Why Wi-Fi Needs 6GHz?

As the most commonly used Internet access technology, Wi-Fi is closely related to each of our lives.

Especially in the past two years, due to the epidemic, more and more social activities have shifted from offline to online, and Wi-Fi has played a huge role in it, significantly reducing the impact of the epidemic on society and the economy.

According to data provided by Cisco Networking (Figure 1), in 2021, 50% of the world's Internet traffic will come from Wi-Fi.

Figure 1 Access technology proportion of global data traffic in 2021 (data from Cisco Networks)

In the past 20 years, Wi-Fi has carried the growing network demand by relying on the only two frequency bands of 2.4GHz and 5GHz (a total of more than 600 MHz of spectrum).

However, even if wireless engineers can use numerous black technologies to expand network capacity, in recent years, the rapid increase in the number of wireless devices and the higher and higher speed requirements brought by applications have eventually led to spectrum becoming the bottleneck of network capacity. 

Currently, the 2.4GHz and 5GHz frequency bands used by Wi-Fi are already very crowded . Reflected in the user experience, the network delay increases, the user rate decreases, and the interference between Wi-Fi routers becomes more and more frequent.

In order to meet this challenge, shortly after the launch of Wi-Fi 6, the Wi-Fi industry actively promoted the development of Wi-Fi 6E .

Wi-Fi 6E follows the core technology of current Wi-Fi 6, by extending the working frequency band of Wi-Fi 6 to 6GHz and expands network capacity. 

As shown in Figure 2, the newly added 1200MHz has doubled the spectrum resources of Wi-Fi compared to the past.

Figure 2 Development history of Wi-Fi frequency bands

The 6GHz spectrum, for Wi-Fi, can make a qualitative leap in performance. From Figure 3, we can see that 6GHz doubles the number of Wi-Fi channels. 

Figure 3 Number of channels for 2.4, 5 and 6GHz Wi-Fi

As for the most commonly used 40MHz channel, 5GHz can provide 4 ordinary channels and 8 DFS channels . (Note: The function of the DFS channel is to protect the frequency used by the radar from interference. When the Wi-Fi device detects that there is a radar using this frequency band, Wi-Fi will automatically avoid the channel)

On 6GHz, however, there are up to 29 DFS-free 40MHz channels for Wi-Fi devices to choose from.

Why do you need so many channels?

Answering this question requires looking at each node of the network as a whole.

From mobile phones and computers to wireless routing and subsequent fiber optic networks, any bottleneck at any node cannot improve the performance of the network. In the past, in the era of 10-megabit to 100-megabit optical fibers, the bottleneck of the network speed was often the optical fiber network itself. Just increasing the rate of Wi-Fi does not make much sense for the overall performance of the network.

Today, with the advancement of the national dual-gigabit infrastructure project, more and more families can use optical networks with a gigabit rate, and the rate of enterprise fiber optic networks can reach 10Gb.

Optical fiber technology is still constantly updated. Optical fiber technology above 50Gbps appeared under the development blueprint of the International Telecommunication Union (ITU) as early as 2018, and it is expected that commercial products will appear soon.

Figure 4 ITU optical fiber technology development blueprint

In the past, Wi-Fi devices mainly used 20MHz and 40MHz bandwidths . Our mobile phones and Pads are usually equipped with two Wi-Fi antennas to support MIMO.

According to the data rate calculation table given by Aruba network in Figure 5, the theoretical maximum rate of Wi-Fi devices using 2-channel MIMO and 64QAM modulation can only reach about 344Mbps under the bandwidth of 40MHz. (Note: Higher-order modulation requires excellent wireless channel signal-to-noise ratio, which is difficult to meet in daily life use).

Figure 5 The theoretical maximum data rate of a single channel under Wi-Fi 6

When users already have gigabit fiber, such Wi-Fi performance becomes a bottleneck in the network. At this point, it makes sense to increase the speed of Wi-Fi.

By increasing the bandwidth to 80MHz, the maximum rate can exceed 700Mbps , and the 160MHz bandwidth can fully meet the needs of Gigabit fiber.

This trend of bandwidth increase can also be verified from the analysis of the user's router usage. According to Cisco and Aruba's analysis of its users, 80MHz bandwidth is gradually becoming the default option when configuring Wi-Fi networks in homes and businesses .

At this point, you may have questions. Didn't the article in the last issue mention that technologies such as OFDMA, high-order modulation and more MIMO can improve the rate and network capacity? Why do you need to increase channel resources?

In fact, the reason is very simple, there is no free lunch in the world.

Although MIMO can provide multiple channels to increase the data rate, the cost is that the additional channels require corresponding transceiver channels, which increases the power consumption of Wi-Fi devices.

Second, the introduction of high-order modulation and more channel MIMO means that the RF receiver has higher requirements for the signal-to-noise ratio of the wireless channel, which reduces the cell coverage and the anti-interference degree of the device.

The fundamental of OFDMA is how to distribute the cake to users more effectively, and cannot make the cake bigger. Therefore, the most direct and effective way to increase capacity is to widen the bandwidth and increase the spectrum resources.

You may still have questions, can't Wi-Fi 6 on 5GHz now also support 80 and 160MHz bandwidth? Why do you need Wi-Fi 6E?

To answer this question, we need to discuss it from the perspective of network multi-router deployment.

The current industry gold standard for dense Wi-Fi network deployments is the 7-channel reuse scheme. This solution is an optimal point for balancing spectrum usage efficiency and inter-cell interference.

The so-called 7-channel reuse scheme means that six adjacent routers around a wireless router use different Wi-Fi channels.

Take the Wi-Fi deployment of the first floor office space in Figure 6 as an example.

