CLARQ: A Dynamic ARQ Solution for Ultra-high Closed-loop Reliability

TL;DR

CLARQ is a novel dynamic ARQ protocol designed to meet ultra-high reliability and strict latency requirements for wireless control applications, outperforming traditional methods in reliability and energy efficiency.

Contribution

It introduces a dynamic resource allocation ARQ protocol that guarantees latency and reliability for URLLC, with efficient offline optimization and real-time low-cost implementation.

Findings

Outperforms baseline ARQ schemes in reliability and energy efficiency

Achieves closed-loop error rate below 1e-7 within 10ms latency

Suitable for practical 5G-and-beyond URLLC applications

Abstract

Emerging wireless control applications demand for extremely high closed-loop reliability under strict latency constraints, which the conventional Automatic Repeat reQuest (ARQ) solutions with static schedules fail to provide. To overcome this issue and enable data-link layer error control for ultra reliable low-latency communication (URLLC) services, we propose a novel protocol: the Closed-Loop ARQ (CLARQ), which forces to accomplish an information exchange round within a fixed loop-back latency, and dynamically re-allocates the remaining resource between uplink and downlink slots upon the result of last uplink transmission. The proposed method guarantees to meet the latency requirement, while delivering high communication reliability and power efficiency. It can be efficiently offline optimized by means of dynamic programming techniques, and is capable of real-time deployment with a low-cost implementation based on look-up tables. Numerical evaluations have verified that CLARQ outperforms baselines with significantly improved closed-loop reliability and reduced energy consumption. Especially, over a Rayleigh channel with 0dB mean SNR, it is able to provide a closed-loop error rate below 1e-7 within 10ms loop-back latency, which makes our proposal competitive for practical URLLC applications in future 5G-and-beyond networks.