RoamNPN: A Roaming Framework for Non-Public and Private 5G Networks

5G mobile systems are expanding to non-public and private deployments, going beyond the conventional wide-area operator connectivity. To meet the specific privacy, isolation, and connectivity service customization requirements of various industries such as healthcare, manufacturing, and enterprises, customized networks are being deployed on-premises each with its own infrastructure and administration, creating a communication environment with a very high number of localized micro-operators. To surpass the limitation of isolated environments and to enable device mobility and interworking, these non-public or campus networks need to interoperate. The support of this new type of dynamic, on-demand roaming on top of mostly best-effort, third-party fixed network infrastructure, functionality is currently not developed or standardized. This article examines the necessity of device connectivity in visited domains and presents various options for connectivity services. Additionally, a high-level architectural solution is proposed as an extension of existing 5G network standards, along with its practical implementation and validation, underlining its limitations, benefits, and opportunities.