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By 2030 there should be around 17 billion of mobile-connected devices, with monthly data traffic in the order of thousands of exabytes. Although the Fifth Generation (5G) communications systems present far more features than Fourth Generation (4G) systems, they will not be able to serve this growing demand and the requirements of innovative use cases. Therefore, Sixth Generation (6G) Networks are expected to support such massive connectivity and guarantee an increase in performance and quality of service for all users. To deal with such requirements, several technical issues need to be addressed, including novel multiple-antenna technologies. Then, this survey gives a concise review of the main emerging Multiple-Input Multiple-Output (MIMO) technologies for 6G Networks such as massive MIMO (mMIMO), extremely large MIMO (XL-MIMO), Intelligent Reflecting Surfaces (IRS), and Cell-Free mMIMO (CF-mMIMO). Moreover, we present a discussion on how some of the expected key performance indicators (KPIs) of some novel 6G Network use cases can be met with the development of each MIMO technology.<\/jats:p>","DOI":"10.3390\/s23041921","type":"journal-article","created":{"date-parts":[[2023,2,9]],"date-time":"2023-02-09T01:37:07Z","timestamp":1675906627000},"page":"1921","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":64,"title":["Emerging MIMO Technologies for 6G Networks"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8033-5606","authenticated-orcid":false,"given":"Victoria","family":"Dala Pegorara Souto","sequence":"first","affiliation":[{"name":"National Institute of Telecommunications, Santa Rita do Sapuca\u00ed 37540-000, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pl\u00ednio Santini","family":"Dester","sequence":"additional","affiliation":[{"name":"Department of Communications, University of Campinas, Campinas 13083-970, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michelle","family":"Soares Pereira Facina","sequence":"additional","affiliation":[{"name":"Centro de Pesquisa e Desenvolvimento em Telecomunica\u00e7\u00f5es, Campinas 13083-970, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5777-9797","authenticated-orcid":false,"given":"Daniely","family":"Gomes Silva","sequence":"additional","affiliation":[{"name":"National Institute of Telecommunications, Santa Rita do Sapuca\u00ed 37540-000, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2167-7286","authenticated-orcid":false,"given":"Felipe Augusto Pereira","family":"de Figueiredo","sequence":"additional","affiliation":[{"name":"National Institute of Telecommunications, Santa Rita do Sapuca\u00ed 37540-000, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gustavo","family":"Rodrigues de Lima Tejerina","sequence":"additional","affiliation":[{"name":"National Institute of Telecommunications, Santa Rita do Sapuca\u00ed 37540-000, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jos\u00e9 C\u00e2ndido","family":"Silveira Santos Filho","sequence":"additional","affiliation":[{"name":"Department of Communications, University of Campinas, Campinas 13083-970, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5106-5603","authenticated-orcid":false,"given":"Juliano","family":"Silveira Ferreira","sequence":"additional","affiliation":[{"name":"National Institute of Telecommunications, Santa Rita do Sapuca\u00ed 37540-000, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luciano Leonel","family":"Mendes","sequence":"additional","affiliation":[{"name":"National Institute of Telecommunications, Santa Rita do Sapuca\u00ed 37540-000, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7389-6245","authenticated-orcid":false,"given":"Richard Demo","family":"Souza","sequence":"additional","affiliation":[{"name":"Department of Electrical and Electronic Engineering, Federal University of Santa Catarina, Florian\u00f3polis 88040-900, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7761-0240","authenticated-orcid":false,"given":"Paulo","family":"Cardieri","sequence":"additional","affiliation":[{"name":"Department of Communications, University of Campinas, Campinas 13083-970, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,2,8]]},"reference":[{"key":"ref_1","unstructured":"Goyal, J., Singla, K., and Singh, S. 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