Throughput Simulator
Why one slow client can drag everyone down. Clients take turns on the same channel, and a slow client's turns take much longer. See what airtime fairness changes.
How to use this tool controls and what to look for
Watch clients take turns on one channel, then add a slow client and see what happens to everyone's throughput.
Controls to change
- Add a slow client: add a client with a low data rate. Remove the slowest takes it away again, and Add a client adds another one.
- Scheduler: switch between Equal chances (standard) and Airtime fairness.
- Data per turn: change how much data each client sends per turn (16, 64 or 256 KB).
- Overhead per turn: set the fixed cost of every transmission in microseconds.
- Longest transmission: limit how long one turn may last.
What to look for
- With equal chances, one slow client uses most of the airtime and the total throughput drops for everyone.
- Airtime fairness gives each client the same time, not the same data, so fast clients recover their speed.
- Sending more data per turn spreads the fixed overhead, but it also lets a slow client hold the channel for longer.
About this tool
Wi-Fi clients take turns on the same channel, and a slow client's turns take much longer. This simulator shows why one slow device can drag everyone down: add clients with different data rates and see each one's share of airtime and the total throughput, with and without aggregation and airtime fairness.
What you'll learn
- Why Wi-Fi shares airtime, not throughput
- How much airtime a slow client uses up compared with a fast one
- What the fixed overhead of every transmission costs
- What aggregation and airtime fairness change
Common questions
Why is Wi-Fi slow for everyone when one device is far away?
A distant device uses a low data rate, so each of its transmissions takes much longer, and everyone else waits while it sends.
What is airtime fairness?
A way for the access point to give each client a similar share of time on the air, instead of a similar number of frames, so slow clients can't hog the channel.
Does frame aggregation help?
Yes: packing many packets into one transmission pays the fixed overhead once. But a slow client that aggregates also holds the channel longer each turn.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.