Improve performance of tcp new reno over mobile ad-hoc network using abra

In a mobile ad hoc network, temporary link failures and route changes occur frequently. With the assumption that all packet losses are due to congestion, TCP performs poorly in such an environment. There are many versions of TCP which modified time to time as per need. In this paper modifications introduced on TCP New Reno over mobile ad-hoc networks using calculation of New Retransmission Time out (RTO), to improve performance in term of congestion control. To calculate New RTO, adaptive backoff response approach (ABRA) in TCP New Reno was applied which suggest ABRA New Reno. It utilizes an ABRA by which congestion window and slow start threshold values were decreased whenever an acknowledgement is received and new backoff value calculate from smoothed round trip time. Evaluation based on comparative study of ABRA New Reno with other TCP Variants like New Reno and Reno was done using realistic parameters like TCP Packet Received, Packet Drop, Packets Retransmitted, Throughput, and Packet Delivery Ratio calculated by varying attributes of Node Speed, Number of Nodes and Pause Time. Implementation and simulations were performed in QualNet 4.0 simulator

Improve performance of tcp new reno over mobile adhoc network

ABSTRAC

Throughput analysis of TCP congestion control algorithms in a cloud based collaborative virtual environment

Collaborative Virtual Environment (CVE) has become popular in the last few years, this is because CVE is designed to allow geographically distributed users to work together over the network. In CVE the state of the virtual objects is witnessing unprecedentant change. When a user performs an action in CVE, the information of the action needs to be transmitted to other users to maintain consistency in the cooperative work. TCP is the most widely used protocol in the design of CVE, and its throughput deteriorates in the network with large delay. Gital et al, 2014 proposes a cloud based architectural model for improving scalability and consistency in CVE. Therefore, this paper aim at evaluating and comparing the performance of different TCP variant (Tahoe, Reno, New Reno, Vegas, SACK, Fack and Linux) with the cloud based CVE architecture to determine the suitability of each TCP variant for CVE. A comparative analysis between the different TCP variants is presented in terms of throughput verses elapse time, with increasing number of users in the system. TCP with the cloud based model was found to be effective, promising and robust for achieving consistency requirement in CVE system

Node Feedback TCP Based Mechanism for Mobile Ad-hoc Network

A mobile ad-hoc network is an autonomous system of mobile nodes establishing a network in the absence of any fixed infrastructure. Mobile ad-hoc network due to potentially high mobility have provided new challenges by introducing special consideration differentiating from the unique characteristics of the wireless medium and the dynamic nature of the network topology. Due to unique network formation, routing in mobile ad-hoc network is a challenging issue. Effort has been undergoing to transform TCP so that it could support routing function in an ad-hoc network. This research has discovered that most of the TCP based variant routing solutions of mobile ad-hoc network has not been successful in addressing problem at full. Taking TCP based routing solution as a main problem, this research has proposed a novel routing solution called Node feedback TCP based mechanism as a routing scheme for mobile ad-hoc network.Node feedback TCP based mechanism introduces a new flavor of TCP for mobile ad-hoc network. It follows an intermediate approach in between some of the existing mechanisms of TCP based schemes for mobile ad-hoc network. We have addressed TCP slow start mechanism in the context of mobile ad-hoc network and introduce measures through whom TCP can differentiate between real congestion and congestion assumed by TCP due to packet lost or route failure in mobile ad-hoc network. In addition our proposed mechanisms also deal with out-of-order delivery problem of TCP in mobile ad-hoc network. It is important to mention that NFBTCP not only address TCP related issues but also provides a number of different operations to assists in the smooth running of an ad-hoc network.The scheme has been developed in Java and Evaluated in SWANS. In the light of the simulation experiments, it could be seen that NFBTCP performed well in all simulation environment. It can be confirmed that NFBTCP has proven itself as a fully functional and operationalable for mobile ad-hoc network, thus should be seen or taken as a new novel TCP based solution for mobile ad-hoc network. A higher number of route requests and route replies representing networking activities were observed with the increase of mobile nodes. In addition to the messages activities, good numbers of routes were added at the end of each simulation cycle. It is quite understandable that the more routes available for data transfer in mobile ad-hoc network, the better. Moreover, such additions to the available routes could directly impact overall throughout. Lastly, nodes in mobile ad-hoc network suffer with limited resources. That makes conservation of all such resources an important issue in the context of mobile ad-hoc network. The results of simulation experiments validate the main concepts of the scheme especially congestion avoidance and out-of-order packet delivery. The scheme generates a higher number of routes suggesting that the implemented congestion avoidance and out-of-order packet delivery mechanisms of NFBTCP are successful in reducing the impact of link breakage since subsequently it was not possible for more routes to be added. The addition of more routes demonstrates that more packets are broadcast and suggests smooth flow of data and control packets. We believe NFBTCP offers a complete and an effective TCP based routing solution for mobile ad-hoc network

