Shulou(Shulou.com)06/03 Report--

For the 802.11ax wireless LAN standard, which is very likely to be standardized in 2019, it may be the beginning of the market warm-up. Many manufacturers have published their own product technology white papers and even product line diagrams, and some manufacturers can't wait to "launch" related products.

However, as wireless network engineers, we should be soberly aware that technology serves the business of users, and the willingness of each generation of new technologies, standards and related products to launch is good. Try to solve a series of problems that users are facing now, unfortunately, the ideal is very plump, showing a very bony feeling. The new era is facing new problems, new technologies and related products may not be able to completely solve the pain points faced by users, or to solve related problems need to involve a complex ecological chain in the industry, which is a mountain that we need to cross in this era.

This article won't go back to the technical details of 802.11ax, which I had a special article on last July. The following is about what 802.11ax can do under what conditions, and his limitations (what can't be done).

Since the 802.11n era, the spectrum on which Wi-Fi works has basically been developed, and unless more spectrum resources are opened up, it will be difficult for the 802.11 protocol to improve too much in the way of making roads wider and wider. Therefore, 802.11ac begins to work on how to increase system performance and capacity, such as multi-user multiple-input multiple-output (MU-MIMO) and more intensive modulation, but generally speaking, 802.11ac 's efforts in this area are not satisfactory. The industry is also aware of this. A series of enhancements to the 802.11 physical layer (PHY) by 802.11ax will help us to use the limited channel space more effectively to achieve higher efficiency.

But the realization of these innovations requires certain conditions, and it is by no means the ultimate solution to all the problems we face. The following is a list of misunderstandings about 802.11ax reflected in some of the frequently asked questions recently.

Misunderstanding that 1:802.11ax can cure all diseases!

Truth: 802.11ax can't solve the problems caused by wrong planning and design.

We used to spend a lot of space on the wireless network, planning and design is the top priority!

Adhering to the correct planning and design is the first step towards successful deployment!

Only under the premise of correct design and planning, good product and system characteristics can be brought into full play!

No matter how good the product and technology can make up for the defects in the design!

The compromise in planning and design and product selection will open the door to failure!

In the actual design and deployment, simple speed improvement is not a panacea, and the upgrading of the 802.11 technical standard itself will not solve the various mistakes we made in the planning, design and deployment stage.

This is because in today's actual deployment environment of wireless local area network, aiming at high-capacity access, the distance between wireless access points is much closer than the previous way for coverage, and the limited spectrum resources will lead to the efficiency of channel multiplexing. The primary task of reasonable planning and design is to reduce media competition and radio frequency interference, that is, efficient channel reuse to minimize empty port sharing between wireless access points. This is the premise, and then it is to increase the efficiency of air port utilization in the coverage cell of a single channel, that is, to establish a higher data connection rate between the client and the wireless access point, which is also the continuous improvement of the 802.11 standard. In the case that the premise cannot be realized, there is no point in simply improving the latter!

If you can upgrade your client to support 802.11ax as soon as possible, the 802.11.ax-based wireless network infrastructure may and may add capacity to your network. I say "maybe" and "maybe" because as an engineer with 12 years of wireless network experience, I have seen that more than 80% of Wi-Fi network designs and deployments have more or less design planning and deployment problems, so that there are no "magic" technologies or products that can help them correct these problems. This is not an exaggeration, a lot of users are blood lessons and real pain.

Misunderstanding 2:802.11ax can solve the problems faced by 2.4GHz spectrum.

Truth: 802.11ax cannot cure the problems facing 2.4GHz spectrum

2.4GHz spectrum is "dead"! Although 802.11ac and 802.11ax wireless access points still support the 2.4GHz spectrum, this does not mean that these protocols can do more in the 2.4GHz spectrum. Apart from a large number of Wi-Fi and non-Wi-Fi devices as well as interference sources, the core problem of the 2.4GHz spectrum is that only three non-overlapping channels are available. Because of the large number of traditional clients, 802.11ax will not help you on 2.4GHz at all.

Of course, from another point of view, if a large number of clients of enterprises use 5GHz spectrum connection, then the dilemma of 2.4GHz spectrum will certainly be alleviated, but this has nothing to do with the 802.11ax protocol itself, and the same effect can be achieved by using 802.11ac.

Misunderstanding 3:802.11ax can easily help you improve the performance or coverage of traditional (11a/b/g/n/ac) clients

Truth: 802.11ax is difficult to effectively improve the performance of traditional clients

Although you don't have to worry about the interoperability between 802.11ax wireless access points and traditional protocol clients, 802.11ax wireless access points are difficult to cost-effectively help you improve the performance or coverage of traditional (11a/b/g/n/ac) clients.

