Most Wi-Fi dashboards flash red the moment Busy_Time / Channel_Active_Time climbs past 70-80 %. That number tells you how crowded the air is, but not who is doing the talking. Add TX_Time / Busy_Time to the mix and the picture changes completely.
Sample output from “iw dev wlan0 survey dump”
(works the same on OpenWiFi, OpenWrt, or any Linux-based AP)
ffrequency: 5500 MHz [in use]
noise floor: -105 dBm
channel active time: 8 980 102 µs # total time the radio has been listening
channel busy time: 4 016 120 µs # portion of that time the channel was sensed busy
channel receive time: 267 534 µs # time spent receiving frames
channel transmit time: 3 134 252 µs # time spent transmitting frames
Important: These counters are cumulative.
To compute utilisation for a one-second sample, take the difference between two successive readings:
Δbusy = busy_time(t1) – busy_time(t0)
Δactive = active_time(t1) – active_time(t0)
Channel Utilization (%) = (Δbusy / Δactive) × 100
The attached screenshot is a 10-second capture from an OpenWiFi AP (Channel 149 @ 5825 MHz). Each row is a 1-second delta in µs:
What the two percentages really say:
Busy / Active Time:
- What it measures? → "How busy is the channel overall?”
- Why it matters? → “Includes AP, clients, and interference”
TX / Busy Time:
- What it measures? → "How much of that busy time is my AP’s?”
- Why it matters? → “Shows whether congestion is external or self-inflicted”
Example #1 — First two seconds
Busy / Active ≈ 86 %
TX / Busy ≈ 85 %
The channel looks slammed, but we are using almost all of that airtime.
No neighbouring AP interference—just a hungry transmitter doing its job.
Example #2 — Third second
Busy ÷ Active = 22 % but TX ÷ Busy = 45 %
A quieter moment overall, yet nearly half of the airtime still comes from our AP.
Take-away for any OpenWrt / OpenWiFi—and every other—AP
Busy / Active Time alone is a blunt instrument.
High numbers could be neighbors, clients, microwave ovens, or—yep—you.
Add TX / Busy Time to see who owns the air.
If TX / Busy is high, your AP dominates the channel (good for throughput, bad for coexistence).
If TX / Busy is low and Busy / Active is high, external congestion is your problem.
Next time your controller screams “Channel Utilization 80 %!”, don’t panic. Check whether that 80 % is you first. If it is, you’re simply maximizing clean airtime. If it isn’t, it’s time to channel-plan, lower power, or shoot down neighbors’ APs 
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