{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T00:51:12Z","timestamp":1760230272662,"version":"build-2065373602"},"reference-count":54,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2022,7,19]],"date-time":"2022-07-19T00:00:00Z","timestamp":1658188800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Universidad de Las Am\u00e9ricas (UDLA)","award":["ERT.NOG.22.01","2021\/03923-9"],"award-info":[{"award-number":["ERT.NOG.22.01","2021\/03923-9"]}]},{"DOI":"10.13039\/501100001807","name":"S\u00e3o Paulo Research Foundation (FAPESP)","doi-asserted-by":"publisher","award":["ERT.NOG.22.01","2021\/03923-9"],"award-info":[{"award-number":["ERT.NOG.22.01","2021\/03923-9"]}],"id":[{"id":"10.13039\/501100001807","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>For the receiver of multiple-input multiple-output (MIMO) systems, linear detectors are an interesting option due to their good performance and low complexity. Nevertheless, MIMO systems lose diversity in exchange for eliminating interference when linear detectors are used. Aiming to maintain the system diversity while mitigating interference between users, this work proposes a scheduling scheme for the uplink of multiuser MIMO (MU-MIMO) systems that employ A antennas and the zero-forcing (ZF) detector at the receiver in the base station (BS). The channel model includes Rician fading and additive white Gaussian noise (AWGN) in an imperfect channel estimation scenario. The proposed scheme selects U users from a group of Ut users to transmit simultaneously, so that the signal-to-noise ratio (SNR) is maximized. For this, an exact expression to evaluate the SNR of the users is obtained. With this result, the scheduling strategy is proposed. Results show that as Ut increases, the outage probability (OP), and the bit error rate (BER) decrease as the system diversity increases, even when the system is completely loaded, i.e., when U=A. Moreover, it is shown that the scheduling scheme counteracts the imperfect channel estimation effects as Ut increases. Finally, the proposed scheme is tested in presence of an external eavesdropper trying to decode the information sent by the users. The results show that the presented proposal allows for a reduction of the secrecy-outage-probability (SOP) as Ut increases.<\/jats:p>","DOI":"10.3390\/s22145369","type":"journal-article","created":{"date-parts":[[2022,7,19]],"date-time":"2022-07-19T05:37:53Z","timestamp":1658209073000},"page":"5369","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A Scheduling Scheme for Improving the Performance and Security of MU-MIMO Systems"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0529-8224","authenticated-orcid":false,"given":"Henry","family":"Carvajal","sequence":"first","affiliation":[{"name":"Faculty of Engineering and Applied Sciences (FICA), Telecommunications Engineering, Universidad de Las Am\u00e9ricas (UDLA), Quito 170124, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5232-7529","authenticated-orcid":false,"given":"Nathaly","family":"Orozco","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Applied Sciences (FICA), Telecommunications Engineering, Universidad de Las Am\u00e9ricas (UDLA), Quito 170124, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Stalin","family":"Cacuango","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Applied Sciences (FICA), Telecommunications Engineering, Universidad de Las Am\u00e9ricas (UDLA), Quito 170124, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Paola","family":"Salazar","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Applied Sciences (FICA), Telecommunications Engineering, Universidad de Las Am\u00e9ricas (UDLA), Quito 170124, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Edgar","family":"Rosero","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Applied Sciences (FICA), Telecommunications Engineering, Universidad de Las Am\u00e9ricas (UDLA), Quito 170124, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3747-1511","authenticated-orcid":false,"given":"Fernando","family":"Almeida","sequence":"additional","affiliation":[{"name":"School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Campinas 13083-970, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Kiani, S.H., Altaf, A., Anjum, M.R., Afridi, S., Arain, Z.A., Anwar, S., Khan, S., Alibakhshikenari, M., Lalbakhsh, A., and Khan, M.A. (2021). MIMO Antenna System for Modern 5G Handheld Devices with Healthcare and High Rate Delivery. Sensors, 21.","DOI":"10.3390\/s21217415"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1109\/JMW.2020.3034648","article-title":"Implementation Challenges and Opportunities in Beyond-5G and 6G Communication","volume":"1","author":"Gustavsson","year":"2021","journal-title":"IEEE J. Microw."