WiFi 6 (Wi-Fi 6), also known as 802.11ax, is the latest generation of Wi-Fi industry standards after Wi-Fi 5 (802.11ac). Before the release of Wi-Fi 6, Wi-Fi standards were identified by version numbers from 802.11b to 802.11ac. With the evolution of Wi-Fi standards, the Wi-Fi Alliance chose to rename Wi-Fi using digital numbers to make it easier for Wi-Fi users and device manufacturers to understand Wi-Fi standards.
The Wi-Fi 6 standard introduces new technologies such as OFDMA, uplink/downlink MU-MIMO, BSS Coloring, and TWT, which have made a leap forward in performance. The bandwidth and number of concurrent users have increased by 4 times compared to Wi-Fi 5, and the latency is lower and more energy-efficient.
What problems does Wi-Fi 6 solve?
Wi-Fi 6 was originally designed to cope with high-density wireless access and high-capacity wireless services, such as large outdoor public places, high-density venues, indoor high-density wireless offices, electronic classrooms and other scenarios.
In these scenarios, the number of client devices accessing the Wi-Fi network will show a huge increase. In addition, the increasing voice and video traffic also brings adjustments to the Wi-Fi network. As we all know, 4K video streaming (bandwidth requirements 50Mbps/person), voice streaming (delay less than 30ms), VR streaming (bandwidth requirements 75Mbps/person, delay less than 15ms) are very sensitive to bandwidth and delay. If network congestion or retransmission causes transmission delay, it will have a greater impact on user experience.
Although the existing Wi-Fi 5 (802.11ac) can also provide large bandwidth capabilities, as the access density continues to increase, the throughput performance encounters a bottleneck. Wi-Fi 6 has made a leap forward in performance by introducing new technologies such as OFDMA and uplink/downlink MU-MIMO. The bandwidth and number of concurrent users have increased four times compared to Wi-Fi 5, and the latency is lower. For example, in an electronic classroom, if there were more than 100 students in a large class, the challenges of transmitting videos or uplink and downlink interactions were relatively large, but the Wi-Fi 6 network can easily handle this scenario.
Wi-Fi 6 vs Wi-Fi 5
As the successor of Wi-Fi 5, Wi-Fi 6 is not only faster than Wi-Fi 5, but also more importantly, it improves user performance in high-density scenarios.
Large bandwidth
In the past, each generation of Wi-Fi standards has been committed to improving the speed. After more than 20 years of development, the theoretical maximum speed of Wi-Fi 6 has reached 9.6Gbps at a channel width of 160MHz, which is nearly 900 times that of 802.11b.
In addition to the use of a higher-order 1024-QAM encoding method, the improvement in the speed of Wi-Fi 6 is also due to the increase in the number of subcarriers and spatial streams compared to Wi-Fi 5, and the symbol transmission time (single terminal) has been increased from 3.2μs in Wi-Fi 5 to 12.8μs.
High concurrency
Wi-Fi 6 introduces multi-user technologies such as OFDMA and uplink MU-MIMO, further improving spectrum utilization and increasing the number of concurrent users of Wi-Fi 6 by four times compared to Wi-Fi 5.
Low latency
In low latency scenarios, such as VR/AR-interactive operation simulation, panoramic live broadcast, interactive games, immersive meetings, high-definition wireless projection, etc., the 30ms latency of Wi-Fi 5 can no longer meet the needs, while Wi-Fi 6 effectively reduces conflicts and improves spectrum utilization through OFDMA, and the spatial multiplexing technology BSS Coloring reduces co-channel interference, reducing latency to 20ms.
Energy saving
With the widespread application of IoT devices, in addition to improving terminal speed, Wi-Fi 6 also pays attention to the power consumption of terminals.
Wi-Fi 6 uses TWT technology to wake up terminal Wi-Fi on demand, and with 20MHz-Only technology, it can further reduce the power consumption of terminals.
Wi-Fi 6 Core Technologies
The following are the core new technologies of Wi-Fi 6.
OFDMA frequency division multiplexing technology
Before Wi-Fi 6, data transmission used the OFDM mode, and users were distinguished by different time segments. In each time segment, a user completely occupied all channel resources and sent a complete data packet.
