Approved for public release, distribution is unlimited / In urbanized terrain, radiowave propagation is subjected to fading on large-scales and smallscales that would impede on the quality and reliability of data link transmission. This would have implications in many military applications. One example is the performance of unmanned aerial vehicle (UAV) data and communications links in complex urban environments. The purpose of this research is to study the effectiveness of diversity techniques on the performance of urban UAV data and communications links. The techniques investigated were spatial, polarization, and angle diversities. The ray tracing software, Urbana Wireless Toolset, was used in the modeling and simulation process. The various combinations of diversity techniques were simulated using a realistic urban city model. For the few transmit-receive geometries examined, it was found that angle diversity with a directive antenna provided the greatest increase in signal strength relative to the no diversity case. / Civilian, Singapore DOD

Made available in DSpace on 2016-03-15T19:37:57Z (GMT). No. of bitstreams: 1 RICHARD JOHN LINTULAHTI OLANDIM.pdf: 2276167 bytes, checksum: 0d3c0536034c612074740ab02558a1be (MD5) Previous issue date: 2015-06-25 / In Brazil, the broadcasting system for television content in high definition is the ISDB-Tb. Although robust, the content transmission in this system, like in any radio frequency propagation, can suffer from external attenuating factors, such as distortion by multipath propagation. One of the techniques used in radio communications for minimizing the effects of this type of distortion is the spatial diversity reception, which uses multiple antennas connected to a single receiver. The signals, received by different antennas, are combined, in a technique known as MRC or Maximal Ratio Combiner, so that the output signal-to-noise ratio is greater than the individual signal-to-noise ratios, allowing the successfully decoding of the received content, even though the individual signal in each antenna does not have sufficient quality to be decoded independently. This study aims to establish a method of spatial diversity in receiving television signals in ISDB-Tb, pondering between the advantages and disadvantages of their use in edge regions of coverage, where the reception of the Brazilian digital TV system is not yet total. / No Brasil, o sistema de radiodifusão para conteúdos televisivos em alta definição é o ISDB-Tb. Apesar de robusto, a transmissão de conteúdos neste sistema, como qualquer propagação em radiofrequência, pode sofrer com fatores externos atenuantes, como por exemplo a distorção por propagação em multi-percurso. Uma das técnicas utilizadas em radiocomunicação para que se minimizem os efeitos deste tipo de distorção é a diversidade espacial na recepção, que utiliza múltiplas antenas conectadas a um mesmo receptor. Os sinais, recebidos pelas diferentes antenas, são trabalhados em uma técnica conhecida como MRC ou Combinação de Máxima Razão, de modo que a relação sinal-ruído de saída seja maior do que as relações sinal-ruído individuais, permitindo a decodificação do conteúdo com sucesso, mesmo que os sinais individuais em cada antena não tenham qualidade suficiente para serem decodificados independentemente. Este estudo tem como objetivo propor um método de diversidade espacial na recepção de sinais televisivos no padrão brasileiro ISDB-Tb, ponderando entre as vantagens e desvantagens de sua utilização em regiões de borda de cobertura, onde a recepção do sistema brasileiro de TV digital ainda não é total.

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Single Carrier Frequency Division Multiple Access (SC-FDMA) is a multiple access transmission scheme that has been adopted in the 4th generation 3GPP Long Term Evolution (LTE) of cellular systems. In fact, its relatively low peak-to-average power ratio (PAPR) makes it ideal for the uplink transmission where the transmit power efficiency is of paramount importance. Multiple access among users is made possible by assigning different users to different sets of non-overlapping subcarriers. With the current LTE specifications, if an SC-FDMA system is operating at its full capacity and a new user requests channel access, the system redistributes the subcarriers in such a way that it can accommodate all of the users. Having less subcarriers for transmission, every user has to increase its modulation order (for example from QPSK to 16QAM) in order to keep the same transmission rate. However, increasing the modulation order is not always possible in practice and may introduce considerable complexity to the system. The technique presented in this thesis report describes a new way of adding more users to an SC-FDMA system by assigning the same sets of subcarriers to different users. The main advantage of this technique is that it allows the system to accommodate more users than conventional SC-FDMA and this corresponds to increasing the spectral efficiency without requiring a higher modulation order or using more bandwidth. During this work, special attentions wee paid to the cases where two and three source signals are being transmitted on the same set of subcarriers, which leads respectively to doubling and tripling the spectral efficiency. Simulation results show that by using the proposed technique, it is possible to add more users to any SC-FDMA system without increasing the bandwidth or the modulation order while keeping the same performance in terms of bit error rate (BER) as the conventional SC-FDMA. This is realized by slightly increasing the energy per bit to noise power spectral density ratio (Eb/N0) at the transmitters.

Single Carrier Frequency Division Multiple Access (SC-FDMA) is a multiple access transmission scheme that has been adopted in the 4th generation 3GPP Long Term Evolution (LTE) of cellular systems. In fact, its relatively low peak-to-average power ratio (PAPR) makes it ideal for the uplink transmission where the transmit power efficiency is of paramount importance. Multiple access among users is made possible by assigning different users to different sets of non-overlapping subcarriers. With the current LTE specifications, if an SC-FDMA system is operating at its full capacity and a new user requests channel access, the system redistributes the subcarriers in such a way that it can accommodate all of the users. Having less subcarriers for transmission, every user has to increase its modulation order (for example from QPSK to 16QAM) in order to keep the same transmission rate. However, increasing the modulation order is not always possible in practice and may introduce considerable complexity to the system. The technique presented in this thesis report describes a new way of adding more users to an SC-FDMA system by assigning the same sets of subcarriers to different users. The main advantage of this technique is that it allows the system to accommodate more users than conventional SC-FDMA and this corresponds to increasing the spectral efficiency without requiring a higher modulation order or using more bandwidth. During this work, special attentions wee paid to the cases where two and three source signals are being transmitted on the same set of subcarriers, which leads respectively to doubling and tripling the spectral efficiency. Simulation results show that by using the proposed technique, it is possible to add more users to any SC-FDMA system without increasing the bandwidth or the modulation order while keeping the same performance in terms of bit error rate (BER) as the conventional SC-FDMA. This is realized by slightly increasing the energy per bit to noise power spectral density ratio (Eb/N0) at the transmitters.