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1109\/TLA.2015.7040626","article-title":"Improved Detection of SM-SMux Signals for MIMO Channels","volume":"13","author":"Castillo","year":"2015","journal-title":"IEEE Lat. Am. Trans."},{"key":"ref_4","unstructured":"Marques, M., and Monteiro, F. (2014). MIMO Processing for 4G and Beyond Fundamentals and Evolution, CRC Press."},{"key":"ref_5","unstructured":"Proakis, J., and Manolakis, D. (2007). Digital Communications, McGraw. [4th ed.]."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1935","DOI":"10.1109\/TWC.2005.852127","article-title":"Diversity with Practical Channel Estimation","volume":"4","author":"Gifford","year":"2005","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2674","DOI":"10.1109\/TCOMM.2009.09.080276","article-title":"Optimized Simple Bounds for Diversity Systems","volume":"57","author":"Conti","year":"2009","journal-title":"IEEE Trans. Commun."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"174482","DOI":"10.1109\/ACCESS.2019.2956828","article-title":"BER Evaluation of Linear Detectors in Massive MIMO Systems Under Imperfect Channel Estimation Effects","volume":"7","author":"Altamirano","year":"2019","journal-title":"IEEE Access"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"127809","DOI":"10.1109\/ACCESS.2019.2939501","article-title":"Leveraging on the Impact of Imperfect Channel Estimation for MIMO Relaying Systems","volume":"7","author":"Miridakis","year":"2019","journal-title":"IEEE Access"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1262","DOI":"10.1049\/iet-com.2018.5860","article-title":"Impact of imperfect channel estimation and antenna correlation on quantised massive multiple-input multiple-output systems","volume":"13","author":"Temiz","year":"2019","journal-title":"IET Commun."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"4398","DOI":"10.1109\/TVT.2009.2021840","article-title":"Capacity of MIMO Rayleigh Fading Channels in the Presence of Interference and Receive Correlation","volume":"58","author":"Wang","year":"2009","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1109\/4234.913150","article-title":"On the estimation of the K parameter for the Rice fading distribution","volume":"5","author":"Abdi","year":"2001","journal-title":"IEEE Comm. Lett."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"3193","DOI":"10.1049\/iet-com.2019.0668","article-title":"Spectral efficiency analysis for massive MIMO systems in Ricean fading channels","volume":"13","author":"Xin","year":"2019","journal-title":"IET Comm."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Kassaw, A., Hailemariam, D., and Zoubirl, A.M. (2018, January 3\u20137). Performance Analysis of Uplink Massive MIMO System Over Rician Fading Channel. Proceedings of the 2018 26th European Signal Processing Conference (EUSIPCO), Rome, Italy.","DOI":"10.23919\/EUSIPCO.2018.8553192"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"4514","DOI":"10.1109\/JSYST.2020.3014647","article-title":"On the Performance of Massive MIMO Systems With Low-Resolution ADCs and MRC Receivers Over Rician Fading Channels","volume":"15","author":"Liu","year":"2020","journal-title":"IEEE Syst. J."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2962","DOI":"10.1049\/iet-com.2019.0905","article-title":"Ergodic spectral efficiency of massive MIMO with correlated Rician channel and MRC detection based on LS and MMSE channel estimation","volume":"14","author":"Sadraei","year":"2020","journal-title":"IET Comm."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Sharma, P.K., Priya, V.H., Raju, G.K., and Sai, K.V. (2018, January 29\u201331). Comparison of MIMO Over Different Fading Channels with and without Channel State Information. Proceedings of the 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA), Coimbatore, India.","DOI":"10.1109\/ICECA.2018.8474831"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Ghacham, S., Benjillali, M., and Guennoun, Z. (2017, January 26\u201330). Low-complexity detection for massive MIMO systems over correlated Rician fading. Proceedings of the 2017 13th International Wireless Communications and Mobile Computing Conference (IWCMC), Valencia, Spain.","DOI":"10.1109\/IWCMC.2017.7986536"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1016\/j.aeue.2017.11.011","article-title":"On the cellular spectral efficiency of MC-CDMA systems with MMSE multiuser detector employing fractional and soft frequency reuse","volume":"84","author":"Carvajal","year":"2018","journal-title":"AEU Int. J. Electron. Commun."