Congestion control in wireless sensor networks

Information-sensing and data-forwarding in Wireless Sensor Networks (WSN) often incurs high traffic demands, especially during event detection and concurrent transmissions. Managing such large amounts of data remains a considerable challenge in resource-limited systems like WSN, which typically observe a many-to-one transmission model. The result is often a state of constant buffer-overload or congestion, preventing desirable performance to the extent of collapsing an entire network. The work herein seeks to circumvent congestion issues and its negative effects in WSN and derivative platforms such as Body Sensor Networks (BSN). The recent proliferation of WSN has emphasized the need for high Quality-of-Service (QoS) in applications involving real-time and remote monitoring systems such as home automation, military surveillance, environmental hazard detection, as well as BSN-based healthcare and assisted-living systems. Nevertheless, nodes in WSN are often resource-starved as data converges and cause congestion at critical points in such networks. Although this has been a primal concern within the WSN field, elementary issues such as fairness and reliability that directly relate to congestion are still under-served. Moreover, hindering loss of important packets, and the need to avoid packet entrapment in certain network areas remain salient avenues of research. Such issues provide the motivation for this thesis, which lead to four research concerns: (i) reduction of high-traffic volumes; (ii) optimization of selective packet discarding; (iii) avoidance of infected areas; and (iv) collision avoidance with packet-size optimization. Addressing these areas would provide for high QoS levels, and pave the way for seamless transmissions in WSN. Accordingly, the first chapter attempts to reduce the amount of network traffic during simultaneous data transmissions, using a rate-limiting technique known as Relaxation Theory (RT). The goal is for substantial reductions in otherwise large data-streams that cause buffer overflows. Experimentation and analysis with Network Simulator 2 (NS-2), show substantial improvement in performance, leading to our belief that RT-MMF can cope with high incoming traffic scenarios and thus, avoid congestion issues. Whilst limiting congestion is a primary objective, this thesis keenly addresses subsequent issues, especially in worst-case scenarios where congestion is inevitable. The second research question aims at minimizing the loss of important packets crucial to data interpretation at end-systems. This is achieved using the integration of selective packet discarding and Multi-Objective Optimization (MOO) function, contributing to the effective resource-usage and optimized system. A scheme was also developed to detour packet transmissions when nodes become infected. Extensive evaluations demonstrate that incoming packets are successfully delivered to their destinations despite the presence of infected nodes. The final research question addresses packet collisions in a shared wireless medium using distributed collision control that takes packet sizes into consideration. Performance evaluation and analysis reveals desirable performance that are resulted from a strong consideration of packet sizes, and the effect of different Bit Error Rates (BERs)

Reliable data communication for mobile IP based systems

In der Vergangenheit wurden Endgeräte im wesentlichen mittels drahtgebundener Übertragungstechniken an das Internet angebunden. Derzeit sich im Aufbau befindende bzw. zukünftige drahtlose Mobilkommunikationssysteme bieten auch für mobile Endgeräte einen Internetzugang mit akzeptablen Datenraten. Als Konsequenz wird auch im Bereich der Mobilkommunikation die zuverlässige Datenübertragung im Vergleich zur bereits etablierten - für den Telefondienst eingesetzten - unzuverlässigen Datenübertragung zunehmend an Bedeutung gewinnen. Die zuverlässige Datenübertragung über fehleranfällige, drahtlose Kanäle mittels des im Internet etablierten Transportprotokolls TCP ist Gegenstand der Betrachtungen in dieser Arbeit. Es werden die negativen Auswirkungen der höheren Fehlerwahrscheinlichkeiten auf die einzelnen Protokollmechanismen im Detail diskutiert. Es folgt eine umfassende Analyse in der Literatur vorgeschlagener Verfahren hinsichtlich ihrer Praktikabilität und ihrer Eignung, die Performance Probleme von TCP im drahtlosen Umfeld zu lösen. Der sogenannte 'Indirekte Transportansatz', ein proxybasierter Ansatz, kristallisiert sich bei dieser Analyse als der Ansatz der Wahl heraus. Auf Grund der bei diesem Ansatz in Routern zusätzlich zu verwaltenden verbindungsspezifischen Statusinformation der Transportprotokolle sind - beispielsweise durch die Mobilität der Endgeräte bedingte - Routenänderungen problematisch. Für die hierzu erforderliche sogenannte 'Mobilitätstunterstützung für indirekte Transportansätze' existieren bisher lediglich Verfahren, die aufgrund der sich ergebenden signifikanten Unterbrechungen der Ende-zu-Ende Kommunikation nur schlecht geeignet sind. Die in dieser Arbeit entwickelte, simulativ bewertete und prototypisch implementierte 'Optimierte Mobilitätsunterstützung für indirekte Transportansätze' (OMIT), kann diese Unterbrechungen mittels der Verfahren 'Fast-Forwarding' und 'nebenläufige Migration' vermeiden.In the past, end systems have primarily been connected to the Internet using wired transmission technologies. Presently installed and future wireless mobile communication systems will also provide Internet access and acceptable data rates for mobile end systems. As a consequence, comparing the reliable data service with the available - mainly for the audio service used - unreliable service, the importance of the reliable service will increase within mobile communication systems. The focus of this work is on reliable services and the realization over error prone wireless channels using the transport protocol TCP, that is used within the Internet to implement a reliable end-to-end service. The negative influence of higher error probabilities on TCP's protocol mechanisms is discussed in detail. Furthermore, an extensive analysis of in the literature described proposals to address TCP's performance deficits is included within this work. Practicability and the ability to address TCP's performance deficits are the main criteria of this analysis. The so called 'Indirect Transport Approach', a proxy based approach, turns out to be an appropriate approach. However, the indirect transport approach requires within routers additional - per transport connection - state information. This state information is problematic in the context of routing changes, e.g. caused by the mobility of a mobile end system. Existing proposals for the required so called 'Mobility Support of Indirect Transport Approaches' significantly interrupt the end-to-end communication. Thus, they are unsuitable. These interruptions can be avoided by the so called 'Optimized Mobility Support of Indirect Transport Approaches' (OMIT). Within this work this approach has been developed, investigated via simulations and implemented. The two key mechanisms are: 'Fast-Forwarding' and the 'Concurrent Migration'

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI