Radio propagation in the presence of fire is known to be problematic to communications. In this thesis we use both experimental and theoretical approaches to examine and understand radio propagation in fire environments. Propagation is examined for three small scale fires with broadband equipment operating from 50MHz to 1GHz. Results for line of sight propagation show a strong interaction of fire with electromagnetic propagation. The next section develops electromagnetic modelling of the fire environment. A model of the combustion induced plasma is developed, as well as a refractive index model of the surrounding atmosphere of a fire. Simple propagation calculations are undertaken, using the developed fire models, to provide an intial understanding of propagation in fire environments. The next portion of the thesis considers propagation using a more rigorous electromagnetic simulation technique. A modified Finite Difference Time Domain method is presented and is utilised to examine three dimensional propagation in the small scale fire experiments. The outcome is a more solid understanding of propagation and the contributing factors. The last portion of the thesis is the application of the above electromagnetic modelling and simulation methods to bushfire scenarios. Various scenarios that are problematic to radio communication are examined. Discussion and recommendations are made concerning radio communication frequency selection and considerations for propagation in fire environments. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1457560 / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2009

Radio propagation in the presence of fire is known to be problematic to communications. In this thesis we use both experimental and theoretical approaches to examine and understand radio propagation in fire environments. Propagation is examined for three small scale fires with broadband equipment operating from 50MHz to 1GHz. Results for line of sight propagation show a strong interaction of fire with electromagnetic propagation. The next section develops electromagnetic modelling of the fire environment. A model of the combustion induced plasma is developed, as well as a refractive index model of the surrounding atmosphere of a fire. Simple propagation calculations are undertaken, using the developed fire models, to provide an intial understanding of propagation in fire environments. The next portion of the thesis considers propagation using a more rigorous electromagnetic simulation technique. A modified Finite Difference Time Domain method is presented and is utilised to examine three dimensional propagation in the small scale fire experiments. The outcome is a more solid understanding of propagation and the contributing factors. The last portion of the thesis is the application of the above electromagnetic modelling and simulation methods to bushfire scenarios. Various scenarios that are problematic to radio communication are examined. Discussion and recommendations are made concerning radio communication frequency selection and considerations for propagation in fire environments. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1457560 / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2009

GSM has been developed during more than a decade and has grown to a very complex system. Due to the wide range of functionality, the high capacity and the complexity of the BSC the testing of stability and performance is time consuming. A simulator is needed for these tests as live networks are not available at this stage in the development process. The performance and stability need to be verified for each new release of functionality. This thesis describes a conceptual model of a GSM network. The conceptual model can be used to configure a simulated radio network and to communicate what is simulated on a conceptual level rather than a detailed level. The model presented consists of several sub models. The subscriber model describes the actions and movement of subscribers; the cell model describes the radio conditions experienced by a subscriber moving within one cell; and the cell network model describes the geographical and structural properties of the network. Together the models are used to compose scenarios with the aim to describe varying radio conditions, varying subscriber behavior and varying cell structures. The aim is that different features of the Ericsson base station controller shall be used in the different scenarios. The scenarios represent different parts of a radio network connected to the same base station controller.

[pt] O esforço de caracterização da influência da vegetação sobre enlaces de radiocomunicação é de grande importância para o dimensionamento de modernos sistemas de comunicação. Baseado em uma extensa campanha de medições, este trabalho pretende caracterizar e propor um modelo de predição de perda de propagação sobre espaços vegetados em banda estreita na faixa de 700 MHz adequado às características morfológicas brasileiras. / [en] The characterization effort of vegetation influence on radiocommunication link fading has a great importance on the design of modern communication systems. Based on an intensive narrow band measurement campaign, this work intends to characterize and propose a model for predicting propagation loss over vegetated areas at the UHF range of 700 MHz.

