Understanding Wi-Fi 7: Key Features and Benefits

Following the Wi-Fi 6E, the 7th generation Wi-Fi technology (also known as IEEE 802.11be or Wi-Fi 7) is about to be released! This will be the fastest Wi-Fi technology ever, revolutionizing the game and providing a better user experience for our online activities and networks in daily life. It will support and accelerate many demanding applications such as 8K video streaming, fully immersive AR/VR, gaming, and cloud computing. This article will review the key features supported in 802.11be Release 1, and explore the benefits of Wi-Fi 7 and how it achieves future connectivity.

With the 6 GHz band opened for Wi-Fi applications, Wi-Fi 7 supports a maximum channel bandwidth of 320 MHz in the 6 GHz band, while also supporting 20/40/80/160 MHz channel bandwidth in the 5 GHz and 6 GHz bands as well as 20/40 MHz in the 2.4 GHz band. Compared to existing Wi-Fi 6/6E, the 320 MHz channel bandwidth alone doubles the maximum speed of Wi-Fi 7.

Figure 1: 320 MHz Channel Bandwidth

Quadrature Amplitude Modulation (QAM) is a widely used Wi-Fi modulation scheme that varies both the amplitude and phase in a mixed carrier. Wi-Fi 6 supports up to 1024 QAM—where the constellation points on the left in Figure 2 represent 10 bits of data (symbols). Wi-Fi 7 supports 4096 QAM—where each constellation point on the right represents 12 bits of data (symbols). In other words, each QAM-modulated point in Wi-Fi 7 can carry 2 more bits of information than in Wi-Fi 6, resulting in a 20% speed increase.

Figure 2: 1024 QAM vs 4096 QAM

Multi-Link Operation (MLO) is an important and useful feature in Wi-Fi 7. It allows devices to send and receive simultaneously across multiple bands and channels. It is similar to link aggregation or clustering functions in wired (i.e., Ethernet) networks but is more complex and flexible. It creates multiple links (radios) bundled or bonded across different bands and channels as a virtual link between connected peers. Each link (radio) can work independently and simultaneously with other links, or coordinate for optimal aggregation speed, latency, range (coverage), or power savings. Wi-Fi 7 MLO is a MAC layer solution that can use multiple links simultaneously, transparent to upper-layer protocols and services. MLO can enhance throughput, link robustness, roaming, interference mitigation, and reduce latency.

Figure 3: Multi-Link Operation

For example, in a home mesh network consisting of tri-band (6GHz, 5GHz, 2.4 GHz) mesh nodes or APs, MLO can form a high-speed, low-latency wireless backbone for the home network, providing backhaul for devices connected to the mesh nodes/APs. If each mesh node supports a 4×4 tri-band concurrent configuration, the aggregated backhaul speed can reach 21.6 Gbps. With MLO, the backhaul is also more robust and reliable. When the 5GHz link is disrupted by DFS (radar), traffic can automatically switch to the 6GHz and 2.4 GHz links without causing service interruptions and QoS (Quality of Service) degradation. Compared to Wi-Fi 7’s MLO-based backhaul, today’s Wi-Fi 6 and 6E mesh solutions use 4×4 radios to form wireless backhauls, providing only 4.8 Gbps speeds. If that link faces interference or disruption, the entire backhaul will be affected or interrupted, leading to QoS degradation or interruption.

When client devices (such as smartphones, laptops, etc.) support multiple wireless links, MLO creates a larger pipeline between the device and the AP for higher speeds, lower latency, and increased reliability, improving the user experience of seamless roaming.

Wi-Fi 7 introduces a new RU resource allocation mechanism. In Wi-Fi 6, APs could only allocate one RU to each user (non-AP users), whereas Wi-Fi 7 allows multiple MRUs (resource units) to be set for a non-AP user. MRUs further enhance spectrum utilization efficiency, providing users with more flexible bandwidth (QoS) control as needed, and strengthening the coexistence capability of existing devices operating on the same band or channel.

Figure 4: RU and MRU of 320 MHz OFDMA PPDU

This MRU mechanism supports Orthogonal Frequency Division Multiple Access (OFDMA) and non-OFDMA (i.e., MU-MIMO) modes. The OFDMA mode supports small MRUs and large MRUs, allowing for more flexible allocation of RUs/MRUs without complicating MAC and scheduler design. The non-OFDMA mode provides maximum flexibility in the preamble puncturing of subchannels.

