What not to expect from 802.11ax?
Not yet approved 802.11ax (“Next generation Wi-Fi”) is already quite popular for poor marketing to fog your mind to potential customers. The specification is scheduled for approval only in December 2018, but you can already buy points!
It's time to write arevealing clarifying post. While I was going with my thoughts, another authoritative comrade, Devin Akin ( if you are professionally engaged in WLAN, you should follow him ) did it for me, and all I had to do was tell his excellent article and add a couple of comments. Remember, this is not a translation - but a retelling!
In terms of the development of Wi-Fi, the last significant event was the release of 802.11n:
The subsequent 802.11ac didn’t really bring anything new, and in many ways was just redundant: Wi-Fi: new speeds required wide channels, special RF conditions and the absence of “old” 802.11a / n devices. In general, as was the Wi-Fi hub - and remained. A hub with a bunch of clients cannot be fast in principle. Now, if we move from the hubs to switches ...
')
The first attempt was with the introduction of the MU-MIMO mechanism in 802.11ac Wave2 based on the spatial separation of flows. If this sounds dull to you, you are absolutely right: the mechanism of work turned out to be too complicated, and the exhaust — too insignificant. But PR was more than, and all this resulted in a complete disappointment.
The task of 802.11ax was to increase not the speed, but the capacity of the network and so that this time not to disgrace. With the help of the “adult” OFDMA technology ( coming from LTE / WiMax ), the channel could be “chopped” into subchannels and many more clients could be launched there, as it happens in the “adult” cellular communication. Simply, before the GSM base station was difficult to shove in a box the size of an access point, and now - quite real :)
Wifi is still half duplex. The miracle did not happen, and it is unlikely to happen. The old restrictions still apply. Welcome to the year 1990 again.
802.11ax supports 2.4 ( 802.11ac, for example, did not support ). But there is no sense to it. I repeat: zero sense. Considering the huge number of old b / g / n clients, interference and a large ( compared to 5 GHz ) range - you will never get out of the compatibility mode. If you speak English - see my performance here .
Your happiness, if you don’t know what it is. However, this is part of the standard ( optional, almost unrealized ), in which the access point could command customers, when and how to speak ( instead of the current market with CSMA / CA and DCF ) . But, 802.11ax does not use PCF, but EDCA ( since the time of 802.11a / g ).
When the turn of the point arrives, it can transmit to 9 clients at once (20 MHz channel) or request data transmission from the same 9 clients simultaneously. This is the very OFDMA in action and it's awesome!
Noooo ... These 9 (or less) clients should be able to use 802.11ax. All the rest remain overboard. So, if you have enough old clients, you almost never get out of compatibility mode. In order for 802.11ax to have at least some benefit, you need to change everything to 802.11ax and everything at once .
As well as 802.11n and 11ac, the new standard will come out "waves." First generation
However, there will be a lot of new things both to speed up and compact data transmission:
However, given the OFDMA leapfrog, it is now even harder to understand how fast the client is working, because the speed is now generally floating ( in principle, it started with 802.11ac, where some parameters changed with each packet ). The total number of data rates (MSC) in 802.11ax exceeded 2500 !
It is not clear why, but this question is often asked. Not needed.
Points 11ax can do nothing to help customers 11a / b / g / n / ac. They will not be more sensitive (nowhere else), they are unlikely to have more antennas to “restore” the signal with the help of MRC . Quallcom Atheros (QCA), of course, promises 8x8: 8 chipsets, but they are promised with 802.11ac. In reality, the exhaust from everything above 4x4: 4 is irrelevant, although marketers, of course, will still convince us otherwise.
As mentioned before, the 802.11ac MU-MIMO based on Beamforming was stillborn, useless and frustrating. Do not believe? See here .
OFDMA-based MU-MIMO is a completely different technology. As well as an airplane and a submarine are both types of transport.
Do not. For this, there is 802.11ah (HaLow). True, there are already articles on the subject of “ HaLow in the span - waiting for 802.11ax ” and there will be more for sure. And for sure the corresponding products will be released. Do not. 2.4 already lost .
"Well, yes," you say. But in reality, each new generation of Wi-Fi is accompanied by such a level of frantic marketing, as if we are sold a solution to a problem with cancer, world hunger, an energy crisis, and so on. If the network is completely ( and correctly! ) Rebuilt under 802.11ax - the effect will be. In all other cases ( 95% + ) - will be as always.
Even with the release of 802.11ac, it became clear that for large networks there would be more benefit from channels at 5 MHz than from channels at 160Mz - the narrower the channels, the less clients interfere with each other.
That is why all serious networks are even now being built on 20 MHz channels, even on 802.11ac Wave2. This is precisely what is interesting for 802.11ax, which promises “how-to” to cut channels into pieces up to 2 MHz ( but only for 802.11ax clients ). In conclusion, an illustration from the article with real data from Aruba Networks for 802.11ac on 20/40/80 MHz channels.
Here you can see (English) technical details of the implementation: habrahabr.ru/post/350738
It's time to write a
Background:
In terms of the development of Wi-Fi, the last significant event was the release of 802.11n:
- standardization was carried out (with a / b / g and a heap of functional additions such as 802.11e / i)
- MIMO implementation has greatly changed the approach to radio planning
- Radically new levels of speed were achieved, which led to a revision of the principles of WLAN construction - the role of controllers and points changed, the architecture changed.
