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Wi-Fi spectrum topics: Wi-Fi Bands 6 GHz Wi-Fi band U-NII bands
The 6 GHz band of frequencies provides a large number of new channels for Wi-Fi 6E, Wi-Fi 7 and beyond. The new 6GHz Wi-Fi band provides additional channels and a huge amount of additional bandwidth to cater for the high data rate capabilities that are required.
With the launch of Wi-Fi 6E, IEEE 802.11ax and Wi-Fi 7, IEEE 802.11be, the new spectrum at 6GHz is essential to be able to provide the levels of performance required.
Although the 6 GHz band is not available in all countries, the spectrum is being readied for use by Wi-Fi as well as being shared alongside other services. As Wi-Fi is relatively short range and low powered, this is perfectly acceptable and a wise usage of the available spectrum.
The Wi-Fi 6E 6 GHz band has been organised into a variety of different channels with allocated frequencies and various bandwidths to enable the services to utilise these new frequencies as effectively as possible.
The 6 GHz Wi-Fi 6E & Wi-Fi 7 band provides 59 20-MHz channels, 29 40-MHz channels, 14 80-MHz channels, and 7 160-MHz channels. Therefore, in addition to the 2.4GHz and 5GHz, Wi-Fi 6E and beyond have access to a lot of addition channels, including many wide band channels enabling much higher speed operation.
6 GHz Wi-Fi band background
With the latest Wi-Fi standards including Wi-Fi 6E and Wi-Fi 7 with products including routers, laptops, Internet enabled televisions, and other devices requiring high download speeds, it was thought necessary to be able to utilise the spectrum in the most efficient manner and as a result, legacy versions of Wi-Fi would not operate in this band.
The IEEE 802.11ax standards group made the decision to disallow older generation devices from using the 6 GHz band. For new devices to remain compatible with legacy ones considerably slows down operation, it was decided that the use of the 6 GHz frequency allocation would be restricted to the latest devices only.
In many respects this is not a problem, because old devices would need to be upgraded and this would not be a practicable solution. However it also means that when a Wi-Fi 6E or Wi-Fi 7, etc device operates in these bands, they are free of legacy operation - although they can still operate in legacy mode in the 2.4 and 5 GHz bands.
Also a new scanning procedure has been introduced. The 6 GHz Wi-Fi band has 1200 MHz of spectrum and 59 new 20 MHz channels. This means that for scanning the whole band, a devices that has a dwell time of 100 ms per channel - a perfectly reasonable figure - would require almost 6 seconds to complete a passive scan of the entire band.
The standards implement a new and more efficient process for devices to discover nearby access points. A process called fast passive scanning is used to focus on a reduced set of channels called preferred scanning channels, PSCs.
PSCs are a set of 15 20-MHz channels that are spaced every 80 MHz. The APs will set their primary channel to coincide with the PSC so that it can be easily discovered by a device, and these devices will use passive scanning in order to just scan PSCs to look for an access point, i.e. router, etc..
6 GHz Wi-Fi band, channels, channel numbers, frequencies and bandwidths
The new 6 GHz spectrum allocation gives significantly more bandwidth for Wi-Fi 6E, Wi-Fi 7 and beyond. The new Wi-Fi 6E & Wi-Fi 7 channels and bandwidth will enable Wi-Fi 6E and further iterations to offer a much higher level of performance which is in keeping with the ongoing requirements for Wireless LANs for today and the future.
|6 GHz Wi-Fi 6E & Wi-Fi 7 Channel Frequencies, Numbers & Bandwidths
|U-NII Classification||Channel Centre Frequency (MHz)||20 MHz Channel Number||40 MHz Channel Number||80 MHz Channel Number||160 MHz Channel Number|
* The border between U-NII 7 and 8 occurs at a frequency of 6875 MHz which means that half of the bandwidth of the 20 MHz channel number 185 falls within U-NII-7 and half within U-NII-8
FCC U-NII bands
U-NII standard for Unlicensed National Information Infrastructure and these refer to bands used for Wireless Lan, WLAN usage and they are defined by the US Federal Communications Commission, FCC.
There are currently eight ranges: U-NII 1 to 4 are for 5 GHz WLAN usage, and U-NII 5 to 8 are for 6 GHz WLAN. U-NII 2 is subdivided into three subsections.
Interference avoidance with primary users
The 6 GHz band is a shared frequency band, the concept being that Wi-Fi is a low powered user and signals will not travel far and cause interference with the primary users. By sharing radio spectrum in this way, it opens up more valuable space for low power users increasing spectrum usage efficiency and unlocking wide bandwidths to enable high data rates to be attained with Wi-Fi.
As part of this, the FCC defines two types of device classifications. These have with their own transmit power rules. In this way any undue interference with the existing users of the 6 GHz spectrum can be avoided.
Different classes of Wi-Fi Access Points are defined to for the various U-NII bands according to the conditions where the APs will be operating.
Standard Power, SP: Devices using power levels have a significant risk of interfering with the existing 6GHz users which include the fixed satellite service used by many broadcasters and cable providers for various links.
The basic concept is that a 6 GHz wireless access point interrogates a a registered database to confirm its operation will not impact a registered user with a system called Automated Frequency Coordination, AFC.
Low Power Indoor LPI: The low power APs, as the name implies, have reduced power levels since they are only used indoors.
Very Power Power VLP: These devices operate at very low power levels and are very unlikely to cause any interference.
These power classifications are important in terms of the way the access points with different power levels can operate.
The 6 GHz Wireless LAN, WLAN band, is a significant addition to the frequency spectrum available for use for Wi-Fi, bring not only many more channels, but also the possibility of the much wider bandwidths for the very high data rates increasingly being required.
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