Efficient receivers for cellular massive mimo systems and random access in cell-free networks.

• Ano de defesa: 2021
• Autor(a) principal: Rodrigues, Victor Croisfelt
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: 5G; 6G; Cell-free networks; Cellular networks; Extra-large scale massive MIMO; Kaczmarz; Massive MIMO; Random access; Receiver design; SUCRe; Telecomunicações
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/3/3142/tde-17092021-112812/

This dissertation addresses two problems of interest to enable future wireless networks of fifth and sixth generation (5G and 6G, respectively): the design of efficient receivers and massive random access. The first problem is discussed in the context of cellular networks in which a massive number of antennas, hundreds to thousands, at the base station (BS) serves a large number of users, tens to hundreds, constituting a system of massive multiple-inputs multipleoutputs (M-MIMO). To make these systems more scalable, we consider the design of iterative receivers based on the Kaczmarz algorithm. We study acceleration techniques to increase the efficiency of such receivers, as well as robustness to the different effects of wireless channels. In addition to classical effects of pathloss and of spatial correlation, the considered channel effects cover the regime of extra-large-scale MIMO systems (XL-MIMO), with the emergence of the so-called spatial non-stationarities. Receiver designs also consider centralized and decentralized baseband hardware architectures. The results show that our receiver designs based on accelerated iterative methods allow better control of the trade-off between performance and complexity under different wireless channel conditions. The second problem is related to the study of how massive random access can be solved in cell-free M-MIMO systems. We adapt the strongest user collision resolution (SUCRe) protocol for the cell-free M-MIMO system, which was initially proposed for cellular M-MIMO systems. This study allows us to better understand how the fact that antennas are geographically distributed can further help support a large number of simultaneous accesses in future wireless networks conceptually centered on mobile users.