{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,3]],"date-time":"2026-03-03T16:11:45Z","timestamp":1772554305637,"version":"3.50.1"},"reference-count":41,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2021,9,9]],"date-time":"2021-09-09T00:00:00Z","timestamp":1631145600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["2020.05621.BD"],"award-info":[{"award-number":["2020.05621.BD"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100015494","name":"Instituto de Telecomunica\u00e7\u00f5es","doi-asserted-by":"publisher","award":["UIDB\/50008\/2020"],"award-info":[{"award-number":["UIDB\/50008\/2020"]}],"id":[{"id":"10.13039\/501100015494","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Millimeter-wave and terahertz technologies have been attracting attention from the wireless research community since they can offer large underutilized bandwidths which can enable the support of ultra-high-speed connections in future wireless communication systems. While the high signal attenuation occurring at these frequencies requires the adoption of very large (or the so-called ultra-massive) antenna arrays, in order to accomplish low complexity and low power consumption, hybrid analog\/digital designs must be adopted. In this paper we present a hybrid design algorithm suitable for both mmWave and THz multiuser multiple-input multiple-output (MIMO) systems, which comprises separate computation steps for the digital precoder, analog precoder and multiuser interference mitigation. The design can also incorporate different analog architectures such as phase shifters, switches and inverters, antenna selection and so on. Furthermore, it is also applicable for different structures, namely fully-connected structures, arrays of subarrays (AoSA) and dynamic arrays of subarrays (DAoSA), making it suitable for the support of ultra-massive MIMO (UM-MIMO) in severely hardware constrained THz systems. We will show that, by using the proposed approach, it is possible to achieve good trade-offs between spectral efficiency and simplified implementation, even as the number of users and data streams increases.<\/jats:p>","DOI":"10.3390\/s21186054","type":"journal-article","created":{"date-parts":[[2021,9,9]],"date-time":"2021-09-09T21:36:58Z","timestamp":1631223418000},"page":"6054","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Low Complexity Hybrid Precoding Designs for Multiuser mmWave\/THz Ultra Massive MIMO Systems"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4759-4817","authenticated-orcid":false,"given":"Jo\u00e3o Pedro","family":"Pavia","sequence":"first","affiliation":[{"name":"Department of Information Science and Technology, ISCTE-Instituto Universit\u00e1rio de Lisboa, 1649-026 Lisboa, Portugal"},{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vasco","family":"Velez","sequence":"additional","affiliation":[{"name":"Department of Information Science and Technology, ISCTE-Instituto Universit\u00e1rio de Lisboa, 1649-026 Lisboa, Portugal"},{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Renato","family":"Ferreira","sequence":"additional","affiliation":[{"name":"Department of Information Science and Technology, ISCTE-Instituto Universit\u00e1rio de Lisboa, 1649-026 Lisboa, Portugal"},{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3823-4470","authenticated-orcid":false,"given":"Nuno","family":"Souto","sequence":"additional","affiliation":[{"name":"Department of Information Science and Technology, ISCTE-Instituto Universit\u00e1rio de Lisboa, 1649-026 Lisboa, Portugal"},{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marco","family":"Ribeiro","sequence":"additional","affiliation":[{"name":"Department of Information Science and Technology, ISCTE-Instituto Universit\u00e1rio de Lisboa, 1649-026 Lisboa, Portugal"},{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jo\u00e3o","family":"Silva","sequence":"additional","affiliation":[{"name":"Department of Information Science and Technology, ISCTE-Instituto Universit\u00e1rio de Lisboa, 1649-026 Lisboa, Portugal"},{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8520-7267","authenticated-orcid":false,"given":"Rui","family":"Dinis","sequence":"additional","affiliation":[{"name":"Instituto de Telecomunica\u00e7\u00f5es, 1049-001 Lisboa, Portugal"},{"name":"Department of Electrical and Computer Engineering, Faculty of Science and Technology, Universidade Nova de Lisboa, 1099-085 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,9,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"335","DOI":"10.1109\/ACCESS.2013.2260813","article-title":"Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!","volume":"1","author":"Rappaport","year":"2013","journal-title":"IEEE Access"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"62367","DOI":"10.1109\/ACCESS.2020.2984204","article-title":"A Comprehensive Survey on Millimeter Wave Communications for Fifth-Generation Wireless Networks: Feasibility and Challenges","volume":"8","author":"Uwaechia","year":"2020","journal-title":"IEEE Access"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"133995","DOI":"10.1109\/ACCESS.2020.3010896","article-title":"6G and Beyond: The Future of Wireless Communications Systems","volume":"8","author":"Akyildiz","year":"2020","journal-title":"IEEE Access"},{"key":"ref_4","unstructured":"Tan, J., and Dai, T. 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