{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T18:47:41Z","timestamp":1784573261710,"version":"3.55.0"},"reference-count":24,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2021,12,7]],"date-time":"2021-12-07T00:00:00Z","timestamp":1638835200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"MEiN","award":["0312\/SBAD\/8158 and 2021 0312\/SBAD\/8159"],"award-info":[{"award-number":["0312\/SBAD\/8158 and 2021 0312\/SBAD\/8159"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The development of cellular wireless systems has entered the phase when 5G networks are being deployed and the foundations of 6G solutions are being identified. However, in parallel to this, another technological breakthrough is observed, as the concept of open radio access networks is coming into play. Together with advancing network virtualization and programmability, this may reshape the way the functionalities and services related to radio access are designed, leading to modular and flexible implementations. This paper overviews the idea of open radio access networks and presents ongoing O-RAN Alliance standardization activities in this context. The whole analysis is supported by a study of the traffic steering use case implemented in a modular way, following the open networking approach.<\/jats:p>","DOI":"10.3390\/s21248173","type":"journal-article","created":{"date-parts":[[2021,12,7]],"date-time":"2021-12-07T11:00:23Z","timestamp":1638874823000},"page":"8173","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":75,"title":["Toward Modular and Flexible Open RAN Implementations in 6G Networks: Traffic Steering Use Case and O-RAN xApps"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5906-6413","authenticated-orcid":false,"given":"Marcin","family":"Dryja\u0144ski","sequence":"first","affiliation":[{"name":"Rimedo Labs, 61-131 Pozna\u0144, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3434-1917","authenticated-orcid":false,"given":"\u0141ukasz","family":"Ku\u0142acz","sequence":"additional","affiliation":[{"name":"Rimedo Labs, 61-131 Pozna\u0144, Poland"},{"name":"Institute of Radiocommunications, Poznan University of Technology, 61-131 Pozna\u0144, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6766-7836","authenticated-orcid":false,"given":"Adrian","family":"Kliks","sequence":"additional","affiliation":[{"name":"Rimedo Labs, 61-131 Pozna\u0144, Poland"},{"name":"Institute of Radiocommunications, Poznan University of Technology, 61-131 Pozna\u0144, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1109\/MCOM.001.1900411","article-title":"Toward 6G Networks: Use Cases and Technologies","volume":"58","author":"Giordani","year":"2020","journal-title":"IEEE Commun. Mag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1109\/MVT.2019.2921208","article-title":"6G Wireless Networks: Vision, Requirements, Architecture, and Key Technologies","volume":"14","author":"Zhang","year":"2019","journal-title":"IEEE Veh. Technol. Mag."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Rekkas, V.P., Sotiroudis, S., Sarigiannidis, P., Wan, S., Karagiannidis, G.K., and Goudos, S.K. (2021). Machine Learning in Beyond 5G\/6G Networks\u2014State-of-the-Art and Future Trends. Electronics, 10.","DOI":"10.3390\/electronics10222786"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"144820","DOI":"10.1109\/ACCESS.2021.3119524","article-title":"Artificial Intelligence for Radio Communication Context-Awareness","volume":"9","author":"Wasilewska","year":"2021","journal-title":"IEEE Access"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Singh, S.K., Singh, R., and Kumbhani, B. (2020, January 25\u201328). The Evolution of Radio Access Network towards Open-RAN: Challenges and Opportunities. Proceedings of the 2020 IEEE Wireless Communications and Networking Conference Workshops (WCNCW), Seoul, Korea.","DOI":"10.1109\/WCNCW48565.2020.9124820"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1523","DOI":"10.1007\/s11277-020-07231-3","article-title":"From Cloud RAN to Open RAN","volume":"113","author":"Gavrilovska","year":"2020","journal-title":"Wirel. Pers. Commun."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Ruiz, L., Dur\u00e1n, R.J., De Miguel, I., Khodashenas, P.S., Pedre\u00f1o-Manresa, J.-J., Merayo, N., Aguado, J.C., Pav\u00f3n-Marino, P., Siddiqui, S., and Mata, J. (2018). A Genetic Algorithm for VNF Provisioning in NFV-Enabled Cloud\/MEC RAN Architectures. Appl. Sci., 8.","DOI":"10.3390\/app8122614"},{"key":"ref_8","unstructured":"(2021, May 14). O-RAN Alliance. Available online: https:\/\/www.o-ran.org\/specifications."