Figure 6 7-channel Wi-Fi cell deployment plan

In a network using the 7-channel reuse scheme, Wi-Fi cells with the same frequency can be separated from each other by two cells with different frequencies. Due to the long distance, the risk of co-channel interference between cells is very small.

In the past, based on the use of 40MHz channels, this deployment has no pressure on the spectrum.

However, when users upgrade channels to 80MHz bandwidth, the current 5GHz spectrum is not enough.

This is where Wi-Fi 6E comes in handy.

From the channel diagram above, we can see that 6GHz has as many as 14 channels of 80MHz , which can fully meet the requirements. Even if users upgrade to 160MHz bandwidth in the future, 6GHz can still provide 7 channels to meet network deployment.

The current global development of Wi-Fi 6E

Wi-Fi 6E devices generally support the entire 6GHz range, but in terms of specific usable frequency ranges, device manufacturers need to meet the frequency band requirements of various countries .

The international spectrum allocation for 6GHz Wi-Fi mainly has two directions. Fi use.

The second is a step-by-step approach, first opening the 500MHz of the low 6GHz band (5925-6425MHz) for Wi-Fi use, and continuing to study and wait-and-see attitude in the planning of the high 6GHz (6425-7125MHz).

The regions that hold this strategy are mainly the European Union, Australia, Japan and other countries.

One of the main reasons for this is that an important topic in Agenda 1.2 of WRC-23 has implications for spectrum allocations in these countries and regions.

In this issue, the 6425-7125MHz band may be identified as a mobile communication band in some regions for future 5G or even 6G use. my country is also one of the active supporters of this issue.

Figure 7 The development of global Wi-Fi 6E (data from Wi-Fi Alliance)

Starting in 2021, there have been a large number of terminals and network devices that support Wi-Fi 6E. At present, the entire Wi-Fi 6E ecosystem is developing very well. It is expected that more mainstream devices will support Wi-Fi 6E this year. 

Figure 8 Wi-Fi 6E Ecosystem

Will China approve the use of Wi-Fi 6E?

On the issue of 6GHz, the attitude of our Ministry of Industry and Information Technology before and after WRC-19 has always been to support the allocation of the entire 6GHz to 5G and future 6G mobile communications. Wi-Fi 6E has not received much attention in China.

This has a lot to do with our country's 5G industrial policy and the amount of spectrum available in the current 5G mid-band.

From the data released by Qualcomm below, China's 5G spectrum in the mid-band is only 100MHz on 2.6GHz and 300MHz on 3.5GHz, which also includes 3.3-3.4GHz dedicated to indoor 5G use.

Overall, the total amount of mid-band spectrum is less than the EU, North America, and Japan and South Korea.

Figure 9 Global 5G spectrum allocation (data from Qualcomm)

However, starting last year, the Hong Kong SAR government took the lead in planning the use of Wi-Fi 6E in Hong Kong. In the public call for comments issued by the SAR government last year, the impact of the current congestion on Wi-Fi networks on businesses and individuals was mentioned.

After several months of consultation and discussion, in the final decision document issued by the Hong Kong Communications Authority in April this year, Hong Kong adopted a step-by-step model, that is, to follow the EU, first open the lower 500MHz of 6GHz for Wi-Fi use. For the high 700MHz, Hong Kong will focus on the discussion on agenda item 1.2 of WRC-23.

I have attached the policy document of the Communications Authority in the references, and interested students can study it by themselves.

Figure 10 Hong Kong Communications Authority Wi-F i6E Public Call for Comments

This spectrum policy in Hong Kong gives a glimpse of the dawn of Wi-Fi 6E in mainland China.

From the past C-band and millimeter-wave 5G plans, Hong Kong is basically the same as the mainland, but it is often one step ahead of the mainland in terms of policy release time. If this rule holds true, the MIIT may consider the demand for Wi-Fi in the future for 6GHz spectrum planning .

In fact, the problem of Wi-Fi network congestion is not only in Hong Kong, but also in large and medium-sized cities in the Mainland. In order to improve the performance of enterprise and home networks in the future, relying on 5G alone is far from enough in terms of enterprise cost, equipment ecology and the load capacity of the three major operators.

In addition, even if it cannot be compared with companies such as ZTE, Huawei and China Mobile, which have significant influence in the international mobile communication industry, my country also has large companies such as H3C, Fiberhome, TP-link, and even ZTE in the Wi-Fi industry. And Huawei's own enterprise network division is also an important partner in the Wi-Fi ecosystem.

If 6GHz is fully allocated to mobile communications, it will be nothing more than a major blow to enterprises whose main business is Wi-Fi products and services. In particular, whether Wi-Fi 7 can develop in China in the future will largely depend on whether there are enough spectrum resources.

From the perspective of the development history of technology at home and abroad, the update of technology is often unpredictable. Led by government policy, betting on a certain technology often has the risk of miscalculation.

Industrial policies are usually less effective than market policies for the long-term dynamism of markets and the international competitiveness of products. Allowing enterprises to decide the future direction of technological development through fair market competition will make the allocation of capital more reasonable, the allocation of resources more effective, and the enterprise itself will have stronger vitality.

The future of Wi-Fi

Wi-Fi technology is still being updated.

Shortly after Wi-Fi 6 came out in 2019, the 802.11 working group began research on the next-generation Wi-Fi technology, Wi-Fi 7. The academic name of Wi-Fi 7 is 802.11be, and it uses the exact same spectrum resources as the current Wi-Fi 6E .

At present, the standard work of Wi-Fi 7 is still in full swing, and the first Release has been determined at the beginning of this year. Work on the full standard will not be finalized until after 2024. Certified Wi-Fi 7 devices will not be available on the market until 2025.

Regarding the key technologies of Wi-Fi 7, I will give you a key introduction in the next article.

Figure 11 Time node of Wi-Fi 7