Efficient Timer Optimization Method for RLC in Mobile Communication

Abstract

To support various use cases, 5G has enhanced the design and functionalities of its protocol layers. 5G Radio Link Control (RLC) layer supports Automatic Repeat Request (ARQ) for loss recovery and complete packet delivery in Acknowledgement Mode (AM). In AM mode, the RLC receiver maintains a t-Reassembly timer to wait for recovery and reordering at lower layers and to update Acknowledgement (ACK)/ Negative Acknowledgement (NACK) status to the transmitter side. Also, it maintains a t-StatusProhibit timer to prohibit frequent transmission of a Status Report. These legacy timers are generally implemented using software timers, which require significant memory and processing for the timer start, restart, stop, and expiry events. A single UE can support up to 32 different RLC AM entities, and a single gNodeB can support thousands of UEs, with each entity supporting at least three timers. These require considerable memory and processing to support the timer framework. This paper provides a novel approach to merging the functionalities of the RLC receiver timers i.e., t-Reassembly timer and t-StatusProhibit timer into a single timer to reduce the memory and processing overheads of the timers. Experimental results show a 50% reduction in RLC receiver timer events and timer processing cycles and a 30% reduction in the number of timers without any impact on RLC protocol functional requirements when tested with multiple RLC entities in packet-loss scenarios.