Support of a Multi-access Session in 5G Mobile Network

The 5
^th
Generation (5G) mobile network, being standardized in 3GPP, is a convergence network that supports both 3GPP Radio Access Technology (RAT) and a non-3GPP RAT. The 3GPP RAT is a new RAT to provide much increased data rate for enhanced mobile broadband service. Wi-Fi and fixed wireline are mainly considered for non-3GPP access technologies but we only discuss Wi-Fi as a non-3GPP RAT for the sake of simplicity. This paper discusses a multi-access packet data unit (PDU) session, whose traffic is sent over 3GPP access, or over non-3GPP access, or over both accesses. 3GPP specification group 2 (SA2) is studying technical problems and solutions for this issue with a name of Access Traffic Steering, Switching and Splitting (ATSSS). ATSSS is expected to enrich user experience by distributing user traffic across 3GPP RAT and non-3GPP access technologies. This paper shows an implementation of multiple-access PDU session (MAPS) to support ATSSS in 5G mobile network. We briefly introduce ATSSS concept and discuss design issues of ATSSS in our 5G trial system. The design issues focus on minimal modification to the existing signaling procedures in the architecture of the 5G system with a single-access PDU session. We designed legs on each access to extend a session, which are managed together as a single PDU session.