Performance improvements to the AODV routing protocol and multiple hop wireless routes : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Engineering in Computer Systems Engineering at Massey University, Palmerston North, New Zealand

This research focused on improving the performance of the Ad-hoc On-demand Distance Vector (AODV) routing protocol over multiple hop routes. The two specific areas that this research addressed were the dramatic decrease in throughput over multiple hop IEEE 802.11 wireless routes and the problems caused by the use of hello messages by AODV implementations to detect broken routes. To help ensure that this research was suitable for real world scenarios, only off-the-shelf software and hardware was used for both the implementations and the tests. This thesis firstly presents an overview of IEEE 802.11 based wireless networking and the AODV protocol, along with wireless networking and networking in general within the Linux operating system. The thesis then presents the problems caused by hello messages and shows how the IEEE 802.11 wireless standard contributes to the dramatic decrease in throughput over multiple hop routes. To overcome the hello message problems, an AODV implementation was developed which used existing mechanisms on the data link layer, specifically the transmit retry limit, rather then hello messages to detect broken links. To address the multiple hop route throughput problem, the use of two and four IEEE 802.11 based wireless network interfaces per node were investigated, rather than using just a single wireless interface per node. These proposed solutions, and the AODV implementation that was developed as part of this research, were then tested in the areas of functionality and throughput performance improvements. The thesis concludes by presenting the performance improvements resulting from using multiple interfaces per node and the non hello message based AODV implementation along with outlining possible future research in this area

Reading list: 8 must-read books on religion and the public sphere

Last month, June 2016, the LSE Religion and the Public Sphere blog launched, exploring the place and role of religion in British public life today. To celebrate the launch, the blog’s Editor Esther Kersley has brought together 8 must-read books on the topic, ranging from philosophical debates on religion, secularism and the public sphere to detailed accounts of how religion exists in Britain today

Study of disturbed boundary layers using a hot-wire anemometer

One of the most important problems in fluid mechanics which has attracted the interest of investigators for many years is the transition from laminar to turbulent flow. This problem is of greatest importance in practice for flows over aerofoils and in closed channels, where the effects of transition are marked. Little is known, however, about the fundamental physical processes which cause a laminar flow to break down to turbulence. The particular case of boundary-layer flow has received considerable attention and has been treated with some measure of success. Linearized theories have been useful in predicting the nature of the mechanism of instability of a laminar flow; but the non-linear problem, namely, the transition from an unstable laminar to a fully developed turbulent flow, presents formidable mathematical difficulties, so that few theoretical results have been obtained. The development of air and water tunnels together with improved measuring techniques in fluid flow has led to attempts by engineers and experimental physicists to relate the unstable laminar to the turbulent flow regime. The aim of the work reported in this thesis was to gain further insight into the mechanism of transition in the boundary layer. The present experimental work was confined to the simplest example, the flow of an incompressible fluid along a smooth flat plate at zero angle of incidence with zero pressure gradient in the flow direction. The intention was to develop a hot -wire anemometer system to study the downstream development of disturbances introduced under controlled conditions into the boundary layer. As the work progressed emphasis was placed on one particular aspect of the non- linear development of the disturbances, the generation of higher harmonics of the fundamental wave

Ionospheric tomography and its applications in radio science and geophysical investigations

The paper reviews recent progress in the development of radio tomographic imaging of the ionized atmosphere, particularly in relation to the use of the technique to assist in the mitigation of propagation effects on practical radio systems

A Preliminary Population Inventory of Ctenitis maritima (Cordem.)Tardieu at Gris Gris, South Coast of Mauritius (Aspidiaceae).

ABSTRACT: The Mascarenes endemic fern species Ctenitis maritima (Cordem.) Tardieu has been collected in Mauritius and Réunion Island only. The preliminary population survey undertaken at Gris Gris, in the south coast of Mauritius has indicated the presence of 80 clumps. We measured only 52 fronds due to inaccessibility of some clumps and the frond sizes varied from 4.3 to 42.8 cm in length and from 3.1 to 13.2 cm in width. Most clumps georeferenced, were at an elevation of 7 to 13 m. Nearly 90% of the population surveyed bears fertile fronds.RÉSUMÉ: Lafougère endémiqueCtenitismaritima (Cordem.) Tardieu a été recueillieà l'île Mauriceet à la Réunionuniquement. L'enquêtepréliminaire de la populationentreprise àGris Gris, sur la côte sudde l'île Mauricea indiquéla présence de80touffes.Nous avons mesuréseulement 52frondesen raison del'inaccessibilité de certainestouffeset les tailles des frondesvariaientde 4,3 à 42,8cm de longueuretde 3,1 à 13,2cmde largeur.La plupart destouffesgéoréférencées, étaientà une altitudecomprise entre 7 et 13m.Près de 90% des individus mesurés portent des feuillesfertiles

Dayside ionospheric response to changes in IMF polarity: optical and plasma-flow observations

International audienceThe response of the dayside ionosphere to changes in polarity of the interplanetary magnetic field was observed by two independent techniques. The signatures were seen in the 630.0 nm red-line emission, measured by a meridian scanning photometer at Ny-Ålesund on Svalbard, and also in the line-of-sight plasma velocities monitored by the Finland CUTLASS SuperDARN radar. A time difference of some 6 to 8 min occurred between the responses of the two techniques, with the flows being first to respond. In the present case study, the longer delay in the optics suggests that ion precipitation controls the auroral emission

Polar patches observed by ESR and their possible origin in the cusp region

International audienceObservations by the EISCAT Svalbard radar in summer have revealed electron density enhancements in the magnetic noon sector under conditions of IMF Bz southward. The features were identified as possible candidates for polar-cap patches drifting anti-Sunward with the plasma flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar and DMSP satellites, in a multi-instrument study, suggested that the origin of the structures lay upstream at lower latitudes, with the modulation in density being attributed to variability in soft-particle precipitation in the cusp region. It is proposed that the variations in precipitation may be linked to changes in the location of the reconnection site at the magnetopause, which in turn results in changes in the energy distribution of the precipitating particles