Onward and upward with Wi-Fi 7

Can you remember the last time you plugged a laptop into an ethernet connection? Most devices are not even designed with wired ports anymore. Instead, everything defaults to a wireless connection for network access. The evolution in wireless technology over the past 25 years has created entirely new classes of applications and things. Even though Wi-Fi is everywhere and in everything, what is most exciting about this new generation of Wi-Fi is not only the speed, but the capacity and latency improvements. 

Back in 1999, first-generation Wi-Fi offered a mere speed of 11 Mbps. In its sixth generation, Wi-Fi 6 offered a theoretical speed limit of a little less than 10 Gbps. This speed increase helped spur applications of the past – like email and web browsing – into the bandwidth-hungry video conferencing and AR/VR applications of today and tomorrow. Looking at the development of Wi-Fi from Wi-Fi 1 through Wi-Fi 6E, it was typically two to four years between each generation for signiciant improvements in speed, capacity, efficiency, and security. This increase in capacity and optimization fueled the exponential growth of Wi-Fi-enabled devices, with chipsets embedded in everything from low-end consumer devices to enterprise-class devices. For consumers, Wi-Fi is no longer a luxury, but a necessity. 

Figure 1. Evolution of Wi-Fi standards from 1999 to near future

With this explosive growth in devices and applications, 2.4 and 5 GHz spectrum space is crowded. This has led to the Federal Communications Commission in the U.S., and other regulatory bodies globally, to release 6 GHz spectrum space for unlicensed use of Wi-Fi. This extra spectrum (1200 MHz or 500 MHz, depending on the country), dubbed Wi-Fi 6E, is a huge boost to the market. Even with the release of Wi-Fi 6E, there is great anticipation for what the next generation, Wi-Fi 7, will bring.

What’s new in Wi-Fi 7?

Wi-Fi 7 is the latest release in Wi-Fi based on the IEEE 802.11be amendment, also known as “Extremely High Throughput (EHT).” The amendment is yet to be finalized, but offers many enhancements that will benefit enterprises, as well as end users by increasing speeds up to four times compared to Wi-Fi 6. In addition, it offers super low latency, more robust connection, higher spectral efficiency, better interference mitigation, more power-saving techniques, better roaming experience, and increased security. The Wi-Fi 7 will be split into two releases taking features from the 802.11be amendment, as its draft evolves and matures. The launch of the first release of Wi-Fi 7 is expected in early 2024 and release 2 is anticipated in early 2026.

Wi-Fi 7 will operate in all three bands, 2.4, 5, and 6 GHz, and offers these key features in PHY and MAC layer:

Higher data rates

• 4096 QAM also known as 4K QAM (Quadrature Amplitude Modulation) \'96 With 4K QAM, the number of bits encoded in a sub-carrier is 12 bits, when compared to 10 bits of data encoded in a sub-carrier for 1024 QAM in Wi-Fi 6. This helps to increase the PHY data rate by 20%.

• 320 MHz Channel Width - The max channel width is doubled to 320 MHz when compared to 160 MHz in Wi-Fi 6. With 1200 MHz spectrum space available in the 6 GHz band, it’s possible to achieve 3x 320 MHz channel-wide channels.

Spatial Streams
The max number of spatial streams remains the same as in the previous Wi-Fi generations at 8. More spatial streams help achieve higher aggregate performance in a MU-MIMO environment while simultaneously communicating with multiple clients.

Figure 2. Illustrations of PHY features in Wi-Fi 7 compared to current features in Wi-Fi 6

The above PHY enhancements help increase the max data rate to a theoretical limit of approximately 23 Gbps, compared to 9.6 Gbps with Wi-Fi 6.

Multi-Link Operation (MLO):

Multi-Link Operation is an aggregation of multiple bands or channels. With MLO, the Wi-Fi 7 wireless client devices capable of multi-link are referred to as multi-link devices (MLDs) and can associate and simultaneously exchange traffic on multiple bands  (or multiple channels in the same band if the access point has a dual 5 GHz radio).

Figure 3. Image depicting Wi-Fi 6 singular link compared to simultaneous traffic exchange on 2.4, 5, and 6 GHz with Wi-Fi 7 via MLO.

Existing Wi-Fi generations allow the association and exchange of data in one band only. Distributing traffic across different bands increases overall speed, reduces latency, and improves reliability by using the best link available. Based on the application's needs, specific links can be assigned for data flows that would help achieve the SLA for that specific application.

MLO will benefit applications like VR/AR, online gaming, cloud access, and remote office tools. MLO can also improve backhaul for mesh and avoid roaming delays between bands. MLO can help stations at the cell edge switch to a better band with a longer range, seamlessly. For example, the stations can switch to 6 GHz when closer to the access point and then to 2.4 or 5 GHz at cell edges.

