Wireless and the edge
Wi-Fi is a shared medium with a queue. Full bars means the signal is strong, not that there is room to send.
- You can explain why a laptop at full signal can still be slow, using airtime rather than signal strength.
- You can name the two design mistakes that make an office Wi-Fi network worse as it grows.
Forty people in a meeting room, all on the same access point, all with four bars. The video call stutters. Someone checks the signal, sees it is excellent, and concludes the network is fine — so the problem must be the application.
Four bars is true. It is also irrelevant. Signal strength is how well one client can hear one access point; throughput is how much airtime it gets out of a shared channel, and forty clients divide it forty ways.
8.1One radio, one conversation at a time
An access point on a channel transmits to one client at a time. Everyone else waits. That waiting is not a bug — it is the medium. Adding clients does not share a fixed pipe; it lengthens the queue.
| Factor | Effect |
|---|---|
| Number of active clients | Each gets a smaller slice of the same airtime |
| Channel width | Wider is faster, and collides with more neighbours |
| Interference | Retries double the airtime cost of every frame |
| Distance and walls | Lower rate, so the same bytes take longer |
| Spatial streams | A 2-stream phone cannot use an 8-stream access point |
| Legacy clients | One old device can drag the whole channel to a slower rate |
Retries deserve their own sentence: a frame that fails is sent again, and the retry occupies airtime exactly like a successful transmission. On a noisy channel, half your capacity can go to repeating yourself.
8.2Channels, bands, and the 1/6/11 myth
2.4 GHz has three non-overlapping channels (1, 6, 11) and everything else overlaps. 5 GHz has many more, plus channels that must vacate on radar detection. 6 GHz has the most spectrum and the shortest range.
So a four-access-point floor cannot use 1/6/11 twice without interference, and "set everything to channel 1" is a configuration rather than a plan. In practice you want 5 GHz for density, 2.4 GHz for reach, and band steering so clients do not all choose the band with the best signal and the worst capacity.
8.3Security in one table
| Mode | Status | Why |
|---|---|---|
| Open | No protection | Captive portals only; everything readable |
| WEP / WPA (TKIP) | Broken | Crackable in minutes with commodity tools |
| WPA2-PSK | Acceptable at home | One shared key; every device and every ex-employee knows it |
| WPA2/WPA3-Enterprise | Correct for organizations | Per-user credentials via 802.1X; revoking access is per person |
| WPA3-SAE | Better handshake | Protects against offline guessing of the passphrase |
Turning off the SSID broadcast hides the name from a casual scan and from nobody else. It breaks roaming, confuses guests, and provides no protection whatsoever — the name is broadcast the moment a client connects. Security comes from the handshake, not from obscurity.
Why does adding clients to one access point slow everyone down, even at full signal?
60-second recap
- Airtime is the resource. Signal strength measures reach, not capacity.
- Retries cost twice. Interference shows up as slowness before it shows up as errors.
- Design for capacity. One access point per floor covers the floor and collapses in the meeting room.