Wi-Fi 6 (formerly known as IEEE 802.11.ax), the sixth generation of wireless network technology, has been confirmed and promoted by the Wi-Fi Alliance for more than four years since 2019. According to the previous 5-6-year update rhythm of the Wi-Fi Alliance, it is time for Wi-Fi 6 to be updated. According to data from the Wi-Fi Alliance, the next generation of 360-degree AR/VR applications has a maximum demand for wireless bandwidth of 200Mbps, which shows that today's Wi-Fi speeds have gradually reached a bottleneck for the new generation of entertainment devices. Now is the time to need faster, more stable and lower latency network connections to provide a better user experience. Not only that, a survey report of 2,000 gamers in the UK and the US also showed that as many as 97% of gamers have encountered latency issues, which further emphasizes the importance of low latency for wireless connections.

In order to meet higher network connection requirements, a new generation of IEEE 802.11be standard, namely Wi-Fi 7, was launched. According to the Wi-Fi Alliance, Wi-Fi 7 will further enhance the functionality and performance of Wi-Fi networks, including higher data transfer rates, lower latency, and better network coverage. These improvements will help promote the development of AR/VR, gaming, and other high-bandwidth applications, and provide a better user experience. So for Wi-Fi 7, which will be fully promoted in 2024, what upgrades does it have over the previous generation standards? This article will take readers to sort out in detail the upgrades and differences between the upcoming Wi-Fi 7 and Wi-Fi 6.

First, let’s compare the differences between Wi-Fi 7 and Wi-Fi 6/Wi-Fi 6E.

We can see that compared with Wi-Fi 6, Wi-Fi 7 has significantly improved in transmission speed, frequency band support and performance. First of all, the maximum transmission speed of Wi-Fi 7 can reach 46Gbps (30Gbps in China), which is nearly five times that of Wi-Fi 6. This significant improvement is due to the new technology and more efficient signal processing algorithm adopted by Wi-Fi 7, which enables it to transmit large amounts of data more quickly. Secondly, Wi-Fi 7 will support more frequency bands, including 2.4GHz, 5GHz and 6GHz. In contrast, Wi-Fi 6 only supports two frequency bands, 2.4GHz and 5GHz, while Wi-Fi 6E only supports the 6GHz frequency band. Multi-band support means that Wi-Fi 7 devices can better adapt to different network environments and application requirements, and provide more stable and reliable data transmission services. However, it should be noted that due to the problem of frequency band allocation in different regions, especially the fact that my country has not allocated the 6GHz frequency band to Wi-Fi, the 6GHz frequency band supported by Wi-Fi 7 may be different at home and abroad.

Multi-link transmission technology (MLO)

Multi-link transmission technology (MLO) is a multi-path transmission protocol that allows data to be transmitted through multiple paths to improve the utilization and reliability of network bandwidth. In MLO, data is divided into multiple data blocks, each of which is transmitted along a different path. After receiving the data blocks, the receiver will reassemble them into complete data according to a certain algorithm. In actual use, in the Wi-Fi 6 era, most routers will send out signals in two frequency bands, such as 2.5G and 5G signals. The 2.5G signal has a wide coverage range and high stability, but the speed is slow; and although the 5G signal has an extremely high speed, its coverage is often limited. We can only choose one of the two signals according to our usage environment. With Wi-Fi 7, which uses multi-link transmission technology, our single network device can connect to two Wi-Fi hotspots at the same time, such as 2.4G+5G, 5G+5G, and the 6G frequency band has been opened abroad, and even 5G+6G is possible. The advantages of doing so are obvious: since the network speeds of Link 1 and Link 2 are aggregated, a higher network speed is obtained, so it can allow faster throughput; since the two signals are connected at the same time, when one of them encounters interference, it can dynamically switch to another better Wi-Fi link, thereby obtaining a more stable and low-latency network connection.

Perhaps someone familiar with Wi-Fi 6 will say: "Wi-Fi 6 also has MU-MIMO spatial stream technology, which can also support similar multi-path transmission. What is the difference between them?"

Admittedly, both MLO technology and MU-MIMO spatial stream technology can establish multiple links between an AP and STA to send and receive information at the same time. However, MU-MIMO spatial stream technology is limited to the same radio chip in the AP, while the new MLO technology means that multiple radio chips in an AP can establish communication links with the same STA at the same time. If we make an analogy: now we have three different modes of transportation: sea, land, and air. MU-MIMO spatial stream technology can only choose one of these three modes for transportation, and improve performance by increasing the number of the same mode of transportation. For example, if there are 16 roads for transportation (communication) at the same time, that is MU-MIMO spatial stream technology; while MLO technology can use all media at the same time, and sea, land, and air are all transporting (communication).

In wireless communication, the basic channel is generally 20MHz, which is like the lanes in our city roads, and is the basis of communication. 20MHz is the most basic single lane. If we widen the road and use the adjacent land resources as lanes, double lanes, that is, 40MHz channels, and so on, we have 80MHz channels and 160MHz channels. The benefits of doing this are very obvious. Wider channels can obtain higher information transmission capabilities.

