Source: Fresh Date Classroom
Original Author: Tang Xin
Wi-Fi, as the most commonly used internet access technology, is closely related to each of our lives.
Especially in the past two years, due to the pandemic, more and more social activities have shifted from offline to online, and Wi-Fi has played a huge role in significantly reducing the impact of the pandemic on society and the economy.
According to data provided by Cisco (as shown in Figure 1), in 2021, 50% of global internet traffic came from Wi-Fi.
Figure 1 Proportion of Access Technologies for Global Data Traffic in 2021 (Data Source: Cisco)
In the past 20 years, Wi-Fi has relied on only two frequency bands, 2.4GHz and 5GHz (over 600MHz of spectrum), to carry the ever-growing network demand.
In the previous article, we discussed some new technologies in Wi-Fi 6. These technologies can help alleviate the problem of network congestion.
However, even if wireless engineers can use numerous advanced technologies to expand network capacity, in recent years, the rapid growth of wireless devices and the increasing speed requirements brought by applications have ultimately led to spectrum becoming the bottleneck for network capacity.
Currently, the 2.4GHz and 5GHz frequency bands used by Wi-Fi are already very crowded. This is reflected in user experience as increased network latency, decreased user speeds, and more frequent interference between Wi-Fi routers.
To address 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 extends the working frequency band of Wi-Fi 6 to 6GHz (5925-7125MHz) to expand network capacity.
As shown in Figure 2, the additional 1200MHz doubles the spectrum resources available for Wi-Fi compared to the past.
Figure 2 Development History of Wi-Fi Frequency Bands
The 6GHz spectrum can bring a qualitative leap in performance for Wi-Fi. 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
For the currently most commonly used 40MHz channel, 5GHz can provide 4 regular channels and 8 DFS channels.(Note: The role of DFS channels is to protect the frequencies used by radar from interference. When Wi-Fi devices detect that radar is using this frequency band, they will automatically avoid this channel.)
In 6GHz, there are up to 29 40MHz channels available for Wi-Fi devices to choose from without DFS restrictions.
█ Why Are So Many Channels Needed?
Answering this question requires viewing all nodes of the network as a whole.
From mobile phones and computers to wireless routers and subsequent fiber networks, any bottleneck at one node will prevent network performance from improving. In the past, during the era of 10Mbps to 100Mbps fiber, the bottleneck of network speed often lay in the fiber network itself. Simply increasing Wi-Fi speed does not significantly impact overall network performance.
Now, with the advancement of the national dual-gigabit infrastructure project, more and more households can access gigabit-speed fiber networks, and enterprise fiber networks can even reach 10Gb.
Fiber technology is continuously being updated, with fiber technologies above 50Gbps appearing in the ITU’s development roadmap as early as 2018, and commercial products are expected to emerge soon.
Figure 4 ITU Fiber Technology Development Roadmap
In the past, Wi-Fi devices primarily used bandwidths of 20MHz and 40MHz. Our mobile phones and tablets typically come with two Wi-Fi antennas to support MIMO.
As shown in the data rate calculation table provided by Aruba Networks in Figure 5, a Wi-Fi device using 2x MIMO and 64QAM modulation can theoretically achieve a maximum speed of only about 344Mbps at a 40MHz bandwidth.(Note: Higher-order modulation requires excellent signal-to-noise ratios in wireless channels, which is difficult to meet in daily use.)
Figure 5 Theoretical Maximum Data Rate of a Single Channel under Wi-Fi 6
In cases where users already have gigabit fiber, such Wi-Fi performance becomes a bottleneck in the network. At this point, increasing Wi-Fi speed becomes meaningful.
By increasing the bandwidth to 80MHz, the maximum speed can exceed 700Mbps, and a 160MHz bandwidth can fully meet the demands of gigabit fiber.
Analysis of router usage among users also confirms this trend of increasing bandwidth. According to analyses by Cisco and Aruba of their users, 80MHz bandwidth is gradually becoming the default option for configuring Wi-Fi networks in homes and enterprises.
