What’s so special about Wi-Fi 6?

Latest update time：2021-08-31 08:39

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▋ What is Wi-Fi 6?

Wi-Fi 6 is the alias given by the Wi-Fi Alliance to IEEE Std. P802.11ax .

As we all know, our Wi-Fi used to be called 802.11a/b/n/g/ac/ax. This naming method is really confusing and it is difficult to tell the order. Therefore, starting from 802.11ax, it is named in a numerical way.

The TGax working group of the IEEE Standards Association is currently responsible for the formulation of the Wi-Fi 6 standard . The current version is Draft 4.20 (D1 and D2 were submitted separately but failed to pass the vote, and D3 passed the group vote and was re-written again).

As of now, the 802.11ax standard has not been formally submitted, but the general framework has been established and is in the sponsor voting stage.

Wi-Fi 6 Standard Development Timeline

The TGax project team is expected to submit a formal version in January 2020 for verification by the 802.11 team.

The Wi-Fi Alliance is a non-profit industry organization, but it owns the Wi-Fi trademark and is primarily responsible for Wi-Fi certification and authorization. It also participates in the formulation of the 802.11 series of standards. Devices that have passed the Wi-Fi 6 product certification can have a Wi-Fi 6 certification label added to the device, which looks something like this:

Please pay attention to the relationship between the Wi-Fi 6 trademark and the 802.11ax standard. In fact, because the member companies of the IEEE TGax working group and the Wi-Fi Alliance are largely consistent, it is not wrong to say that passing the Wi-Fi 6 certification is equivalent to supporting 802.11ax.

▋ What improvements does Wi-Fi 6 have?

In fact, compared with the communication standards in recent years (5G/Wi-Fi 6), it can be felt that the focus of the communication industry in the next few years will always be on the Internet of Things . This generation of new access standards also mainly considers dense terminals, low power consumption and large bandwidth access .

There are several specific methods:

OFDM → OFDMA
Supports Target Wake Time (TWT) to reduce power consumption and improve battery life
Improve throughput with 1024-QAM and support up to 8x8 MIMO
Supports spatial reuse and coloring

Well... let me just say that most of these improvements are already available in LTE systems (1024QAM is available in 5G).

Let’s look at each of these improvements:

1. OFDM → OFDMA

It continues the MU-MIMO brought by 802.11ax and changes the original OFDM to OFDMA. The added A here means that it can be used for multiple access and allocate carriers to different users to increase the system user connection capacity.

ax/ac/n comparison

In previous Wi-Fi protocols, such as 802.11ac, multiple wireless access users are supported by spatial separation (MU-MIMO) or time separation (round-robin transmission/EDCA), while OFDMA means adding another multi-user resource allocation method - frequency division .

Comparison of OFDM and OFDMA multi-user resources, image from cisco

In this way, the original smallest resource unit in Wi-Fi, which was just a time frame, has now become a time/frequency resource block similar to LTE, which can support more fine-grained wireless resource allocation, such as allocating different resource blocks to different users.

Image from https://zhuanlan.zhihu.com/p/24416610

2. Target wake-up time TWT

Wi-Fi 6 continues the TWT (Target Wake Time) function in 802.11ah, which is a device resource scheduling method.

It allows devices and access nodes to negotiate when to wake up after entering sleep mode, instead of the previous timed access to the network. Access points that support Wi-Fi 6 can group client devices into different TWT cycles, thereby waking up in groups at a fixed time. This also helps reduce the number of devices competing for the channel.

TWT Features

3. 1024QAM

OFDM waveforms usually use QAM (quadrature amplitude modulation) as the modulation method.

QAM schematic diagram image from cisco

As the name implies, 1024-QAM allows a single symbol to transmit 10 bits (1024=2 to the 10th power) of data, which is a very effective way to increase the speed of wireless systems. It is also because of 1024-QAM that a single antenna can achieve gigabit-level data transmission.

At the same time, WiFi 6 can support 8x8 MIMO. Of course, current mobile phones do not support such a high number of MIMO layers because the antennas cannot be placed.

So the current maximum theoretical speed of Wi-Fi 6 is approximately:

2.4Gbps (4x4 MIMO@80MHz)

4.8Gbps (8x8 MIMO@80MHz)

4.8Gbps (4x4 MIMO@160MHz)

9.6Gbps (8x8 MIMO@160MHz)

The 80/160MHz above refers to the single carrier bandwidth.

From the perspective of increasing single-carrier bandwidth and modulation order, the speed of Wi-Fi 6 will undoubtedly increase, even if the mobile phone does not support 8x8 MIMO...

But the question is, is your home broadband that fast?

4. Spatial Reuse and Coloring

This is also a variation of the inter-cell interference coordination technology that has been used in LTE systems for a long time.

In the past, Wi-Fi, as a wireless local area network, did not consider too many networking and co-frequency interference issues between different access nodes. If you need to deploy such a network, you can find more professional networking personnel. However, as Wi-Fi applications become more and more widespread, coverage of medium and large-scale scenarios (such as corporate buildings) is becoming a widespread problem. (Of course, it may also be because everyone's houses are getting bigger and bigger)

In such medium and large scenarios, it is common that, for example, a mobile phone receives signals from two different wireless access points at the same time, but they are in the same wireless local area network (same BSS/SSID).

To address this situation, Wi-Fi 6 provides a BSS coloring mechanism. If the signal received by the mobile phone comes from the same wireless local area network in the same frequency band (for example, from two repeaters), the mobile phone will promptly identify the interference signal and raise the identification threshold, and stop receiving in time to avoid interference.

▋ Relationship between Wi-Fi 6 and 5G

In fact, the main difference lies in the different application scenarios. It is precisely because of the different application scenarios that although 5G and Wi-Fi 6 use very similar wireless communication technologies, the user experience is actually different. The current various 5G to Wi-Fi solutions are also because the current operator network cannot well solve the privacy issues required by users in wireless LANs. SIM cards are not a problem, because IoT devices are now using eSIM cards, which support air reading and writing and do not need to be replaced manually.

For more details, see this answer:

https://www.zhihu.com/question/307558418/answer/568526548

To prevent confusion, I need to emphasize this paragraph in the news description.

According to foreign media reports, there is a competition between 5G technology and Wi-Fi in the world regarding the communication technology between connected vehicles and cars. Companies such as Volkswagen Group, Renault Group, Toyota Motor, General Motors, and NXP support the use of Wi-Fi technology, while companies such as BMW, Daimler, Ford, Nissan, Peugeot Citroen, Bosch, Deutsche Telekom, Intel, Qualcomm, and Samsung support the use of 5G technology.

The 802.11p protocol that competes with the operators' C-V2X communication is a dedicated short-range communication (DSRC) protocol developed for the Internet of Vehicles, which is different from the 802.11 a/g/n/ac/ax series used for wireless LAN. Whether car companies support DSRC or 5G is a matter of interest and has nothing to do with the technical application scenario, nor does it have anything to do with the survival of Wi-Fi.

As long as there is a requirement for private data transmission in wireless LANs, Wi-Fi will be difficult to disappear.