Recipe: Wi-Fi in a warehouse or large building

Goal: usable Wi-Fi everywhere in a warehouse or a large building, with access points you placed beforehand instead of moving afterwards.

What you need

A floor plan with measurements in metres. A builder's drawing is fine, so is a sketch, as long as the distances are right.
Knowing what the walls are made of, and where the racking stands.
A PoE switch, or injectors, and room to run cables.
Knowing what has to be on the network: handheld scanners are a different animal from laptops, and a ten-year-old scanner is often still on 2.4 GHz.

Step 1: draw the floor

Go to the Wi-Fi plan and add a floor. Set the height to what it really is; a six-metre warehouse is not a 2.8-metre office.
Pick the floor type: wooden floor, hollow-core slab, concrete, or concrete with underfloor heating. That only counts for floors above or below each other.
Draw the walls with their material: plasterboard, wood, aerated concrete, brick, tiled wall, glass, coated low-e glass, concrete, reinforced concrete or metal. Per wall you can give the thickness in centimetres, and the tool scales the loss with it.
Draw rooms as named rectangles. Those are what later give you a coverage percentage per room.
Put openings in walls where the doors and passages are. An opening costs no signal; a closed door does.

Step 2: the racking

The plan has no racking object, and racking is exactly what sets a warehouse apart from an office. Do it like this:

A row of full pallet racking shields like a wall. Draw the row as a metal wall where there is steel plate or solid stock in it, and as wood or brick for a row of cardboard boxes.
Single obstacles go in as objects: a metal cabinet for a switchgear cabinet or a rack, a meter cupboard (with how much cabling and whether the door is metal), a fridge or freezer for cold rooms.
Racking fills up and empties again. Draw the situation where coverage is worst, because that is the situation the scanner has to work in.

Step 3: place the access points

Put an access point down and pick the model; the bands and the transmit power come from the catalogue.
Set the height per access point. In a warehouse you do not hang them at 2.4 metres but off the roof steels; fill in what you are really going to do, because the distance to a scanner at working height counts.
Choose the antenna: omnidirectional, or a sector with a beam width and a direction you can turn. Above an aisle, a sector looking down the aisle often beats an omni that sends half its power into the roof.
Switch radios off per band where you do not want them. In a dense layout, 5 GHz only is sometimes better than adding 2.4 GHz, because 2.4 GHz carries much further and so interferes with the neighbours.
Adjust the EIRP per band if you want to transmit more softly.

Step 4: reading the map

The map colours the signal per spot, through the walls you drew. As a guide: −55 dBm is excellent, −67 dBm is good, −75 dBm is fair and −82 dBm is weak. Per room you get the share that sits at −67 dBm or better, the weakest spot and the average. The advice flags a room that stays under 70 per cent, and an access point hanging within a metre of a heavy obstacle.

Do not aim for the strongest signal everywhere, aim for overlap: every spot should be able to see a second access point, or a gap falls open the moment one fails or a forklift parks in front of it.

Step 5: channels and power

In the Wi-Fi section:

Set the country correctly: it decides which channels and what power are allowed.
Channel width 2.4 GHz at 20 MHz. That band holds only three non-overlapping channels (1, 6 and 11, or 2412, 2437 and 2462 MHz); 40 MHz makes it worse.
Channel width 5 GHz: in a building with many access points, 20 or 40 MHz beats 80. Narrower means more channels and so fewer access points waiting for each other.
Frequency left empty is automatic. If you fill it in yourself, spread the channels so neighbours never share one. Indoor in the EU: 5180 to 5320 (DFS from 5260) and 5500 to 5700 (DFS). On a DFS channel a radio moves when it thinks it sees radar; in a busy building that is an interruption now and then.
TX power empty is the maximum. If they hang close together, set it lower. A client that clings to a far-away access point is not worth more power.

Step 6: cabling and PoE

One cable per access point, Cat6 or better. Draw them on the network board: the cable shows the speed it runs at, and the board tells you when a gigabit port meets a 10-gigabit one.
On a MikroTik with PoE-out you set auto-on, forced-on or off per port, in the Bridge & ports section or by right-clicking a port on the board.
forced-on is for passive-PoE devices that do not negotiate. Never set it on a port where something else is plugged in.
The PoE budget is not in this tool. Add up what your access points draw yourself and lay that next to the total budget of your switch. A switch with eight ports does not have to be able to power eight.

Step 7: making it one network

For roaming, the name, security and passphrase have to match on every access point; that is why they belong in a site's shared settings. 802.11r fast roaming makes the handover faster, but some older gear chokes on it: turn it on and test with your scanners before you convert the whole hall. Band steering pushes clients towards 5 GHz. If you manage more than a handful, look at CAPsMAN, so the Wi-Fi settings come from one place.

Step 8: measuring afterwards

Walk the building with the device that will really work there, not with the newest phone. A handheld scanner has a smaller antenna and sees less.
On the access point: /interface wifi registration-table print (wifi package) or /interface wireless registration-table print (legacy package) shows the signal and the rate per client.
Walk the forklift's route, not the guided tour's. Standing still in an aisle says nothing about driving past full racking.
Measure with the racking full. The plan is an estimate and stays one; a survey on site always has the final word.

What to watch out for

Hanging them too high. An omni on an eight-metre steel sends most of its power to the floor directly below and to the walls. Lower, or directional, is usually better.
An access point in or against a metal cabinet. Metal costs 40 dB or more; the plan warns when one hangs within a metre.
Everything at full power. Then a client hears something everywhere and picks well nowhere.
Older gear on 2.4 GHz. Do not switch that band off until you are sure nothing still needs it.