FEATUREDApplication Development & Modernization
PETER WELCHER | Solutions Architect
A prior blog covered the business aspects of Wi-Fi 7 – what is different, how it improves on Wi-Fi 6 and 6E, and what applications may benefit from Wi-Fi 7. HPE has announced a Wi-Fi 7 AP, and the other major networking vendors including Cisco/Meraki are expected to announce and/or ship products later this year (2024).
This blog takes a deeper dive into the technology of Wi-Fi 7. The goal is to provide a general technical background without getting into the minute technical details. For those who can’t get enough tech details, there are links to blogs/articles containing more details scattered throughout this blog.
Getting Our Tech On
Here are the basics of Wi-Fi 7:
- Wi-Fi 7 is a networking standard, IEEE 802.11be. It provides “Extremely High Throughput.” Various sources cite up to 46 or 40 Gbps, roughly 4 times Wi-Fi 6E’s maximum throughput capability.
- The good old IT caveat of “it depends” still applies: your APs must be positioned well, and overall capacity is still finite and shared by all associated devices, full speed assumes lack of competition from e.g. adjacent floors in a high-rise building, lack of other RF noise, etc.
- Wi-Fi 7 uses the 2.4, 5, 6 GHz bands, as with Wi-Fi 6 (2.4 and 5) and 6E (all three bands). It can do so in backwards-compatible fashion, although some of the new capabilities are not backwards-compatible.
- So, you can think of Wi-Fi 7 as taking Wi-Fi 6 to higher speeds, with lower latency, less congestion, and generally more throughput. It does take proper design and implementation to maximize those benefits. Phasing out legacy Wi-Fi devices also matters. Mixing old and new in one location pretty much limits you to only the older feature set.
- If you need it, and in the absence of impediments, Wi-Fi 7 can provide up to 320 MHz wide channels for higher data rates. In comparison, version 6E allows for up to 160 MHz wide channels. Also as before: doing this does consume the frequency range space available rather quickly.
About Channels
Each frequency band is broken into channels, each of which independently supports wireless traffic.
- The 2.4-GHz band consists of 11 channels of 20 megahertz (MHz) each.
- The 5-GHz band has in principle 45 channels of width 20 MHz. They can be combined to create 40-MHz or 80-MHz channels. Of course, that results in fewer channels.
- The 6-GHz band has in principle 60 channels of 20 MHz. With Wi-Fi 6E they can be combined up to 160 MHz wide. Wi-Fi 7 supports up to 320 MHz wide channels.
The wider the channel, the more data it can carry (transmit/receive). The trade-off is fewer channels, fewer simultaneous conversations.
Each country may limit the channels available. Thanks to my co-worker Martijn Van Overbeek for providing some useful links about this:
Advanced Tech Concepts
MU-MIMO: multi-user multi-input multi-output. Starting with Wi-Fi 5, MU-MIMO supports more devices using an AP at a time: it allows one AP to transmit or receive data from multiple devices at the same time on a given frequency (channel). This reduces bottlenecks, e.g. waiting for another device’s transmission to finish.
MU-MIMO leverages spatial streams or spatial separation to do that. This refers to beamforming across multiple antennas to “steer” signal from the AP to each client. Think of beamforming as coordinating antenna outputs so the RF signal is strongest in the direction of the client.
https://blogs.cisco.com/networking/too-fast-too-furious-with-catalyst-wi-fi-6-mu-mimo
This technology does require the AP to have multiple antennas or antenna “elements.” The end user devices (phone or laptop) generally would have at least one antenna (or element), with premium devices having more. For example, high-end cell phones might have two (“2×2 MIMO”), and the MacBook Pro has 3, supporting “3×3 MIMO”. The two numbers refer to simultaneous transmits and receives. As one might expect, bigger numbers are “better.”
Some Wi-Fi 7 APs may support 16×16 MIMO, using 16 antennas/elements. This would allow simultaneous communication with up to 16 devices on each frequency. I suspect such APs probably would cost more. So, the degree of MIMO may be a tech factor to consider between competing products, if that matters to you.
https://www.tp-link.com/us/blog/1066/what-is-16×16-mu-mimo-an-intro-to-wifi-7-s-key-tech/
OFDMA (Orthogonal Frequency Division Multiple Access) enables shared bandwidth, for better transmission latency and delay when there is congestion. It allows channel bandwidth to be allocated and grouped in small units, “Resource Units” (RUs). An RU is a chunk or slice of a radio frequency (omitting further details). The RUs are assigned to different end-stations. With OFDMA, the AP can transmit/receive to the clients simultaneously.
Note there is still contention with older stations that are not OFDMA capable, especially pre-Wi-Fi 6 stations.
