Novas propostas para otimização de receptores de TV digital baseados em OFDM em ambientes de redes de frequencia unica regionais

Esta tese trata da otimizacao de receptores de TV Digital baseados em OFDM, com avaliacao de desempenho em redes de retransmissao em frequencia unica (SFN . Single Frequency Networks) regionais. Tal ambiente facilita a distribuicao de canais, porem possui caracteristicas que dificultam o trabalho do receptor. Sao tratados, inicialmente, de projetos de filtros canceladores de elos de realimentacao em estacoes retransmissoras, que ocorrem quando a antena de transmissao interfere na antena de recepcao. Um novo filtro, baseado em tecnicas que utilizam informacao temporal e proposto. Novas propostas sao feitas para as partes de sincronismo, estimacao e equalizacao de canal, e codificacao/decodificacao. Uma tecnica, vinda da teoria de reconhecimento de padroes, e aplicada para diminuicao da complexidade no processo de sincronismo temporal. Um sistema de estimacao de canal 2D e equalizacao adaptativa, usando o LMS (Least Mean Square), e comparado com tecnicas classicas da literatura, e um ganho significativo e encontrado. Como novo esquema de codificacao e decodificacao e proposto um esquema iterativo, baseado em codigos turbo, com numero reduzido de iteracoes. Tal codigo melhora o desempenho do sistema em relacao ao uso combinado dos decodificadores Viterbi e Reed Solomon. Todas as propostas sao combinadas para se avaliar o desempenho do receptor diante de condicoes tipicas de SFN e multicaminhos tipicos em recepcao de TV do Brasil Abstract

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