The subsequent 802.11ac didn’t really bring anything new, and in many ways was just redundant: Wi-Fi: new speeds required wide channels, special RF conditions and the absence of “old” 802.11a / n devices. In general, as was the Wi-Fi hub - and remained. A hub with a bunch of clients cannot be fast in principle. Now, if we move from the hubs to switches ...
')
The first attempt was with the introduction of the MU-MIMO mechanism in 802.11ac Wave2 based on the spatial separation of flows. If this sounds dull to you, you are absolutely right: the mechanism of work turned out to be too complicated, and the exhaust — too insignificant. But PR was more than, and all this resulted in a complete disappointment.
The task of 802.11ax was to increase not the speed, but the capacity of the network and so that this time not to disgrace. With the help of the “adult” OFDMA technology ( coming from LTE / WiMax ), the channel could be “chopped” into subchannels and many more clients could be launched there, as it happens in the “adult” cellular communication. Simply, before the GSM base station was difficult to shove in a box the size of an access point, and now - quite real :)
Well, now to the article (retelling)
802.11ax - not a switch
Wifi is still half duplex. The miracle did not happen, and it is unlikely to happen. The old restrictions still apply. Welcome to the year 1990 again.
802.11ax won't solve 2.4GHz problems
802.11ax supports 2.4 ( 802.11ac, for example, did not support ). But there is no sense to it. I repeat: zero sense. Considering the huge number of old b / g / n clients, interference and a large ( compared to 5 GHz ) range - you will never get out of the compatibility mode. If you speak English - see my performance here .
802.11ax - not PCF (Point Coordination Function)
Your happiness, if you don’t know what it is. However, this is part of the standard ( optional, almost unrealized ), in which the access point could command customers, when and how to speak ( instead of the current market with CSMA / CA and DCF ) . But, 802.11ax does not use PCF, but EDCA ( since the time of 802.11a / g ).
When the turn of the point arrives, it can transmit to 9 clients at once (20 MHz channel) or request data transmission from the same 9 clients simultaneously. This is the very OFDMA in action and it's awesome!
Noooo ... These 9 (or less) clients should be able to use 802.11ax. All the rest remain overboard. So, if you have enough old clients, you almost never get out of compatibility mode. In order for 802.11ax to have at least some benefit, you need to change everything to 802.11ax and everything at once .
802.11ax - not all at once
As well as 802.11n and 11ac, the new standard will come out "waves." First generation
However, there will be a lot of new things both to speed up and compact data transmission:
- Acceleration: Even more dense modulation 1024QAM, more subcarriers (256 to 20 MHz), speed MCS10, MCS11, changing the duration of characters and indents during transmission.
- Compaction: grouping subcarriers in Resource Units (RUs) on 26/52/106/242 pieces, equivalent to 2/4/8/20 MHz channels, OFDMA up and down
- Other: new frame formats, Low Density Parity Checking (LDPC), Target Wake Time (TWT) to improve the energy efficiency of mobile customers.
However, given the OFDMA leapfrog, it is now even harder to understand how fast the client is working, because the speed is now generally floating ( in principle, it started with 802.11ac, where some parameters changed with each packet ). The total number of data rates (MSC) in 802.11ax exceeded 2500 !
802.11ax does not need new antennas
It is not clear why, but this question is often asked. Not needed.
802.11ax will not improve performance of old clients.
Points 11ax can do nothing to help customers 11a / b / g / n / ac. They will not be more sensitive (nowhere else), they are unlikely to have more antennas to “restore” the signal with the help of MRC . Quallcom Atheros (QCA), of course, promises 8x8: 8 chipsets, but they are promised with 802.11ac. In reality, the exhaust from everything above 4x4: 4 is irrelevant, although marketers, of course, will still convince us otherwise.
802.11ax will not fix MU-MIMO (from 802.11ac)
As mentioned before, the 802.11ac MU-MIMO based on Beamforming was stillborn, useless and frustrating. Do not believe? See here .
OFDMA-based MU-MIMO is a completely different technology. As well as an airplane and a submarine are both types of transport.
802.11ax is not oh so good for IoT
Do not. For this, there is 802.11ah (HaLow). True, there are already articles on the subject of “ HaLow in the span - waiting for 802.11ax ” and there will be more for sure. And for sure the corresponding products will be released. Do not. 2.4 already lost .
802.11ax - not a panacea
"Well, yes," you say. But in reality, each new generation of Wi-Fi is accompanied by such a level of frantic marketing, as if we are sold a solution to a problem with cancer, world hunger, an energy crisis, and so on. If the network is completely ( and correctly! ) Rebuilt under 802.11ax - the effect will be. In all other cases ( 95% + ) - will be as always.
Total
Even with the release of 802.11ac, it became clear that for large networks there would be more benefit from channels at 5 MHz than from channels at 160Mz - the narrower the channels, the less clients interfere with each other.
That is why all serious networks are even now being built on 20 MHz channels, even on 802.11ac Wave2. This is precisely what is interesting for 802.11ax, which promises “how-to” to cut channels into pieces up to 2 MHz ( but only for 802.11ax clients ). In conclusion, an illustration from the article with real data from Aruba Networks for 802.11ac on 20/40/80 MHz channels.
Update
Here you can see (English) technical details of the implementation: habrahabr.ru/post/350738
Source: https://habr.com/ru/post/348472/
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