Does China need Wi-Fi 6E?

As WRC-23 (2023 World Radiocommunication Conference) approaches, discussions on 6GHz planning at home and abroad are becoming increasingly heated.

The entire 6GHz band has a total bandwidth of 1200MHz (5925-7125MHz). The focus of the debate is whether to allocate it to 5G IMT (as licensed spectrum) or Wi-Fi 6E (as unlicensed spectrum).

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The call for allocating licensed spectrum to 5G comes from the IMT camp based on 3GPP 5G technology.

For IMT 5G, 6GHz is another mid-band spectrum after 3.5GHz (3.3-4.2GHz, 3GPP n77). Compared with the millimeter wave band, the mid-band has stronger coverage. Compared with the low-band, the mid-band has more abundant spectrum resources. Therefore, it is the most important frequency band support for 5G.

6GHz can be used for mobile broadband (eMBB), and with the help of high-gain directional antennas and beamforming, it can also be used for wireless broadband (Fixed Wireless Access). GSMA recently even called for: "If governments fail to use 6GHz as a licensed spectrum, the development prospects of 5G around the world will be jeopardized."

The Wi-Fi camp based on IEEE802.11 technology has put forward a different view: Wi-Fi is of great significance to homes and businesses, especially during the 2020 COVID-19 pandemic, when Wi-Fi has assumed the main data business. Currently, the 2.4GHz and 5GHz Wi-Fi bands, which can only provide a few hundred MHz, have become very crowded, affecting the user experience. Wi-Fi needs more spectrum to support the increasing demand. As an extension of the current 5GHz band, 6GHz is crucial to the future Wi-Fi ecosystem.

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Current status of 6 GHz allocation

Globally, ITU Region 2 (US, Canada, Latin America) has already made it a foregone conclusion that the entire 1.2 GHz band will be used by Wi-Fi. The most prominent example is the US and Canada, which allow standard output power APs with 4W EIRP in some frequency bands.

Europe has adopted a balanced attitude. CEPT and Ofcom have opened the low-frequency band (5925-6425MHz) to low-power Wi-Fi (200-250mW), while Europe has not yet reached a conclusion on the high-frequency band 6425-7125MHz. In Agenda 1.2 of WRC-23, Europe will consider planning 6425-7125MHz for IMT mobile communications.

In Region 3 Asia Pacific, Japan and South Korea have both opened up their entire frequency bands to unlicensed Wi-Fi. Australia and New Zealand have also started soliciting public opinions, and their main plans are similar to those of Europe, namely, opening up low-frequency bands to unlicensed use and taking a wait-and-see attitude towards high-frequency bands.

Although spectrum management bureaus in various countries all adopt a "technology standard neutral" policy, that is, both Wi-Fi and 5G NR unlicensed can be used, judging from the current equipment ecosystem and past experience with 5GHz, as long as the frequency band is unlicensed, Wi-Fi can dominate the market with its low-cost, easy-to-deploy, and multi-player strategy.

As the world is opening up part or all of the 6 GHz spectrum for Wi-Fi 6E use, China, as the country with the best momentum in communications development, currently advocates allocating all of the 6 GHz spectrum for 5G licensed spectrum use.

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Considering that China currently leads the world in 4G and 5G network coverage, it seems that consumers are not as dependent on Wi-Fi networks as in the past. So, is it necessary for China to consider supporting Wi-Fi 6E and Wi-Fi 7 in the future?

Should 6GHz be allocated to 5G IMT and how much should be allocated to Wi-Fi? I have done some research on these issues in the process of planning 6GHz in New Zealand. I believe that the planning of 6GHz needs to consider the following points from a technical macro perspective:

1. Fiber coverage

As mentioned earlier, 6GHz is a mid-band spectrum for 5G and is very important, which is very attractive to countries with weak fiber optic infrastructure and high construction costs.

By utilizing the abundant spectrum resources of 6GHz, FWA can achieve the effect of Wireless Fibre. At the same time, FWA may have more advantages than fiber in terms of construction cost and network deployment speed.

However, if the fiber-to-the-home penetration rate is high, the importance of 6GHz as mobile broadband or wireless broadband will be reduced accordingly.

For example, in New Zealand, where I live, the government's planned GPON fiber network will cover 87% of the population by 2022. Fiber optics has stable performance, price advantages, and lower energy consumption, and will continue to be the first choice for users' broadband access in the future.

In Europe, due to the cost and difficulty of construction, the penetration of optical fiber is not that high. If we blindly pursue the population coverage of fiber to the home (FTTH), it may not be economically advantageous. At this time, the use of 5G-based FWA technology to achieve the last 1 kilometer of access will be very beneficial to both operators and users.

The popularization of optical fiber will reduce users' reliance on FWA or mobile broadband eMBB on the one hand, and increase users' reliance on Wi-Fi networks on the other hand. As the access of the last few dozen meters in the network, Wi-Fi needs to match the speed of optical fiber to fully reflect the capacity advantage of optical fiber.