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"3658","DOI":"10.1109\/TSP.2006.879269","article-title":"Low complexity user selection algorithms for multiuser MIMO systems with block diagonalization","volume":"54","author":"Shen","year":"2006","journal-title":"IEEE Trans. Signal Proc."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"He, S., Du, J., and Liao, Y. (2021). Multi-User Scheduling for 6G V2X Ultra-Massive MIMO System. Sensors, 21.","DOI":"10.3390\/s21206742"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1344","DOI":"10.1109\/LCOMM.2011.101811.111667","article-title":"Outage Probability of Zero Forcing Precoded Scheduling System for Multiple Input Multiple Output Broadcast Transmission","volume":"12","author":"Lee","year":"2011","journal-title":"IEEE Comm. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"6803","DOI":"10.1109\/TVT.2020.2986466","article-title":"Joint User Identification and Channel Estimation Over Rician Fading Channels","volume":"69","author":"Wu","year":"2020","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Zhang, Q., Chang, Y., and Wang, Y. (2019, January 6\u20139). LOS\/NLOS Based User Grouping Scheduling Algorithm for Downlink Massive MIMO Systems. Proceedings of the 2019 IEEE 5th International Conference on Computer and Communications (ICCC), Chengdu, China.","DOI":"10.1109\/ICCC47050.2019.9064385"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Wang, S.D., and Wang, H.M. (2020, January 9\u201311). Impact of Cooperative Attack on User Scheduling in Massive MIMO Systems. Proceedings of the IEEE\/CIC International Conference on Communications in China (ICCC), Chongqing, China.","DOI":"10.1109\/ICCC49849.2020.9238790"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Chataut, R., and Akl, R. (2020, January 26\u201328). An Efficient and Fair Scheduling for Downlink 5G Massive MIMO Systems. Proceedings of the IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), Waco, TX, USA.","DOI":"10.1109\/WMCS49442.2020.9172382"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3781","DOI":"10.1109\/TLA.2015.7404908","article-title":"User Scheduling Algorithms in Multiuser Massive MIMO Systems Towards 5G","volume":"13","author":"Maciel","year":"2015","journal-title":"IEEE Lat. Am. Trans."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Mir, A., Zuhairi, M.F., Musa, S., Syed, T.A., and Alrehaili, A. (2020, January 3\u20135). A Survey of Security Challenges with 5G-IoT. Proceedings of the 2020 First International Conference of Smart Systems and Emerging Technologies (SMARTTECH), Riyadh, Saudi Arabia.","DOI":"10.1109\/SMART-TECH49988.2020.00063"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Khalid, W., Yu, H., Ali, R., and Ullah, R. (2021). Advanced Physical-Layer Technologies for Beyond 5G Wireless Communication Networks. Sensors, 21.","DOI":"10.3390\/s21093197"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1109\/TIFS.2020.3015548","article-title":"Physical Layer Secure MIMO Communications Against Eavesdroppers With Arbitrary Number of Antennas","volume":"16","author":"Tang","year":"2020","journal-title":"IEEE Trans. Inf. Forensics Secur."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Madeira, J., Guerreiro, J., Dinis, R., Montezuma, P., and Campos, L.M. (2021). On the Physical Layer Security Characteristics for MIMO-SVD Techniques for SC-FDE Schemes. Sensors, 19.","DOI":"10.3390\/s19214757"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"727","DOI":"10.1109\/LWC.2022.3141711","article-title":"Secrecy Outage Probability of MIMO Diversity Schemes Over Integer and Real-Valued Nakagami Fading Channels","volume":"11","author":"Lee","year":"2022","journal-title":"IEEE Wirel. Commun. Lett."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Shrestha, A.P., and Kwak, K.S. (2014). Performance of opportunistic scheduling for physical layer security with transmit antenna selection. EURASIP J. Wirel. Commun. Netw., 33.","DOI":"10.1186\/1687-1499-2014-33"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1109\/TCOMM.2016.2606396","article-title":"Physical Layer Security with Threshold-Based Multiuser Scheduling in Multi-antenna Wireless Networks","volume":"64","author":"Yang","year":"2016","journal-title":"IEEE Trans. Commun."},{"key":"ref_35","unstructured":"Carvajal, H., Orozco, N., and de Almeida, C. (2016, January 18\u201321). On the Performance of MC-CDMA Cellular Systems Employing Multiuser Decorrelating Detector and Antenna Array. Proceedings of the 2016 IEEE 84th Vehicular Technology Conference (VTC-Fall), Montreal, QC, Canada."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Barry, J.R., Lee, E.A., and Messerschmitt, D.G. (2004). Digital Communication, Kluwer Academic Publishers. [3rd ed.].","DOI":"10.1007\/978-1-4615-0227-2"},{"key":"ref_37","unstructured":"Papoulis, A., and Pillai, S. (2002). Probability, Random Variables and Stochastic Processes, McGraw-Hill. [4th ed.]