For example, any 20 MHz subchannel can be punctured in the 320 MHz bandwidth, aside from the main channel or 40/80 MHz channels. This allows transmission to maximize the use of channel spectrum in the presence of interference and provides optimal coexistence when any device operates on specific spectrum segments of the channel.

Wi-Fi 7 has many new features and improvements. These features include: Preamble Pulsing, Target Wake Time (TWT), Restricted Time Wake (rTWT), Extended Range (MCS 14 and MCS 15), etc. Other features such as Multi-AP Coordination (Coordinated Beamforming, Coordinated OFDMA, Coordinated Spatial Reuse, Joint Transmission), 16 Spatial Streams, and HARQ may be supported in Release 2, which will not be covered in this article.

Wi-Fi 7 supports lightning-fast speeds. Built on its predecessor Wi-Fi 6 (also known as 802.11ax), Wi-Fi 7 supports Extremely High Throughput (EHT) with raw data rates of up to 46 Gbps and 16 spatial streams defined in the standard specifications. This is much faster than the 10 Gbps Ethernet running on Cat 6/6a/7 cables. The closest access and connection technologies are Thunderbolt 3/4, USB 4, and HDMI 2.1, which offer maximum raw data rates of 40Gbps or higher.

Wi-Fi 7 will support a 320MHz channel bandwidth, which is double that of Wi-Fi 6. Wi-Fi 7 also increases the QAM granularity from 1024 (1K) to 4096 (4K), resulting in a 20% speed increase compared to Wi-Fi 6/6E or Wi-Fi 5 Wave 3. Additionally, Wi-Fi 7 doubles the maximum number of spatial streams, which in some cases can be interchangeable with the number of antennas, from 8 to 16. Therefore, the maximum of 9.6 Gbps supported by Wi-Fi 6/6E with 8 spatial streams translates to a maximum of 46 Gbps with Wi-Fi 7 supporting 16 spatial streams (9.6 Gbps x2 (double bandwidth) x1.2 (QAM improvement) x2 (spatial streams)).

At this extremely high speed, users can achieve maximum speeds of up to 5.8 Gbps on common devices such as smartphones and laptops using two Wi-Fi antennas (two spatial streams). Many devices that use a single antenna can also support data rates of up to 2.9 Gbps due to strict power or form factor constraints. Users can achieve over double the speed without paying for additional antennas or higher electricity costs, as there is no need for extra power amplifiers or front-end modules—this represents a paradigm shift for many future applications.

Latency is another key parameter for Quality of Service (QoS) and user experience. It is especially critical for real-time applications. Many multimedia applications, such as high-resolution real-time video streaming, virtual reality, augmented reality, cloud gaming, and real-time programming, require latency of less than 20 milliseconds. Achieving such low latency in a wireless environment is not easy. For fiber access, the latency between the WAN side modem and the cloud/server is about 10 milliseconds or slightly longer. Considering this, the latency budget between the WAN modem and endpoint client devices should be around 10ms or less for a good user experience. Wi-Fi 6 achieves 10-20ms latency. Moreover, Wi-Fi 6E can achieve even lower latencies in much less congested environments. Wi-Fi 7 will help reduce latency to below 10 milliseconds and ultimately to below 1 millisecond range with deterministic boundaries by utilizing various tools in the 802.11be standard. These tools include MLO, Time-Wake Transform (TWT), rTWT, improved trigger transmission, and ultimately integrated Time-Sensitive Networking (TSN) capabilities.

As mentioned earlier, MLO provides a dynamic mechanism to adapt connections between multiple links. MLO can dynamically balance the transmission load between two link peers (such as AP and client devices) based on metrics such as link performance and robustness, i.e., load balancing. If there is interference or link loss on one link (for example, due to range), the connection can still run on the remaining links, and the transmission can seamlessly switch from the failed link to the good link (also known as fast failover). The MRU/RU and preamble puncturing also contribute to the robustness of the connection. For example, when a specific subchannel or spectrum segment of the running channel is interfered with, the AP can avoid using those interfered subchannels or RUs/MRUs and optimize transmissions based on current environmental situations and channel states.

Additionally, MCS 14 and MCS 15 are defined to improve the signal-to-noise ratio, thereby enhancing the robustness of the connection as the distance between link peers increases.

Wi-Fi 6 and Wi-Fi 6E have enhanced many interference reduction and coexistence features based on Wi-Fi 5. Wi-Fi 6 provides more flexible subchannel puncturing modes and can use RUs in OFDMA mode to avoid finer-grained interference, detailed to 2 MHz (the minimum RU has 26 tones). Wi-Fi 6E supports Automatic Frequency Coordination (AFC) for coexistence with existing devices. Wi-Fi 7 has MRU and maximum flexibility in preamble puncturing, supporting all possible subchannels and high-resolution puncturing modes in both OFDMA and non-OFDMA (MU-MIMO) modes, providing better interference mitigation and optimal QoS for different types of services.

Figure 5: Mitigating Interference and Coexistence through Preamble Puncturing, MRU/RU, and AFC

MLO also improves the user experience of seamless roaming. It provides built-in roaming enhancements defined in the 802.11be standard. For example, when a device moves away from an AP, MLO maintains the ML (multi-link) connection between the AP and the device, allowing it to operate automatically on the 2.4 GHz band without needing to switch bands. Conversely, if the device approaches the AP, MLO can automatically and dynamically operate on the 5 GHz and 6 GHz bands for better performance. Today’s Wi-Fi 6 and 6E APs must rely on application-layer band steering or client steering features to force clients to different bands. This does not always work as expected because APs cannot control client devices; client devices decide whether to switch bands. Additionally, compatibility between vendors is another significant challenge for seamless roaming.

Figure 6: Achieving Seamless Roaming Experience with MLO

In terms of spectrum utilization, Wi-Fi 7 offers higher efficiency than Wi-Fi 6/6E. Additional efficiencies can benefit from various Wi-Fi 7 features, MRU, preamble puncturing, MLO, 4096 QAM, future 16 spatial streams, and coordinated multi-AP features such as coordinated beamforming, coordinated OFDMA, joint transmission, etc.

By leveraging higher speeds, thanks to the wider 320 MHz channel bandwidth, 4096 QAM, and lower latency, Wi-Fi 7 delivers data with higher power efficiency. Based on the power-saving features of Wi-Fi 6, Wi-Fi 7 improves these features in various ways to achieve optimal power-saving effects.

With MLO, client devices do not need to listen for every Delivery Traffic Indication Message (DTIM) beacon frame or perform group time key, integrity group time key, or beacon integrity group time key (GTK/IGTK/BIGTK) updates. Clients can maintain a link for DTIM beacon updates, traffic indications, and BSS key updates while putting other links into deep sleep without needing to wake up regularly for DTIM beacon updates.

In addition to the most promising power-saving feature TWT in Wi-Fi 6, Wi-Fi 7 also supports a so-called Trigger Transmission Opportunity (TXOP) sharing feature, further saving power. It allows the AP to allocate a portion of the time within the TXOP obtained to associate client devices for transmission, so that the AP does not need to wake up in the next service period (SP).

Onsemi also supports many proprietary dynamic adaptive energy-saving features based on actual application, real-time throughput, and environmental (such as temperature) demands.

In recent years, Wi-Fi sensing applications, such as motion detection, location based on Wi-Fi Channel State Information (CSI) (especially indoors), fine time measurement/round-trip time (FTM/RTT), have garnered significant interest from service providers and end users.

Wi-Fi channels are susceptible to interference, exhibiting strong dynamics and frequency selectivity, and CSI contamination can significantly reduce the accuracy of motion detection. Thanks to the 320 MHz channel bandwidth, Wi-Fi 7 supports richer CSI data, with up to 3984 tones, improving the accuracy of motion detection. Additionally, since so much CSI data can be captured in the 320 MHz transmission, sufficient interference-free CSI blocks can be selected for motion detection while avoiding noisy CSI data.

Through 2x or 4x oversampling and upsampling techniques, RTT timestamps and measurement accuracy can achieve sub-nanosecond resolution for 320 MHz signals. In other words, Wi-Fi 7 supports sub-meter (i.e., 30 cm) accuracy for ranging and indoor positioning, making many exciting new Wi-Fi sensing applications possible.

Wi-Fi 7 will significantly enhance the user experience in many ways and become more cost-effective. It can enable and enhance many demanding applications such as cloud gaming, immersive AR/VR, 8K video streaming, Industry 4.0, etc. Users can expect Wi-Fi 7 to provide higher speeds, lower latency, and stronger performance than existing Wi-Fi 6/6E.