NOMA-RA: protocolo de acesso aleatório baseado em múltiplo acesso não ortogonal para MIMO massivo

• Ano de defesa: 2021
• Autor(a) principal: Pereira, Hebert Douglas
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Tecnológica Federal do Paraná; Curitiba; Brasil; Programa de Pós-Graduação em Engenharia Elétrica e Informática Industrial; UTFPR
• Palavras-chave em Português: Protocolos de acesso múltiplo; Internet das coisas; Sistemas de telefonia celular; Múltiplos sistemas de entrada-saída múltipla; Multiple access protocols; Internet of things; Cell phone systems; Multiple input-multiple output systems; CNPQ::ENGENHARIAS::ENGENHARIA ELETRICA::TELECOMUNICACOES; Engenharia Elétrica
• Link de acesso: http://repositorio.utfpr.edu.br/jspui/handle/1/27985

In this thesis, we investigate the random access (RA) problem in a massive MIMO scenario. In 5G networks, devices/users willing to connect to the base station (BS) need to choose a pilot sequence from a set of available orthogonal sequences. However, considering the internet of things (IoT) scenario, the number of users/devices trying to access the BS is much higher than the number of available pilot sequences, só that collisions may occur frequently. Considering this scenario, the strongest-user collision resolution (SUCRe) protocol is modified to include a non-orthogonal multiple access (NOMA) approach. The proposed NOMA-RA protocol allows to resolve collisions between users who try to access the medium using the same pilot signal. Numerical results show that the proposed NOMA-RA strategy achieves a better performance in terms of sum-rate with lower average delay in comparison with the traditional SUCRe scheme, even considering imperfect channel estimation and successive interference cancellation (SIC). For instance, in a scenario when 10 pilot sequences are available and 20 devices compete to access the channel, comparing with the SUCRe protocol, the average delay is reduced by 30% while the sum-rate is improved by 33% and 22% considering, respectively, perfect and imperfect SIC decoders, when the imperfection of SIC was fixed in 10%. In addition, the percentage of users that fail to access the BS in this situation drops from 66.5% with SUCRe to 38.5% with the proposed NOMA-RA scheme.