At this point, you might wonder, didn’t the previous article mention that technologies like OFDMA, higher-order modulation, and more MIMO can improve speed and network capacity? Why is there still a need to increase channel resources?
The reason is quite simple: there is no such thing as a free lunch.
While MIMO can provide multiple channels to increase data rates, one cost is that the additional channels require corresponding transmitter-receiver channels, which increases the power consumption of Wi-Fi devices.
Secondly, introducing higher-order modulation and more MIMO channels means that the RF receiver has higher requirements for the signal-to-noise ratio of wireless channels, which reduces the coverage area and the anti-interference capability of devices.
The essence of OFDMA is to allocate the cake more effectively to users; it cannot enlarge the cake. Therefore, the most direct and effective way to increase capacity is to widen the bandwidth and increase spectrum resources.
You may still have questions. Isn’t Wi-Fi 6 on 5GHz also capable of supporting 80 and 160MHz bandwidths? Why is Wi-Fi 6E needed?
Answering this question requires discussing it from the perspective of multi-router network deployment.
Currently, the industry’s golden rule for dense Wi-Fi network deployment is the 7-channel reuse scheme. This scheme represents an optimal point balancing spectrum usage efficiency and inter-cell interference.
The so-called 7-channel reuse scheme means that the 6 adjacent routers surrounding a wireless router all use different Wi-Fi channels.
For example, in the Wi-Fi deployment of an office space shown in Figure 6.
Figure 6 7-Channel Wi-Fi Cell Deployment Scheme
In networks using the 7-channel reuse scheme, Wi-Fi cells using the same frequency can be spaced apart by two different channels. Due to the greater distance, the risk of same-frequency interference between cells is minimal.
In the past, this deployment was stress-free for the spectrum based on using 40MHz channels.
However, when users upgrade to 80MHz bandwidth, the current 5GHz spectrum is no longer sufficient.
This is where Wi-Fi 6E comes into play.
From the above channel diagram, we can see that 6GHz has up to 14 80MHz channels available to meet demands. Even in the future, if users upgrade to 160MHz bandwidth, 6GHz can still provide 7 channels to meet network deployment needs.
█ The Current Global Development of Wi-Fi 6E
Devices supporting Wi-Fi 6E generally support the entire 6GHz band, but manufacturers need to comply with the frequency band requirements of different countries in terms of specific usable frequency ranges.
Internationally, there are mainly two directions for the spectrum allocation of 6GHz Wi-Fi. The first is a one-step approach, primarily led by ITU Region 2 (the Americas), which opens the entire 1.2GHz spectrum (5925-7125MHz) for Wi-Fi use.
The second adopts a gradual approach, first opening the lower 500MHz of the 6GHz band (5925-6425MHz) for Wi-Fi use, while remaining cautious regarding the planning of the higher 6GHz (6425-7125MHz) band.
Regions adopting this strategy mainly include the European Union, Australia, Japan, and others.
One main reason is that an important agenda item in WRC-23 Agenda 1.2 affects the frequency allocation in these countries and regions.
In this agenda item, the 6425-7125MHz band may be identified as a mobile communication band for future 5G or even 6G use, and our country is also one of the active supporters of this agenda item.
Figure 7 Global Development of Wi-Fi 6E (Data Source: Wi-Fi Alliance)
Since 2021, a large number of terminals and network devices supporting Wi-Fi 6E have emerged. Currently, the entire Wi-Fi 6E ecosystem is developing well, and it is expected that more mainstream devices will begin to 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, our country’s Ministry of Industry and Information Technology has consistently supported allocating the entire 6GHz band for 5G and future 6G mobile communication use, and Wi-Fi 6E has not received much attention in China.
This is closely related to our country’s 5G industrial policy and the currently available spectrum in the mid-band for 5G.
From the data released by Qualcomm below, China has only 100MHz at 2.6GHz and 300MHz at 3.5GHz in the mid-band for 5G, which includes 3.3-3.4GHz specifically allocated for indoor 5G use.
