Wi-Fi Planning & Design Guide

This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.

What a Wi-Fi design is deciding

Wi-Fi design decides where the radios go, which channels they may use, how wide those channels are, and which VLAN an SSID lands on. It does not decide your WAN speed. A fast access point on a congested channel, or on the wrong VLAN, feels slow in a way no firewall change will fix. Measure the air and the wired VLAN separately.

An SSID is a name. The VLAN is where the frames go after the access point bridges them. A guest SSID that lands on the user VLAN is not a guest network. Write the SSID, the VLAN, and the prefix on one line. Authentication is a third decision: an open guest network with a captive portal is not the same control as a staff network with 802.1X. Do not mix staff and guest on one PSK because it was the setting you could remember.

Power is not a volume knob you turn to maximum. A radio that shouts across the floor prevents other radios from reusing the channel. Lower power and more APs, placed for the rooms, beat one loud AP. Clients decide when to roam. A client that sticks to a distant loud AP will show a good SSID and a bad time. Design so the near AP is the obvious choice.

The calculators on this page estimate counts and channel plans from numbers you type. They do not hear your air. A planner's count is a shopping list. A survey is the design. Do not skip the survey in a hospital, a warehouse, or any building with thick walls and then blame the access point model.

Counts you can defend before a survey

a small office of 80 square metres and 12 clients, with a planning cell of about 25 metres in open space, is not a survey. A crude count from area, using one AP per 150 square metres, is 1. A crude count from clients, using 25 active devices per AP, is 1. The higher of those, and not less than a planner's minimum of 2, is 2 access points before you account for walls. Elevators, brick, and racking can double that. A site survey measures it. This arithmetic only stops you ordering one AP for a floor that needs eight. Place APs in rooms where people sit, not only in the corridor where the cable was easy. Corridor APs serve the corridor. Channel reuse still applies: in 2.4 GHz the usable non-overlapping set is 1, 6, and 11 in most regions. Reusing channel 1 on two APs that can hear each other is interference you bought. In 5 GHz you have more channels and less patience for 80 MHz widths. A wide channel is faster when it is alone and slower when every AP uses it. Prefer 20 or 40 MHz until a survey says the air is empty. 6 GHz, where you are allowed to use it, is extra spectrum, not a reason to ignore placement.

one floor of 400 square metres and 40 clients, with a planning cell of about 30 metres in open space, is not a survey. A crude count from area, using one AP per 150 square metres, is 3. A crude count from clients, using 25 active devices per AP, is 2. The higher of those, and not less than a planner's minimum of 6, is 6 access points before you account for walls. Elevators, brick, and racking can double that. A site survey measures it. This arithmetic only stops you ordering one AP for a floor that needs eight. Place APs in rooms where people sit, not only in the corridor where the cable was easy. Corridor APs serve the corridor. Channel reuse still applies: in 2.4 GHz the usable non-overlapping set is 1, 6, and 11 in most regions. Reusing channel 1 on two APs that can hear each other is interference you bought. In 5 GHz you have more channels and less patience for 80 MHz widths. A wide channel is faster when it is alone and slower when every AP uses it. Prefer 20 or 40 MHz until a survey says the air is empty. 6 GHz, where you are allowed to use it, is extra spectrum, not a reason to ignore placement.

a crowded floor of 1200 square metres and 150 clients, with a planning cell of about 20 metres in open space, is not a survey. A crude count from area, using one AP per 150 square metres, is 8. A crude count from clients, using 25 active devices per AP, is 6. The higher of those, and not less than a planner's minimum of 10, is 10 access points before you account for walls. Elevators, brick, and racking can double that. A site survey measures it. This arithmetic only stops you ordering one AP for a floor that needs eight. Place APs in rooms where people sit, not only in the corridor where the cable was easy. Corridor APs serve the corridor. Channel reuse still applies: in 2.4 GHz the usable non-overlapping set is 1, 6, and 11 in most regions. Reusing channel 1 on two APs that can hear each other is interference you bought. In 5 GHz you have more channels and less patience for 80 MHz widths. A wide channel is faster when it is alone and slower when every AP uses it. Prefer 20 or 40 MHz until a survey says the air is empty. 6 GHz, where you are allowed to use it, is extra spectrum, not a reason to ignore placement.

a warehouse aisle plan, not a survey of 2500 square metres and 200 clients, with a planning cell of about 15 metres in open space, is not a survey. A crude count from area, using one AP per 150 square metres, is 17. A crude count from clients, using 25 active devices per AP, is 8. The higher of those, and not less than a planner's minimum of 14, is 17 access points before you account for walls. Elevators, brick, and racking can double that. A site survey measures it. This arithmetic only stops you ordering one AP for a floor that needs eight. Place APs in rooms where people sit, not only in the corridor where the cable was easy. Corridor APs serve the corridor. Channel reuse still applies: in 2.4 GHz the usable non-overlapping set is 1, 6, and 11 in most regions. Reusing channel 1 on two APs that can hear each other is interference you bought. In 5 GHz you have more channels and less patience for 80 MHz widths. A wide channel is faster when it is alone and slower when every AP uses it. Prefer 20 or 40 MHz until a survey says the air is empty. 6 GHz, where you are allowed to use it, is extra spectrum, not a reason to ignore placement.

a training room that is dense for two hours of 400 square metres and 80 clients, with a planning cell of about 10 metres in open space, is not a survey. A crude count from area, using one AP per 150 square metres, is 3. A crude count from clients, using 25 active devices per AP, is 4. The higher of those, and not less than a planner's minimum of 8, is 8 access points before you account for walls. Elevators, brick, and racking can double that. A site survey measures it. This arithmetic only stops you ordering one AP for a floor that needs eight. Place APs in rooms where people sit, not only in the corridor where the cable was easy. Corridor APs serve the corridor. Channel reuse still applies: in 2.4 GHz the usable non-overlapping set is 1, 6, and 11 in most regions. Reusing channel 1 on two APs that can hear each other is interference you bought. In 5 GHz you have more channels and less patience for 80 MHz widths. A wide channel is faster when it is alone and slower when every AP uses it. Prefer 20 or 40 MHz until a survey says the air is empty. 6 GHz, where you are allowed to use it, is extra spectrum, not a reason to ignore placement.

a clinic corridor where walls, not people, dominate of 200 square metres and 20 clients, with a planning cell of about 40 metres in open space, is not a survey. A crude count from area, using one AP per 150 square metres, is 2. A crude count from clients, using 25 active devices per AP, is 1. The higher of those, and not less than a planner's minimum of 4, is 4 access points before you account for walls. Elevators, brick, and racking can double that. A site survey measures it. This arithmetic only stops you ordering one AP for a floor that needs eight. Place APs in rooms where people sit, not only in the corridor where the cable was easy. Corridor APs serve the corridor. Channel reuse still applies: in 2.4 GHz the usable non-overlapping set is 1, 6, and 11 in most regions. Reusing channel 1 on two APs that can hear each other is interference you bought. In 5 GHz you have more channels and less patience for 80 MHz widths. A wide channel is faster when it is alone and slower when every AP uses it. Prefer 20 or 40 MHz until a survey says the air is empty. 6 GHz, where you are allowed to use it, is extra spectrum, not a reason to ignore placement.

Channels and widths

In 2.4 GHz, plan on channels 1, 6, and 11. Channel 2 is not a secret extra lane. It overlaps both of its neighbours. If a neighbour building already occupies channel 1 at high power, you still do not invent channel 4 as a solution. You place your radios so fewer of them need 2.4 GHz at all. Modern clients can use 5 GHz. Leave 2.4 GHz for the devices that have no choice, and do not give it an 40 MHz width.

