When considering the addition of a mobile presentation channel to an existing web-based application, a key question that has to be answered even before development begins is how the mobile channel’s characteristics will impact the user experience and the cost of using the application. If either of these factors is outside acceptable limits, economical considerations may forbid adding the channels, even if it would be feasible from a purely technical perspective. Both of these factors depend considerably on two metrics: The time required to transmit data over the mobile network, and the volume transmitted. The PETTICOAT method presented in this paper uses the dialog flow model and web server log files of an existing application to identify typical interaction sequences and to compile volume statistics, which are then run through a tool that simulates the volume and time that would be incurred by executing the interaction sequences on a mobile channel. From the simulated volume and time data, we can then calculate the cost of accessing the application on a mobile channel.

In this paper we introduce an analysis framework for mobile workforce automation. The framework is based on the findings from earlier research as well as on an analysis of 27 recent case studies conducted within the field of mobile workforce automation. It consists of a general reference process for mobile work and of a model explaining influencing factors (worker, task, coordination system, information system), optimization goals and their relationships in mobile business processes. The framework can be applied to process modeling, simulation, and optimization as well as to requirements analysis and return on investment calculations. Based on the results of case study evaluation, it is furthermore shown, that recent mobile IT solutions are mainly built for relatively simple processes and cooperation models. Mobilizing more complex processes still seems to be a challenge.

This paper introduces a graphical modeling notation based on coloured petri nets for the performance and cost evaluation of mobile applications. When developing such an application some restrictions due to the low bandwith of mobile networks need to be considered. The notation can be used to model the workflow of a mobile application with just a small effort. The resulting model can be (automatically) transformed into a coloured petri net for simulating the communication behaviour depending on typical user interactions. The simulation results are an important basis for improving the applications performance and the occuring costs for using mobile networks.

The Southern African Development Community (SADC) experiences high levels of cross border human traffic due to trade, cultural and language links across the fifteen countries. Technological advances and increased domestic competition have contributed to lower domestic retail tariffs for mobile cellular services. Unfortunately, this has not extended to international mobile roaming (IMR) retail tariffs which remain unacceptably high. These high tariffs have attracted harsh criticism from commentators and prompted calls for regulatory intervention. This study investigates the level of international mobile roaming (IMR) retail tariffs, usage and demand elasticity. It further considers whether competition or regulation play a greater role in reducing these tariffs and whether regulatory intervention is likely to reduce competition. The research took the form of a quantitative study and used an online survey questionnaire as the data collection tool. The results of the study confirmed that international mobile roaming (IMR) retail tariffs are indeed high, resulting in poor uptake by cost conscious travellers who pay for their own cellular usage. The finding that competition plays a greater role than regulation in reducing IMR retail tariffs is not significant. It was concluded that neither competition nor regulation are sufficient on their own to provide increased social welfare. The best result is obtained when competition is allowed to flourish, underpinned by an enabling regulatory framework. Copyright / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

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"This thesis addresses important challenges in the areas of streaming and spatio-temporal databases. It focuses on continuous querying of spatio-temporal environments characterized by (1) a large number of moving and stationary objects and queries; (2) need for near real-time results; (3) limited memory and cpu resources; and (4) different accuracy requirements. The first part of the thesis studies the problem of performance vs. accuracy tradeoff using different location modelling techniques when processing continuous spatio-temporal range queries on moving objects. Two models for modeling the movement, namely: continuous and discrete models are described. This thesis introduces an accuracy comparison model to estimate the quality of the answers returned by each of the models. Experimental evaluations show the effectiveness of each model given certain characteristics of spatio-temporal environment (e.g., varying speed, location update frequency). The second part of the thesis introduces SCUBA, a Scalable Cluster Based Algorithm for evaluating a large set of continuous queries over spatio-temporal data streams. Unlike the commonly used static grid indices, the key idea of SCUBA is to group moving objects and queries based on common dynamic properties (e.g., speed, destination, and road network location) at run-time into moving clusters. This results in improvement in performance which facilitate scalability. SCUBA exploits shared cluster-based execution consisting of two phases. In phase I, the evaluation of a set of spatio-temporal queries is abstracted as a spatial join between moving clusters for cluster-based filtering of true negatives. There after, in phase II, a fine-grained join process is executed for all pairs identified as potentially joinable by a positive cluster-join match in phase I. If the clusters don’t satisfy the join predicate, the objects and queries that belong to those clusters can be savely discarded as being guaranteed to not join individually either. This provides processing cost savings. Another advantage of SCUBA is that moving cluster-driven load shedding is facilitated. A moving cluster (or its subset, called nucleus)approximates the locations of its members. As a consequence relatively accurate answers can be produced using solely the abstracted cluster location information in place of precise object-by-object matches, resulting in savings in memory and improvement in processing time. A theoretical analysis of SCUBA is presented with respect to the memory requirements, number of join comparisons and I/O costs. Experimental evaluations on real datasets demonstrate that SCUBA achieves a substantial improvement when executing continuous queries on highly dense moving objects. The experiments are conducted in a real data streaming system (CAPE) developed at WPI on real datasets generated by the Network-Based Moving Objects Generator."

Esta tesis tiene como objetivo final la propuesta de un protocolo de acceso al medio imbricado con los parámetros de nivel físico que dan soporte a dicho protocolo. Puesto que la propuesta se basa en un esquema TDMA, se eligen como base del análisis los sistemas de segunda generación GSM, TETRA y DECT, a partir de los cuales se extrapolan determinados parámetros a fin de sintonizarlos con los sistemas de tercera generación en su especificación TDMA. Se evalúan dichos sistemas a nivel físico sobre diferentes modelos de canal de propagación y distintas técnicas de compensación implementadas en el receptor: ecualizadores implementados sobre filtros transversales y antenas adaptativas. Además, se implementan y evalúan algoritmos de ecualización sencillos como LMS o RLS y más complejos como algoritmos bidireccionales sobre ecualizadores DFE. La elección de una u otra opción condicionará fuertemente el diseño del protocolo de acceso propuesto en el subnivel MAC. / This thesis has as final aim the proposal of a medium access protocol (MAC) closely related to the physical layer parameters that support such protocol. As the proposal is based on a TDMA scheme, three representative systems belonging to the second generation of mobile communication systems have been chosen: GSM, TETRA and DECT, which are employed to extract some parameters in order to tune them with the third generation systems in its TDMA specification. Such systems are evaluated at physical layer over different propagation channel models with several compensation techniques implemented on the receiver. As well, equalizers based on digital filters and adaptive antennas are utilized. The equalization algorithms evaluated include from the simplest ones like LMS or RLS to bidirectional algorithms over DFE structure. Choosing one or another option will strongly condition the design of the proposed access protocol within the MAC sublayer.

The world of information technology and communications is in a stage of continuous improvement. These new developments are accompanied by a very rapid data traffic growth, particularly for mobile wireless networks. An important effect is the increase of the consumed energy by the network, particularly the radio access section, i.e. the base station systems. This latter issue causes that operational costs associated to energy consumption become more significant for telecommunication operators. In addition to the question of the availability of energy, this problem has an ecological aspect, due to the CO2 emissions associated with the operation of the network but also an issue related to public health given the effects of electromagnetic radiation from wireless transmission. For these reasons, great research efforts in the so-called field of Green Radio are being done in the recent years. The aim of this thesis consisted of finding ways to reduce the energy consumption in wireless and mobile networks respecting the QoS levels assigned to users. After a study of the state of the art analysing the possible approaches, we proposed a set of energy efficient techniques supported on the cell breathing and hybrid cellular networks (macro/femtocells). Our proposed decision making mechanisms include distributed strategies and other features such as the use of a novel multimetric approach. In our work, we also take into account the energy consumption of mobile devices, an issue that to the best of our knowledge was not quite analysed so far. The use of renewable energy sources is also considered into our proposals. Our thesis work includes the study of the consequences of our radio resource management algorithms on the electromagnetic radiation taking into account the acceptable EM exposure thresholds. In the perspectives of future work, we can mention the improvement of our techniques with learning mechanisms and cognitive radio.

This thesis describes the development of antennas suitable for mobile coinmunication systems based on a dielectric rod antenna fed from circular waveguide. Pattern control of the antenna is implemented using a combination of Frequency Selective Surface (FSS) elements and metallic endcaps placed on the antenna Both linear and circular polarised feeds have been made for these antennas to ensure they are suitable for a wide range of applications. The suitability of the dominant and next, higher order, waveguide mode were investigated and conclusions drawn as to their suitability for this type of antenna. The antennas were extensively modelled using a commercial TLM based solver and the results of these simulations were compared to the comprehensive set of antenna pattern measurements and S-parameter measurements obtained for the prototype antennas.

Thesis (M.Eng. (Computer Enginnering)) -- University of Pretoria, 2007. / Includes bibliographical references (leaves 105-109)