The full spatial covariance matrix of the multiple input multiple-output (MIMO) channel is an important quantity in channel modeling, communication system signal processing, and performance analysis, and therefore this matrix forms the heart of the research outlined in this dissertation. The work begins with an investigation of a generalized framework for computing the full MIMO spatial covariance based on the power angular spectrum (PAS) of the multipath field and the transmit and receive antenna element radiation patterns. For the case of uniform linear arrays and when the PAS clusters satisfy uniform, truncated Gaussian, or truncated Laplacian distributions, a series expansion is used to allow analytic evaluation of the required integrals in the formulation. The study also demonstrates the validity of some simplifying assumptions used to reduce the complexity of the covariance computation by applying the technique to ray tracing data as well as considers an analysis of the convergence properties of the series when computed using a finite number of terms. The insights and tools obtained from this covariance analysis are then used to develop a general approach for constructing MIMO transmit and receive beamforming vectors based on the full spatial covariance. While transmit and receive beamforming for the MIMO channel is a well-studied topic, when the transmit precoding is based on channel covariance information, developing near-optimal transmit and receive beamformers when the receiver is constrained to use linear processing remains an unsolved problem. This iterative beamforming algorithm presented here can accommodate different types of available channel information and receiver capabilities as well as either a sum power constraint or a per-antenna power constraint. While the latter is more realistic, construction of the optimal transmit precoder is less understood for this constraint. Simulation results based on measured channels demonstrate that the approach generates beamformer solutions whose performance rivals that achieved for an optimal nonlinear receiver architecture.

[pt] A previsão da perda de propagação em áreas urbanas na faixa de UHF tem crescente importância por suas amplas aplicações em novos sistemas de telecomunicações. Neste trabalho o problema é analisado com ênfase em sistemas de TV digital. Dados disponíveis de testes de propagação em cerca de 600 pontos na região da Grande São Paulo foram utilizados para testar modelos de previsão de aplicação geral propostos na literatura técnica. A partir dos dados é proposto um ajuste destes modelos para a região em questão e realizada uma previsão do desempenho de três sistemas atualmente propostos para implementação da TV digital no Brasil. / [en] Methods for the prediction of propagation loss in the UHF band in urban areas are increasingly important for its application in new telecommunication systems. In this work, the problem is analyzed with focus on digital TV systems. Available data from propagation measurements at 593 MHz for about 600 sites in the Great São Paulo region are used to test recommended general purpose prediction methods. Based on this data base, a model fitting applicable for the measurements regions is proposed. The method derived is used to predict the performance of the three digital TV technologies currently under consideration for adoption in Brazil.

This thesis has two major objectives. The first objective is to investigate the seasonal and diurnal variations in occurrence of HF coherent echoes. We assess F-region echo occurrence rates for the PolarDARN HF radars at Inuvik (INV) and Rankin Inlet (RKN) and the auroral zone SuperDARN radars at Saskatoon (SAS) and Prince George (PGR) for the period of 2007-2010. We show that the INV and RKN PolarDARN radars show comparable rates of echo occurrence all the time and they detect 1.5-2.5 times more echoes through ½-hop propagation mode (MLATs=80°-85°) than the SAS and PGR SuperDARN radars through 1½-hope propagation mode (MLATs=75°-80°). For all four radars, the winter occurrence rates are about ~2 times higher than the summer rates. For observations in the dusk, midnight and dawn sectors, equinoctial maxima are evident. The pattern of echo occurrence in terms of MLT/season is about the same for all radars with clear maxima near noon during winters and summers and enhanced (as compared to other time of the day) occurrence rates during equinoctial dusk and dawn hours. Additionally, to investigate the effect of solar cycle on occurrence of F-region echoes, we consider the near noon and near midnight echo occurrence rates for the Saskatoon radar over the period of 1994-2010. We show that there is a strong, by a factor of ~10, increase in SAS night-side echo occurrence towards solar maximum. The effect does not exist for the dayside echoes; moreover, a decrease in number of echoes, by a factor of ~2, was discovered for the declining phase of the solar cycle. The second objective is to evaluate the electron density and the electric field as factors controlling the occurrence of F-region echoes. We use observations of these two ionospheric parameters measured by CADI ionosonde and RKN observations of echo occurrence rates over Resolute Bay (MLAT=83°). We show that there is a correlation in changes of echo occurrence and electron density changes for 3 years of radar-ionosonde joint operation (2008-2010). The comparison of radar-ionosonde data shows that the enhanced echo occurrence at near noon hours during summer months correlate with the enhanced electric field during these periods.

