Compared with previous generations of Wi-Fi technology, Wi-Fi 6 has been improved and optimized in many aspects, such as physical frame, modulation, encoding, multi-user concurrency and so on. The focus of Wi-Fi 6 is more than just peak rate on a single device. Wi-Fi 6 is more about optimization of applications, user experience and the overall wireless environment.
The design goals and concerns of Wi-Fi 6 protocol are more suitable for the current multi-Wi-Fi terminal and multi-application popularization scenario. At present all kinds of terminal and application is various, such as video, instant messaging application, etc., thus more wireless scenario concurrency, short message, more and more early wi-fi agreement dealing with this situation, there is no technical advantage, and wi-fi 6 for these scenarios do a lot of improvement and optimization, can significantly enhance your wireless experience.
Wi-Fi 6, as a standard aimed at improving wireless efficiency and the real user experience, defines a number of technical specifications that are radically different from previous protocols. For example, higher modulation order (1024-QAM), narrower sub-carrier interval, upstream and downstream OFDMA technology, upstream and downstream MU-MIMO technology (where downstream MU-MIMO is introduced in Wi-Fi 5), spatial multiplexing technology, etc.
The following are the key technologies used in 802.11ax
As shown in the figure above, before 802.11ax (WIFI6), data transmission was carried out in OFDM mode, and only one user's data packet could be transmitted in a time period.
802.11ax introduced a more efficient mode, OFDMA, as shown in the figure above, which can transmit packets of user1, user2, and user3 simultaneously over a period of time. OFDMA generally has three advantages over OFDM:
- Finer channel resource allocation
- Provide better QoS and lower latency
- More user concurrency and higher user bandwidth
2.1 MIMO technology
As shown in the figure above, we can simply understand the data communication of WIFI as the faucet filling the birdbasin with water. The faucet is WIFI AP, and the birdbasin can be regarded as a mobile phone. So how to increase the water flow (increase throughput)?
- Increase the bandwidth
- increase the number of antenna (as shown in the figure below), by double antenna to send mobile phone two data flow, increase the rate of data
|Single slip rate
|Maximum spatial flow
||Up and down
Wifi6 supports eight antennas to stream data, which can increase network speed up to eight times.
MU-MIMO uses the spatial diversity of the channel to send independent data streams on the same bandwidth. By introducing MU-MIMO technology into AP, simultaneous data transmission between AP and multiple terminals can be realized at the same time, which greatly improves the throughput.
Although the 802.11ax standard allows OFDMA to be used in conjunction with MU-MIMO, do not confuse OFDMA with MU-MIMO.OFDMA supports multiple users to improve concurrency efficiency and reduce latency by subdividing channels (subchannels), which is suitable for low bandwidth applications.MU-MIMO supports multiple users to improve throughput by using different spatial streams and is suitable for high-bandwidth applications.
As shown in the figure above, with the help of DL OFDMA technology (downlink), MU-MIMO transmission can be carried out at the same time and different RU can be allocated for multi-user multi-access transmission, which not only increases the amount of concurrent access of the system, but also balances the throughput.
- 802.11 ax standard's main goal is to increase the system capacity, reduce the time delay, improve the efficiency of the multi-user density scenarios.
- 802.11 ac 256 - QAM quadrature amplitude modulation (am), each symbol 8 bit data (2 ^ 8 = 256),802.11ax
- will use 1024 - QAM quadrature amplitude modulation (am), each symbol a 10 bit data (10 ^ 2 = 1024), The increase from 8 to 10 is 25%, which means that 802.11ax has another 25% more data throughput per spatial stream than 802.11ac.
4. Spatial Reuse & BBS Coloring
Wi-fi rf transmission principle is at any given time, only allow a user in a channel to transmit data, such as fruit wi-fi AP and the client on the same channel to listen to the other 802.11 radio transmission, will produce the same frequency interference problems, will automatically to avoid conflict, transmission delay, so each user must take turns to use.
If there are multiple routers in an area, when data is transmitted, two or more routers use the same frequency and the same channel for data transmission, the same frequency interference will occur.
802.11 introduces a new kind of same frequency transmission in ax recognition mechanism, called BSS Coloring mechanism, the BSS color is added in the PHY packet header field was carried out on the data from different BSS "dyeing", for each channel to distribute a color, the color logo one group should not interfere with the basic service set (BSS), the receiver can identify the frequency transmission interference signal and stop receiving, avoid the waste of transceiver. If the color is the same, it is considered to be the interference signal in the same BSS, and the transmission will be delayed; If the colors are different, it is considered that there is no interference between the two, and the two Wi-Fi devices can transmit in parallel on the same channel and frequency.