminorar este inconveniente, en esta tesis se propone un nuevo algoritmo de predicci on de bajo coste, (Referrer Graph, RG). / De La Ossa Pérez, BA. (2011). Web Prefetching Techniques in Real Environments [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15574 / Palancia

La rupture prématurée des membranes avant terme (RPMAT) est une complication de la grossesse responsable d’une importante morbi-mortalité périnatale. La prise en charge anténatale vise à réduire les conséquences délétères de cette pathologie, liées à l’inflammation intra-utérine et à la prématurité, à la fois pour la mère et pour l’enfant. L’objectif de cette thèse était d’étudier les déterminants obstétricaux du pronostic de L’enfant prématuré né dans un contexte de RPMAT, à partir des données de la cohorte EPIPAGE 2. Nous avons d’abord évalué l’impact de la durée de latence, comprise entre la RPMAT et l’accouchement, sur le pronostic néonatal. Nos résultats montrent que pour un âge gestationnel de naissance donné, la durée de latence après une RPMAT entre 24 et 32 SA n’est pas associée à la survie ou à la survie sans morbidité sévère. Le principal déterminant du pronostic néonatal est l’âge gestationnel à la naissance. Nous avons ensuite étudié la tocolyse, un traitement médicamenteux largement utilisé après une RPMAT dans le but de prolonger la grossesse. L’administration d’une tocolyse après une RPMAT n’est associée ni à l’amélioration de la survie sans morbidité du prématuré, ni à la prolongation de la grossesse. Enfin, une analyse descriptive des cas de RPMAT entre 22 et 25 SA montre qu’à ces âges gestationnels extrêmes, la RPMAT est associée à un risque élevé de mortalité périnatale et de morbidité à court et à long terme, avec de grandes variations selon l’âge gestationnel à la rupture. Nos travaux fournissent des informations pertinentes pour les équipes médicales et les femmes enceintes et questionnent certaines pratiques obstétricales, notamment l’administration d’une tocolyse après une RPMAT. Ils soulèvent des questions qui feront l’objet de nouveaux projets de recherche, en particulier un essai contrôlé randomisé sur la tocolyse après RPMAT, financé par le PHRC-N 2016 (essai TOCOPROM). / Preterm premature rupture of membranes (PPROM) is a complication of pregnancy responsible for significant perinatal mortality and morbidity. Antenatal management aims to reduce adverse consequences, relating to intrauterine inflammation and prematurity, for both mother and child. This thesis aimed to study obstetric determinants impacting the outcome of preterm babies born following PPROM, using data from the EPIPAGE 2 cohort. We first evaluated the impact of latency duration, i.e. the time from PPROM to delivery, on neonatal prognosis. For a given gestational age at birth, latency duration after PPROM at 24-32 weeks' gestation was not associated with survival or survival without severe morbidity. The principal determinant of neonatal prognosis was gestational age at birth. We then studied tocolysis, a treatment widely used after PPROM to prolong pregnancy. Administration of tocolysis after PPROM was not associated with either improved survival without morbidity of the preterm infant or prolongation of pregnancy. Finally, a descriptive analysis of cases of PPROM occurring at 22-25 weeks’ gestation demonstrated that, at these extreme gestational ages, PPROM was associated with high risks of perinatal mortality and short- and long-term morbidity, with large variations according to gestational age at rupture. Our work provides relevant information for medical teams and pregnant women and questions some obstetric practices, particularly the use of tocolysis after PPROM. They raise issues that will be the subject of future research projects, specifically a randomized controlled trial on tocolysis after PPROM, already funded by PHRC-N 2016 (TOCOPROM trial).

Despite the existence of a treatment, there is still not a cure for HIV-1 infection and there arearound 700 000 deaths per year from AIDS-related diseases. A major barrier for a cure is theestablishment of latent reservoirs that are impossible to distinguish from healthy cells and thuscan escape the immune system. One potential solution is called shock-and-kill strategy, whichaims to induce HIV-1 reactivation, exposing latently infected cells to the immune system andmaking them susceptible to cell death. In our lab, it was seen that when NK cells are stimulatedwith a pan-caspase inhibitor, they acquire the “shock” ability, but it is still unknown how. Inthis project, we observed that the supernatant from pan-caspase inhibitor-stimulated NK cellscan increase HIV-1 reactivation in two different latency models. Furthermore, the protein levelsof three HIV-1 suppressors were found to be increased in the same supernatant. For this reason,their effect in HIV-1 reactivation in latently infected cells was analysed. Although we did notobserve an increase in HIV-1 reactivation, the upregulation of these three proteins can be usefulin the clinical context. Since they are HIV-1 suppressors, their presence can prevent theinfection from spreading after latent cells are reactivated. Altogether, our results show that NKcells stimulated with a pan-caspase inhibitor are secreting a biological product that inducesHIV-1 reactivation. This indicates that there is a pathway in NK cells that can potentially beexploited in order for them to be able to induce HIV-1 reactivation.

