Wi-Fi Channels, Frequencies, Bands & Bandwidths

WiFi IEEE 802.11 Includes:
Wi-Fi IEEE 802.11 introduction     Standards     Wi-Fi Alliance generations     Security     How to stay safe on public Wi-Fi     Wi-Fi Bands     Router location & coverage     How to get best Wi-Fi performance     How to buy the best Wi-Fi router     Wi-Fi boosters, range extenders & repeaters     Wi-Fi mesh network     Wi-Fi wired & powerline extender     Buy Wi-Fi equipment    

Wi-Fi spectrum topics:     Wi-Fi Bands     6 GHz Wi-Fi band     U-NII bands    

Wi-Fi IEEE 802.11 is used by very many devices from smartphones to laptops and tablets to remote sensors, actuators televisions and many more. It is used as the main wireless communications bearer in wireless LANs as well as for small home WLANs as well.

There are several frequency bands within the radio spectrum that are used for the Wi-Fi and within these there are many channels that have been designated with numbers so they can be identified.

Although many Wi-Fi channels and Wi-Fi bands are normally selected automatically by home Wi-FI routers, for larger wireless LANs and systems it is often necessary to plan the frequencies used. Using many Wi-Fi access points around a large building or area, frequency planning is essential so that the best performance can be obtained from the wireless LAN.

Even for home systems where Wi-Fi extenders and Wi-Fi repeaters are used, it is helpful to understand which frequencies are available and how these can be best used. By using some simple settings in the Wi-Fi router and wireless extenders, it is possible to make improvements to the Wi-Fi installation network speed.

Wi-Fi & ISM bands

Wi-Fi is aimed at use within unlicensed spectrum - the ISM or Industrial, Scientific and Medical bands. These bands have been internationally agreed and unlike most other bands, they can be used without the need for a transmitting licence. This gives access to everyone to use them freely.

The ISM bands are not only used by Wi-Fi, but everything from microwave ovens to many other forms of wireless connectivity and many industrial, scientific and medical uses.

Whilst the ISM bands are available globally, there are some differences and restrictions that can occur in some countries.

In addition to the main ISM bands, other allocations are now being used to enable the level of traffic and the high data rates to be handled.

The main bands used for carrying Wi-Fi are those in the table below:

It can be seen that the 2.4 GHz band is widely used for other applications including microwave ovens (as a result of the signal absorption in water) as well as Bluetooth, and many other wireless communications applications. Sometimes using other bands can improve the WLAN performance as a result of the lower interference levels.

802.11 systems & frequency bands

There are several different 802.11 variants in use. Different 802.11 variants use different bands. A summary of the bands used by the 802.11 systems is given below:

2.4 GHz 802.11 channels

There is a total of fourteen channels defined for use by Wi-Fi installations and devices in the 2.4 GHz ISM band. Not all of the Wi-Fi channels are allowed in all countries: 11 are allowed by the FCC and used in what is often termed the North American domain, and 13 are allowed in Europe where channels have been defined by ETSI. The WLAN / Wi-Fi channels are spaced 5 MHz apart (with the exception of a 12 MHz spacing between the last two channels).

The 802.11 Wi-Fi standards specify a bandwidth of 22 MHz and channels are on a 5 MHz incremental step. Often nominal figures 0f 20 MHz are given for the Wi-Fi channels. The 20 / 22 MHz bandwidth and channel separation of 5 MHz means that adjacent channels overlap and signals on adjacent channels will interfere with each other.

The 22 MHz Wi-Fi channel bandwidth holds for all standards even though 802.11b Wireless LAN standard can run at variety of speeds: 1, 2, 5.5, or 11 Mbps and the newer 802.11g standard can run at speeds up to 54 Mbps. The differences occur in the RF modulation scheme used, but the WLAN channels are identical across all of the applicable 802.11 standards.

When using 802.11 to provide Wi-Fi networks and connectivity for offices, installing Wi-FI access points, or for any WLAN applications, it is necessary to ensure that parameters such as the channels are correctly set to ensure the required performance is achieved. On most Wi-Fi routers these days, this is set automatically, but for some larger applications it is necessary to set the channels manually, or at least under central control.

Wi-Fi routers often use two bands to provide dual band Wi-Fi, the 2.4GHz band is one of the primary bands and it is most commonly used with the 5GHz Wi-Fi band.

2.4 GHz Wi-Fi channel frequencies

The table given below provides the frequencies for the total of fourteen 802.11 Wi-Fi channels that are available around the globe. Not all of these channels are available for Wi-Fi installations in all countries.

2.4 GHz WiFi channel overlap and selection

The channels used for WiFi are separated by 5 MHz in most cases but have a bandwidth of 22 MHz. As a result the Wi-Fi channels overlap and it can be seen that it is possible to find a maximum of three non-overlapping ones.