Backscatter radio - the broad class of systems that communicate using scattered electromagnetic waves - is the driving technology behind many compelling applications such as radio frequency identification (RFID) tags and passive sensors. These systems can be used in many ways including article tracking, position location, passive temperature sensors, passive data storage, and in many other systems which require information exchange between an interrogator and a small, low-cost transponder with little-to-no transponder power consumption. Although backscatter radio is maturing, such systems have limited communication range and reliability caused, in part, by multipath fading. The research presented in this dissertation investigates how multipath fading can be reduced using multiple antennas at the interrogator transmitter, interrogator receiver, and on the transponder, or RF tag. First, two link budgets for backscatter radio are presented and fading effects demonstrated through a realistic, 915 MHz, RFID-portal example. Each term in the link budget is explained and used to illuminate the propagation and high-frequency effects that influence RF tag operation. Second, analytic envelope distributions for the M x L x N, dyadic backscatter channel - the general channel in which a backscatter system with M transmitter, L RF tag, and N receiver antennas operates - are derived. The distributions show that multipath fading can be reduced using multiple-antenna RF tags and by using separate transmitter and receiver antenna arrays at the interrogator. These results are verified by fading measurements of the M x L x N, dyadic backscatter channel at 5.8 GHz - the center of the 5725-5850 MHz unlicensed industrial, scientific, and medical (ISM) frequency band that offers reduced antenna size, increased antenna gain, and, in some cases, reduced object attachment losses compared to the commonly used 902-928 MHz ISM band. Measurements were taken with a custom backscatter testbed and details of its design are provided. In the end, this dissertation presents both theory and measurements that demonstrate multipath fading reductions for backscatter-radio systems that use multiple antennas.

[pt] A busca constante pela melhoria dos meios de comunicação em banda larga demandou o surgimento de novas tecnologias visando atender a real necessidade de seus usuários. O uso de mobilidade no acesso à internet banda larga como propõem os padrões WiMAX e LTE, impõe a necessidade de se estudar com mais profundidade os parâmetros que caracterizam um canal rádio móvel. Este trabalho objetiva apresentar os resultados experimentais que permitem caracterizar em banda estreita o comportamento do canal de radiopropagação num ambiente urbano. Como resultado das campanhas de medições, são identificados modelos do canal que possibilita ao projetista definir os melhores critérios para a implantação de uma rede móvel de acesso sem fio. Desta forma, são apresentadas duas campanhas de medições, operando nas frequências de 2,5 GHz e 3,5 GHz, destinadas para novos serviços móveis banda larga. / [en] The constant search for improvement of broadband communication systems requires new technologies to attend the increasing needs of the users. The use of mobility in broadband Internet access as proposed in WiMAX and LTE standards, imposes the need to further understand the parameters that characterize a channel mobile radio. This dissertation presents experimental results that allow characterizing the narrow band channel behavior of radio propagation in an urban environment. As a result of measurement campaigns, channel models are identified which allow the designer to define the best criteria to implement a mobile wireless network. The work presents results of two measurement campaigns, at the frequencies of 2.5 GHz and 3.5 GHz, designed for new mobile broadband services.

The dissertation concerns about the path loss calculation of Radio Frequency (RF) propagation models for 4G Long Term Evolution (LTE) Network to prefer the best Radio Frequency propagation model. The radio propagation models are very significant while planning of any wireless communication system. A comparative analysis between radio propagation models e.g. SUI model, Okumura model, Cost 231 Hata Model, Cost 231-Walfisch Ikegami and Ericsson 9999 model that would be used for outdoor propagation in LTE. The comparison and performance analysis has been made by using different geological environments e.g. urban, sub-urban and rural areas. The simulation scenario is made to calculate the lowest path loss in above defined environments by using selected frequency and height of base station antennas while keeping a constant distance between the transmitter and receiver antennas. / Asad Saeed C/O Muhammad Awais Hovslagargatan 47 LGH 1004 19431 Stockholm Sweden Mob: 0046723333734