In high speed applications of visual servoing, latency from the recognition algorithm can cause significant degradation of in response time. Hardware acceleration allows for recognition algorithms to be applied directly during the raster scan from the image sensor, thereby removing virtually all video processing latency. This paper examines one such method, along with an analysis of design decisions made to optimize for use during high speed airborne object tracking tests for the US military. Designing test equipment for defense use involves working around unique challenges that arise from having many details being deemed classified or highly sensitive information. Designing tracking system without knowing any exact numbers for speeds, mass, distance or nature of the objects being tracked requires a flexible control system that can be easily tuned after installation. To further improve accuracy and allow rapid tuning to a yet undisclosed set of parameters, a machine learning powered auto-tuner is developed and implemented as a control loop optimizer.

This study aims to examine the effects of transforming a monolithic server system into a microservice architecture, focusing on the increased latency introduced by using a microservice orchestrator. The microservice orchestrator was implemented using an OpenFlow switch controlled by the Beacon and Ryu OpenFlow controllers. These controllers, along with the round robin, random assign and a server-aware load balancing algorithm, were all compared in order to find the combination resulting in the lowest latency and highest achieved server balance in varying network environments. We show that the OpenFlow switch enforces a client-aware load balancing policy and that only the initial request is handled by the controller, effectively reducing the importance of choosing the optimal OpenFlow controller. In addition, the round robin load balancer was preferred when dealing with homogeneous requests, and a server-aware load balancer was required for heterogeneous requests. For most requests, the system would only slow down by a few microseconds using the proposed architecture. However, for 0.001\% of all requests, the slowdown was much more significant, with each of those requests being at least 100 times slower than when using a monolithic server architecture.

Interactive data visualizations must respond fluidly to user input to be effective, or so we assume. In fact it is unknown exactly how fast a visualization must run to present every facet within a dataset. An engineering team with limited resources is left with intuition and estimates to determine if their application performs sufficiently well. This thesis studies how latency affects users' comprehension of data visualizations, specifically 3D geospatial visualizations with large data sets. Subjects used a climate visualization showing temperatures spanning from the 19th to the 21st century to answer multiple choice questions. Metrics like their eye movements, time per question, and test score were recorded. Unbeknownst to the participants the latency was toggled between questions, subjugating frame rendering times to intervals between 33 1/3 and 200 milliseconds. Analysis of eye movements and question completion time and accuracy fail to show that latency has an impact on how users explore the visualization or comprehend the data presented. User fixation times on overlaid 2D visualization tools however are impacted by latency, although the fixation times do not significantly differ over 3D elements. The finding speaks to how resilient users are in navigating and understanding virtual 3D environments --- a conclusion supported by previous studies about video game latency.

No description available.

Context: Node.js is an established web framework built using JavaScript. As a result, there are a wide variety of frameworks that have emerged that specialize in different quality attributes and functionalities. Some of which are heavily geared to performance and benchmarking while others might focus on security, availability, robustness, etc. Objectives: The project aims to explore different Node.js server-side frameworks and determine their maintainability using metrics such as Halstead metrics, Maintainability index, source line of code as well as Logical source lines of code. This thesis also explores if there is a correlation between the quality attributes maintainability and performance. Realization: In order to explore the different quality attributes, the thesis relied upon experiments and a literature review. The hierarchical method in this thesis was first to examine their performance, later examine their overall maintainability. Examined is also the impact of comments and how they can affect the results of the maintainability index Results: The results indicate all the selected frameworks have a low-to borderline medium cyclomatic complexity, also a high degree of maintainability using two different 3 metric maintainability index formulas. The latency tests indicate the different frameworks produce similar performance results. Conclusion: Concluded in this thesis is, there seems to be no relationship between both lines of code, logical lines of code, and cyclomatic complexity. There also seems to be no correlation between Halstead volume and the overall maintainability index for both the 3 metric formulas used. There is a slight indication of a relationship between Halstead Effort and Cyclomatic Complexity using one of the 3 metric formulas i.e., as the cyclomatic complexity decreases the overall maintainability (using Halsted’s effort instead of Halstead’s volume) increases.