Multi-3GPP Connectivity Concept, Architecture and Specific Implementation Details

Multi-access in systems up to 5G have been limited to support a 3GPP and a non-3GPP connection, multi-5G connectivity being implemented in the RAN through solutions like 5G Coordinated Multi-Point (CoMP) or secondary RAN. However, with the advent of multiple frequency ranges and 5G Non-Terrestrial Networks (NTN)-Terrestrial Networks (TN) convergence, multi-access across two independent accesses of the same 3GPP technology type has become a new high capacity and reliable communication opportunity where RAN solutions like CoMP cannot be realized as the two RANs may pertain to different subnetworks requiring signaling and data path aggregation at core network level. To answer to this opportunity, we present a new connectivity concept and 5G architectural advancements required to achieve this type of multi-access, with focus on TN-NTN, although the principles and architecture would apply to other scenarios briefly mentioned as well. Following a background analysis of the multi-connectivity concept in 5G system, we propose the necessary architectural additions to support multi-access across two independent 5G connections. We assess the feasibility of the solution by considering the additional functionality to be added in the Fraunhofer FOKUS Open5GCore core network practical implementation. This study demonstrates that despite its complexity, such a solution is feasible for 5G deployments and can be easily implemented in the foreseen 6G architecture.