Multi-Connectivity for Enhanced Throughput: a Critical Study

Multi-connectivity is anticipated to provide more reliable, higher data rate connections for cellular network users by leveraging all available radio resources across base stations within one or multiple radio access technology(ies) (RAT). It aims to improve user mobility through multi-RAT connections or mitigate quality of service (QoS) degradation when users connect to congested cells through load-balancing traffic among base stations and distributing the user's flow across multiple links. Although many studies have investigated the benefits of multi-connectivity across various network deployments using analytical models or simulated environments, we critically assess these reported gains, particularly regarding system throughput. We argue that multi-connectivity's advantages are primarily restricted to scenarios with a low user-to-base station ratio and that dense networks are less likely to benefit. We formulate the user-to-base station association and resource allocation within a proportional fair (PF) setting across varying user densities to examine this. Our findings demonstrate that multi-connectivity offers no superiority over the PF single-connectivity baseline in dense networks. Furthermore, in sparse networks, we show that while multi-connectivity can potentially enhance system throughput, it does not significantly improve individual users' QoS, as the PF single-connectivity scheme can offer sufficient resources to every user.