Contribución a la mejora del control de flujo en redes de acceso inalámbrico

[SPA] Esta tesis se enmarca en el estudio de la red de transporte de las redes de acceso radio (Radio Access Networks, RANs), también denominado Backhaul. En particular esta tesis aborda los problemas asociados a la congestión en el Backhaul mediante una aproximación basada en teoría de control y la optimización matemática. Los problemas causados por la congestión en el Backhaul son de distinta naturaleza dependiendo de la tecnología RAN a la que da soporte. En esta tesis elaboramos un recorrido histórico por la evolución de las tecnologías RAN durante las dos últimas décadas, en el que nos centramos en las funcionalidades que dependen del Backhaul, y en las diferentes y en general, más exigentes, demandas que éstas imponen en la infraestructura de Backhaul. Iniciamos nuestro recorrido en las redes 3G (Universal Mobile Telecommunication System, UMTS), proseguimos con 3.5G (High Speed Data Access, HSDA) y finalizamos con 4G (Long Term Evolution, LTE). Describimos el impacto que la congestión del Backhaul tiene en cada una de ellas y se proponen mecanismos de control para contrarrestar sus efectos negativos. Los objetivos de esta tesis son los siguientes: 1. Proponer y evaluar mecanismos de control que mejoren el rendimiento de la sincronización de canal de transporte en FP en situaciones de congestión del backhaul. El marco tecnológico de este objetivo son las redes 3G (UMTS). 2. Proponer y evaluar mecanismos de control de flujo que consideren conjuntamente el interfaz radio y en el backhaul. El marco tecnológico de este objetivo es 3.5G (HSPA). 3. Proponer y evaluar un scheduling radio que considere conjuntamente los recursos del interfaz radio y del backhaul. El marco tecnológico de este objetivo es 4G (LTE). 4. Proponer y evaluar mecanismos de asignación coordinada de recursos en el interfaz radio y el backhaul. El marco tecnológico de este objetivo es 4G (LTE). 5. Abordar los objetivos anteriores dentro de la compatibilidad con las especificaciones técnicas de los protocolos implicados. Con respecto al último objetivo, consideramos que no resulta realista plantear algoritmos que impliquen un cambio en sistemas ya estandarizados y de amplio despliegue. Sin embargo, las especificaciones del 3GPP no tienen vocación de definir el funcionamiento de todos los algoritmos involucrados ya que su objetivo último es determinar claramente las interfaces para facilitar la interconexión entre dispositivos y equipos de distintos fabricantes y operadores. Los mecanismos que internamente emplean muchos protocolos para realizar ciertas tareas, en particular algoritmos de gestión de recursos o scheduling, se dejan abiertos a la implementación de los fabricantes, de forma que estos pueden diferenciarse tecnológicamente unos de otros en un entorno de competencia. Esto permite que nuevos mecanismos como los propuestos en este trabajo tengan cabida en los sistemas considerados. El objetivo principal de la Sincronización de Canal de Transporte en redes UMTS es que las tramas enviadas por la RNC lleguen a tiempo a los Nodos B para su transmisión a través del interfaz radio. Para ello, el 3GPP especifica un algoritmo conocido como Timing Adjustment que se encarga de controlar el retraso que experimentan las tramas en el interfaz Iub sumando o restando una cantidad constante. Este algoritmo reacciona con demasiada lentitud ante variaciones abruptas del retardo del interfaz Iub y, además, se puede volver inestable en escenarios de alta demora. Son situaciones que pueden estar propiciadas, entre otros motivos, por la congestión en el backhaul. Aplicando teoría de control en tiempo discreto, proponemos un nuevo mecanismo que garantiza la estabilidad en cualquier situación y mejora el rendimiento del algoritmo clásico. Las medidas de rendimiento se realizan mediante un simulador de la red UTRAN (UMTS RAN) teniendo en cuenta condiciones reales de tráfico en el interfaz Iub. Con la incorporación de HSPA en las redes UMTS la función de scheduling se ha desplazado desde la RNC hasta el Nodo B, generando la necesidad de unos buffers en el Nodo B. A su vez, esta nueva distribución de la capacidad de almacenamiento entre la RNC y el Nodo B requiere de un mecanismo de control de flujo que regule la transferencia de datos entre ambos. En esta tesis realizamos un detallado estudio analítico de este control de flujo abordándolo como un problema de optimización cuadrática. Partiendo de este análisis desarramos un nuevo algoritmo de control de flujo que consigue minimizar el retardo extremo a extremo gracias a que incorpora como parámetro la ocupación de los buffers de la RNC (además de la ocupación en el backhaul en el algoritmo de gestión de recursos radio, o scheduling. Para ello consideramos un escenario sencillo compuesto por una sola celda y una infraestructura backhaul consistente en un enlace punto-a-punto de capacidad C. Mostramos que cuando el backhaul es el cuello de botella, el rendimiento del scheduler radio con consideraciones de backhaul es claramente superior al scheduler convencional. Haciendo uso de técnicas de optimización de la utilidad de la red (NUM), abordamos de forma conjunta la gestión de recursos radio y del backhaul. Empleando descomposición dual, proponemos un mecanismo distribuido y de baja carga computacional que permite generar decisiones de asignación de recursos en el backhaul y en el interfaz radio, de forma coordinada y subtrama a subtrama. Finalmente, incorporamos en nuestro algoritmo el control _optimo de colas tandem, mejorando aun más el rendimiento respecto a los schedulers no coordinados. el Nodo B), algo que no se había considerado en algoritmos anteriores. Se trata, por tanto, de un control de flujo consciente del backhaul (backhaul-aware). Desde la implantación de LTE (4G), las tasas máximas de transmisión alcanzables en el interfaz radio se han disparado con respecto a las anteriores generaciones de sistemas móviles. Por primera vez operadores, fabricantes y comunidad académica coinciden en la necesidad de optimizar el uso los recursos del backhaul además de los recursos radio. En esta tesis estudiamos el impacto que tiene el backhaul en el algoritmo de gestión de recursos radio, o scheduling. Para ello consideramos un escenario sencillo compuesto por una sola celda y una infreastructura backhaul consistente en un enlace punto-a-punto de capacidad C. Mostramos que cuando el backhaul es el cuello de botella, el rendimiento del scheduler radio con consideraciones de backhaul es claramente superior al scheduler convencional. Haciendo uso de t_ecnicas de optimización de la utilidad de la red (NUM), abordamos de forma conjunta la gestión de recursos radio y del backhaul. Empleando descomposición dual, proponemos un mecanismo distribuido y de baja carga computacional que permite generar decisiones de asignación de recursos en el backhaul y en el interfaz radio, de forma coordinada y subtrama a subtrama. Finalmente, incorporamos en nuestro algoritmo el control _optimo de colas tandem, mejorando aun más el rendimiento respecto a los schedulers no coordinados.