For more fine details, see https://blogs.cisco.com/networking/wi-fi-6-ofdma-resource-unit-ru-allocations-and-mappings
Unlike Wi-Fi 6/6E, Wi-Fi 7 supports multiple RU operations: Multi-RU. In prior Wi-Fi versions, a given user is assigned a single RU, some chunk of bandwidth. RUs can come in different sizes. With Multi-RU, a given user (wireless station) can be assigned multiple RUs if there are some not in use. That gives them more bandwidth, and provides more efficient use of bandwidth, i.e. not “wasting” what would be otherwise unused capacity.
Wi-Fi 7 adds to this Multi-RU Puncturing, which was optional in Wi-Fi 6, and is now mandatory in Wi-Fi 7. This feature is also called “Preamble Puncturing.” With puncturing, the AP and client can omit using part of a channel where there is interference from some other RF source.
https://www.ruckusnetworks.com/blog/2023/wi-fi-7-and-punctured-transmission/
Multi-link operation (MLO): Wi-Fi 7 can also use multiple links to communicate with a device. That is, MLO simultaneously uses different frequency bands. This can greatly reduce latency (the wait time before transmitting).
4K-QAM: Wi-Fi 7 uses a higher-order modulation scheme named 4K-QAM. This enables each transmitted “symbol” to carry 12 rather than 10 bits of information, providing a 20% speed increase. Some sources note that the extra modulation may require slightly stronger signal, possibly to offset background noise or interference, which translates into slightly shorter ranges (transmission distances). That in turn may or may not mean that you need a slightly more dense (closer together) AP deployment.
See also https://www.wired.com/story/what-is-wi-fi-7/.
Triggered Uplink Access: Allows for more predictability. AP triggers client when to send, reducing wait time/contention. See also https://www.maxlinear.com/news/quality-of-service-(qos)-mechanisms-in-wi-fi.
Emergency Preparedness Communication Services (EPCS): provides a seamless National Security & Emergency Preparedness (NSEP) service experience to users while maintaining the priority and quality of service in Wi-Fi access networks. Think E-911 priority. See also Facilitation Fast Emergency Wi-Fi Access in an Openroaming Environment.
Things to Consider
Wi-Fi 7 in the AP is backwards compatible. So, you can migrate APs to Wi-Fi 7, and then gradually migrate/replace client computers to support use of Wi-Fi 7, or do it in the other order.
Wi-Fi 7 AP placement does need to be considered. Some of what provides higher speed capability may require a slightly stronger signal to achieve max speed. Consequently, your current AP placement may be fine, in which case you can then just swap out the APs for new ones. But a current “frugal” deployment with longer distances between APs may not fully support the highest speeds Wi-Fi 7 is potentially capable of. If that matters to you, it’s better to figure that out in advance, rather than having to buy and add more APs and fiddle with AP locations and LAN connections, after discovering speed limitations the hard way.
For discussion of this, see also https://www.ekahau.com/blog/wi-fi-7-whats-new-and-how-it-will-impact-your-network/.
- To provide 1024 QAM, one needs line of sight (LOS), 7-11 meters to a “good” AP, SNR 35 dB or greater.
- For 4096 QAM: they expect 5-7 meters to AP, LOS, SNR >= 40 dB.
- Real world: APs every 10-12 meters in open space will mean clients already within 5-7 meters.
- Real-world: 320 MHz is not recommended if an AP can “hear” neighbors. In particular, don’t expect enterprise use, because there will likely be high co-channel interference. 160 Mhz channels can be used without overlap when all other traffic is restricted to the 5 Ghz band. As always, there are trade-offs, costs.
Conclusion
There are many technical improvements (lessons learned!) built into Wi-Fi 7. Most are covered above.
As the saying goes: it takes two to tango. That is, not just the Wi-Fi AP but also all the end-user devices (laptops, phones, etc.) need to also support Wi-Fi 7 to achieve the full benefits.
More Links
- Good overall summary: https://www.tp-link.com/us/Wi-Fi 7/
- Lots of tech details: https://en.wikipedia.org/wiki/IEEE_802.11be
- Mentions some candidate features, including : Multi-Access Point Coordination. The goal would be reduced interference, better performance in crowded settings.
- And a Time-Sensitive Networking (TSN) extension for low-latency real-time traffic.
- Plus a lot more info, with links to technical publications.
- Cisco and Wi-Fi 7: https://outshift.cisco.com/blog/onward-and-upward-with-wi-fi-7
- Good coverage of the tech fine points
- Some Cisco, Meraki availability in 2024 (maybe)
- Fully baked standard and gear: Feb 2025 or longer (other sources appear to contradict this?)
- Wi-Fi 8 development is in progress:
- Some general Wi-Fi 6E advice that also applies to Wi-Fi 7: https://www.networkworld.com/article/2096280/7-tips-for-deploying-wi-fi-6e.html
