ByAdan Flannigan 2019-06-30 11056
WiFi 6 is the sixth generation of WiFi behind the 802.11ax specification. But why is it called WiFi 6 instead of using the canonical number to name it as before? This is not actually a technical problem, but merely an advertising medium. In the past, routers and network card products were directly marked with the number of their own specifications such as 802.11n and 802.11ac known to users. Of course, this is not a problem for players who are familiar with network specifications. A consumer will know what the standard stands for and even the meaning of the combination of these numbers and letters is not known. Therefore, the router products that meet the old and new specifications seem to have no generational difference in the eyes of these consumers, as long as they are new. Production is listed, they are all "new routers", of course with the latest technology.
In this way, some router products that are cheap but still use the old specifications cannot withdraw from the market due to good sales. two or even three generations of routers will often be mixed in the end-to-end and mainstream market, obviously for the new specification. The advertising for the product is very unfriendly. The solution to this problem is actually very simple, which means that consumers can immediately see that this is the first generation of standardized router products. The sixth generation of wireless network specifications is 802.11ax and is called WiFi 6. 802.11ac and 802.11n have new names called WiFi 5 and WiFi 4, so the difference between the three standards can be seen at a glance.
Theoretically 802.11a / b / g should also be renamed to WiFi 1/2/3 by the way, but in fact the WiFi Alliance has not done this, at least not so publicly, maybe because of these three. The standard is really old and the corresponding product has completely withdrawn from the market. There is no need to make a distinction. Although many people believe that 802.11ad will be a new generation of WiFi standards, the transmission distance from 802.11ad is too short, and it is difficult to popularize it on a large scale. Therefore, it is only a help from the beginning. Standards exist, and of course there is no formal WiFi rating.
Of course, the new name is not the reason why WiFi can crash 6 802.11ac or WiFi 5. Although WiFi 6 emerged from WiFi 5, it has actually brought many technical breakthroughs Stronger reasons than its predecessors.
First, consider the difference in specifications between WiFi 6 and WiFi 5. As current public information indicates, both WiFi 6 and WiFi 5 support the 20/40/80/80 + 80 / 160MHz band, but only WiFi 5 Including the 5GHz band, while WiFi 6 covers the 2.4GHz and 5GHz bands, both low and high speed devices are covered. In modulation mode, WiFi is 5-256-QAM, WiFi-6 1024-QAM and the former has a maximum data stream of 4, the latter supporting a maximum of eight, so the theoretical throughput of WiFi 5 can be 3.5 Gbps, while WiFi 6 can reach an amazing 9.6 Gbps. WiFi 6 can be so powerful, and the following five technologies are inextricably linked.
The 802.11ac, which corresponds to WiFi 5, is divided into two phases: Wave 1 and wave 2. The latter can be considered as a whole of WiFi 5. An important difference between the two is that the latter introduces MU-MIMO (multiple users). The extra is) and the first is SU-MIMO (Single-User-Multi-Input and Multi-Out). WiFi 6 continues the MU-MIMO of WiFi 5 and the supported data connections have been updated from 4 to 8. This means it can support 8x8 MU-MIMO, which is also a significant increase in the wireless bandwidth of WiFi 6 compared to WiFi 5. The important reason.
More importantly, however, WiFi 5 MU-MIMO supports only downlink MU-MIMO, i.e., the upper-layer network device can use MU-MIMO when data is distributed to the lower-layer device Uplink MU-MIMO and downlink MU-MIMO, i.e., MU-MIMO, can be used when the upper and lower layers of network equipment transmit data to each other, which theoretically improves the use of wireless bandwidth further.
The higher the QAM level, the more data is contained in the signal. WiFi 5 uses 256-QAM, while WiFi 6 uses 1024-QAM, which is 25% more data capacity than the former, meaning that the latter has higher data transfer speeds.
The performance gap between WiFi 5 and WiFi 6 depends on many factors, and the OFDMA technology used in WiFi 6 is an important reason. OFDMA is also the OFDM technology (Orthogonal Frequency Division Multiple Access), a technological advancement of OFDM. This technology uses OFDM to perform parent carrierization on one channel and then load transmission data onto some sub-carriers. On our current 4G network. The application of OFDMA technology.
WiFi 5 uses OFDM technology. So what is the disadvantage of WiFi 6 OFDMA technology? The picture above is explained very clearly: When using WiFi technology with OFDM technology, each user occupies one channel in the transmission of user data. No matter how much data you have, this channel must transmit a user After the data is passed to the next user, this mode of operation cannot fully utilize the bandwidth, while WiFi 6 allows different users to share a channel using OFDMA so that not only wireless bandwidth but also network response time can be fully utilized. The more devices connected, the more obvious the advantages of WiFi 6 over WiFi 5 become.
However, if so many devices use a channel at the same time, how does the WiFi 6 router distinguish the corresponding data during data transmission? Since data transmission on the WiFi 5 device requires one channel, the device uses a mechanism called CSMA / CA (Carrier Sense Multiple Access with collision avoidance). Simply put, it must be checked whether the corresponding channel has a channel before transmission. Other devices are used. In this case, the device is marked as busy and is not used until the channel is inactive. Although this transmission method is simple, the channel utilization rate is not high, and the more devices that use the same channel, the more severe the network congestion.
In WiFi 6, OFDMA technology allows multiple devices to share a channel and transmit data simultaneously, so WiFi 6 also introduces a BSS coloring coloring mechanism. Simply put, each device is independently tagged, and then the corresponding tags are added to the data so that even if different devices are on the same channel, corresponding addresses are present during data transmission and sent directly to other devices without being sent incorrectly. Combined with the characteristics of the shared OFDMA channel, each channel in the network can always maintain the most efficient operation and further improve network efficiency.
The above four technical features paved the way for the high performance of WiFi 6, but these are more intended for high-speed devices. With the gradual promotion of smart homes, our routers often connect more than just mobile phones, computers, etc. For terminals with high network requirements, there are also various smart home devices for which there are no obvious bandwidth requirements. To some extent, these devices also affect our network status, especially when they transmit data, and to some extent slow down the network's response speed. For this reason, WiFi introduces 6 TWT, the target wake-up time mechanism.
The TWT mechanism is specifically implemented for low-speed devices, mainly smart home products that do not require high network bandwidth, such as WiFi devices with only 2.4 GHz band and 20 MHz band. When the router exchanges data with these low-speed devices, an activation schedule is created at the same time. Only when the activation time is required does the router activate the device for data exchange. In addition, the router can also sort the wake-up time of various slow devices in advance to prevent multiple devices from waking up at the same time and causing network congestion. This is also a technical means to optimize network bandwidth utilization.
The above five points are the main reasons why WiFi 6 can destroy WiFi 5. Each of them has its own unique characteristics and can lead to higher strength after combination. However, as shown in the first paragraph, replacing the router often takes a long time. Even if WiFi 6 offers such obvious advantages, it is really impossible to replace the location of WiFi 5 on the market in the short term and for the time being. For the vast majority of users, WiFi 5 is not enough to meet their needs.
The time that WiFi 6 replaces WiFi 5 may be shorter than you think because WiFi 6 is no longer the same as WiFi 5 when it was first launched. The more and more the WiFi 6 router is not alone after the debut, the more the corresponding WiFi 6 devices, including mobile phones, wireless network cards, etc., have started to compete in the market. Therefore, WiFi 6 will replace WiFi 5, which is easier than WiFi 5 to replace WiFi 4. Perhaps in the near future we will see that the wireless network around us has gradually become WiFi 6.
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