What is channel bonding?
Channel bonding combines two or more adjacent 20 MHz Wi-Fi channels into one wider channel. A wider channel carries more data at once, so throughput roughly doubles each time the width doubles. One 20 MHz slice is the primary channel, which carries beacons and management traffic; the others are secondary channels that add capacity.
On an access point or wireless router you set it as the channel width: 20, 40, 80, 160 or 320 MHz, or Auto.
Channel widths by standard
| Width | Introduced with | Bands |
|---|---|---|
| 20 MHz | The basic Wi-Fi channel | 2.4, 5 and 6 GHz |
| 40 MHz | 802.11n (Wi-Fi 4) | 5 and 6 GHz (allowed in 2.4 GHz, but avoid it) |
| 80 MHz | 802.11ac (Wi-Fi 5) | 5 and 6 GHz |
| 160 MHz | 802.11ac (optional), also 802.11ax (Wi-Fi 6 and 6E) | 5 and 6 GHz |
| 320 MHz | 802.11be (Wi-Fi 7) | 6 GHz only |
The trade-off: speed vs. channels
Every time the width doubles, the number of channels that don't overlap roughly halves:
| Width | 5 GHz (US) | 6 GHz (US) |
|---|---|---|
| 20 MHz | 25 | 59 |
| 40 MHz | 12 | 29 |
| 80 MHz | 6 | 14 |
| 160 MHz | 2 | 7 |
| 320 MHz | None | 3 |
The 5 GHz counts include the DFS channels and leave out the UNII-4 channels (169 to 177). Wider channels also:
- Pick up more noise and interference, because the radio listens across more spectrum, and a busy neighbor on any part of a wide channel cuts into its throughput.
- Raise the odds of sharing spectrum with nearby access points, which hurts in offices and apartment buildings.
- Often include DFS channels in 5 GHz. The 160 MHz channels 50 and 114 both do, so a radar detection can force the access point to move or narrow the channel.
A common rule of thumb: 80 MHz on 5 GHz suits a single home access point, while networks with many access points usually run 20 or 40 MHz so neighbors don't overlap.
Why 2.4 GHz stays at 20 MHz
In the US the 2.4 GHz band has channels 1 to 11, and only 1, 6 and 11 don't overlap. A 40 MHz channel covers most of the band, so only one fits without overlap, and it runs into every neighboring network plus more of the interference from Bluetooth devices and microwave ovens. Keep 2.4 GHz at 20 MHz on channel 1, 6 or 11, and use bonding on 5 GHz or 6 GHz.
Not the same as NIC teaming
On wired networks, combining several Ethernet links into one logical link is called link aggregation or NIC teaming, often using LACP (IEEE 802.3ad). That joins separate cables and switch ports. Wi-Fi channel bonding widens a single radio channel. The goal (more capacity) is similar, but the technology is unrelated.
For the CompTIA A+ exam
Core 1 (220-1201) objective 2.2 covers the 802.11 standards and channel selection, including channel widths. Remember that 40 MHz bonding arrived with 802.11n, 80 and 160 MHz with 802.11ac, and 320 MHz with 802.11be in 6 GHz. If a question asks how to reduce interference on 2.4 GHz, the answer is a 20 MHz channel on 1, 6 or 11, not a wider one.