Multi-Connectivity Enhancements for the 6G Era

In the dawn of 6G and the stupendous use cases it is anticipated to support, the ever-growing requisites for higher data rates and ultra-reliable low latency communications (URLLC) stipulate ubiquitous and robust connectivity. In this direction, architectural enhancements beyond the existing 3GPPbased 5G-Advanced specifications are deemed indispensable. The multi-connectivity domain is a cornerstone in this architectural evolution, laying the ground for technology convergence, and rendering resilient, high-performing, and energy-efficient communications. This work seeks to unveil the various multiconnectivity methods available in standards and propose new paths in this area, envisioning the network architecture evolution in the 6G era. Some new, innovative, multi-access solutions are presented, shedding light on the multi-connectivity aspects envisioned in 3GPP Rel-20 and beyond. In particular, this paper emphasizes on the envisaged use cases necessitating multi-access connectivity, and delineates how Access Traffic Steering, Switching, and Splitting (ATSSS) functionality can be further optimized to support the imminent demand. Based on this request, current work proposes ATSSS enhancements entailing the use of the QUIC protocol to convey NAS signalling over non3GPP access networks (QUIC for NAS over Non-3GPP), as well as an alternative to the legacy ATSSS which enables direct communication between the User Equipment (UE) and the network, by eliminating the use of N3IWF on the non-3GPP access path (ATSSS with Offloaded Non-3GPP Access). Finally, we propose potential extensions in the ATSSS functionality to support UE's connectivity over two 3GPP access networks, while maintaining its connection over the non-3GPP access path (DualSteer). Such kind of architectural enhancements to provide capacity aggregation and incessant connectivity, are expected to be the norm in 6G networks, so that the extreme demands of the upcoming applications can be sufficiently satisfied.