CSMA/CA Basics: One Talker per Channel
Only one Wi-Fi device can transmit on a channel at a time. Add clients and watch each one's share shrink, then see why a second AP adds capacity only on a different channel.
How to use this tool controls and what to look for
Add clients and watch them take turns on the channel. Then try a second AP, first on the same channel, then on a different one.
Controls to change
- Setup: choose 1 AP, 2 APs on different channels, or 2 APs on the same channel.
- Add client: add clients one at a time. Remove client takes one away.
- Play: run the simulation, or use Next event to step through it.
- Speed: choose Slow, Normal or Fast.
What to look for
- Only one device talks on a channel at a time. Every client you add gets a smaller slice.
- Two APs on the same channel still share one channel's airtime, so the total barely changes.
- Two APs on different channels double the capacity, because each channel has its own airtime.
- Now and then two clients pick the same moment and collide. Watch the collision count.
About this tool
A Wi-Fi channel works like a meeting with one microphone: only one device can talk at a time, and everyone else waits. This simulator lets you add clients and watch each one's share of the air shrink, then shows how a second access point helps, but only when it's on a different channel.
What you'll learn
- Why only one device can transmit on a channel at a time
- How listen-before-talk (CSMA/CA) decides who goes next
- Why more clients means a smaller share for each one
- Why two APs on the same channel still share one channel's airtime
Common questions
Can two Wi-Fi devices transmit at the same time?
Not on the same channel in the same area: they would collide. They take turns, which is why airtime is shared between everyone on the channel.
Does adding an access point increase capacity?
Only if it's on a different channel, or far enough away not to hear the first. Two APs on the same channel that can hear each other still share one channel's airtime.
What is co-channel interference?
Waiting caused by other devices on the same channel: not noise, but other Wi-Fi traffic that has to be taken in turns.
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.