Why your office Wi-Fi is slow, and how to fix it

It is always the same room. The one at the far end, past the kitchen, where the Thursday meeting happens. Everybody's video freezes, somebody says the internet is down again, and the person who is nearest the router says it is fine at their desk.

The internet is almost never down. What has run out is radio.

First, prove it is not the line

Before anything else, settle which half of the problem you have.

Plug a laptop into the router with an actual cable and run a speed test. Then take the same laptop to the desk that complains, disconnect the cable, and run it again over Wi-Fi. If the wired number is healthy and the wireless one collapses, your broadband is not the fault and your provider cannot help you.

That takes four minutes and it saves a month of pointless emails. We ask for both numbers before we quote anything, because the two problems have nothing to do with each other and only one of them is ours.

The bit nobody tells you: there are only three channels

Wi-Fi runs in shared public spectrum, and in the UK Ofcom sets what is allowed in each band. The oldest and most crowded is 2.4 GHz.

Ofcom's UK Interface Requirement IR 2030, entry IR2030/7/1, permits wideband data transmission across 2400 to 2483.5 MHz at up to 100 mW e.i.r.p. That is 83.5 MHz of space in total. A standard Wi-Fi channel is 20 MHz wide. Do the arithmetic and you get three channels that do not overlap each other at all, conventionally 1, 6 and 11.

Three. Not three for you, three for the whole building and the buildings either side of it. Your neighbour's router is in there, along with their guest network, the card machine, the wireless doorbell, a Bluetooth headset and, on a good day, somebody's microwave.

This is why the office that was fine in 2019 is not fine now. Nothing broke. The air got busier.

5 GHz, and the rules that decide where you can put things

5 GHz has room, which is the main reason to be on it. It is not one band though, it is four, and Ofcom treats each of them differently. This matters more than it sounds, because the differences decide where an access point is allowed to go.

From Ofcom's own RLAN information sheet:

Band	Range	Max power	Where
A	5150–5350 MHz	200 mW	Indoor only. DFS assumed above 5250 MHz
B	5470–5730 MHz	1 W	Indoor or outdoor. DFS and TPC assumed
C	5725–5850 MHz	200 mW	No fixed outdoor use
D	5925–6425 MHz	250 mW indoor, 25 mW very low power	Indoor only at 250 mW

Read the last column rather than the power figures. If you want to cover a yard, a car park or a loading bay, most of what covers your office is not legal outside it. Band B is the one that allows a watt indoors or out, and there is a light-licensed 4 W option in Band C that requires a licence and the registration of every terminal, which is a real thing people use for point-to-point links between buildings and not something you buy in a box.

DFS is worth knowing about because it produces a symptom that looks like a fault. Dynamic Frequency Selection means the access point listens for radar and moves off the channel if it hears any. Near an airport or a coastal weather radar, that can mean a brief drop while everything re-associates, on a schedule nobody controls.

And none of this is optional. Ofcom's sheet spells out that installing and using RLAN equipment that does not meet the conditions risks prosecution under the Wireless Telegraphy Act 2006, with an unlimited fine and up to a year in prison. Turning the transmit power up past the limit because the far room is weak is not a clever workaround.

6 GHz is genuinely empty, and mostly useless to you today

Ofcom made 5925 to 6425 MHz available licence exempt on 24 July 2020, which is where Wi-Fi 6E and Wi-Fi 7 live. It is quiet because almost nothing is on it yet.

The problem is that both ends have to support it. Your new access point can broadcast on 6 GHz all it likes; a laptop from 2019 has no radio that can hear it. If your team is on four-year-old hardware, buying 6E kit today buys you a band nobody in the room can use, and you would do better spending the money on more access points in better places.

Worth having on the specification if you are buying anyway. Not worth buying for.

Why the second router made it worse

This is the most common self-inflicted one. The far room is weak, so somebody buys another router or an extender, plugs it in near the weak spot, and the whole office gets slower.

