{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,22]],"date-time":"2025-10-22T04:45:43Z","timestamp":1761108343806,"version":"build-2065373602"},"reference-count":42,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2020,10,30]],"date-time":"2020-10-30T00:00:00Z","timestamp":1604016000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Due to large spectral efficiency and low power consumption, the Massive Multiple-Input-Multiple-Output (MIMO) became a promising technology for the 5G system. However, pilot contamination (PC) limits the performance of massive MIMO systems. Therefore, two pilot scheduling schemes (i.e., Fractional Pilot Reuse (FPR) and asynchronous fractional pilot scheduling scheme (AFPS)) are proposed, which significantly mitigated the PC in the uplink time division duplex (TDD) massive MIMO system. In the FPR scheme, all the users are distributed into the central cell and edge cell users depending upon their signal to interference plus noise ratio (SINR). Further, the capacity of central and edge users is derived in terms of sum-rate, and the ideal number of the pilot is calculated which significantly maximized the sum rate. In the proposed AFPS scheme, the users are grouped into central users and edge users depending upon the interference they receive. The central users are assigned the same set of pilots because these users are less affected by interference, while the edge users are assigned the orthogonal pilots because these users are severely affected by interference. Consequently, the pilot overhead is reduced and inter-cell interference (ICI) is minimized. Further, results verify that the proposed schemes outperform the previous proposed traditional schemes, in terms of improved sum rates.<\/jats:p>","DOI":"10.3390\/s20216213","type":"journal-article","created":{"date-parts":[[2020,10,30]],"date-time":"2020-10-30T21:34:47Z","timestamp":1604093687000},"page":"6213","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["Pilot Decontamination Using Asynchronous Fractional Pilot Scheduling in Massive MIMO Systems"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7597-2304","authenticated-orcid":false,"given":"Muhammad Irshad","family":"Zahoor","sequence":"first","affiliation":[{"name":"College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zheng","family":"Dou","sequence":"additional","affiliation":[{"name":"College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3340-1161","authenticated-orcid":false,"given":"Syed Bilal Hussain","family":"Shah","sequence":"additional","affiliation":[{"name":"School of Software, Dalian University of Technology, Dalian 116000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3268-4844","authenticated-orcid":false,"given":"Imran Ullah","family":"Khan","sequence":"additional","affiliation":[{"name":"College of Underwater Acoustics Engineering, Harbin Engineering University, Harbin 150001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sikander","family":"Ayub","sequence":"additional","affiliation":[{"name":"College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0097-801X","authenticated-orcid":false,"given":"Thippa","family":"Reddy Gadekallu","sequence":"additional","affiliation":[{"name":"School of Information Technology and Engineering, VIT-Vellore, Tamil Nadu 632014, India"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,10,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1109\/MSP.2011.2178495","article-title":"Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays","volume":"30","author":"Rusek","year":"2013","journal-title":"IEEE Signal Process. Mag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"186","DOI":"10.1109\/MCOM.2014.6736761","article-title":"Massive MIMO for next generation wireless systems","volume":"52","author":"Larsson","year":"2014","journal-title":"IEEE Commun. Mag."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Marzetta, T.L. (November, January 29). How Much Training is Required for Multiuser Mimo?. Proceedings of the 2006 Fortieth Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, USA.","DOI":"10.1109\/ACSSC.2006.354768"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"3590","DOI":"10.1109\/TWC.2010.092810.091092","article-title":"Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas","volume":"9","author":"Marzetta","year":"2010","journal-title":"IEEE Transac. Wirel. Commun."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"604","DOI":"10.1109\/TSP.2014.2376886","article-title":"Massive MIMO Channel-Aware Decision Fusion","volume":"63","author":"Ciuonzo","year":"2015","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3005","DOI":"10.1109\/TSP.2015.2417508","article-title":"Massive MIMO for Wireless Sensing With a Coherent Multiple Access Channel","volume":"63","author":"Jiang","year":"2015","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"6853","DOI":"10.1109\/TWC.2018.2864756","article-title":"Analyzing Random Access Collisions in Massive IoT Networks","volume":"17","author":"Jiang","year":"2018","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2499","DOI":"10.1109\/TSP.2016.2523459","article-title":"Massive MIMO for Decentralized Estimation of a Correlated Source","volume":"64","author":"Shirazinia","year":"2016","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"5788","DOI":"10.1109\/TCOMM.2018.2854275","article-title":"Random Access Analysis for Massive IoT Networks Under a New Spatio-Temporal Model: A Stochastic Geometry Approach","volume":"66","author":"Jiang","year":"2018","journal-title":"IEEE Trans. Commun."