Abstract
The ongoing virtualization of Radio Access Networks (vRANs) promises increased velocity for updating RAN software with new features and bug fixes. To support this, we developed SwapRAN, a live update system for both vRAN software components: the Distributed Unit (DU) and the Centralized Unit (CU). Unlike previous systems, SwapRAN operates in-place without requiring additional hardware like staging servers or a programmable switch. For DU updates, SwapRAN presents two techniques: (1) using OS thread priorities to safely initialize the new DU while overlapping with the old DU which is active, and (2) using the network interface card's embedded switch to redirect fronthaul traffic to the new DU. For CU updates, SwapRAN is the first working live update system, which we achieve by (1) decoupling the stateful CU-DU connection and transparently rerouting DU messages to the new CU, and (2) repurposing existing midhaul control plane messages to move users to the new CU. We evaluate SwapRAN on real 5G testbeds and demonstrate its practical deployability via integration with Kubernetes. Our evaluations show that SwapRAN completes DU or CU updates with just 1–2 seconds of user downtime.