1
Diagnostic step 1
Perform a controlled A/B test: keep airtime-fairness disabled on one AP and enabled on another in same RF environment and capture simultaneous pcap on both sides and client to compare 802.11 sequences.
FULL AI ANALYSIS
5 GHz AP cluster sees high retransmits and video call stalls after enabling airtime-fairness
Generated Oct 14, 2026, 9:39:02 AM
Analysis summary
Symptoms (5 GHz-only, improvement when airtime-fairness disabled on a test AP) point at an interaction between airtime-fairness scheduling and either client rate selection or a firmware/driver bug on the AP. High MAC retransmits with stable RSSI suggests scheduling or aggregation mishandling rather than RF interference. Possible misconfiguration (too-aggressive fairness thresholds), bugs in AP firmware's airtime implementation, or a client driver reacting poorly to altered TX opportunities are the top suspects. Environmental RF interference is less likely because 2.4 GHz unaffected and RSSI stable.
Possible causes
AP firmware airtime-fairness implementation bug (scheduling/aggregation causing excessive retransmits on 5 GHz)
78%Airtime-fairness parameters set too aggressively (per-client TX cap / short TXOPs) causing rapid rate oscillation on clients
60%Client Wi‑Fi driver incompatibility with airtime-fairness (older devices mis-handle altered TXOPs leading to retransmits)
45%New radio configuration (channel-width/DFS) combined with airtime changes exposing hardware bug under 5 GHz
30%Suggested fixes
2
Diagnostic step 2
Collect full AP and controller logs (debug/trace if available) during a failing call and capture client driver logs; preserve timestamps and client MACs.
3
Diagnostic step 3
On a test AP, revert airtime-fairness but incrementally enable gentler fairness parameters (increase TXOP, raise per-client minimum) to determine threshold that triggers retransmits.
4
Diagnostic step 4
Test with multiple client OS/drivers: reproduce with a known-up-to-date laptop and with an older smartphone to differentiate AP vs client cause.
5
Diagnostic step 5
If firmware bug suspected (high-likelihood), upgrade AP firmware on a single isolated test AP to vendor recommended stable release that mentions airtime fixes; validate before cluster-wide rollout. If vendor advises, escalate to vendor TAC with packet captures and controller logs attached and request known-issues for current firmware/given airtime settings.