Wi-Fi planning
Why the instinct to turn the radios up and use the widest channels makes coverage worse, and what to do instead. Covers the three bands and what each is for, the trade between channel width and usable capacity, co-channel versus adjacent-channel interference, and where access points actually belong in a ceiling.
Doing it
Planning a floor, in the order that stops the common failure: plenty of signal and no usable capacity.
- 01
Treat 2.4 GHz as coverage, not capacity
There are three non-overlapping channels — 1, 6 and 11 — and that is the whole budget. Anything else overlaps and makes things worse for everyone. Keep 2.4 GHz at 20 MHz, use it for devices that have no choice, and accept that it is a legacy band rather than trying to make it perform.
CautionNever use 40 MHz channels on 2.4 GHz. It consumes most of the band and degrades every network in range, including yours.
- 02
Do the real work on 5 GHz
Far more channels, much less legacy noise, and enough range for a normal ceiling mount. This is where capacity comes from. Check which channels are DFS at your site and decide deliberately whether to use them — they are genuinely available, but a radar event moves clients off them without warning.
- 03
Choose channel width against client count, not headline speed
Wider channels are faster for one client and worse for a room full of them, because width is bought by consuming channels that other access points could have used. On a dense floor, 20 or 40 MHz across many cells beats 80 MHz across few. The wide channel wins a speed test and loses the actual deployment.
- 04
Turn the power down
An access point shouting at full power hears clients no better — the client's radio is small and its reply is quiet — and it extends its cell until it overlaps neighbours on the same channel. Lower power, more cells, and clients that roam sooner is the arrangement that performs. Match the AP's transmit power roughly to what a phone can manage.
CautionA single high-power AP covering a large floor is the classic failed design: coverage on a survey, unusable under load.
- 05
Plan the channel reuse pattern, then mind the edges
Adjacent cells must not share a channel, and cells two apart may. Co-channel interference makes access points politely wait for each other and halves throughput; adjacent-channel interference is worse still, because the radios cannot decode each other and simply corrupt. Remember the floors above and below — they are adjacent cells too.
- 06
Mount in the open, below the obstructions
Ceiling, face down, in open space. Not above a metal grid or ductwork, not inside a ceiling void, not behind a bulkhead. An access point in a plant room serving the corridor outside is a design that cannot be fixed by configuration.
- 07
Survey after, not only before
A predictive plan is a hypothesis about a building you have not measured. Walk the floor with the access points live and check signal, noise, and where clients actually roam. The gap between the prediction and the measurement is the deliverable.
- Why is my Wi-Fi slow when signal strength is full?
- Signal strength says the client can hear the access point; it says nothing about how much airtime is available. Full bars with poor performance usually means co-channel interference — several access points on the same channel taking turns — or a wide channel on a dense floor, or one client on an old standard consuming disproportionate airtime for everybody.
- Should I use 80 MHz channels?
- On a home network or a sparse site, yes. On a dense office floor, usually not. Width is bought by consuming spectrum other cells needed, so 80 MHz gives one client a fast speed test and gives the floor fewer usable channels to reuse. Narrower channels across more access points is the arrangement that survives a full room.
- How many access points do I need?
- Count clients and airtime, not square footage. A floor with plenty of coverage can still be saturated by density, and coverage-based counts systematically under-provision open-plan space and meeting rooms. Where a real answer matters, a survey with the hardware live is the only way to know rather than guess.
- What is DFS and should I use those channels?
- Dynamic frequency selection channels are shared with radar. They are legitimately usable and give you significantly more 5 GHz spectrum, but on a radar detection the access point must vacate the channel, which moves clients and interrupts sessions. Near an airport, coastline or weather radar, be cautious; elsewhere they are often worth the extra capacity.
- Is 6 GHz worth deploying?
- Where clients support it, yes — it is a large amount of clean spectrum with none of the legacy noise. Its range is shorter and it is stopped more readily by walls, so it complements 5 GHz rather than replacing it. Deploy it as an additional band on the same access points, not as the plan.
The rest of the section
- 01RJ45 Wiring: T568A and T568BBoth colour codes, pin by pin, side by side.
- 02RJ11 Wiring and Phone PinoutsSix positions, three lines, two colour systems.
- 03Keystone Jack TerminationStrip, seat, punch, snap — without failing the certification.
- 0466 Block WiringFifty rows, four columns, and where the bridging clips go.
- 05110 Block WiringLay the pairs in, press the connecting block on.
- 06Cat5e vs Cat6 vs Cat6a vs Cat8Speed, distance, and power decide it — not the bigger number.
- 07Fibre Types, Connectors and PolishRead the jacket, read the connector, don't mate blue to green.
- 08Subnetting, ExplainedWhere the numbers come from, and the meaning behind them.
- 09PoE Standards and Why It Won't PowerThe switch reserves the class, not the draw.
- 10Camera Lens, Field of View and Pixel DensityCovering the room is not the same as identifying a face in it.
- 11Patch Panels and Labelling to TIA-606A label that survives is worth more than a tidy rack.
- 12Rack Planning: Units, Depth, Weight and HeatIt fits vertically. That was never the hard part.
- 13Writing a Switch ConfigurationFrom factory default to a switch you would hand over.
- 14Networking and Cabling GlossaryThe terms, and what they mean on a job.
- 15POTS to VoIP: What BreaksThe lines nobody remembers until they stop working.
- 16Testing an Analogue Phone LineTip, ring, and the four numbers that tell you whose fault it is.
- 17Toning and Tracing a CableFinding one pair in a bundle of two hundred.
- 18Reading a Cable Certifier ReportWhat PASS* actually means, and which number to look at first.
- 19Which Cable Tester Do You Need?Three tiers, and the one most people actually need.
- 20Running an Office Floor RestackEveryone sits down Monday and their machine works.
- 21Cable Management for Desks and RacksTidy is a by-product. Serviceable is the point.
- 22Asset Tagging and CMDB AuditsThe scan is easy. Scanning it into the right record is the job.
- 23Cabling an Office Fit-OutHow many drops, run where, and what it takes to add one later.
- 24Parcel Locker Site SurveysWhether the unit fits, powers, connects — and gets in the door.
- 25VLANs and TrunkingAccess, trunk, tagged, native — and which one is the security hole.
- 26Spanning Tree and Switching LoopsWhy one patch cord can take a whole floor down in seconds.
- 27Reading a TracerouteWhich loss is real, and whose network it is in.
- 28DHCP, DNS and Helper AddressesWhy the new VLAN gets no addresses, and why it is always DNS.
- 29SMART Attributes That Predict FailureA drive can report PASSED while it is visibly dying.
- 30BitLocker: Keys, Recovery and EscrowThe key exists somewhere, or the data does not.
- 31Grounding and Bonding a Telecom RoomOne ground, one path, and no loops between rooms.
- 32UPS Sizing: VA, Watts and RuntimeThe number on the box is not the number you need.
- 33Mounting Displays on Any WallFind the structure. Everything else is a repair bill.
- 34Mounting IP CamerasHeight, angle, and the surfaces that ruin the picture at night.
We do this work
as well as document it
Anyone placing access points on a floor plan, or trying to work out why a site with plenty of signal still performs badly.