Therefore if there are adjacent pieces of WLAN equipment, for example in a Wi-Fi network consisting of multiple access points that need to work on non-interfering channels, there is only a possibility of three. There are five combinations of available non overlapping channels are given below:

From the diagram above, it can be seen that Wi-Fi channels 1, 6, 11, or 2, 7, 12, or 3, 8, 13 or 4, 9, 14 (if allowed) or 5, 10 (and possibly 14 if allowed) can be used together as sets. Often WiFi routers are set to channel 6 as the default, and therefore the set of channels 1, 6 and 11 is possibly the most widely used.

As some energy spreads out further outside the nominal bandwidth, if only two channels are used, then the further away from each other the better the performance.

It is found that when interference exists, the throughput of the Wi-Fi installation is reduced. It therefore pays to reduce the levels of interference to improve the overall performance of the WLAN equipment.

With the use of IEEE 802.11n, there is the possibility of using signal bandwidths of either 20 MHz or 40 MHz. When 40 MHz bandwidth is used to gain the higher data throughput, this obviously reduces the number of channels that can be used.

2.4 GHz Wi-Fi channel availability

In view of the differences in spectrum allocations around the globe and different requirements for the regulatory authorities, not all the WLAN channels are available in every country. The table below provides a broad indication of the availability of the different Wi-Fi channels in different parts of the world.

This chart is only provides a general view, and there may be variations between different countries. For example some countries within the European zone Spain have restrictions on the Wi-Fi channels that may be used (France: channels 10 - 13 and Spain channels 10 and 11) use of Wi-Fi and do not allow many of the channels that might be thought to be available, although the position is always likely to change.

3.6 GHz WiFi band

This band of frequencies is only allowed for use within the USA under a scheme known as 802.11y. Here high powered stations can be used for backhaul Wi-Fi links in data networks, etc.

The 3.6 GHz Wi-Fi band may be divided into eight 5 MHz channels, four 10 MHz channels, or two 20 MHz channels.

Channels for these Wi-Fi network systems are detailed below.

Note: the channel centre frequency depends upon the bandwidth used. This accounts for the fact that the centre frequency for various channels is different if different signal bandwidths are used.

5 GHz WiFi channels & frequencies

As the 2.4 GHz band becomes more crowded, many users are opting to use the 5 GHz ISM band for their wireless LANs, general Wi-Fi networks, home systems, etc. This not only provides more spectrum, but it is not as widely used for other appliances including items such as microwave ovens, etc. - microwave ovens work best around 2.4 GHz because of the absorption of the radiation by the food peaks around 2.4 GHz. Accordingly 5GHz Wi-Fi generally encounters less interference.

Many Wi-Fi routers provide the option for dual band Wi-Fi operation using this band and 2.4 GHz as do most smartphones and other Wi-Fi enabled electronic devices. Using frequencies in the 5GHz band generally provides faster Wi-Fi network speeds.

It will be seen that many of the 5 GHz Wi-Fi channels fall outside the accepted ISM unlicensed band and as a result various restrictions are placed on operation at these frequencies.

Note 1: there are additional regional variations for countries including Australia, Brazil, China, Israel, Korea, Singapore, South Africa, Turkey, etc. Additionally Japan has access to some channels below 5180 MHz.

Note 2: DFS = Dynamic Frequency Selection; TPC = Transmit Power Control; SRD = Short Range Devices 25 mW max power.

6 GHz Wi-Fi band

As the use of Wi-Fi has grown, and with the wider bandwidths required for the very high data rates being introduced, more spectrum is required. To accommodate this, a 6 GHz allocation has been provided.

Although it is not using a standard Industrial, Scientific and Medical band, the relatively low power levels used by Wi-Fi are deemed not to interfere with the existing users and as a result the spectrum has been opened up in many countries.

Additional bands and frequencies

In addition to the more established forms of Wi-Fi, new formats are being developed that will use new frequencies and bands. Technologies employing white space usage, etc. and also new standards using bands that are well into the microwave region and will deliver gigabit Wi-Fi networks. These technologies will require the use of new spectrum for Wi-Fi.

As Wi-Fi technology use has increased out of all proportion and the data transfer speeds have risen significantly, so too has the way in which the bands are used.

Wi-Fi is available in many areas, in the home, office and in coffee shops etc. Wi-Fi access points are widely available, often providing dual band Wi-Fi band operation - both 2.4 GHz and 5GHz Wi-Fi to enable fast operation at all times.

Originally the 2.4GHz band was favoured for Wi-Fi, but as the costs for the 5GHz technology fell, this band came into much greater use in view of its wider channel bandwidth capability.

As other Wi-Fi technologies come to the fore, many other frequencies are being used. Other unlicensed bands that are below 1 GHz as well as white space for White-Fi using the unused TV spectrum and also now increasingly higher frequencies into the microwave region where even greater bandwidths are available, but at the cost of shorter distance.

Each Wi-Fi technology has its own frequencies or bands and sometimes a different use of the Wi-Fi channels available.

  Written by Ian Poole .
  Experienced electronics engineer and author.

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