IEEE 802.11ax 6-GHz Band (Wi-Fi 6E) Advantages & Considerations
Launch of 6-GHz Band
2020 marked a revolution in WLAN history. On April 23, the U.S. FCC decided to permit unlicensed use of the 6-GHz band (5925 to 7125 MHz), and other regions and countries are expected to follow soon. New applications and services are expected to be developed using high-speed and large-capacity data communications based on the extremely wide frequency band of 1200 MHz. WLAN was the first unlicensed wireless communications technology to support the 6-GHz band.
Spread and History of WLAN Technology
WLAN is a cable-less technology for data communications typically using Ethernet over a local area. It was first adopted by battery-operated devices, such as laptop PCs, but spread rapidly with the appearance and growth of smartphone usage.
When the first IEEE 802.11 standard regulating WLAN technology was released in 1997, it supported only the 2.4-GHz band with maximum transmission speeds of 2 Mbps. Use of the 5-GHz band started with the 1999 release of the IEEE 802.11b standard (for 2.4-GHz band and max. transmission speed of 11 Mbps) as well as the 802.11a standard (for 5-GHz band and max. transmission speed of 54 Mbps).
Although there was some subsequent expansion in the 5-GHz band, there was no dramatic change in usable frequencies. However, this addition of a new frequency-band allocation in about 20 years is attracting great attention.
Challenges of WLAN Usage in 2.4/5 GHz Bands
At the first appearance of WLAN, the number of supported devices was small and since the data traffic was also small, there were no major issues with frequency restrictions. However, with the explosive growth and evolution of smartphone usage as well as the growth of new video-streaming distribution services, there has also been a major change in the increased demand for WLAN communications.
To meet this continually growing demand, WLAN technology evolved to incorporate wider channel bandwidths, high-order modulation, and spatial multiplexing. However, because the frequency width available to rapidly growing WLAN communications hardly changed at all over 20 years, the WLAN allocated frequencies became congested, making it difficult to achieve stable high-speed data communications, until now.
Furthermore, these difficulties have been exaggerated by new communications demand resulting from changing work styles, such as teleworking and online study, caused by the COVID-19 pandemic. Some of the problems with the 2.4/5 GHz band are explained below.
Fixed frequency range cannot meet demand
Total 580 MHz Width max.*
- 2.4-GHz band: 80 MHz
- 5-GHz band: 500 MHz*
*The 5-GHz band can only be used up to a width of about 180 MHz, depending on radar usage conditions.
Frequency sharing with other systems
Since the 2.4-GHz band permits unlicensed use by microwave ovens and many kinds of wireless equipment, such as Bluetooth, ZigBee and other low-power communication devices, simultaneous use over short-distance ranges can cause problems with communications interference. More recently, serious congestion is occurring due to the rapid increase in not only WLAN devices but also in Bluetooth (e.g., True Wireless Stereo and smart speakers).
The 5-GHz band gives priority to weather and shipping radar for 320 MHz of the 500 MHz bandwidth and WLAN is licensed for use only under the condition that it does not impact these other services. Devices without the Dynamic Frequency Selection (DFS) function for automatically switching the WLAN frequency when a radar wave is detected can only use communications up to a width of about 180 MHz, consequently there are some devices only supporting frequencies not requiring DFS.
Low utility of 160-MHz channel bandwidth
To implement high-speed data communications using a wide 5-GHz band, IEEE 802.11ac/ax specifies use of channel bandwidths up to 160 MHz. However, when excluding the frequency range with radar priority, even one channel cannot be secured. Even at the locations where there are normally no radar waves, since only two channels can be secured using 160 MHz, fewer client devices can be connected. Since there may be clients that cannot communicate, generally operation is supported by limiting the channel bandwidth to within 40 MHz and increasing the number of channels. In anticipation of this issue, there are many devices that do not support channel bandwidths of more than 80 MHz.
Low network capacity due to interoperability with old standards
When there is a client device supporting an old standard in a cell, unless there are some restrictions, the access point (AP) will operate on the old standard to maintain connectivity. At this time, client devices supporting the latest standards will experience a drop in communications capacity because they can only communicate using the old standard within that cell.
Implementation of spatial multiplexing technology
To increase transmission speeds, the WLAN standards support up to 8 streams. Accommodating multiple built-in antennas requires that the separation between antennas must be at least a certain distance. Power consumption also increases according to the number of streams.
Due to the size of mobile devices, such as smartphones, the number of built-in antennas and battery capacity are limited, so there are many devices supporting only one stream, and two streams at most.
Advantages of WLAN 6-GHz Band
The opening of the 6-GHz band as an unlicensed band solved many of the problems of the 2.4/5 GHz bands.
- Wide frequency band of up to 1.2 GHz solves congestion
- Operation using 160 MHz channels finally practical
- Supports high-speed, high-efficiency networks configured only of devices supporting IEEE 802.11ax
- Supports secure networks protected by latest WPA3 technology
Challenges of using 6-GHz Band
As explained above, the 6-GHz band has many notable advantages. However, this band is not freely usable as a WLAN resource because priority is given to use of the licensing system used so far. Some issues with using the 6 GHz band are listed below.
Rules to protect existing systems
Licensed systems in the 6-GHz band are used for communication services that require high reliability. Therefore, in order not to interfere with them, WLAN devices have AFC (Automated Frequency Coordination) functions to limit Tx power and suppress interference. Since the permitted frequency, Tx power, and power density differ according to the device role (AP/base station) and location (indoors/outdoors), development of 6-GHz band WLAN products requires adequate evaluation of whether the product can meet the rules according to the product classification.
Predominant Licensed Services
*Automated Frequency Coordination
When operating an outdoor WLAN AP, information about frequencies that do not interfere with licensed systems at that location is captured from the AFC system.
Immature RF components
The 6-GHz band has been used previously by wireless communications, but only specific businesses were licensed and the number of wireless products was limited. The majority do not communicate while moving, but due to usage for communication between two fixed points, the wireless equipment is large and used with a stabilized power supply. Additionally, one communications device in the pair uses part of the frequencies but not the entire 1200 MHz band.
Since smartphones are very different in terms of size, mass, power supply, and other characteristics,, parts used by the limited 6-GHz area cannot be diverted. Despite the need for size reduction, weight reduction, and power saving, the licensing system must implement equal, consistent communications performance across an entire 1200 MHz, which has never been done previously. Additionally, this performance must be offered to consumers at an acceptable, reasonable price.
The process of solving this issue has just started, and many developers may face previously unknown challenges.
Solutions for New Applications at 6-GHz Band WLAN Product Development
As seen so far, the 6-GHz band freed for unlicensed use by the U.S. FCC is now starting to be utilized, and many challenges may be solved as WLAN communications continue to increase. However, development of 6-GHz band WLAN products will require consideration of the following:
New strategy for developing 6-GHz band WLAN products
- Incorporating functions for coexistence with licensed systems
- Supporting large-scale mass-production of 6-GHz consumer products
- Implementing homogenous high RF performance across 1200 MHz width
- Support 160 MHz channel bandwidth
Anritsu’s Wireless Connectivity Test Set MT8862A is a measuring instrument targeted at development of WLAN devices. It offers stable and reliable testing solutions to product engineers developing the 6 GHz band products. With its functionality for measuring RF TRx characteristics, the MT8862A supports the 6-GHz band.
Please contact us to discuss your 6 GHz band support and testing needs.