In the 2.4GHz band, there are only 3 consecutive non-overlapping 20MHz channels, of which two consecutive non-overlapping 20MHz channels can be bound to a 40MHz channel (usually not recommended in the 2.4GHz band); the 5GHz band has up to 13 consecutive non-overlapping 20MHz channels, and under the Wi-Fi 5 and Wi-Fi 6 standards, it supports up to 160MHz channels.

Knowing this information, let's get back to the topic. In the era of Wi-Fi 5, each channel can only send information to one receiver at the same time. In order to improve utilization, the concept of resource unit (RU) is introduced in Wi-Fi 6. Wi-Fi 6 uses a new orthogonal frequency division multiple access (OFDMA) technology: multiple users can use a channel at the same time without interfering with each other. OFDMA technology divides the spectrum into multiple subcarriers, which can be used independently by different users. Each subcarrier can carry different data symbols, thereby achieving the purpose of multi-user simultaneous data transmission. Let's take a 20MHz channel as an example. In this frequency band, there are a total of 256 subcarriers, but only 242 of them are valid. According to the regulations of the Wi-Fi Alliance, the smallest resource unit (RU) consists of 26 subcarriers. This means that within a channel, resources can be divided into different RUs, each of which contains a different number of valid subcarriers.

Specifically, an RU can contain 26 (26-tone RU), 52 (52-tone RU), 106 (106-tone RU) or 242 (242-tone RU) effective subcarriers.

In the Wi-Fi 6 standard, the Wi-Fi Alliance stipulates that the number of subcarriers in an RU is mainly as follows:

l 26-tone RU: A resource unit consists of 26 subcarriers.

l 52-tone RU: A resource unit consists of 52 subcarriers.

l 106-tone RU: A resource unit consists of 106 subcarriers.

l 242-tone RU: A resource unit consists of 242 subcarriers.

l 484-tone RU: A resource unit consists of 484 subcarriers.

l 996-tone RU: A resource unit consists of 996 subcarriers.

l 1992-tone RU: A resource unit consists of 1992 subcarriers.

In addition, in Wi-Fi 6, one user can only correspond to one RU.

In Wi-Fi 7, the concept of multiple resource units (MRU) is introduced, that is, one user can correspond to a combination of multiple RUs. For example, a user can use a combination of 26-tone RU and 52-tone RU at the same time, or a combination of 484-tone RU and 996-tone RU. This flexible resource allocation method enables Wi-Fi 7 to better adapt to communication needs in different scenarios, improve network bandwidth utilization and user communication experience.

Preamble puncturing is not a new technology. It has been used in Wi-Fi 6. However, due to cost constraints, it is an optional technology in the Wi-Fi 6 standard and has not been widely promoted. In Wi-Fi 7, this technology has become a mandatory standard, and all products that meet the Wi-Fi 7 standard will support preamble puncturing.

In the above, we mentioned that we generally increase the rate by channel bundling, that is, bundling 8 20MHz channels into a 160MHz channel. However, in practice, based on the transmission requirements, priority control, compatibility and other reasons of the channel, channel bundling is divided into main channels and auxiliary channels. For example, a 40MHz channel is often composed of a 20MHz main channel and a 20MHz auxiliary channel; and an 80Mhz channel is generally composed of two 20MHz main channels and two 20MHz auxiliary channels, and so on.

According to the channel bundling protocol, channel bundling must comply with two major principles: first, only continuous channels can be bundled; second, in the channel bundling mode, the auxiliary channel can only transmit information when the main channel is clean and interference-free.

Before Wi-Fi 7, this situation often occurred. Once the auxiliary channel in the combination was interfered, it could not be combined into a wider main channel. For example, if an 80Mhz channel has a 20MHz auxiliary channel interfered, then the 40MHz main channel composed of it is an unclean channel as a whole, and the 40MHz auxiliary channel cannot transmit information; further, if they are bundled into an 80MHz main channel, it will also be useless. In the end, a 160MHz channel will only have 20MHz left for normal use due to the interference of a 20MHz channel, and 7/8 channel resources will be wasted.

And preamble puncturing was born to solve this problem. It can actively shield the interfered 20MHz auxiliary channel without affecting the main channel to form a wider channel. The 20MHz main channel can still form a 60MHz channel with the 40MHz auxiliary channel, and then form a 140MHz channel with the 80MHz auxiliary channel. Compared with the previous Wi-Fi standards, the anti-interference ability of Wi-Fi 7 is greatly improved, and information can still be transmitted quickly even in an interference environment.

Compared with Wi-Fi 6/6E, Wi-Fi 7 has a maximum transmission rate of 30Gbps, which is a huge improvement over Wi-Fi 6's 9.6Gpbs. In terms of bandwidth, Wi-Fi 7 can reach up to 320MHz, which is twice the maximum of Wi-Fi 6's 160MHz. In terms of modulation, Wi-Fi 7's 4096-QAM can adapt to stronger transmission changes compared to Wi-Fi 6's 1024-QAM. Finally, combined with Wi-Fi 7's stronger anti-interference ability in complex environments, according to relevant information, Wi-Fi 7's overall rate will have the opportunity to reach about 3 times that of Wi-Fi 6.