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Lee, H., Cha, J., Kwon, D., Jeong, M., and Park, I. (2020, January 7\u201311). Hosting AI\/ML Workflows on O-RAN RIC Platform. Proceedings of the 2020 IEEE Globecom Workshops (GC Wkshps), Taipei, Taiwan.","DOI":"10.1109\/GCWkshps50303.2020.9367572"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Kumar, H., Sapru, V., and Jaisawal, S.K. (2020, January 7\u201311). O-RAN based proactive ANR optimization. Proceedings of the 2020 IEEE Globecom Workshops (GC Wkshps), Taipei, Taiwan.","DOI":"10.1109\/GCWkshps50303.2020.9367582"},{"key":"ref_11","unstructured":"Niknam, S., Roy, A., Dhillon, H.S., Singh, S., Banerji, R., Reed, J.H., Saxena, N., and Yoon, S. (2020). Intelligent O-RAN for beyond 5G and 6G wireless networks. arXiv, Available online: https:\/\/arxiv.org\/abs\/2005.08374."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Koufos, K., Haloui, K., Dianati, M., Higgins, M., Elmirghani, J., Imran, M., and Tafazolli, R. (2021). Trends in Intelligent Communication Systems: Review of Standards, Major Research Projects, and Identification of Research Gaps. J. Sens. Actuator Netw., 10.","DOI":"10.3390\/jsan10040060"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1109\/MCOM.001.1900796","article-title":"A Hierarchical and Modular Radio Resource Management Architecture for 5G and Beyond","volume":"58","author":"Dryjanski","year":"2020","journal-title":"IEEE Commun. Mag."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1109\/MCOM.2016.7509383","article-title":"A unified traffic steering framework for LTE radio access network coordination","volume":"54","author":"Dryjanski","year":"2016","journal-title":"IEEE Commun. Mag."},{"key":"ref_15","unstructured":"(2021, November 10). O-RAN.WG3.RICARCH-v01.01. Near-Real-time RAN Intelligent Controller (Near-RT RIC) Architecture, O-RAN Alliance. Available online: https:\/\/www.o-ran.org\/specifications."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Perveen, A., Abozariba, R., Patwary, M., and Aneiba, A. (2021). Dynamic traffic forecasting and fuzzy-based optimized admission control in federated 5G-open RAN networks. Neural Comput. Appl., 1\u201319.","DOI":"10.1007\/s00521-021-06206-0"},{"key":"ref_17","unstructured":"(2021, November 10). O-RAN.WG2.AIML-v01.03, AI\/ML Workflow Description and Requirements, O-RAN Alliance. Available online: https:\/\/www.o-ran.org\/specifications."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1109\/MWC.2016.1600059WC","article-title":"Beyond Coexistence: Traffic Steering in LTE Networks with Unlicensed Bands","volume":"23","author":"Zhang","year":"2016","journal-title":"IEEE Wirel. Commun."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1109\/MCOM.2017.1700022","article-title":"Energy-Sustainable Traffic Steering for 5G Mobile Networks","volume":"55","author":"Zhang","year":"2017","journal-title":"IEEE Commun. Mag."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Choi, Y.-I., and Kim, J.H. (2020, January 21\u201323). Reliable data transmission in 5G Network using Access Traffic Steering method. Proceedings of the 2020 International Conference on Information and Communication Technology Convergence (ICTC), Jeju, Korea.","DOI":"10.1109\/ICTC49870.2020.9289535"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Anwar, M.R., Wang, S., Akram, M.F., Raza, S., and Mahmood, S. (2021). 5G Enabled MEC: A Distributed Traffic Steering for Seamless Service Migration of Internet of Vehicles. IEEE Internet Things J., 1.","DOI":"10.1109\/JIOT.2021.3084912"},{"key":"ref_22","unstructured":"(2021, November 10). O-RAN.WG2.Use-Case-Requirements-v02.01, Non-RT RIC & A1 Interface: Use Cases and Requirements, O-RAN Alliance. Available online: https:\/\/www.o-ran.org\/specifications."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1612","DOI":"10.1109\/TVT.2017.2749058","article-title":"Adaptive Cell Zooming and Sleeping for Green Heterogeneous Ultradense Networks","volume":"67","author":"Xu","year":"2017","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_24","unstructured":"(2021, November 10). O-RAN.WG1.Slicing-Architecture-v05.00, Slicing Architecture, O-RAN Alliance. Available online: https:\/\/www.o-ran.org\/specifications."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/24\/8173\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:42:28Z","timestamp":1760168548000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/24\/8173"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,12,7]]},"references-count":24,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2021,12]]}},"alternative-id":["s21248173"],"URL":"https:\/\/doi.org\/10.3390\/s21248173","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,12,7]]}}}