Many people will say that since 802.11ax wireless access points have more antenna and MIMO processing power (8 × 8: 8), does that mean that wireless access points will be more sensitive to signals from wireless clients? The ability to recover client signals will be better? That's true, but chip / network vendors don't do that. Why? Because it goes too far, any commercial wireless access point exceeding 4 × 4: 4 is wasteful, difficult to implement, and costly, and the ultimate effort to achieve additional uplink gain through increased sensitivity has made little improvement in sensitivity and reliability. This is why the second generation of 802.11ac does not commercialize 8 × 8: 8 (also specified in the 802.11ac standard) wireless access point products.

Of course, we do not rule out the possibility that chip / network manufacturers may launch related products, then I believe the cost must also be high, and this part of the cost is bound to be shared with users.

Misunderstanding 4: only talk about the effect, not the prerequisites for realization

Truth: 802.11ax needs wireless network infrastructure and wireless client collaboration to achieve its goals

To put it simply, the meaning of 802.11ax wireless client relative to 802.11ax wireless access point is the same as that of 802.11ac wireless client relative to 802.11ac wireless access point. Without the support of established clients, it is very difficult for wireless network infrastructure to display its talents.

For example, if you use 802.11n clients to connect to 802.11ac wireless access points, or first-generation 802.11ac wireless clients to connect to second-generation 802.11ac wireless access points, the access point must be downgraded to be compatible with these wireless clients, and the performance improvement you get is negligible.

In real-world deployments, it is difficult to ensure that the wireless access point works in an ideal pure mode because of the lifecycle of the wireless client. Even today, with the explosive growth of wireless network terminals, although the clients of the second generation of 802.11ac standards are still emerging, we have only achieved the popularity of the first generation of 802.11ac wireless clients.

Here are two categories of 802.11ax 's many technical highlights, which are also the key to improving the performance of the wireless network. The red font means that it can only be achieved with the cooperation of the client.

1. Physical layer enhancement and efficiency, including:

Uplink and downlink orthogonal frequency division multiple access (OFDMA)-requires client cooperation

Uplink and downlink multi-user-multiple input multiple output (MU-MIMO)-downstream MU-MIMO requires the cooperation of the second generation 802.11ac client, and uplink MU-MIMO requires the cooperation of 802.11ax wireless client.

Uplink resource scheduling-requires client cooperation

Up to 8 transmit antennas and 8 receive antennas, 8 spatial streams

Higher modulation, 1024QAM-requires client cooperation

2. MAC layer enhancement and efficiency, including:

Basic service set coloring (BSS Coloring)-requires client cooperation

Dual NAV mechanism-requires client cooperation

Target wake-up time (Target Wakeup Time-TWT)-requires client cooperation

As you can see, without the cooperation of the client, the effect of the 802.11ac wireless client connecting to the 802.11ax wireless access point is roughly the same as connecting the 802.11ac wireless access point. Even in the mixed environment of 802.11ax and 802.11ac wireless clients, the final system energy efficiency is determined by the number of 802.11ax wireless clients.

Misconception that 5:802.11ax is a switched wireless network

Truth: 802.11ax does not achieve Wi-Fi switching capacity

Wi-Fi (802.11) still relies on shared media, or half-duplex air media, to transmit electromagnetic waves. The way to occupy the media is still carrier sense multiple access / collision avoidance (CSMA/CA). We used to use Ethernet hubs to make analogies.

The MU-MIMO mechanism introduced by 802.11ac (802.11ac is downlink [DL], 802.11ax also introduces uplink [UL]) does not achieve "switching" capability based on shared air media. Only when the wireless endpoint wins the opportunity to occupy the media, it can send to multiple clients in the downlink at the same time, or enable multiple clients to use the uplink to send at the same time. This access mechanism is more efficient than sending one after another. However, the MU-MIMO of 802.11ax uplink requires that the client must be a 802.11ax client, and the traditional client cannot participate.

Misunderstanding that 6:802.11ax will achieve all innovations at once

Truth: 802.11ax won't innovate all at once

Just as the 802.11ac agreement is launched in two waves, 802.11ax will enter the market in the same way. The first generation of 802.11ax chipsets will not have the following features:

MCS 10 and 11 (1024QAM) modulation mode

8 spatial flow

BSS coloring mechanism

Uplink multi-user-multi-input and multi-output

Misunderstanding that the era of 7:802.11ax has come, buy related products now

Truth: enterprise-level 802.11ax products are not yet mature

802.11ax draft 1.0 and 2.0 were not approved by a vote, and draft 3.0 is currently under discussion, and formal standardization is expected to be completed in the second half of 2019, of course, commercial products are expected to be based on the launch of draft 2.0 or 3.0, and the final standard is expected to be supported through software upgrades.

Many advanced features of 802.11ax wireless network can only be realized with the participation of 802.11ax clients, and there are no signs of the popularity of 802.11ax clients in a short period of 2-3 years.

The "so-called" 802.11ax wireless access point products launched by some manufacturers on the market are actually based on the early draft version of the chip, but cannot be upgraded to even the draft version through the software.

To sum up, looking at an innovation requires an omni-directional perspective, and any blindly following the trend is not desirable.

It is a rational way to choose the final technology according to your actual application scenario.

The code word is not easy, I hope it will be helpful to you!

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