WiFi6 or 802.11ax is well into its widespread adoption in enterprise and consumer products. At the same time the work for WiFi7 or 802.11be has already started. The IEEE 802.11 working group has the first meeting scheduled in May 2021 and a projected finalized amendment for May 2024.
WiFi6’s focus was on improving spectrum efficiency utilization by introducing new capatilibies such as MU-OFDMA and 1024-QAM, but also security with WPA3 and power consumption with the Target Wake Time mechanism. WiFi7 is going to fine tune the existing standard, and build upon them based on the problems is trying to address.
The Needs behind WiFi7
Each new protocol amendment aims to address and set of real-life applications and requirements for WiFi connectivity. Per the 802.11be Working Groups Project Authorization Request, WiFi7’s purpose is to address the following:
Video streaming: The emergence of 4K and 8K video streaming is creating a need for higher throughput requirements for mobile devices. 8K video stream requires 50 Mbps of throughput, and consumers will soon expect the highest level of video streaming definition on multiple devices in their home and work environment.
Virtual and augmented reality, gaming, videoconferencing: all these applications require not only high throughput, but also low latency and jitter for a good user experience.
As we can see, the goals for WiFi7 are mostly around improving multimedia user experience, while maintaining improvements introduced by WiFi6 (e.g. better high density support) and backwards compatibility, like all new 802.11 amendments.
New Features in Wi-Fi 7
Wi-Fi 7 aims to increase the WLAN throughput to 30 Gbps and provide low-latency access assurance. To achieve this goal, the standard defines modifications to both the physical layer (PHY) and MAC layer. Compared with Wi-Fi 6, Wi-Fi 7 brings the following technical innovations:
Up to 320 MHz Bandwidth
The 2.4 GHz and 5 GHz frequency bands are unlicensed spectrums that limited and congested. When running emerging applications (such as VR/AR), existing Wi-Fi networks inevitably encounter low quality of service (QoS). To achieve a maximum of 30 Gbps throughput, Wi-Fi 7 will support the 6 GHz of frequency band and extend new bandwidth modes, including contiguous 240 MHz, non-contiguous 160+80 MHz, contiguous 320 MHz, and non-contiguous 160+160 MHz.
Multi-RU
In Wi-Fi 6, each user can send or receive frames only on the RUs allocated to them, which greatly limits the flexibility of spectrum resource scheduling. To resolve this problem and further improve spectrum efficiency, Wi-Fi 7 defines a mechanism for allocating multiple RUs to a single user. To balance the implementation complexity and spectrum utilization, the standard specifications impose certain restrictions on RU combination. That is, small RUs (containing fewer than 242 tones) can be combined only with small RUs, and large RUs (containing greater than or equal to 242 tones) can be combined only with large RUs. Small RUs and large RUs can be combined together.
Higher-Order 4096-QAM
The highest order modulation supported by Wi-Fi 6 is 1024-QAM, which allows each modulation symbol to carry up to 10 bits. To further improve the rate, Wi-Fi 7 introduces 4096-QAM so that each modulation symbol can carry 12 bits. With the same coding, 4096-QAM in Wi-Fi 7 can achieve a 20% rate increase compared with 1024-QAM in Wi-Fi 6.
Multi-Link Mechanism
To efficiently utilize all available spectrum resources, the industry is in urgent need to introduce new spectrum management, coordination, and transmission mechanisms on the 2.4 GHz, 5 GHz, and 6 GHz frequency bands. The TGbe defines multi-link aggregation technologies, including the MAC architecture of enhanced multi-link aggregation, multi-link channel access, and multi-link transmission.
More Data Streams and Enhanced MIMO
Wi-Fi 7 increases the number of spatial streams from 8 to 16, increasing the theoretical physical transmission rate by more than twice than Wi-Fi 6. With more data streams, Wi-Fi 7 supports distributed MIMO. That is, 16 data streams can be provided by multiple access points at the same time, meaning that multiple APs need to coordinate with each other.
Multi-AP Coordination
In the current 802.11 protocol framework, there is not much coordination between APs. Common WLAN functions, such as automatic radio calibration and smart roaming, are vendor-defined features. Multi-AP coordination aims to optimize channel selection and adjust loads between APs to achieve efficient utilization and balanced allocation of radio resources. Coordinated scheduling between multiple APs in Wi-Fi 7 involves inter-cell coordinated planning in the time and frequency domains, inter-cell interference coordination, and distributed MIMO. This reduces interference between APs and greatly improves the utilization of air interface resources.
