Wi-Fi problems are usually density problems

The complaint arrives in a predictable form. “The Wi-Fi is terrible in the north-east corner.” Somebody walks around with a phone, sees three bars, and concludes the signal is fine. Somebody else orders two more access points.

A month later it is worse, and now there is a second problem nobody can name.

Coverage and capacity are different problems

Coverage is whether a client can hear the access point. Capacity is whether the access point can serve every client that can hear it, at once, with the airtime available.

Almost every Wi-Fi complaint in an office is a capacity problem, and almost every instinctive fix addresses coverage. This is why adding access points so often makes things worse: more radios in the same space, on the same channels, in earshot of each other, means more contention for the same airtime.

Wi-Fi is a shared medium. Two access points on the same channel are not two lanes — they are one lane with two cars politely waiting for each other.

The three things that are actually wrong

Channel reuse. In 2.4 GHz there are three non-overlapping channels. Three. Anything you deploy densely in that band is interfering with itself, plus every neighbouring tenancy, plus the microwave. 5 GHz is where the capacity is, and 6 GHz is where the clean spectrum is if the client fleet supports it.

Channel width set too wide. Wide channels look excellent in a single-client speed test and are frequently wrong in a dense deployment, because they consume the very spectrum diversity you need to avoid reuse. In a busy office, narrower channels and more of them beats wider channels and fewer.

Legacy clients holding the floor. A slow client transmitting at a low data rate occupies airtime disproportionately — the same frame takes far longer to send. One old device can measurably degrade a cell for everybody in it. Disabling the lowest legacy data rates is one of the highest-value changes available and costs nothing.

Then check the parts that are not radio at all

Half the Wi-Fi tickets we resolve are not Wi-Fi tickets.

Backhaul. An access point capable of multi-gigabit throughput connected to a switch port doing 1 Gb is capped at 1 Gb, and a room full of clients will find that ceiling. Check the negotiated port speed, not the specification sheet.

PoE budget. Modern access points draw more power than the ones they replaced. A switch that could power 24 old APs may quietly deliver reduced power to the new ones, which respond by disabling a radio or dropping transmit power — and nothing in the wireless console says “your switch is underpowered”.

DHCP scope. A /24 with a long lease time and a device count that has doubled produces intermittent association failures that look exactly like a coverage problem.

DNS and upstream. “The Wi-Fi is slow” is the way users report every network problem, including the ones on the internet link.

Design for the room, not the floor plate

Density planning starts with a question nobody asks: how many devices, in which rooms, doing what, at the worst moment of the week?

That worst moment has moved. Hybrid working means offices are near-empty on Monday and Friday and at genuine peak on Wednesday, when everyone is also in a video call — which is a sustained bidirectional load, not the bursty web traffic that older designs assumed. A network sized on average occupancy fails on the day everyone is in.

Practical consequences:

• Meeting rooms need their own treatment. Twelve people in a video call in a glass-walled room is a capacity problem in a small space, and glass and plasterboard behave very differently.
• Do not centre APs in a corridor. Corridors propagate signal beautifully, which means one AP covers a lot of area and serves all of it badly.
• Survey before and after. A predictive survey from the floor plan, then a validation survey once the furniture and the people are in. Both, not one.

Get the failure modes right before the throughput

The measure of a well-run wireless network is not peak throughput. It is what happens when things go wrong:

• Does a client roaming between APs drop the call?
• Does the guest network failing take the corporate SSID with it?
• Does an AP losing power leave a hole, or do its neighbours adjust?
• Can you tell, from the console, which of those happened last Tuesday?

Roaming is the one users notice most and designs address least. Walking from a desk to a meeting room while on a call crosses two or three cells, and if the handoff is slow the call breaks — which the user reports as “the Wi-Fi dropped out”, sending everyone back to hunting for coverage that was never missing.

The short version

Before adding an access point, check the channel plan, the data rates, the port speed and the PoE budget. Adding radios to a contention problem is the one intervention guaranteed to make it worse.

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