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"905","DOI":"10.1109\/COMST.2015.2504379","article-title":"A Comprehensive Survey of Pilot Contamination in Massive MIMO\u20145G System","volume":"18","author":"Elijah","year":"2016","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Zheng, X., Zhang, H., Xu, W., and You, X. (2014, January 8\u201312). Semi-orthogonal pilot design for massive MIMO systems using successive interference cancellation. Proceedings of the 2014 IEEE Global Communications Conference, Austin, TX, USA.","DOI":"10.1109\/GLOCOM.2014.7037386"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Mahyiddin, W.A.W.M., Martin, P.A., and Smith, P.J. (2014, January 14\u201317). Pilot Contamination Reduction Using Time-Shifted Pilots in Finite Massive MIMO Systems. Proceedings of the 2014 IEEE 80th Vehicular Technology Conference (VTC2014-Fall), Vancouver, BC, Canada.","DOI":"10.1109\/VTCFall.2014.6966130"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"742","DOI":"10.1109\/JSTSP.2014.2317671","article-title":"An Overview of Massive MIMO: Benefits and Challenges","volume":"8","author":"Lu","year":"2014","journal-title":"IEEE J. Sel. Top. Signal Process."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2640","DOI":"10.1109\/TWC.2011.060711.101155","article-title":"Pilot Contamination and Precoding in Multi-Cell TDD Systems","volume":"10","author":"Jose","year":"2011","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Zahoor, M.I., Zheng, D., Ayub, S., and Waqas, M. (2018, January 20\u201322). Bayesian Channel Estimation in Massive MIMO System. Proceedings of the 2018 2nd International Conference on Imaging, Signal Processing and Communication (ICISPC), Kuala Lumpur, Malaysia.","DOI":"10.1109\/ICISPC44900.2018.9006706"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Ashikhmin, A., and Marzetta, T. (2012, January 1\u20136). Pilot contamination precoding in multi-cell large scale antenna systems. Proceedings of the 2012 IEEE International Symposium on Information Theory, Cambridge, MA, USA.","DOI":"10.1109\/ISIT.2012.6283031"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"617","DOI":"10.1109\/LWC.2014.2361518","article-title":"Successive Pilot Contamination Elimination in Multiantenna Multicell Networks","volume":"3","author":"Vu","year":"2014","journal-title":"IEEE Wirel. Commun. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Jin, F., Zhang, R., and Hanzo, L. (2012, January 1\u20134). Frequency-swapping aided femtocells in twin-layer cellular networks relying on fractional frequency reuse. Proceedings of the 2012 IEEE Wireless Communications and Networking Conference (WCNC), Paris, France.","DOI":"10.1109\/WCNC.2012.6214337"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Zhou, Y., Liu, L., Du, H., Tian, L., Wang, X., and Shi, J. (2014, January 19\u201321). An overview on intercell interference management in mobile cellular networks: From 2G to 5G. Proceedings of the 2014 IEEE International Conference on Communication Systems, Macau, China.","DOI":"10.1109\/ICCS.2014.7024797"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Wu, Y., Liu, T., Cao, M., Li, L., and Xu, W. (2018). Pilot contamination reduction in massive MIMO systems based on pilot scheduling. Eurasip J. Wirel. Commun. Netw., 2018.","DOI":"10.1186\/s13638-018-1029-1"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"461","DOI":"10.1109\/TSP.2003.821107","article-title":"Zero-forcing methods for downlink spatial multiplexing in multiuser MIMO channels","volume":"52","author":"Spencer","year":"2004","journal-title":"IEEE Trans. Signal. Process."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Yan, S., Zhou, X., Yang, N., Abhayapala, T.D., and Swindlehurst, A.L. (2017, January 21\u201325). Channel training design in full-duplex wiretap channels to enhance physical layer security. Proceedings of the 2017 IEEE International Conference on Communications (ICC), Paris, France.","DOI":"10.1109\/ICC.2017.7996663"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Zhang, X., Xu, J., and Tao, X. (2018, January 12\u201314). A Dynamic Pilot Allocation Scheme in Massive MIMO Systems. Proceedings of the 2018 24th Asia-Pacific Conference on Communications (APCC), Ningbo, China.","DOI":"10.1109\/APCC.2018.8633536"},{"key":"ref_24","unstructured":"Khan, K., Sun, S., Irfan, M., Fu, M., Banoori, F., Alam, S., and Khan, I. (2017, January 13\u201315). An Efficient Pilot Allocation Scheme for Pilot Contamination Alleviation in Multi-cell Massive MIMO Systems. Proceedings of the Signal and Information Processing, Networking and Computers, Singapore."