A Low Complexity Network-Coded ARQ protocol for Ultra-Reliable Low Latency Communication

Abstract

Random Linear Network Coding (RLNC) schemes that use a sliding window, also known as Sliding Window RLNC schemes, have proved to be efficient for reliable data transmission over an unreliable link. They combine the concept of the sliding window from (Automatic Repeat reQuest) ARQ protocols with RLNC in order to maximize the data flow and quickly recover from losses through redundant coded packets. We make the observation that, in these protocols, optimizing the data flow rate and the coding operation are two distinct objectives that cannot be met only by fine-tuning the sliding window size. To tackle the problem, we propose rapidARQ, a sliding window RLNC scheme with feedback that uses two distinct windows; the sliding window, which is used to optimize the data flow based on the link’s bandwidth-delay product, and the coding window, which is used exclusively in the coding process. We experimentally show that rapidARQ outperforms other state-of-the-art sliding window RLNC schemes and achieves superior throughput-delay performance that better fits in the context of Ultra-Reliable Low-Latency Communication (URLLC). More interestingly, it does so while significantly reducing the coding complexity at the same time. The superior performance of rapidARQ is more prominent in channels with large bandwidth-delay products, a fact that renders its utility to current and future networks more essential.