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 span frequencies from roughly 5.150 GHz to 5.895 GHz (these are band edges, not center frequencies). 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 framework. For example, the Federal Communications Commission (FCC) sets the rules in the US, while in Europe the rules are set by CEPT/ECC and national regulators, based on harmonized standards developed by the European Telecommunications Standards Institute (ETSI), such as EN 301 893.
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 68-92 (not allocated for unlicensed Wi-Fi by the FCC or most regulators, so effectively unused)
- UNII-2C band:
- 5470–5725 MHz
- Channels 96, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 144 (channel 96 sits at the lower edge and is rarely used in practice; usable channels typically start at 100)
- UNII-3 band:
- 5725–5850 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 non-overlapping channels in most regulatory domains
- Each 160 MHz channel spans eight adjacent 20 MHz channels
- Typically limited to 2 channels, since contiguous 160 MHz blocks require DFS spectrum
- Examples: 36-64 (channels 36+40+44+48+52+56+60+64) and 100-128 (channels 100+104+108+112+116+120+124+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-2B | Yes |
| 72 | 5.350 – 5.370 | 5.360 | UNII-2B | Yes |
| 76 | 5.370 – 5.390 | 5.380 | UNII-2B | Yes |
| 80 | 5.390 – 5.410 | 5.400 | UNII-2B | Yes |
| 84 | 5.410 – 5.430 | 5.420 | UNII-2B | Yes |
| 88 | 5.430 – 5.450 | 5.440 | UNII-2B | Yes |
| 92 | 5.450 – 5.470 | 5.460 | UNII-2B | 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: