Why adding access points made your Wi-Fi worse

A facilities manager rings you: the third floor is slow. Someone orders four more access points. They go in on a Friday. On Monday the third floor is slower, and now the second floor has started complaining too.

This happens constantly, and the reason is simple enough to explain in a sentence: Wi-Fi access points on the same channel do not add capacity, they share it.

The arithmetic

Wi-Fi is half-duplex and contention-based. Every device that can hear the channel takes turns. Two APs on channel 36 within earshot of each other are not two channels of capacity — they are one channel of capacity, divided, with additional management overhead on top.

Say you have eight APs on a floor and, after DFS is switched off and 80 MHz channels are configured, four available 5 GHz channels. That is two APs per channel already. Add four more APs and you have three per channel. Each one now gets a third of the airtime instead of half. Aggregate capacity has not increased. Beacon overhead has.

What actually went wrong

The original complaint was almost certainly capacity, and the metric that would have shown it is channel utilisation. Not client count, not signal strength, not "bars".

Above roughly 50 percent utilisation, latency and jitter become noticeable. Above 70 percent, people describe the network as broken while their laptop shows a full-strength connection — which is precisely why the complaint gets misdiagnosed as coverage.

What to do instead

Measure first. Pull channel utilisation for the affected area at the affected time. If it is high, work out whose energy it is.

Narrow the channels. Going from 80 MHz to 40 MHz doubles your channel count. You lose peak throughput per client and gain a great deal of aggregate capacity.

Reconsider DFS. Enabling DFS takes you from around nine usable 5 GHz channels to around twenty-five. If the site is not near an airport or coastal radar, this is the single largest capacity lever available, and it costs nothing.

Turn radios off. Specifically 2.4 GHz. In a dense deployment, disabling the 2.4 GHz radio on half to two-thirds of your APs measurably improves 2.4 GHz performance.

Then, if the plan genuinely supports it, add APs at lower power. More APs at 40 MHz with DFS enabled is a real upgrade. More APs at 80 MHz without DFS is a downgrade with an invoice attached.

The uncomfortable part

Sometimes the answer to a Wi-Fi complaint is that someone needs to remove access points. We did exactly that on a six-floor law firm and ended up with sixteen fewer than we started with, performing three times better.

That is a harder conversation than raising a purchase order, which is exactly why the purchase order usually wins.