The working group started working on the standard back in 2014 and is currently working on draft3.0. Which is somewhat different from previous generations of 802.11 standards, because there all the work fit into two drafts. This happens due to a fairly large number of planned complex changes, which, accordingly, require more detailed and complex compatibility testing. The team's initial goal was to improve spectrum efficiency in order to increase the throughput of WLANs with a high density of subscriber stations and access points. The main drivers for the development of the standard were: an increase in the number of mobile subscribers, live broadcasts in social networks (emphasis on upload traffic) and, of course, IoT.
Schematically, the innovations look like this:
MIMO 8x8, more spatial streams
There will be support for MIMO 8x8, up to 8SS (Spatial Streams). The 802.11ac standard also described support for 8 SS in theory, but in practice, 802.11ac “wave 2” access points were limited to supporting 4 spatial streams. Accordingly, access points with support for MIMO 8x8 will be able to simultaneously serve up to 8 1x1 clients, four 2x2 clients, etc.
MU-MIMO DL/UL (Multi-User MIMO Downlink/Uplink)
Simultaneous multiuser support for both download and upload channels. The possibility of simultaneous competitive access to the upload channel, grouping both the date and the control frames will significantly reduce the "overhead", which will lead to an increase in throughput and a decrease in response time.
Long OFDM symbol
OFDM has been operating in 802.11a/g/n/ac standards for ~20 years without any changes. According to the standard, a channel with a width of 20MGz contains 64 subcarriers spaced from each other with an interval of 312,5 kHz (20MHz/64). Since the semiconductor industry has advanced so much during this time, 802.11x offers a 4-fold increase in subcarriers to 256, with an interval between subcarriers of 78,125 kHz. The OFDM symbol length (time) is inversely proportional to the frequency, and accordingly it will also increase by 4 times from 3,2 μs to 12,8 μs. This improvement will increase the efficiency and reliability of data transmission, especially in “outdoor” WLAN.
Extended Range
Added new values for protection intervals between frames, which can now be equal to 1,6 µs and 3,2 µs for "outdoor" WLAN, for "indoor" the interval is left 0,8 µs. New packet format with more robust (longer) preamble. All of the above will allow you to get up to a 4-fold increase in connection speed at the network edge.
OFDMA DL/UL (Orthogonal Frequency Division Multiple Access)
One of the major changes is the introduction of OFDMA instead of OFDM. OFDMA technology is used in LTE networks and has proven to be highly efficient. The difference is that when transmitting in OFDM, the entire frequency channel is occupied, and until the transmission is completed, the next client cannot occupy the frequency resource. In OFDMA, this problem is solved by dividing the channel into subchannels of various widths, the so-called RU (Resource Units). In practice, this would mean that the 256 subcarriers of a 20MHz channel could be split into RUs of 26 subcarriers. Each RU can be assigned its own MCS coding scheme as well as transmission power.
In general, this will bring a significant increase in network capacity in general, as well as throughput for each individual client.
1024 QAMs
Added new MCS (Modulation and Coding Sets) 10 and 11 for 1024-QAM modulation. That is, now one character in this scheme will carry 10 bits of information, and this is a 25% increase compared to 8bit in 256-QAM.
TWT (Target Wake Time) - "Up Link resource scheduling"
A power saving mechanism that has proven itself in the 802.11ah standard and is now adapted to 802.11ax. TWT allows access points to tell clients when to enter power save mode and provides a schedule for when to wake up to receive or transmit information. These are very short periods of time, but being able to sleep for a bunch of short periods will go a long way in battery life. Reducing "contention" and collisions between clients will increase the time spent in power saving mode. Depending on the type of traffic, power consumption improvements can range from 65% to 95% (according to Broadcom tests). For IoT devices, TWT support is critical.
BSS Color - Spatial Reuse
In order to increase the network capacity of high-density WLANs, it is necessary to increase the channel resource reuse frequency. In order to reduce the influence of neighboring BSSs operating on the same channel, it is proposed to mark them with "color-bit". This will allow dynamic adjustment of the CCA (clear channel assessment) sensitivity and transmitter power. The capacity of the network will increase due to the compression of the channel plan, while the existing interference will have less influence on the choice of MCS.
Due to the upcoming update of security standards to , not everyone will be able to solve security issues with a simple software update, so Extreme Networks will introduce access points with hardware support for 2018ax and WPA802.11 already in the fourth quarter of 3.
More about .
Source: habr.com