An Overview of Network-Related Challenges in Cell-Free 6G

Abstract

User-centric Cell-Free architectures are envisioned to be deployed in 6G networks to overcome the limitations inherent to the current cell-based architectures. While they offer drastic improvements on the physical layer, they bring new challenges to many other parts of the network. Due to their user-centric approach, many long standing principles of RAN design need to be reconsidered. This comes at an opportune time as there is currently a large push to break apart the monolithic base station based approaches and disaggregate functionalities. The O-RAN architecture in particular is a potentially good fit to accommodate cell-free networks. In this work, we highlight and discuss several major open issues related to architecture, protocols, and other network aspects encountered on the path to cell-free deployments. We give initial pointers on how the O-RAN architecture would need to evolve to enable cell-free use cases. Finally, we report first results on how different fronthaul topologies could overcome some of the cell-free knock-on effects. This work serves as a notice to the network community to make it aware of these challenges.