Currently, commercial optical fiber has reached the level of 10-GPON, with a symmetrical upstream and downstream rate of 10Gbs. The ITU standard for GPON has also evolved to 50G upstream and downstream rates.

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The theoretical rate supported by 5GHz Wi-Fi 6 is 9.6Gbs, but this is only possible when the wireless environment is very ideal. In actual deployment scenarios, multiple Wi-Fi devices are usually connected to one hotspot, and multiple hotspots coexist in the same location. Co-channel or adjacent channel interference between devices and hotspots is inevitable.

Wi-Fi uses carrier sense multiple access (CSMA) technology, which means that devices can only send signals when they are sure that the frequency band is not occupied. The congestion level of the frequency band will have a significant impact on the performance of the Wi-Fi network.

In terms of technical standards, the IEEE802.11 group is currently working intensively on planning the Wi-Fi 7 standards.

Wi-Fi 7 will be based on 6E, using the same frequency band and supporting 320MHz carriers. The current 2.4GHz and 5GHz do not have such conditions. In other words, without the support of 6GHz, the performance improvement brought by Wi-Fi 7 in the future will be weakened.

China's dual-gigabit infrastructure project is in full swing. As early as 2017, the three major operators have begun to gradually upgrade their optical networks to 10G fiber.

According to the China Broadband Development White Paper (2019), "the number of Internet broadband access ports in my country has reached 903 million, and the optical fiber network has reached 98% of administrative villages." It can be seen that China's penetration rate of optical fiber is already very high. Allocating part of the spectrum to Wi-Fi will help to fully utilize the improvement brought by the 10G-PON optical fiber network, which will bring social and economic benefits to enterprises, retail and households with high broadband demand in the future.

2. 3.5GHz spectrum redundancy

3.5GHz and 6GHz are both the most important mid-frequency bands for IMT 5G. As mentioned earlier, if you want to truly enjoy the improvements brought by 5G mobile communications, the spectrum capacity of the mid-frequency band is very critical.

When countries plan at a macro level, if there are not enough spectrum resources at 3.5 GHz, they need to find a mid-frequency band supplement at 6 GHz.

According to the data released by Qualcomm and GSMA below, China currently has 300MHz of 5G spectrum at 3.5GHz, including 3.3-3.4GHz for indoor use. The total amount of mid-band spectrum is less than that in the European Union, North America, Japan and South Korea.

In the future, satellite services in the C band (3.3-4.2GHz) will continue to be used in important services such as broadcasting and meteorology in China. There are also a large number of microwave transmission services above 3.6GHz, and there is not much room for spectrum development for 5G in the short term.

To further improve 5G and post-5G, more mid-band spectrum is needed to support it. From this perspective, planning 6GHz for 5G is very reasonable.

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Qualcomm - Global 5G Spectrum Allocation

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GSMA - Global 3.5GHz 5G Spectrum Holdings

3. Difficulty of spectrum refarming

Spectrum planning inevitably involves considering current occupancy. How to reasonably share and coexist or clean up legacy communications equipment is a very thorny issue in many countries.

For example, in the recent FCC 3.7GHz spectrum auction, $1.3 billion of the $8.1 billion in spectrum auction revenue will be used to relocate the current C band satellite occupancy.

Currently, there are a large number of point-to-point microwave transmission communication systems in Europe and North America at 6GHz. In order to solve the problem of shared use, Europe only allows low-power Wi-Fi use of 23dBm indoors and 14dBm outdoors. The United States and Canada, on the other hand, have adopted an Automatic Frequency Coordination intelligent database coordination method, which is similar to Dynamic Spectrum Sharing and will automatically evaluate the impact of new Wi-Fi APs on fixed services, thereby allocating spectrum and power.

6GHz is also allocated to point-to-point microwave transmission services in China. At the same time, the China Radio Administration’s special CHN21 footnote emphasizes the need to protect microwave communications for new services. Even if China decides to use all of 6GHz for 5G, there will still be a lot of work to be done in the future in terms of planning and implementation.

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To sum up, 6GHz is an important frequency band for the next 5G in China, and it is also crucial at the national 5G strategic level.

However, using part of 6GHz as unlicensed Wi-Fi can also make the currently developed fiber optic access more convenient. At the same time, opening up more unlicensed Wi-Fi spectrum can also support the development of the future Wi-Fi 7 ecosystem in China. This will also greatly promote China's chip, communication equipment, consumer electronics and other industries.

Let's wait and see who will win the 6GHz race!

References:

[1] Qualcomm, 5G spectrum innovation and global update. December 8th, 2020

[2] GSMA, The WRC Series, 3.5 GHz in the 5G Era Preparing for New Services in 3.3-4.2 GHz. April 2021

[3] Cisco, IEEE 802.11ax: The Sixth Generation of Wi-Fi White Paper. Apr 2020

[4] Khorov, E., Levitsky, I., & Akyildiz, IF (2020). Current status and directions of IEEE 802.11be, the future Wi-Fi 7. IEEE Access, 8, 88664-88688.

[5] China Radio Management - Radio Frequency Allocation Regulations of the People’s Republic of China