[ENG] The framework of this thesis is the backhaul of radio access networks (RANs). We refer to backhaul as the infrastructure connecting the base stations of a cellular networks to either the radio network controller (RNCs) nodes or the core network nodes. In particular, this thesis addresses the issues associated to the congestion of the backhaul and the control algorithms that manage the resources of this infrastructure. The potential problems caused in the RAN by the backhaul congestion are of different nature depending on the RAN technology. We will provide a historical overview of the evolution of the RAN technologies over the last two decades, focusing on the functionalities relying on the backhaul, and how each generation imposes different and somewhat more stringent demands on the backhaul infrastructure. Along this work we focus chronologically on a specific RAN generation, starting with 3G, in particular Universal Mobile Telecommunication System (UMTS), then 3.5, High Speed Data Access (HSPA) and 4G Long Term Evolution (LTE). On each one, we study the impact of backhaul congestion on the RAN performance and propose a strategy to optimally control and manage the resources of the system. The objectives of this thesis can be formulated as follows: 1. To develop and evaluate effective control schemes to improve the performance of the transport channel synchronization functionality under backhaul congestion. The technological framework of this first objective is 3G (UMTS). 2. To develop and evaluate own control mechanisms that jointly consider the radio interface and the backhaul. The technological framework of this second objective is 3.5G (HSPA). 3. To study the impact of backhaul congestion on downlink scheduling over the radio interface. The technological framework of this second objective is 3.5G (HSPA). 4. To develop and evaluate mechanisms for coordinate resource allocation at both the radio interface and the backhaul. 5. To address previous objective with proposals that are compliant with the technical specifications of the involved protocols. With regard to this last objective, we consider that it is not fully realistic to come up with algorithms implying changes in systems that are already standardized and widely deployed. However, 3GPP standards do not pretend to define every algorithm involved, since the 3GPP's main objective is to clearly specify the interfaces to allow the interoperability between operators and deferent vendors' devices. The internal mechanisms contained in deferent layers of the protocol stack to accomplish each task are generally left open to operator or vendor choice. Especially resource management functions (such as scheduling or congestion control). This approach leverages innovation and research within the industry and the academia, and allows that mechanisms as the ones presented in this thesis be feasible within existing standardized cellular networks. The main objective of transport channel synchronization in UMTS is to make sure that the frames sent by the RNC arrive on time to the Nodes B (NBs) to be transmitted over the radio interface. For this task, the 3GPP specifies an algorithm known as timing adjustment (TA) that controls the delay suffered by the frames over the interface (Iub) connecting each NB with its corresponding RNC. The TA can add or subtract a certain quantity to the transmission delay. We show that the typical mechanism reacts too slowly in situations where the Iub delay increases abruptly, e.g. under transient congestion of the Iub. Besides, this classic algorithm shows potential instability issues in scenarios of very high delay. We address this problem using the tools of discrete-time control theory, which allows us to propose a new scheme that assures stability under any circumstances and improves the classical mechanism. The performance evaluation is carried out by means of simulation and considering realistic traffic scenarios for the Iub. With the introduction of HSPA (3.5G) in UMTS, the scheduling function was moved from the RNC to the Node B, imposing the inclusion of new data buffers at the NBs. Additionally, this redistribution of the data storage function between the RNCs and the NBs created the need of a flow control mechanism regulating the data transfers on the Iub. We model and analyze this mechanism as a quadratic optimization problem, and exploit this approach to propose a new flow control scheme that minimizes the end-to-end delay over the RAN by considering no only the situation of the NB buffer, but also of the RNC buffers. Our approach is a backhaul-aware optimal flow control system for RAN. Finally, in LTE (4G) systems, the peak transmission rates achievable by a user over the radio interface have boosted compared to previous generations. For the first time operators, vendors and the academic community agree on the need to optimize the backhaul resources, not only the radio resources. In fact, our point is that backhaul congestion impacts the performance of radio resource allocation and this function should be redesigned taking into consideration the capacity limitation of the backhaul. We use network utility maximization (NUM) techniques to address the problem of joint radio-backhaul scheduling. We use a dual decomposition approach to propose a low-complexity, distributed mechanism, that can make resource allocation decisions in a subframe basis. Finally, we incorporate the optimal control policy for tande queues in our mechanism, improving even more the performance compared to non-coordinated schedulers.Universidad Politécnica de Cartagen

