SATNAC 2009 Conference Papers

Network Planning & General Topics

Title:                An Analysis of Logical Network Distance on Observed Packet Counts for Network Telescope Data


Authors:            Barry Irwin (Rhodes University), Richard Barnett (Rhodes University)


Abstract:           This paper investigates the relationship between the logical distance between two IP addresses on the Internet, and the number of packets captured by a network telescope listening on a network containing one of the addresses. The need for the computation of a manageable measure of quantification of this distance is presented, as an alternative to the raw difference that can be computed between two addresses using their Integer representations. A number of graphical analysis tools and techniques are presented to aid in this analysis. Findings are presented based on a long baseline data set collected at Rhodes University over the last three years, using a dedicated Class C (256 IP address) sensor network, and comprising 19 million packets. Of this total, 27% by packet volume originate within the same natural class A network as the telescope, and as such can be seen to be logically close to the collector network. The paper concludes with an evaluation of the hypothesis of there being a relation between the logical distance and volume of traffic received, and addresses some possible vulnerabilities in commonly used anonymization tools for such packet traces.


Title:                Analytical Modeling of Rain Attenuation and its Application to Terrestrial LOS Links


Authors:            Modupe Odedina (University of KwaZulu-Natal), Thomas Afullo (University of KwaZulu-Natal)


Abstract:           The aim of this paper is to propose an analytical model for the calculation of rain attenuation on terrestrial line-of-sight link. This work employs Mie theory for electromagnetic scattering by dielectric sphere on raindrops, under the assumption that the shapes of the raindrops are spherical. Complex forward scattering amplitudes of the spherical raindrops are computed and the extinction cross-sections for the spherical raindrops are calculated. Applying the powerlaw regression to the extinction cross-section calculated, power-law coefficients are determined. The rain attenuation is modeled analytically by integrating the extinction power-law model over different established raindrop-size distribution (DSD) models. From the terrestrial line-of-sight link set-up in Durban, South Africa, experimental rain attenuation measurements were recorded at 19.5 GHz along a 6.73 km propagation path length. These rain attenuation measurements were compared with the results obtained from the analytical models with the same propagation parameters to establish the best attenuation models that describes the behaviour of radio link performance in the presence of rain.


Title:                Multipath Propagation Modeling and Measurement in a Clear-Air Environment for LOS Link Design Application


Authors:            Peter Odedina (University of KwaZulu-Natal), Thomas Afullo (University of KwaZulu-Natal)


Abstract:           The impairment to radio signal propagation in clear-air environment requires accurate prediction method and modelling for terrestrial line of sight links. This is necessary because of the unstable nature of the environment the signal is traversing. Prediction methods based on global radioclimatic models of the ITU-R can currently be made for three significant clear-air propagation effects on terrestrial line of sight links: multipath fading, distortion and depolarization. In addition, such predictions can also be made for multipath fading on very low angle satellite links, and interference between terrestrial and satellite communication systems resulting from duct propagation beyond the horizon. All these predictions explicitly or implicitly use world wide contour maps of refractive index gradient statistics for the lower 100m of the atmosphere. This paper focus on multipath propagation modelling in clear-air environment which can be used for line of sight link design application. The investigation was carried out using clear-air signal level measurement on a terrestrial line of sight link set up between the Howard College and Westville Campuses of the University of KwaZulu Natal, Durban, South Africa for a period of one year in 2004.


Title:                Power Control for Video Transmission over Rural Wireless Mesh Networks


Authors:            Dan Ojwang (Tshwane University of Technology), Elmarie Biermann (Tshwane University of Technology), James Oyedapo (Tshwane University of Technology)


Abstract:           Power problems pose a major challenge when deploying wireless mesh networks (WMNs) in rural areas and hinder the sustainability of wireless mesh network in such areas.  This paper introduces a mechanism for controlling transmission power for efficient video transmission in power-constrained rural areas. The mechanism increases the operational lifetime of WMNs. It ensures that the little power available to the nodes in such areas is optimally used. Simulation studies were used to quantify the performance gains of this mechanism. Simulation is done by considering a classic and power controlled optimized link state  routing protocol (OLSR). We consider an OLSR based wireless mesh network (WMN).

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