Wi-Fi 6 introduced a more efficient data transmission mode called OFDMA (because Wi-Fi 6 supports uplink and downlink multi-user mode, it can also be called MU-OFDMA), which implements multi-user multiplexing of channel resources by allocating subcarriers to different users and adding multiple access methods in the OFDM system. So far, it has been adopted by many wireless technologies, such as 3GPP LTE. In this mode, a single user no longer monopolizes a complete subcarrier, but multiple users share channel resources to improve spectrum utilization.
Uplink/Downlink MU-MIMO Technology
MU-MIMO was introduced in Wi-Fi 5, but only 4x4 MU-MIMO was supported for downlink. The number of MU-MIMO has been further increased in Wi-Fi 6, which can support 8x8 MU-MIMO for uplink/downlink at the same time.
WiFi 6's uplink/downlink MU-MIMO technology
Although the Wi-Fi 6 standard allows OFDMA and MU-MIMO to be used simultaneously, do not confuse OFDMA with MU-MIMO. OFDMA supports multiple users to improve concurrency efficiency by subdividing channels (subchannels), and MU-MIMO supports multiple users to improve throughput by using different spatial streams. The comparison between OFDMA and MU-MIMO is as follows:
Spatial division multiplexing (SR) and BSS Coloring
802.11ax introduces a new co-frequency transmission identification mechanism, called BSS Coloring. The BSS color field is added to the PHY message header to "color" the data from different BSSs, and a color is assigned to each channel. The color identifies a set of basic service sets (BSSs) that should not interfere. The receiving end can identify the co-frequency transmission interference signal early and stop receiving to avoid wasting transceiver time. If the colors are the same, it is considered to be an interference signal within 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. In a network designed in this way, those channels with the same color are far apart from each other, and this signal can be set to insensitive, thereby achieving spatial multiplexing.
Target Wake Time (TWT)
Target Wake Time (TWT) is another important resource scheduling feature supported by 802.11ax, which is based on the 802.11ah standard. It allows devices to negotiate when and how long they will be awakened, and then send or receive data. In addition, Wi-Fi APs can group client devices into different TWT cycles, thereby reducing the number of devices competing for the wireless medium at the same time after waking up. TWT also increases the sleep time of devices, which greatly improves the battery life of battery-powered terminals.
Higher-order modulation technology (1024-QAM)
The main goal of the Wi-Fi 6 standard is to increase system capacity, reduce latency, and improve efficiency in multi-user high-density scenarios, but better efficiency and faster speed are not mutually exclusive. Wi-Fi 5 uses 256-QAM quadrature amplitude modulation, with each symbol transmitting 8 bits of data. Wi-Fi 6 will use 1024-QAM quadrature amplitude modulation, with each symbol bit transmitting 10 bits of data. The improvement from 8 to 10 is 25%, which means that compared with Wi-Fi 5, the single spatial stream data throughput of Wi-Fi 6 has increased by 25%.
Support for 2.4GHz band
We all know that the 2.4GHz band has a narrow bandwidth and only has three 20MHz non-interfering channels (1, 6, and 11). It has been abandoned in the Wi-Fi 5 standard, but one thing is undeniable: 2.4GHz is still an available Wi-Fi band and is still widely used in many scenarios. Therefore, the Wi-Fi 6 standard chooses to continue to support 2.4GHz in order to make full use of the unique advantages of this band.
Improved coverage
Since the Wi-Fi 6 standard adopts the Long OFDM Symbol transmission mechanism, the duration of each data transmission is increased from the original 3.2μs to 12.8μs. The longer transmission time can reduce the terminal packet loss rate. In addition, Wi-Fi 6 can use only 2MHz bandwidth for narrowband transmission, which effectively reduces frequency band noise interference, improves terminal reception sensitivity, and increases coverage distance.
Wi-Fi 6 devices
Huawei released the first Wi-Fi 6 AP in October 2017. Subsequently, Huawei launched a full range of AirEngine Wi-Fi 6 products for all scenarios, which can meet the needs of enterprises, education, finance, medical care, government, manufacturing, commerce, venues and other industries to build digital, wireless, and IoT-connected office and production workspaces.