In 5 GHz, a 20 MHz channel is the polite default in a dense office. 40 MHz is reasonable when neighbouring APs are not on the same width and the same channel. 80 MHz and 160 MHz are for spaces you have measured, not for a template that a controller applied to every floor. A controller that picks channels can help, and it can also chase interference all day. Pin the plan after you have looked at it. Automatic does not mean unreviewed.

DFS channels are usable when the region and the client set allow them, and they are subject to radar events that move the AP off the channel. Do not put a voice SSID only on a DFS channel and then be surprised by a dropout. Know which channels your region permits. This page is not a table of every country's rules. Check the current rule before you lock a plan.

6 GHz adds space for wide channels where clients and regulations allow it. It does not penetrate walls better. An AP placement that failed at 5 GHz because it was in the wrong room still fails at 6 GHz. Survey the new band. Do not copy the 2.4 GHz channel numbers into it.

The wired side of wireless

Each AP needs power, an access or trunk port, and a path to the controller or to the gateway. PoE budgets are a switching problem. An AP that boots and then disables a radio is often a switch that could not spare the watts. Count the switch's PoE budget against the AP's draw, not against the number of free ports.

A trunk to an AP that broadcasts three SSIDs must allow those three VLANs and no extras. Guest must not be the native VLAN. Management of the AP should be a VLAN users cannot join. If the AP management address is on the user subnet, every user is one password away from the AP, and the password is often shared.

DHCP for wireless clients belongs in the VLAN the SSID uses. A scope that is full looks like a Wi-Fi failure. Check the scope before you add APs. Adding APs to a full scope creates more clients who cannot get an address. Roaming between APs on the same VLAN should not force a new address. A client that gets a new subnet every time it walks is attached to the wrong VLAN per AP.

How to roll a floor out

Order from the count, then walk the floor, then move APs that the walk contradicts, then set channels, then test with a client that sits where a person sits. A test in the cupboard next to the AP proves the AP boots. It does not prove the desk by the window works. Test the desk by the window.

Record the AP name, the switch port, the PoE draw, the SSIDs, the VLANs, and the channel. The next person will replace a failed AP and copy the wrong channel if you did not write it down. A controller backup is not a substitute for the port number on the patch panel.

Change channels in a window if the floor is in use. A channel change drops clients briefly. Doing all of them at 10:00 on a Monday is a choice. Doing them once, from a plan, is better than letting an automatic algorithm change them during a call.

Count APs from area and from clients, then take the higher number as a minimum.
Place them for rooms, not for the cable tray.
Assign SSIDs to VLANs and write the prefixes.
Plan 2.4 GHz as 1, 6, and 11, and keep 5 GHz widths narrow until a survey says otherwise.
Check PoE and trunk allowed lists on the switch.
Test from a desk, not from the AP mount.
Write down the channel and the port.

Mistakes that survive a vendor heatmap

One AP per floor because the brochure showed a large circle.

Maximum transmit power on every radio.

80 MHz channels on every 5 GHz radio in a dense office.

A guest SSID bridged to the user VLAN.

Channel 1, 2, and 3 treated as three non-overlapping choices.

A full DHCP scope diagnosed as bad Wi-Fi.

A survey done in an empty building and never repeated with people and doors closed.

Management of the AP on the same subnet as the clients.

Floor checks before you call the design done

Confirm this before you call the change done: The AP count is at least the higher of the area count and the client count, and a survey has either confirmed it or is scheduled before go-live. 2.4 GHz uses channels 1, 6, and 11 only, and neighbouring APs that hear each other are not on the same one of those. 5 GHz widths are 20 or 40 MHz unless a survey named a wider channel for a specific AP. Each SSID maps to one VLAN, and the guest VLAN is not the user VLAN. The switch trunk to the AP allows only those VLANs. The PoE budget on the switch is greater than the sum of the AP draws on that switch. DHCP scopes for the wireless VLANs have free addresses for the client count. A test from a desk by the window passes, not only a test under the AP. The AP name, switch port, channel, and VLAN are written down. And a channel change is scheduled, not left to an automatic plan you have never read. If one of those fails, stop.

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