Decoupling Traffic Management from Listen-Before-Talk in the Unlicensed Spectrum with 5G NR-U

5th Generation (5G) New Radio Unlicensed (NR-U) enables Mobile Network Operators (MNOs) to extend their network capacity by leveraging nearly 2 GHz of mid-band unlicensed spectrum. However, delivering delay-sensitive services over shared spectrum is challenging due to unpredictable contention delays and variable channel conditions. To address this, the 3rd Generation Partnership Project (3GPP) introduced Channel Access Priority Classes (CAPCs), which allow multiple concurrent Listen-Before-Talk (LBT) processes with varying access probabilities. This design aims to balance diverse Quality-of-Service (QoS) requirements alongside fair access in shared spectrum environments. Traffic classes are mapped to one of the four CAPCs, allowing probabilistic time-domain resource slicing. Mapping complex, multi-dimensional QoS requirements to CAPCs, however, remains a non-trivial task, as no single CAPC optimally supports a given traffic flow under varying channel conditions and QoS demands. In this paper, we propose a QoS-aware scheduler that decouples traffic flows from specific CAPC processes. This scheduler prioritizes flows for each Transmit-Time-Interval (TTI) within a valid Channel Occupancy Time (COT) regardless of which CAPC wins contention. Our experimental results demonstrate over a 50% reduction in average delay for high-priority traffic and more than a 43% delay reduction across all traffic classes using this decoupled scheduling mechanism, achieved without modifying contention parameters. By leveraging NR-U's synchronized slot structure and refined QoS controls inherited from licensed-access frameworks, this approach significantly improves COT utilization and the delivery of delay-critical services.