Overall, the total mid-band spectrum is less than that of the European Union, North America, Japan, and South Korea.
Figure 9 Global 5G Spectrum Allocation (Data Source: Qualcomm)
However, since last year, the Hong Kong SAR government has taken the lead in planning the use of Wi-Fi 6E in Hong Kong. In the public consultation document released by the SAR government last year, it mentioned the impact of the current crowded Wi-Fi networks on businesses and individuals.
After several months of consultation and discussion, in April of this year, the Hong Kong Communications Authority released a final decision document, adopting a gradual approach, similar to the EU, first opening the lower 500MHz of 6GHz for Wi-Fi use. For the upper 700MHz, Hong Kong will pay attention to the discussions of agenda item 1.2 of WRC-23.
I have attached the policy document of the Communications Authority in the references, and interested readers can study it themselves.
Figure 10 Hong Kong Communications Authority Wi-Fi 6E Public Consultation Document
This spectrum policy in Hong Kong gives a glimmer of hope for Wi-Fi 6E in mainland China.
From the past planning of the C band and millimeter-wave 5G, Hong Kong and the mainland have generally remained consistent, except that the timing of policy releases often precedes that of the mainland. If this pattern holds, the Ministry of Industry and Information Technology may consider the demand for Wi-Fi in the planning of the 6GHz spectrum in the future.
In fact, the problem of Wi-Fi network congestion is not limited to Hong Kong; major cities in mainland China are facing the same issue. In the future, to enhance the performance of enterprise and home networks, relying solely on 5G, in terms of enterprise costs, device ecosystems, and the capacity of the three major telecom operators, is far from sufficient.
Moreover, even if we cannot compare with influential companies like ZTE, Huawei, and China Mobile in the international mobile communication industry, we have large companies in the Wi-Fi industry, such as H3C, FiberHome, and TP-link. Even ZTE and Huawei’s enterprise network divisions are important partners in the Wi-Fi ecosystem.
If the 6GHz band is entirely allocated to mobile communications, it would be a significant blow to enterprises whose main business is Wi-Fi products and services. Especially whether Wi-Fi 7 can develop in China in the future will largely depend on whether there are sufficient spectrum resources.
From the historical development of technology at home and abroad, technological updates often change unpredictably. When government policies lead the way and make a big bet on a certain technology, there is often a risk of misjudgment.
Industrial policies are usually less effective than market policies in terms of long-term market vitality and international competitiveness of products. Allowing enterprises to determine the future direction of technological development through fair market competition will lead to more reasonable capital allocation, more effective resource distribution, and stronger vitality for enterprises themselves.
Wi-Fi technology continues to evolve.
Shortly after Wi-Fi 6 was introduced in 2019, the 802.11 working group began research on the next-generation Wi-Fi technology—Wi-Fi 7. Wi-Fi 7, academically known as 802.11be, uses the same spectrum resources as the current Wi-Fi 6E.
Currently, the standard work for Wi-Fi 7 is underway, with the first release confirmed at the beginning of this year. The complete standard is expected to be finalized after 2024, and certified Wi-Fi 7 devices are not expected to hit the market until 2025.
I will focus on key technologies of Wi-Fi 7 in the next article.
Figure 11 Timeline for Wi-Fi 7
This article is authored by Dr. Tang Xin, currently the Technical Director of Spectrum Lab.
[1] Aruba Networks white paper — Technical Guide to Wi-Fi 6E and the 6 GHz band.
[2] Wi-Fi Alliance – Countries Enabling Wi-Fi 6E.
[3] Qualcomm, 5G spectrum innovation and global update.
[4] Hong Kong Communications Authority — Establishing category licenses to regulate the use of 6GHz devices for wireless local area networks and the changes in public wireless local area network service category licenses.
[5] Khorov, E., Levitsky, I., & Akyildiz, I. F. (2020). Current status and directions of IEEE 802.11be, the future Wi-Fi 7.
Editor: Mu Xin
