  Ultra-low end-to-end latency is one of the most important requirements in 5G
networks and beyond to support latency-critical applications. Cloud-RAN and MEC
are considered as the key driving technology that can help reduce end-to-end
latency. However, the use of MEC nodes poses radical changes to the access
network architecture. As it brings the processing and the networking services
closer to the edge, it often requires network functions (for example, the CU/DU
stack and the application processing) to be distributed across different MEC
sites. Therefore, a novel transport mechanism is needed to efficiently
coordinate and connect network functions across MEC nodes.
  In order to address this challenge, we propose a novel two-tier virtualized
PON transport method with schedulers coordination over a virtualised and sliced
MESH-PON architecture. While a MESH-PON architecture enables direct
communication between MEC nodes that are hosting CU/DU and/or the application
processing, our method provides a two tier virtualised PON transport scheme
with coordinated schedulers. This approach greatly reduces latency incurred in
transporting signals across the different PON tiers, while maintaining the
flexibility of the multi-tier methods. We show that our proposed scheme can
achieve end-to-end application-level latency below 1ms or 2ms, depending on the
network configurations.
