Freeze-Release: A Transient Supervisory Control Layer for Mixed-Criticality Traffic Under Overload

Shared wireless resources often carry both safety-critical and best-effort traffic, creating a trade-off between safety reliability and throughput under overload. This paper presents Freeze-Release (FR), a lightweight two-mode supervisory controller that temporarily shifts PRBs toward safety traffic when risk is detected from backlog, backlog growth, and head-of-line slack. FR is evaluated in a discrete-event downlink simulator against Always-Normal and Always-Freeze under best-effort overload. Results show that FR maintains zero safety deadline violations while substantially improving best-effort throughput over permanent freezing (2579 vs. 1026.5 pps in the Poisson case) and keeping safety tail latency close to Always-Freeze (Sp99 = 0.299 ms vs. 0.214 ms). Under periodic multi-source safety traffic, FR further reduces freeze usage to 30.3% while achieving 3379 pps with zero violations. These results show that short, risk-aware interventions can protect safety traffic without unnecessary throughput loss.