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: