Evolution to Wi-Fi 6E and Wi-Fi 7

Release Date:2021-07-26  Author:By Zhang Zhigang  Click:

Wi-Fi Proves Its Value Worldwide
After six iterations and especially evolution to Wi-Fi 4, Wi-Fi 5 and Wi-Fi 6, Wi-Fi technologies have been widely deployed across the globe. Wi-Fi 6 provides larger capacity and higher performance, reducing the pressure and urgency for operators to build expensive cellular networks. The complementarity between Wi-Fi 6 and 5G further improves wireless connectivity.

Wi-Fi 6E Addresses Wi-Fi Spectrum Shortage
The demand for Wi-Fi has been increasing steadily over the past 20 years. However, the amount of available unlicensed spectrum remained unchanged until 2020, resulting in a serious spectrum shortage. As a new unlicensed band, 6 GHz is an especially attractive spectrum option for Wi-Fi deployment. Wi-Fi 6E is Wi-Fi 6 extended to the 6 GHz band.
Contiguous spectrum: Because the 6 GHz band is adjacent to existing 5 GHz spectrum, it can reduce the cost of adding 6 GHz capabilities to Wi-Fi devices that support the 5 GHz band. The propagation characteristics of 6 GHz signals are similar to those of 5 GHz signals. This makes it easier to upgrade Wi-Fi devices and enables the reuse of coverage maps and metrics of 5 GHz networks.
Wider bandwidth: The 6 GHz band has 1200 MHz of contiguous spectrum and allows for wider bandwidth, thus meeting the requirements of high-throughput and low-latency services like HD video, AR/VR and telepresence.
Reduced interference: In Wi-Fi applications, the 6 GHz band is relatively not congested because it is used only by Wi-Fi 6 devices. By shifting applications with high requirements for throughput and latency to the 6 GHz band, congestion at the 2.4 GHz and 5 GHz bands is relieved, thereby improving the overall capacity and performance of the Wi-Fi devices already deployed (Fig. 1).

b
Wi-Fi 6E allows Wi-Fi devices to run at the 6 GHz band so that they can deliver 10 Gbps rates, extremely low latency, and a larger capacity. Some issues concerning the adoption of the 6 GHz band still need to be sorted out, however. For example, 
the 2023 World Radiocommunication Conference (WRC-23) is set to discuss the licensing regime of the band. In addition to using the 6 GHz spectrum, Wi-Fi 6E still offers the features and capabilities mandated by the Wi-Fi Certified 6 program.


Wi-Fi 7 Focuses on Boosting Data Rates

Wi-Fi 6 was standardized by the IEEE 802.11ax high efficiency WLAN (HEW) study group with the main purpose of raising efficiency. The study group of Wi-Fi 7 is named IEEE 802.11be extremely high throughput (EHT). As the name indicates, a crucial objective of Wi-Fi 7 is to increase Wi-Fi rates. Video will constitute the bulk of traffic delivered via wireless local area networks (WLANs). New 4K and 8K videos require high uncompressed rates, and their throughput requirements are constantly evolving. High-throughput and low-latency new applications such as AR/VR, gaming, remote office, and cloud computing will also emerge in large numbers. The Wi-Fi 7 (802.11be) standard aims at:
—Configuring at least one mode of operation that supports a maximum throughput of at least 30 Gbps;
—Supporting the frequency bands between 1 GHz and 7.125 GHz (2.4 GHz, 5 GHz, and 6 GHz bands); 
—Enabling downward compatibility with the 802.11a/b/g/n/ac/ax standards. Wi-Fi 7 defines at least one mode of operation capable of improved worst case latency and jitter.

c

The milestones of Wi-Fi 7 standardization is shown in Fig. 2. The standardization project was initiated in 2019 with the establishment of task group be (TGbe) and is intended to release the Wi-Fi 7 standard in 2024.
The main features of Wi-Fi 5, Wi-Fi 6 and Wi-Fi 7 are compared in Table 1. 

d
Wi-Fi 7 (802.11be) has the following main candidate features: 
—Supports a maximum of 16 spatial streams, doubles the total rate of Wi-Fi 6, and enhances the multiple-input multiple-output (MIMO) mechanism.
—Supports up to 320 MHz bandwidth, doubles the per-stream rate of Wi-Fi 6, and allows the aggregation of non-contiguous channels.
—Supports 4096 QAM, improves performance by 20% compared with 1024 QAM, and enhances the MIMO mechanism.
—Adopts multi-link operation (MLO) and multi-RU (via preamble puncturing) techniques, which allow link-layer aggregation and coordination of different bands and channels. Traffic steering and load balancing among multiple bands and channels, concurrent transmission through multiple bands and channels, and repeated transmission are performed to increase reliability.
—Supports multi-AP coordination, which employs methods, such as avoiding interference and collision between basic service sets (BSSs), having multiple APs send the same data frame, and collecting channel state information (CSI) of unassociated STAs, to significantly boost network performance in multi-AP environments. This technology is especially useful as a performance booster in homes and businesses where an increasing number of mesh APs are deployed.
—Uses enhanced link adaptation and transmission protocols, such as hybrid automatic repeat request (HARQ).
—Enhances the low-latency capability. To support real-time application (RTA), TGbe analyzed the main findings of the IEEE 802.1 time-sensitive networking (TSN) task group and discussed how to optimize technologies including enhanced distributed channel access (EDCA) and enhanced uplink OFDMA-based random access (UORA). Ongoing discussions conducted by TGbe cover the backoff procedure, access categories (ACs) and packet service policies.
As an important milestone in the development of next-generation Wi-Fi technologies, Wi-Fi 7 (802.11be) aims to provide extremely high throughput and support low-latency services. Its standardization is still at an early stage. Theoretically, high throughput and low latency can be realized through the EHT PHY specification, which features 4096 QAM, 320 MHz, 16×16 MU-MIMO, and the EHT preamble. In practice, however, due to the unlicensed spectrum, interference, and high overhead, EHT PHY alone cannot achieve significant throughput and latency gains for end users. This is why TGbe is also exploring other important innovations, such as enhanced EDCA, flexible OFDMA, multi-link operation, and reduced channel sounding. Additionally, TGbe is discussing advanced PHY techniques that can improve spectral efficiency, such as HARQ, non-orthogonal multiple access (NOMA), and full duplex (FD), as well as various multi-AP coordination methods. This represents another approach to reducing interference. While the former approach is to perform separate transmissions that are based on time, frequency, space or power, the new one is to conduct joint transmissions in a distributed large-scale antenna system. Although TGbe may delay releasing many advanced PHY and multi-AP coordination features of next-generation Wi-Fi standards, these features indicate the direction of development beyond Wi-Fi 7.
ZTE has actively participated in the formulation of the Wi-Fi 7 standard by providing theoretical support and engineering validation in areas including operation performance of OFDMA, RU allocation mechanisms, media access control (MAC) support for RU allocation, low-latency support in multi-link operation, channel access mechanisms, coordination among multi-link devices (MLDs), and low-latency statistic measurement and optimization.

Wi-Fi to Create More Value in the Future

As Wi-Fi advances, innovations and solutions will continue to emerge to deliver high-quality connectivity anywhere, anytime to meet user needs. The social and economic value of Wi-Fi will keep rising.

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