Microsoft's own network guidance for Teams says why, and it is worth quoting because it is a vendor describing their own product's failure mode rather than a networking company selling you something: when access points of the same channel are too close together, they cause signal overlap and unintentionally compete, which produces a bad experience for the user. Two boxes out of two different shelves will both have picked a sensible default, and sensible defaults are all the same.

What you want instead is access points that were placed deliberately, on channels that were chosen rather than guessed, at a power level low enough that they hand devices over to each other instead of shouting across the building. That is what a coverage plan is. It is not glamorous work and it is the difference between three access points that help and three that fight.

Mesh or cable

Mesh systems are good, and they are good at a specific thing: covering a space where you cannot run a cable.

The cost is that mesh units talk to each other over the air. That backhaul conversation uses the same radio time your laptops want, so every hop takes a bite out of what is left. One hop is usually fine. Two is noticeable. In a small office of six or eight people, mesh is often the right answer and we will say so.

Past about fifteen people, or anywhere with a thick wall or a floor in the way, cabled access points win and it is not close. The uplink is a wire, so nothing is shared, and the units can be small and unobtrusive because they do not need to reach far.

The honest part: if there are no network points where the access points need to go, somebody has to run cable through the fabric of your building. We do that work, and on an older building it is as much a builder's job as an IT one. It is also the thing that fixes the problem for ten years rather than eighteen months.

What actually breaks a video call

People assume bandwidth. It is usually not bandwidth.

Microsoft publish what Teams needs, and the figures are smaller than most people expect. A one-to-one audio call wants 58 kbps up and down for the recommended experience. A one-to-one video call wants 1.5 Mbps. A meeting with video wants 2.5 Mbps up and 4 Mbps down. Microsoft note that Teams can deliver HD video in under 1.5 Mbps, because it is built to be careful with the connection.

So the 500 Mbps line is not what is holding your meeting together. What breaks a call is jitter, packet loss and a weak or contended wireless signal, and those come from the radio side rather than the line. The same Microsoft page lists the fixes in order, and they are all wireless ones: use WMM so media traffic gets priority over somebody's file sync, use band steering to push dual-band devices onto 5 GHz, plan the placement, and keep neighbouring access points off each other's channels.

One more from that page, and it catches a lot of people who work from home: Microsoft recommend keeping Teams traffic off the VPN entirely. Their reasoning is that VPNs are not designed for real-time media, some do not carry the protocol Teams wants, and the traffic ends up encrypted twice and routed the long way round. If your staff dial into a full-tunnel VPN and then complain about call quality, that is the first thing to change.

Five things to check before you ring anyone

• Run the wired and wireless speed tests described at the top. Write both numbers down.
• Count your access points, and count how many are just a router somebody plugged in.
• Look at what your phone connects to in the bad room. If it says 2.4 GHz, that is the answer.
• Check whether the router is in a cupboard, behind a metal cabinet, or on the floor. All three cost you range.
• Find out how old the oldest laptop in the building is, because it sets the ceiling for everything.

What we do, and what it costs

Network design and installation sits under managed IT support, alongside firewalls, switches and servers. In practice a Wi-Fi job is a site visit, a look at the building rather than a look at the router, a channel and power plan, and then either better placement of what you have or new access points where they are actually needed.

The numbers, from our published rate card and excluding VAT. A network or server install is 855 per on-site day, with hardware supplied at cost plus 20% and quoted before we start. Managing a firewall, switch or access point afterwards is 34 per device per month, covering configuration backups, firmware and monitoring. Servers are 162 each per month. Managed IT plans are 50, 77 and 108 per user per month. If the fix is a setting rather than hardware, it is hourly: 86 on a plan, 126 without one, 167 out of hours with a two-hour minimum.

What we will not do is quote you a speed. Anyone who promises a number before walking round your building is guessing, and buildings are the whole problem: plasterboard costs you almost nothing, a Victorian brick wall costs you a lot, and a lift shaft or a foil-backed insulation board will stop a signal dead.

Security is a separate question from coverage and we have written about it separately. If your worry is who can get onto the network rather than how fast it is, start with the firewall and router piece, which covers guest networks, default passwords and remote admin. If your worry is the phone line rather than the network, the PSTN switch-off has its own deadline.