Efficient route discovery for reactive routing

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Information on the location of mobile nodes in Mobile Ad-hoc Networks (MANETs) has the potential to significantly improve network performance. This thesis uses node location information to develop new techniques for route discovery in on-demand routing protocols such as the Ad-hoc On-Demand Distance Vector (AODV), thus making an important contribution to enhancing the experience of using mobile networks. A Candidate Neighbours to Rebroadcast the Route Request (CNRR) approach has been proposed to reduce the deleterious impact, known as the broadcast storm, of RREQ packets flooding in traditional on-demand routing protocols. The main concept behind CNRR is specifying a set of neighbours which will rebroadcast the received RREQ. This is a departure from the traditional approach of all receiving nodes rebroadcasting RREQs and has the effect of reducing the problem of redundancy from which mobile networks suffer. The proposed protocol has been developed in two phases: Closest-CNRR and Furthest-CNRR. The simulation results show that the proposed algorithms have a significant effect as they reduce the routing overhead of the AODV protocol by up to 28% compared to the C-CNRR, and by up to 17.5% compared to the F-CNRR. Notably, the proposed algorithms simultaneously achieve better throughput and less data dropping. The Link Stability and Energy Aware protocol (LSEA) has been developed to reduce the overhead while increasing network lifetimes. The LSEA helps to control the global dissemination of RREQs in the network by eliminating those nodes that have a residual energy level below a specific threshold value from participation in end-to-end routes. The proposed LSEA protocol significantly increases network lifetimes by up to 19% compared with other on-demand routing protocols while still managing to obtain the same packet delivery ratio and network throughput levels. Furthermore, merging the LSEA and CNRR concepts has the great advantage of reducing the dissemination of RREQs in the network without loss of reachability among the nodes. This increases network lifetimes, reduces the overhead and increases the amount of data sent and received. Accordingly, a Position-based Selective Neighbour (PSN) approach has been proposed which combines the advantages of zoning and link stability. The results show that the proposed technique has notable advantages over both the AODV and MAAODV as it improves delivery ratios by 24.6% and 18.8%, respectively.Funded by National Council for Training - Sudan and the Sudan Academy of Science

Estudios comparativo de protocolos de encaminamiento en redes VANET

Las redes inalámbricas han revolucionado los intercambios de datos y defi¬nido un nuevo paradigma, el del “Always On-Always Connected”. Dentro de este paradigma, las comunicaciones en entornos vehiculares abren un nuevo campo de investigación en la comunidad científica. La forma más común de considerar las redes inalámbricas es aquella en la cual los clientes móviles se conectan a una estación base (BS) que controla las comunicaciones. Esta BS cubre una cierta área de cobertura en la cual todos los clientes que controla pueden comunicarse entre sí. El alcance a clientes de otras redes se hace a través de un segmento generalmente fijo. Los clientes son capaces de desplazarse y de cambiar de BS sin corte de cobertura mediante un proceso llamado handover. Las comunicaciones ad-hoc, y más precisamente las comunicaciones VA-NETs (“Vehicular Ad-Hoc Network”) plantean nuevos retos. En este tipo de redes no existe infraestructura de red sino que se compone de los propios nodos móviles autónomos comunicándose entre sí por enlaces inalámbricos. En este entorno desaparece el control centralizado de la red que proporcionaba la BS. Los nodos deben asumir responsabilidades de encaminamiento y de mantenimiento de la red. El control de red está distribuido entre los mismos nodos. A esos nuevos retos de control de red se suman las características de topologías del entorno vehicular. Las características de las redes vehiculares son en general hostil al intercambio de tráfico. El proceso de encaminamiento no se puede asumir de la misma manera que en las redes clásicas. Es necesario que cada nodo por separado y todos en su conjuntos sean capaces de proporcionar un mecanismo dinámico de encaminamiento. Este encaminamiento mulito se basa en las capacidades de cada nodo. Los protocolos de encaminamiento clásicos no sirven en ese entorno ya que no están preparados para variaciones de topología, puede que no converjan. En tal entorno, el envío de paquetes entre nodos se vuelve todo un reto

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks