Why your office Wi-Fi keeps dropping at 2 p.m. — channel planning for non-RF engineers

The 1-6-11 rule

In the 2.4 GHz band, there are 11 channels (in India) but they are 22 MHz wide and spaced 5 MHz apart. So:

- Channel 1 covers 1–3 - Channel 6 covers 6–8 - Channel 11 covers 11–13

Any other "non-overlapping" channel is a marketing lie. Use 1, 6, and 11 only. If you see your APs on channels 3, 4, 7, etc., they are stomping on each other.

In a typical office with 8–15 APs visible from any given desk, three channels (1, 6, 11) is exactly enough — that's why the rule exists. The deployment pattern is:

- AP1 → channel 1 - AP2 → channel 6 - AP3 → channel 11 - AP4 → channel 1 (re-use, far enough away) - ...

The re-use is fine as long as the APs on the same channel are far enough apart. The rule of thumb is same-channel APs at 3× the transmit-power coverage radius. For 2.4 GHz at 10 dBm, that's roughly 30m minimum spacing for "good" re-use.

Channel width

The wider the channel, the more throughput, the more interference you cause to neighbours:

- 2.4 GHz at 20 MHz — correct for nearly every deployment - 2.4 GHz at 40 MHz — almost always wrong. You're stomping on two non-overlapping channels at once. - 5 GHz at 40 MHz — fine for most APs - 5 GHz at 80 MHz — fine if AP density is low (one AP per floor) - 5 GHz at 160 MHz — only for Wi-Fi 6E / 7 in clean 6 GHz airspace - 6 GHz (Wi-Fi 6E) — go wide, it's mostly empty

The default "auto" setting on most enterprise APs is usually fine, but verify it. The day someone manually set a 2.4 GHz channel to 40 MHz wide is the day your Wi-Fi got slow.

Why 5 GHz can be worse than 2.4 GHz

5 GHz is faster but doesn't penetrate walls as well. In a typical Indian office with masonry walls (not drywall), a 5 GHz signal drops off in 1–2 rooms, while 2.4 GHz reaches 3–4 rooms. So the AP you installed for "great coverage" actually has a smaller coverage area than you expected, and clients roam at unexpected times.

Solutions:

- More APs at lower power. Counter-intuitive but correct. A 5 GHz AP at 10 dBm covering one room outperforms a 5 GHz AP at 20 dBm trying to cover three. - Disable lower data rates. Force clients to roam sooner. If the lowest rate is 6 Mbps and a client can't sustain 6 Mbps, the client roams to a closer AP. - Band-steering. Push 5 GHz-capable clients to 5 GHz, keep 2.4 GHz for IoT and older devices.

The 2 p.m. problem

You have a working Wi-Fi at 9 a.m. By 2 p.m. it's terrible. Almost always one of:

1. Co-channel interference. All the office Wi-Fi from neighbouring offices is now active. The spectrum that was clean at 6 a.m. is saturated by 2 p.m. 2. Capacity exhaustion. The break-room AP is now serving 35 clients instead of 12. The AP has hit its client limit. 3. A new device on the network. Someone brought a new AP, or a microwave turned on next to the AP, or someone plugged in a wireless security camera on channel 6.

Walk the site at 2 p.m. with a spectrum analyser (or the free NetSpot / Ekahau tools on a laptop). You'll see the cause in 5 minutes.

Quick field checklist

1. Survey at peak time, not at install time. Don't design the channel plan on an empty floor. 2. Stick to 1-6-11 on 2.4 GHz, 20 MHz wide. 3. 5 GHz at 40 or 80 MHz, depending on AP density. 4. Disable lowest data rates to force faster roaming. 5. Set AP power explicitly — don't trust the auto setting. 6. Band-steer aggressively — keep 2.4 GHz for old devices.

If your Wi-Fi is dropping and you don't know why, raise a ticket with the model numbers of the APs and a screenshot of the channel utilisation. We'll tell you what's wrong in 15 minutes.

When to call us

Site surveys for new Wi-Fi deployments, troubleshooting for "the Wi-Fi worked when we installed it but is bad now" — we do both. The first is a half-day on site. The second is usually a 30-minute remote fix. Toll-free 1800-5GHZ-NET, or raise a ticket.