."},{"key":"ref_38","unstructured":"Abramowitz, M., and Stegun, I.A. (1964). Handbook of Mathematical Functions with Formulas, Graphs and Mathematical Tables, U.S. Department of Commerce, National Bureau of Standards."},{"key":"ref_39","unstructured":"Verd\u00fa, S. (1998). Multiuser Detection, Cambridge University Press."},{"key":"ref_40","unstructured":"Kay, S.M. (1993). Fundamentals of Statistical Signal Processing: Estimation Theory, Prentice-Hall. [2nd ed.]."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"805","DOI":"10.1109\/TWC.2007.05384","article-title":"On the Performance of the MIMO Zero-Forcing Receiver in the Presence of Channel Estimation Error","volume":"6","author":"Wang","year":"2007","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2905","DOI":"10.1109\/TSP.2018.2799164","article-title":"Learning the MMSE Channel Estimator","volume":"66","author":"Neumann","year":"2018","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Wang, C., Au, E.K., Murch, R.D., and Lau, V.K. (2006, January 2\u20135). Closed-Form Outage Probability and BER of MIMO Zero-Forcing Receiver in the Presence of Imperfect CSI. Proceedings of the 2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications, Cannes, France.","DOI":"10.1109\/SPAWC.2006.346359"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"951","DOI":"10.1109\/TIT.2003.809594","article-title":"How much training is needed in multiple-antenna wireless links?","volume":"49","author":"Hassibi","year":"2003","journal-title":"IEEE Trans. Inf. Theory"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1049\/iet-spr.2015.0265","article-title":"Impact of channel estimation error on zero-forcing-based multiple-input\u2013multiple-output two-way relaying","volume":"10","author":"Gurjar","year":"2016","journal-title":"IET Signal Process."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Stoer, J., and Bulirsch, R. (2002). Introduction to Numerical Analysis, Springer. [3rd ed.].","DOI":"10.1007\/978-0-387-21738-3"},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Zhou, B., Bai, B., Li, Y., Gu, D., and Luo, Y. (2011, January 22\u201325). Chordal Distance-Based User Selection Algorithm for the Multiuser MIMO Downlink with Perfect or Partial CSIT. Proceedings of the 2011 IEEE International Conference on Advanced Information Networking and Applications, Biopolis, Singapore.","DOI":"10.1109\/AINA.2011.51"},{"key":"ref_48","unstructured":"Third Generation Partnership Project\u20143GPP (2018). LTE\u2014Evolved Universal Terrestrial Radio Access (E-UTRA): Physical Layer Procedures, ETSI. Available online: https:\/\/www.etsi.org\/deliver\/etsi_ts\/136200_136299\/136213\/14.06.00_60\/ts_136213v140600p.pdf."},{"key":"ref_49","unstructured":"Third Generation Partnership Project\u20143GPP (2020). Physical Channels and Modulation, ETSI. Available online: https:\/\/www.etsi.org\/deliver\/etsi_ts\/138200_138299\/138211\/16.02.00_60\/ts_138211v160200p.pdf."},{"key":"ref_50","unstructured":"Yacoub, M.D. (2003). Foundations of Mobile Radio Engineering, CRC Press. [1st ed.]."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Piziak, R., and Odell, P. (2007). Matrix Theory: From Generalized Inverses to Jordan Form, Chapman & Hall\/CRC.","DOI":"10.1201\/9781420009934"},{"key":"ref_52","unstructured":"Yang, N., Zhou, X., Lee, J., and Gyeongbuk, D. (2019, January 24). Safeguarding the 5G Era and Beyond with Physical Layer Wireless Security. Proceedings of the IEEE International Conference on Communications ICC, Daegu, Korea. Available online: http:\/\/users.cecs.anu.edu.au\/~xyzhou\/ICC_Tutorial_Security_Final.pdf."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"656","DOI":"10.1002\/j.1538-7305.1949.tb00928.x","article-title":"Communication Theory of Secrecy Systems","volume":"28","author":"Shannon","year":"1949","journal-title":"Bell Syst. Tech. J."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"8725","DOI":"10.1109\/TCOMM.2019.2941493","article-title":"Fading Evaluation in the mm-wave Band","volume":"67","author":"Marins","year":"2019","journal-title":"IEEE Trans. Commun."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/14\/5369\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T23:53:33Z","timestamp":1760140413000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/14\/5369"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,7,19]]},"references-count":54,"journal-issue":{"issue":"14","published-online":{"date-parts":[[2022,7]]}},"alternative-id":["s22145369"],"URL":"https:\/\/doi.org\/10.3390\/s22145369","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2022,7,19]]}}}