{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T00:12:11Z","timestamp":1774483931081,"version":"3.50.1"},"reference-count":29,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,1,12]],"date-time":"2023-01-12T00:00:00Z","timestamp":1673481600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Thailand Science Research and Innovation Fund Chulalongkorn University","award":["CU _FRB65_ind(12)_160_21_26"],"award-info":[{"award-number":["CU _FRB65_ind(12)_160_21_26"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Cell-free (CF) networks are proposed to suppress the interference among collocated cells by deploying several BSs without cell boundaries. Nevertheless, as installing several base stations (BSs) may require high power consumption, cooperative CF networks integrated with a reconfigurable intelligent surface (RIS)\/metasurface can avoid this problem. In such cooperative RIS-aided MIMO networks, efficient beamforming schemes are essential to boost their spectral and energy efficiency. However, most of the existing available beamforming schemes to maximize spectral and energy efficiency are complex and entail high complexity due to the matrix inversions. To this end, in this work we present a computationally efficient stochastic optimization-based particle swarm optimization (PSO) algorithm to amplify the spectral efficiency of the cooperative RIS-aided CF MIMO system. In the proposed PSO algorithm, several swarms are generated, while the direction of each swarm is tuned in each iteration based on the sum-rate performance to obtain the best solution. Our simulation results show that our proposed scheme can approximate the performance of the existing solutions for both the performance metrics, i.e., spectral and energy efficiency, at a very low complexity.<\/jats:p>","DOI":"10.3390\/s23020903","type":"journal-article","created":{"date-parts":[[2023,1,12]],"date-time":"2023-01-12T06:25:57Z","timestamp":1673504757000},"page":"903","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Low-Complexity Beamforming Design for a Cooperative Reconfigurable Intelligent Surface-Aided Cell-Free Network"],"prefix":"10.3390","volume":"23","author":[{"given":"Muhammad Zain","family":"Siddiqi","sequence":"first","affiliation":[{"name":"Wireless Communication Ecosystem Research Unit, Department of Electrical Engineering, Chulalongkorn University, Bangkok 10330, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3876-7667","authenticated-orcid":false,"given":"Aisha","family":"Munir","sequence":"additional","affiliation":[{"name":"Wireless Communication Ecosystem Research Unit, Department of Electrical Engineering, Chulalongkorn University, Bangkok 10330, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5810-4983","authenticated-orcid":false,"given":"Syed Agha Hassnain","family":"Mohsan","sequence":"additional","affiliation":[{"name":"Optical Communications Laboratory, Ocean College, Zhejiang University, Zhoushan 316021, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4310-7054","authenticated-orcid":false,"given":"Shashi","family":"Shah","sequence":"additional","affiliation":[{"name":"Wireless Communication Ecosystem Research Unit, Department of Electrical Engineering, Chulalongkorn University, Bangkok 10330, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1715-9689","authenticated-orcid":false,"given":"Sushank","family":"Chaudhary","sequence":"additional","affiliation":[{"name":"Wireless Communication Ecosystem Research Unit, Department of Electrical Engineering, Chulalongkorn University, Bangkok 10330, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5097-6891","authenticated-orcid":false,"given":"Paramin","family":"Sangwongngam","sequence":"additional","affiliation":[{"name":"Spectroscopic and Sensing Devices Research Group, National Electronics and Computer Technology Center, Bangkok 12120, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lunchakorn","family":"Wuttisittikulkij","sequence":"additional","affiliation":[{"name":"Wireless Communication Ecosystem Research Unit, Department of Electrical Engineering, Chulalongkorn University, Bangkok 10330, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1109\/MWC.2006.1678166","article-title":"Network coordination for spectrally efficient communications in cellular systems","volume":"13","author":"Karakayali","year":"2006","journal-title":"IEEE Wirel. 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