Preamble puncturing is one of the feature that allows for better spectrum efficiency than previous gen of Wi-Fi. This feature was actually introduced with 802.11ax/WiFi 6 but now it is mandatory with WiFi-7. We will likely see more clients support this feature since it is a mandatory Wi-Fi 7 feature that will be built on all WiFi 7 vendor APs.
How does this feature work?
The main purpose of this feature is to "puncture" or "carve-out" a portion of the secondary channels in case you have narrow-band interference. Channel bonding is a great feature that allows a BSS to use higher than 20 MHz of spectrum by bonding primary channel with multiple adjacent channels. With 802.11n, you can bond up to 40 MHz of channel and with WiFi 7/802.11be, you can bond up to 320 MHz wide channel.
Without Preamble Puncturing
Let's take an example of an AP operating with 80 MHz of bonded channel in the 5 GHz spectrum. A client would run a CCA on primary channel to make sure its idle before deciding to transmit. It would then also check its secondary channels to ensure they are idle as well. This process happens simultaneously. In case of narrowband interference where one of the secondary channel is experiencing narrowband interference up to a point where the channel is marked as busy, the client will not be able to use that and respective adjacent channels. Even if the BSS is configured for 80 MHz of channel bonding, it would only be able to use a portion of that bonded channel.
With Preamble Puncturing
With Wi-Fi 7 and preamble puncturing, the AP is able to carve out a portion of that bonded spectrum/channel so clients can STILL use the respective adjacent channels that are not experiencing interference, thus increasing the overall spectrum efficiency. The AP does this by sending a PPDU with Downlink OFDMA transmission with that affected portion of the channel punctured, or to explain simply, the AP will not send a preamble on that affected subchannel.
The AP will also advertise this information in the beacon and probe response frames on the channels which are punctured to all the BSS clients as shown here:
Here is how it is explained visually with Cisco Meraki's Wi-Fi 7 Access Point -
In summary, this is an excellent feature that will drive spectrum efficiency and allows the use of channel bonding without severely impacting performance in case of narrowband interference. This is another exciting addition to Wi-Fi 7 features alongside MLO (Multi-Link Operation) that I'm looking forward to.