Design of an Enhanced Bearer Buffer for Latency Minimization in the Mobile RAN

5G will transform the cellular network from a generic supplier of high-speed data to a flexible, super-fast, and highly-reliable communications medium that supports diverse sets of services and applications. Low packet latency is a critical enabler for the interactivity features of many of these applications, but maybe compromised in saturated packets buffers if the buffers are oversized, as is often the case in the RLC layer of the 3GPP RAN stack. To protect all interactive applications from excessive buffering, we completely revise the flow-control component of a prior solution of ours that splits the per-bearer buffer between the RLC and PDCP layers and regulates the packet flow between the two buffers so that queue build-up in the RLC layer is constrained. On a cellular link shared with a greedy TCP flow, our new enhanced bearer buffer (EBB) design with continuous flow control (CFC) reduces the latency of packets from low-bandwidth interactive applications by at least 80% compared to previous EBB versions, and by orders of magnitude compared to the default bearer configuration with a large RLC buffer. The CFC also benefits throughput-intensive interactive applications like augmented and virtual reality because it confines the buffering within the PDCP layer, where it can be effectively controlled with active queue management techniques.