WiFi channel planning decides which channel, channel width and transmit power each access point uses, so that neighbouring access points do not compete for the same airtime. A good plan is what turns more access points into more capacity; a poor one lets them interfere with each other and slow the whole network down.
Why channels matter
WiFi devices on the same channel share it. Only one can transmit at a time within range of the others, so every access point and client that can hear each other on a channel splits that channel's airtime. This is called co-channel contention or co-channel interference. If three access points on the same channel overlap in a busy area, they behave like one access point's worth of capacity shared three ways.
The aim of channel planning is to give each access point a channel that its neighbours are not using, or at least to keep same-channel access points far enough apart, in signal terms, that they do not hear each other strongly.
The bands and their channels
2.4 GHz
In North America there are three non-overlapping 20 MHz channels: 1, 6 and 11. Using any other channel, such as 3 or 9, overlaps two of those and makes interference worse. Because three channels go quickly and signals at 2.4 GHz travel far, dense 2.4 GHz deployments almost always overlap. In many enterprise designs, some 2.4 GHz radios are turned off or used for other purposes to reduce this.
5 GHz
The 5 GHz band offers many more channels, which makes good reuse much easier. Some of those channels are subject to dynamic frequency selection (DFS), which requires access points to watch for radar and move off a channel if they detect it. DFS channels add valuable capacity but can cause sudden channel changes near radar sources, and some client devices do not support them. Availability of specific channels depends on the regulatory domain configured in the equipment, so make sure it is set correctly for Canada.
6 GHz
Canada has opened the 6 GHz band for licence-exempt WiFi, which adds a large block of new, clean spectrum for WiFi 6E and WiFi 7 devices. It allows many more channels, or wider channels, without the legacy devices that crowd the lower bands. Rules on power levels and indoor or outdoor use apply, so check current Innovation, Science and Economic Development Canada (ISED) requirements and your equipment's certification. See 2.4, 5 and 6 GHz: choosing WiFi bands.
Channel width
WiFi can bond adjacent 20 MHz channels into 40, 80, 160 or, with WiFi 7 in 6 GHz, 320 MHz channels. Wider channels give a single device higher peak speed, but they reduce the number of separate channels available for reuse and can pick up more noise.
| Environment | Typical channel width |
|---|---|
| 2.4 GHz, any environment | 20 MHz |
| 5 GHz, high density (auditoriums, classrooms, open offices) | 20 MHz or 40 MHz |
| 5 GHz, lower density | 40 MHz, sometimes 80 MHz |
| 6 GHz | Often 40 MHz or 80 MHz; wider where density is low and spectrum is clean |
These are common starting points rather than rules. The right width depends on how many access points must share the band, how many devices connect and what they do.
Power and automatic management
Transmit power is part of the plan
Channel planning and power go together. An access point running at high power is heard far beyond its intended area, so it overlaps more neighbours on the same channel. Lowering power shrinks each access point's cell, allowing channels to be reused closer together. Power should also be roughly balanced with what client devices can transmit back, so connections work both ways.
Static plans versus automatic channel management
Most enterprise systems include automatic radio resource management that picks channels and power for you. It adapts to change and works well in many buildings, but it can make poor choices, react too often, or drift over time. A sensible approach is to start from a designed plan, decide which settings the system may adjust and within what limits, and review its decisions periodically. In difficult environments such as warehouses or hospitals, fixed channel plans are sometimes preferred for predictability.
Building a plan, step by step
- Start from requirements. Record the devices, their supported bands and channels, and how many gather in each area. These set the channel widths and which bands carry which traffic.
- Survey the neighbours. Map the networks that already occupy each channel, including those on floors above and below and in adjacent buildings.
- Set power first. Choose transmit power so each access point covers its intended area with the designed overlap for roaming, and no more.
- Assign channels. Give neighbouring access points different channels, working floor by floor and checking vertical neighbours. Avoid placing same-channel access points directly above one another.
- Decide what automation may change. Set the limits within which automatic management may adjust channels and power, and which channels it may use.
- Validate and record. Survey after installation, compare the channel overlap map with the plan, and keep the final plan as part of the network documentation.
A worked example
A three-storey office has twelve access points on each floor, installed in the same positions on every floor because the ceiling grids line up. Automatic channel management has been left with no limits, and every radio is set to 80 MHz on 5 GHz. With so few wide channels available, many access points end up on the same channel as a neighbour, and the ones stacked directly above each other often share a channel too. Floors and slabs reduce signal but do not stop it.
The revised plan narrows the 5 GHz channels to 40 MHz to roughly double the number of separate channels, lowers power so cells are smaller, assigns channels so that vertically stacked access points are always on different channels, and turns off some 2.4 GHz radios where they only added overlap. Automatic management keeps the ability to move away from interference, within that channel set. The validation survey shows far less overlap and higher throughput in the busiest areas, although the peak speed a single laptop can reach is a little lower than before.
Practical tips
- Plan in three dimensions: access points on floors above and below are neighbours too
- Survey neighbouring networks before choosing channels
- Use 20 MHz channels in 2.4 GHz and only channels 1, 6 and 11
- Match channel width to density, not to the highest number the equipment supports
- Check that critical client devices support the channels you plan to use, including DFS and 6 GHz
- Validate the plan with a survey after installation
Device support. If key devices such as scanners or handsets cannot use DFS channels or 6 GHz, plan their coverage on channels they can use, or they will cling to whatever they can find.
How ehZee can help
We build channel and power plans as part of every network design, based on survey measurements of your building and its neighbours. Our WiFi design and build service covers the plan, the installation and a validation survey to confirm it works. For an existing network, a WiFi survey will show where channel overlap is costing you capacity.
Common questions
Should we just leave channels on automatic?
Automatic management is a useful tool, but it works best with sensible limits and a designed starting point. Review its choices, especially after changes or complaints.
Why not use 80 MHz channels everywhere for speed?
Wide channels reduce the number of separate channels available. In busy areas, that leads to overlap and lower total capacity, even if one device on its own would be faster.
Can we use 2.4 GHz channel 3 to avoid neighbours on 1 and 6?
No. Channel 3 overlaps both, so it suffers interference from both and causes interference to both. Stick to 1, 6 and 11.