[pt] Atualmente, as redes celulares estão sendo utilizadas como uma saída para prover serviços de banda larga em locais que ainda não são atendidos pelas redes fixas, principalmente em países subdesenvolvidos como o Brasil. As tecnologias empregadas atualmente no Brasil, o GSM (Global System for Mobile) e o UMTS (Universal Mobile Telecommunications System), não são tecnologias desenvolvidas para absorver a grande demanda que vem sendo observada no mercado de banda larga móvel. Devido a essa demanda inesperada, acredita-se que o LTE (Long Term Evolution), a primeira tecnologia desenvolvida com o objetivo de atender não somente as chamadas de voz, mas principalmente as conexões banda larga, apresente condições de suportar com maior eficiência esta crescente necessidade. Para que todas as expectativas relacionadas à capacidade das redes LTE sejam atendidas, é extremamente necessário que um correto dimensionamento dessas redes seja realizado, pois somente desta forma será possível estabelecer o compromisso de se atender os usuários com qualidade. / [en] At the moment, the cellular networks are being used as an option to provide broadband services in places that have not yet been covered by the fixed networks, mainly in underdeveloped countries like Brazil. The employed technologies now in Brazil, GSM (Global System is Mobile) and UMTS (Mobile Universal Telecommunications System), they were not developed to absorb the great demand that has been observed at the broadband mobile market. Due to that unexpected demand, it’s being believed that LTE (Long Term Evolution), the first technology developed with the objective of supporting not only the voice calls, but mainly the broadband connections, is able to hold with larger efficiency this growing needs. For all that expectations about the LTE network’s capacity be achieved, it is extremely necessary that a correct sizing of those networks be accomplished, therefore only this way it will be possible to establish the commitment of supporting the subscribers with quality.

This thesis examines various signal processing techniques that are required for establishing efficient (near optimal) communications in multiuser multiple-input multiple-output (MIMO) environments. The central part of this thesis is dedicated to acquisition of information about the MIMO channel state - at both the receiver and the transmitter. This information is required to organize a communication set up which utilizes all the available channel resources. Realistic channel model, i.e., the spatial channel model (SCM), has been used in this study, together with modern long-term evolution (LTE) standard. The work consists of three major themes: (a) estimation of the channel at the receiver, also known as tracking; (b) quantization of the channel information and its feedback from receiver to the transmitter (feedback quantization); and (c) reconstruction of the channel knowledge at the transmitter, and its use for data precoding during communication transmission. / Communications

No description available.

[pt] A constante evolução e aumento de capacidades multimídia nos dispositivos móveis, prevê um aumento dos serviços baseados em vídeo que apresentam maiores requisitos de taxa de transmissão e restrições nos atrasos. Para enfrondar estes desafios, a tecnologia LTE surge como capaz de atender essa demanda sobre as redes móveis. No entanto, devido a natureza das redes celulares, os terminais que se encontram na borda da célula têm dificuldade para conseguir os níveis de SINR apropriados para aproveitar as taxas oferecidas pelo LTE. Para solucionar este problema, na evolução LTE-Advanced, e considerada a integração de nós de retransmissão (Relay Nodes) na arquitetura da rede. Neste trabalho, através de experimentos de simulação, avalia-se o desempenho de aplicações de vídeo em tempo real, focando-se nos usuários da borda da célula. Os resultados obtidos mostram as vantagens do uso de RN em redes LTE e sua contribuição na diminuição de perda de pacotes, aumento da vazão e por conseguinte melhoras na qualidade de vídeo recebido por aqueles usuários. / [en] The constant evolution and growth of the multimedia applications supported by today s mobile devices leads to an increase on the demand of video based services which impose some new requirements in terms of bitrate and delay. In order to face these challenges, LTE appears as a technology capable of dealing with the video trafic load on mobile networks. However, given the inherent nature of the mobile networks, and in order to take advantage of the bitrates that can be achieved with this technology, the devices located at the cell s edge face some dificulties when a certain SINR must be achieved. To overcome this issue, LTE Advanced comes into the picture as it makes use of Relay Nodes (RN) which were included as part of the network architecture. Based on simulations, the present work evaluates the performance of real time applications on devices located at the cell s edge. The results show the advantage of using Relay Nodes in LTE in aspects such as the reduction of lost packets and the increase of throughput, leading to an improvement of the video quality at the receiver s side.