Lesson Contents
The 5 GHz Wi-Fi band provides a wide range of channels, offering more capacity and less interference than the 2.4 GHz band. These channels have center frequencies that operate between 5.150 GHz and 5.835 GHz. Not all channels in this frequency range can be used for Wi-Fi.
Channel Groups
We can divide the 5 GHz channels into two main categories:
- Non-DFS Channels: These channels, such as 36-48 and 149-165, do not require any special radar detection mechanisms. They are a reliable choice for most environments.
- DFS Channels: Channels 52-64 and 100-144 require Dynamic Frequency Selection (DFS). Because these frequencies are shared with radar systems (like weather radar), an access point (AP) must listen for radar signals and vacate the channel if a signal is detected.
Channel availability (up to 25 non-overlapping 20 MHz channels), power limits, and DFS requirements are all dictated by a country’s regulatory body. For example, the Federal Communications Commission (FCC) in the US and the European Telecommunications Standards Institute (ETSI) in Europe.
Band Structure
The 5 GHz band is divided into distinct frequency bands, each with its own associated channels. Here is an overview:
- UNII-1 band:
- 5150–5250 MHz
- Channels 36, 40, 44, 48
- UNII-2A band:
- 5250–5350 MHz
- Channels 52, 56, 60, 64
- UNII-2B band:
- 5350-5470 MHz
- Channels 68-96
- UNII-2C band:
- 5470–5725 MHz
- Channels 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140
- UNII-3 band:
- 5735–5850 MHz
- Channels 149, 153, 157, 161, 165
Channel Widths
The 5 GHz band supports multiple channel widths, each offering different trade-offs between speed and coverage. For example:
20 MHz
- Up to 25 non-overlapping channels
- Most regulatory domains allow 20-25 channels, depending on local regulations
- Channels are spaced 20 MHz apart (e.g., 36, 40, 44, 48, etc.)
40 MHz
- Up to 12 non-overlapping channels
- Each 40 MHz channel spans two adjacent 20 MHz channels
- Examples: 36+40, 44+48, 52+56, etc.
80 MHz
- Up to 6 non-overlapping channels
- Each 80 MHz channel spans four adjacent 20 MHz channels
- Examples: 36+40+44+48, 52+56+60+64, etc.
160 MHz
- Up to 2-3 non-overlapping channels
- Each 160 MHz channel spans eight adjacent 20 MHz channels
- Limited to 2 channels in most regions, possibly 3 in some areas with more spectrum
- Examples: 36-64 (channels 36+40+44+48+52+56+60+64), 100-128
Channel Overview
This frequency range is separated into specific channels as shown in the following table:
| Channel | Frequency Range (GHz) | Center Frequency (GHz) | UNII Band | DFS Required |
|---|---|---|---|---|
| 32 | 5.150 – 5.170 | 5.160 | UNII-1 | No |
| 36 | 5.170 – 5.190 | 5.180 | UNII-1 | No |
| 40 | 5.190 – 5.210 | 5.200 | UNII-1 | No |
| 44 | 5.210 – 5.230 | 5.220 | UNII-1 | No |
| 48 | 5.230 – 5.250 | 5.240 | UNII-1 | No |
| 52 | 5.250 – 5.270 | 5.260 | UNII-2A | Yes |
| 56 | 5.270 – 5.290 | 5.280 | UNII-2A | Yes |
| 60 | 5.290 – 5.310 | 5.300 | UNII-2A | Yes |
| 64 | 5.310 – 5.330 | 5.320 | UNII-2A | Yes |
| 68 | 5.330 – 5.350 | 5.340 | UNII-2C | Yes |
| 72 | 5.350 – 5.370 | 5.360 | UNII-2C | Yes |
| 76 | 5.370 – 5.390 | 5.380 | UNII-2C | Yes |
| 80 | 5.390 – 5.410 | 5.400 | UNII-2C | Yes |
| 84 | 5.410 – 5.430 | 5.420 | UNII-2C | Yes |
| 88 | 5.430 – 5.450 | 5.440 | UNII-2C | Yes |
| 92 | 5.450 – 5.470 | 5.460 | UNII-2C | Yes |
| 96 | 5.470 – 5.490 | 5.480 | UNII-2C | Yes |
| 100 | 5.490 – 5.510 | 5.500 | UNII-2C | Yes |
| 104 | 5.510 – 5.530 | 5.520 | UNII-2C | Yes |
| 108 | 5.530 – 5.550 | 5.540 | UNII-2C | Yes |
| 112 | 5.550 – 5.570 | 5.560 | UNII-2C | Yes |
| 116 | 5.570 – 5.590 | 5.580 | UNII-2C | Yes |
| 120 | 5.590 – 5.610 | 5.600 | UNII-2C | Yes |
| 124 | 5.610 – 5.630 | 5.620 | UNII-2C | Yes |
| 128 | 5.630 – 5.650 | 5.640 | UNII-2C | Yes |
| 132 | 5.650 – 5.670 | 5.660 | UNII-2C | Yes |
| 136 | 5.670 – 5.690 | 5.680 | UNII-2C | Yes |
| 140 | 5.690 – 5.710 | 5.700 | UNII-2C | Yes |
| 144 | 5.710 – 5.730 | 5.720 | UNII-2C | Yes |
| – | 5.730 – 5.735 | – | Guard Band | – |
| 149 | 5.735 – 5.755 | 5.745 | UNII-3 | No |
| 153 | 5.755 – 5.775 | 5.765 | UNII-3 | No |
| 157 | 5.775 – 5.795 | 5.785 | UNII-3 | No |
| 161 | 5.795 – 5.815 | 5.805 | UNII-3 | No |
| 165 | 5.815 – 5.835 | 5.825 | UNII-3 | No |
| 169 | 5.835 – 5.855 | 5.845 | UNII-4 | No |
| 173 | 5.855 – 5.875 | 5.865 | UNII-4 | No |
| 177 | 5.875 – 5.895 | 5.885 | UNII-4 | No |
There are a couple of things to keep in mind when looking at the above table:
- Each channel is defined by its center frequency. This is the frequency at the very center of the channel width.
- The channel width is the range of frequencies that each channel encompasses. From the Frequency Range column, you can see that each channel is 20 MHz in width.
- The range 5.730 to 5.735 GHz is undefined as far as a specific channel is concerned. In some areas of the world, this is defined as “unknown,” while for others it is usable, but isn’t actually defined.
- Notice also that the channel numbers are not sequential.
Conclusion
You now know about the Wi-Fi 5 GHz Frequency Bands and Channels:
- The 5 GHz Wi-Fi band offers advantages over the 2.4 GHz band, such as more non-overlapping channels, more capacity, and less interference.
- The 5 GHz band is divided into DFS and non-DFS channels.
- To achieve higher bandwidth channels can be bonded together to create wider channels such as 40, 80, and 160 MHz.
- Channel numbers are not sequential.
- Availability varies by regulatory domain.
I hope you enjoyed this lesson. If you have any questions, please leave a comment.