Multiple RU (MRU):

OFDMA (Orthogonal Frequency Division Multiple Access) is arguably the most significant feature of Wi-Fi 6. OFDMA allows multiple clients to transmit or receive from an access point at the same time by sharing available bandwidth. OFDMA’s spectral efficiency improves transmission latency or delay in the RF environment. 

OFDMA allows sub-carriers in a channel bandwidth to be grouped into smaller portions called “Resource Units,” (RUs). These individual RUs are assigned to different stations, which allows access points to serve them simultaneously during uplink and downlink transmissions.

In Wi-Fi 6, access points assign only a single RU to each wireless client. Wi-Fi 7 allows multiple resource units (MRUs) to be assigned to each wireless client. MRUs enhance spectral efficiency and interference mitigation. 

Preamble puncturing:

Preamble puncturing allows access points to ‘carve out’ or ‘puncture’ a portion of channel width that is affected by interference, resulting in the remaining channel being used for data transmission. For example, if there is an interference present in a 20 MHz channel of an 80 MHz channel width that an AP is operating, the 20 MHz channel with interference that is unusable alone is punctured, and the remaining 60 MHz channel is used for data transmission. Overall bandwidth may be reduced, but instead of the entire 80 MHz channel width being incapacitated, only the ‘punctured’ 20 MHz channel is unavailable.

Figure 4. Illustration of channel utilization without preamble puncturing and with preamble puncturing, an expected feature of the new Wi-Fi 7 standard

Restricted Target Wake Time (r-TWT)

Target Wake Time (TWT) was introduced in Wi-Fi 6 to extend the sleep time of the wireless client and reduce medium contention. There are two operational modes in Wi-Fi 6: Individual TWT and Broadcast TWT. Individual TWT sets wake times for individual wireless clients and broadcast TWT sets wake times for a group of STAs.

Wi-Fi 7 introduces a new operational mode called Restricted TWT (R-TWT). The standard defines the mechanism to reserve channel resources and enhances medium-access protection for access points to allocate exclusive access to the medium at specified times. This can improve latency-sensitive traffic delivery.

Other key features of Wi-Fi 7

There are several other features expected: compressed block ack enhancements -increasing the window size up to 1024 MPDUs, compared to 256 MPDUs in Wi-Fi 6. QoS enhancements like Stream Classification Services (SCS) and Mirrored Stream Classification-- where a wireless client can request the access point to apply specific QoS treatment of downlink flows. You can expect to see the Wi-Fi 7 standard build on existing innovations that provide incredible voice and video streaming quality of service in a congested environment. This will result in significant improvements to the experience of Apple iPhones and iPads, by this standardization of SCS in Wi-Fi 7.

Wi-Fi 7 also brings security enhancements using advanced encryption algorithms to secure data transmissions and protect against cyberattacks.

Should you wait for Wi-Fi 7?

If you have a Wi-Fi 5 or Wi-Fi 6 network, you may be wondering if you should wait for Wi-Fi 7 or upgrade to Wi-Fi 6E now. Here are some considerations to keep in mind:

1. The 802.11be amendment is not finalized yet. IEEE’s public timeline for the final ratification of 802.11be amendment is expected around Dec 2024.

2. Enterprise-level Wi-Fi 7 chipsets are in the early stages of development and deployment and many features are still missing with the few available on the market. The stability of software, as well as ecosystem support, also needs consideration.

3. Though the standards have pushed the limits with 4K QAM, 320 MHz channel width, it’s impractical to implement these features immediately. 4K QAM needs a very high signal-to-noise ratio to achieve such high modulation levels. 320 MHz channel width could be achieved in 6 GHz spectrum in those countries with 1200 MHz of spectrum. Currently, there are few countries that have opened the entire 1200 MHz spectrum.

It will be at least a year, if not more, to expect enterprise-class Wi-Fi 7 access points that are fully baked, as well as the ecosystem to be available for any practical deployment.

To get the best user experience, with the increased speed and capabilities in Wi-Fi 7, the network infrastructure requirements have to be thought through for higher port speeds and power budgets.
The biggest boon to the Wi-Fi industry in the recent past is the availability of 6 GHz spectrum space for unlicensed use. The 2.4 GHz spectrum is almost unusable in many customer networks due to the limited number of channels, interference, and high-channel utilization.

The Wi-Fi 6E access points were launched in 2021 as Low Power Indoor (LPI) only access points. Specifications and details on the operation of Standard Power access points in conjunction with Automated Frequency Coordination System (AFC) were still a work in progress at that time. AFC will enable the higher power “Standard Power” mode in 6 GHz and help outdoor and some indoor deployments. It’s now in the final stages of development and is expected to be available for public use early 2024 when there is a final go-ahead from the FCC.

So, should you wait for Wi-Fi 7? While the features and functionality of this new standard will revolutionize wireless for the better, you may be waiting a while to take advantage of them. With all the spectrum available from Wi-Fi 6E, it might make sense for your business to take the leap with 6E, before taking a number for 7.