Calibración de un algoritmo de detección de anomalías marítimas basado en la fusión de datos satelitales

La fusión de diferentes fuentes de datos aporta una ayuda significativa en el proceso de toma de decisiones. El presente artículo describe el desarrollo de una plataforma que permite detectar anomalías marítimas por medio de la fusión de datos del Sistema de Información Automática (AIS) para seguimiento de buques y de imágenes satelitales de Radares de Apertura Sintética (SAR). Estas anomalías son presentadas al operador como un conjunto de detecciones que requieren ser monitoreadas para descubrir su naturaleza. El proceso de detección se lleva adelante primero identificando objetos dentro de las imágenes SAR a través de la aplicación de algoritmos CFAR, y luego correlacionando los objetos detectados con los datos reportados mediante el sistema AIS. En este trabajo reportamos las pruebas realizadas con diferentes configuraciones de los parámetros para los algoritmos de detección y asociación, analizamos la respuesta de la plataforma y reportamos la combinación de parámetros que reporta mejores resultados para las imágenes utilizadas. Este es un primer paso en nuestro objetivo futuro de desarrollar un sistema que ajuste los parámetros en forma dinámica dependiendo de las imágenes disponibles.XVI Workshop Computación Gráfica, Imágenes y Visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI

URI Undergraduate and Graduate Course Catalog 2012-2013

This is a downloadable PDF version of the University of Rhode Island course catalog.https://digitalcommons.uri.edu/course-catalogs/1064/thumbnail.jp

Emerging Pollutants in the Environment

This edited book, Emerging Pollutants in the Environment Current and Further Implications, includes overviews by significant researchers on the topic of emerging pollutants toxicology, which covers the hazardous effects of common emerging xenobiotics employed in our every day anthropogenic activities. We hope that this book will meet the expectations and needs of all those who are interested in the negative implications of several emerging pollutants on living species