WLAN or Wi-Fi primarily employs the following frequency bands for its operation –
- The 2.4 GHz band and
- The 5 GHz band.
- The 6 GHz band.
The 2.4 GHz band channel centre frequencies are placed 5 MHz apart. The Channel width of each channel is 22 MHz. Since the channel centre frequencies are 5 MHz apart and the channel width is 22 MHz, most of the 2.4 GHz channels overlap with one another. The channel centre frequencies and the list of channels are shown below
FIG Courtesy: Wikipedia
From the figure above it is seen that the non-overlapping channels are 1, 6 and 11. Channel 14 is not used in all countries and is specific to Japan.
FIG Courtesy: Wikipedia
The 5 GHz band is divided into different U-NII (Unlicensed National Information Infrastructure) bands. They are
- 5.150 – 5.250 GHz (U-NII -1 band)
- 5.250 – 5.470 GHz (U-NII-2A/2B bands)
- 5.450 – 5.725 GHz (U-NII Worldwide / U-NII-2C / U-NII-2-Extended / U-NII-2e)
- 5.725 – 5.850 GHz (U-NII-3 band)
In addition for vehicular automotive communication, the below band has been incorporated
- 5.850–5.925 GHz (U-NII-4 band)
The regulatory domains of various countries have defined the 5 GHz channels sufficiently apart and as per their specific country requirements. Each channel defined is of 20 MHz channel width. Hence, the 5 GHz channels do not overlap with one another. The 5 GHz channels are shown below
FIG Courtesy: Wikipedia
The DSRC channels are used specifically for automotive communication and support 10 MHz/5 MHz and 20 MHz channels.
Recently, the 802.11 standards body introduced the 6GHz operation which contain the following set of channels.
FIG Courtesy: https://www.juniper.net/us/en/research-topics/what-is-wi-fi-6e.html.
The 6GHz 802.11ax standard operation is based on OFDMA rather than OFDM which was used in previous 802.11 standards for 5GHz. The IEEE 802.11ax and 802.11be standards will employ the 6GHz channels.
In addition to the above bands other bands for specific WLAN implementations were introduced over time. some examples are provided below.
- WiGig – 802.11ad – 60 GHz band
Fig Courtesy: Wikipedia
- 802.11y standard – for longer range Wi-Fi (upto 5 km) – 3.65GHz
Fig Courtesy: Wikipedia
- Public Safety band – 4.9 GHz
- 802.11ah – Sub GHz bands