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)

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 124-128). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 101-107). Also available in electronic format on the Internet.

Thesis (M. Eng.)--Carleton University, 2000. / Includes bibliographical references. Also available in electronic format on the Internet.

Η διπλωματική εργασία υλοποιεί και προσομοιώνει αλγόριθμο για τη βέλτιστη διαχείριση φορητών συσκευών σε ετερογενή ασύρματα δίκτυα. Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στις γενικές αρχές των Κυτταρικών Συστημάτων Κινητών Επικοινωνιών παρουσιάζοντας την βασική ιδέα των διαφόρων γενιών κινητών επικοινωνιών. Στο δεύτερο κεφάλαιο αναλύονται τα συστήματα τρίτης γενιάς – 3G. Στο τρίτο κεφάλαιο αναφέρονται τα τεχνικά χαρακτηριστικά, τα πλεονεκτήματα και οι σχέσεις της πλατφόρμας TETRA. Στο τέταρτο κεφάλαιο περιγράφεται το σύστημα και οι λειτουργίες του TETRAPOL καθώς και τα πλεονεκτήματα και οι υπηρεσίες που προσφέρει αυτό. Στο 5ο κεφάλαιο αναλύονται τα συστατικά οι υπηρεσίες και οι λειτουργίες του iDen. Στο κεφάλαιο 6 γίνεται μια αναφορά στο πρωτόκολλο WiMax. Στα κεφάλαια 7 & 8 παρουσιάζονται ο αλγόριθμος της διαχείρισης συσκευών και η εξομοίωσή του σε MATLAB. / -

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: SRMA currently used on the SUNSAT field station is an effective MAC layer protocol but lacks several features. Sufficient support for flexible communication, acknowledgement of individual data packets, simultaneous communication of multiple instances from a higher layer over a single underlying layer, and a robust FTP procedure to transfer large amounts of data are some of the features that the SUNSA T field station should cater for. ORBCOMM, GSM and WAP implementations are discussed. Some features from these implementations that are useful in the LEO communication environment are designed into an additional layer of software. This additional layer, called middleware, is proposed and uses SRMA services to deliver store-and-forward services. It supports high volumes of short transactions and session suspend and resume facilities between the SUNSA T satellite and field station. Keywords: SUNSAT, Communication, Field station, WAP, GSM, ORBCOMM / AFRIKAANSE OPSOMMING: Die SRMA pakketkommunikasie-protokol op SUNSA T se prototipe grondterminaal is voldoende om die oordrag van boodskappe oor die kommunikasieverbinding te reguleer. Dit is onvoldoende om fasiliteite soos kommunikasie van 'n aantal instansies in 'n hoër kommunikasie laag oor 'n enkele laer laag en om 'n robuuste data oordrag protokol vir groot hoeveelhede data van 'n grondterminaal te ondersteun. ORBCOMM, GSM en WAP stelsel toepassings word bespreek. Resultate wat spruit uit die drie toepassings word gebruik om kommunikasie in 'n lae wentelbaan kommunikasie omgewing te bevorder. 'n Bykomende sagteware laag, bekend as middle-ware, word aanbeveel om voorafgenoemde funksionaliteit mee te implimenteer. Die middle-ware gebruik die beskikbare dienste van die SRMA pakketkommunikasie-protokol om toegang te verkry na die kommunikasie kanaal. Sodoende kan hoë volumes kort transaksies, en sessie-stop en hervat fasiliteite 'n werklikheid gemaak word. Sleutelwoord: SUNS AT, Kommunikasie, grondterminaal, WAP, GSM, ORBCOMM

The beginning of the 21 st century is characterised, among others, by the evolution in telecommunications. The rapid growth of mobile communications and the variety of applications proposed for the third generation (3G) systems require long operation time, low weight and cost for terminals, as well as improved link quality. For this reason a good efficiency and low profile antennas with low absorption losses by the user are desirable. The Planar Inverted-F Antenna (PIFA) is shown to result into low SAR values and high efficiency when operating in the proximity of the user. Despite these advantages, PIFA is also characterised by narrow bandwidth that limits its practical use. The first part of this work is dedicated to the measurements and evaluation of the radiation characteristics of the PIFA and other wire antennas both in the near and far fields. In addition, novel methods of PIFA tuning are presented. These include the repositioning of the shorting pin and modification of its capacitance. By using these techniques, the effective bandwidth of the PIFA can be increased to satisfy the GSM900 and DCS 1800 system bandwidth requirements. Dual-band and electronically tuned PIFA prototypes are also included. The effects of the handset size on the mass averaged Specific Absorption Rate (SAR), and antenna efficiency are investigated. The appropriate choice of handset can result in up to 30%-reduced peak SAR. The computed SAR values from PIFA are compared with those resulting from the use of a handset equipped with quarter wavelength monopole antenna. A new measure referred to as the 3dB SAR volume is proposed. This measure provides better understanding of the absorbed power distribution in the operator's head. Results obtained in the course of study show that low profile handset antennas, such as the PIFA, present in addition to dual resonance and low reflection losses, reduced SAR values, high efficiency and low 3dB SAR volume. Finally, SAR and 3dB SAR volume values from simulations on 5- and 10- years old child head models are compared with their equivalents for adult models from which appropriate conclusions are drawn.

[pt] Este trabalho investiga o comportamento de métodos de alocação de canais para Sistemas Móveis Celulares quando associados ao uso de canais de guarda para priorizar chamadas que estejam em handoff. O objetivo desta associação é uma maior qualidade da ligação comparada à obtida quando não se faz uso dessa técnica. Resultados de simulações mostram que este objetivo pode ser atingido. / [en] This work investigates the behavior of channel allocation schemes for Mobile Cellular Systems, when associated with channel guards giving priority to calls that are in handoff procedure. The objective of this association is a better call quality compared to the one in which this technique is not used. Simulation results show that indeed this can be achieved.

Today's mobile computing devices provide a convenient means to search for points-of-interest (POIs) such as restaurants and accommodation. Mobile Preference-Based Search Tools (PBSTs) allow users to identify POIs such as restaurants or accommodation most suited to their needs and constraints using a mobile device. These devices however, have several design constraints including limited screen space and hardware capabilities. Adaptive User Interfaces (AUIs) have been proposed to address these issues but have not been extensively applied to mobile PBSTs such as mobile tourist guides. In addition, AUIs possess several benefits and advantages over static (traditional) interfaces, which do not take a user's preferences, skill set and experience into account. Little research, however, has been conducted into identifying the potential benefits of AUIs for mobile preference-based searching (PBS). The aim of this research was to determine the extent to which an AUI could improve the effectiveness and user satisfaction of mobile PBS. A literature study was conducted to determine the benefits and limitations of existing mobile PBSTs and determine how these could be improved. The potential benefits of AUIs for mobile PBSTs and a mobile map-based visualisation system were identified. A suitable model for incorporating an AUI into a mobile PBST was identified. The requirements for a mobile PBST were combined with the potentially adaptable objects of a Mobile Map-based Visualisation (MMV) system to provide adaptation suggestions for POInter, an existing mobile tourist guide. A field study using POInter was conducted in order to measure the extent to which participants agreed with suggestions provided for adapting the information, interaction and visualisation aspects of the system. These results were used to derive adaptation requirements for A-POInter, an adaptive version of POInter. Using a model-based design approach, an AUI was designed and implemented for A-POInter. An extensive field study was then conducted to evaluate the usability of the adaptations provided by A-POInter. The quantitative and qualitative data collected from the evaluations allowed the usability of A-POInter to be determined. The results of the field study showed that the participants were highly satisfied with the usability and the usefulness of the adaptations provided by A-POInter. Conclusions and recommendations for future work based on the results of the research were then outlined to conclude the dissertation.