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Pereira de Figueiredo, F., Cardoso, F., Moerman, I., and Fraidenraich, G. (2018). Channel estimation for massive MIMO TDD systems assuming pilot contamination and flat fading. Eurasip J. Wirel. Commun. Netw., 2018.","DOI":"10.1186\/s13638-018-1021-9"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Lu, A., Gao, X., and Xiao, C. (2015, January 6\u201310). Low Complexity Polynomial Expansion Detector for Massive MIMO Uplink with Multiple-Antenna Users. Proceedings of the 2015 IEEE Global Communications Conference (GLOBECOM), San Diego, CA, USA.","DOI":"10.1109\/GLOCOM.2015.7417105"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1109\/MCOM.2012.6146494","article-title":"Coordinated multipoint transmission and reception in LTE-advanced: Deployment scenarios and operational challenges","volume":"50","author":"Lee","year":"2012","journal-title":"IEEE Commun. Mag."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"5016","DOI":"10.1109\/TCOMM.2013.111413.130379","article-title":"Noncoherent Trellis Coded Quantization: A Practical Limited Feedback Technique for Massive MIMO Systems","volume":"61","author":"Choi","year":"2013","journal-title":"IEEE Trans. Commun."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Yue, S., Liu, J., Zhai, C., and Wang, Q. (2015, January 15\u201317). User pilot scheduling in massive MIMO systems. Proceedings of the 2015 International Conference on Wireless Communications & Signal Processing (WCSP), Nanjing, China.","DOI":"10.1109\/WCSP.2015.7341058"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Verenzuela, D., Bjoernson, E., and Sanguinetti, L. (2017, January 4\u20138). Joint UL and DL Spectral Efficiency Optimization of Superimposed Pilots in Massive MIMO. Proceedings of the 2017 IEEE Globecom Workshops (GC Wkshps), Singapore.","DOI":"10.1109\/GLOCOMW.2017.8269159"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Liu, M., Chen, X., Xu, W., Zhang, H., You, X., and Miao, W. (2016, January 13\u201315). Grouped pilot reuse for channel estimation in massive MIMO networks. Proceedings of the 2016 8th International Conference on Wireless Communications & Signal Processing (WCSP), Yangzhou, China.","DOI":"10.1109\/WCSP.2016.7752493"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Atzeni, I., Arnau, J., and Debbah, M. (2015, January 8\u201312). Fractional pilot reuse in massive MIMO systems. Proceedings of the 2015 IEEE International Conference on Communication Workshop (ICCW), London, UK.","DOI":"10.1109\/ICCW.2015.7247312"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"2356","DOI":"10.1587\/transfun.E98.A.2356","article-title":"Fractional Pilot Reuse in Massive MIMO System","volume":"98","author":"Zhang","year":"2015","journal-title":"Ieice Trans. Fundam. Electron. Commun. Comput. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Wang, W., Zhao, X., Zhang, J., Xu, L., Zhang, H., and Li, X. (2018, January 8\u201311). Pilot Allocation Scheme Based on User Grouping in Massive MIMO Systems. Proceedings of the 2018 IEEE 18th International Conference on Communication Technology (ICCT), Chongqing, China.","DOI":"10.1109\/ICCT.2018.8599978"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"35568","DOI":"10.1109\/ACCESS.2018.2845853","article-title":"Increasing the Capacity of Cellular Network With Nested Deployed Cooperative Base Stations","volume":"6","author":"Wu","year":"2018","journal-title":"IEEE Access"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1109\/MWC.2012.6231163","article-title":"Interference management in OFDMA femtocell networks: Issues and approaches","volume":"19","author":"Saquib","year":"2012","journal-title":"IEEE Wirel. Commun."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Yang, X., and Fapojuwo, A. (2015). Performance analysis of hexagonal cellular networks in fading channels. Wirel. Commun. Mob. Comput., 16.","DOI":"10.1002\/wcm.2573"},{"key":"ref_38","unstructured":"Garg, V. (2007). Wireless Communications & Networking, Elsevier."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1293","DOI":"10.1109\/TWC.2015.2488634","article-title":"Massive MIMO for Maximal Spectral Efficiency: How Many Users and Pilots should be Allocated?","volume":"15","author":"Larsson","year":"2016","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"11","DOI":"10.15325\/BLTJ.2015.2407793","article-title":"Massive MIMO: An introduction","volume":"20","author":"Marzetta","year":"2015","journal-title":"Bell Labs Tech. J."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1636","DOI":"10.1109\/25.966592","article-title":"Automatic calibration method using transmitting signals of an adaptive array for TDD systems","volume":"50","author":"Nishimori","year":"2001","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Zhang, D., Wang, H., and Fu, Y. (2016, January 13\u201315). Uplink sum rate analysis with flexible pilot reuse. Proceedings of the 2016 8th International Conference on Wireless Communications & Signal Processing (WCSP), Yangzhou, China.","DOI":"10.1109\/WCSP.2016.7752593"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/21\/6213\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:27:21Z","timestamp":1760178441000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/21\/6213"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,10,30]]},"references-count":42,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2020,11]]}},"alternative-id":["s20216213"],"URL":"https:\/\/doi.org\/10.3390\/s20216213","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2020,10,30]]}}}