Preamble puncturing is a Wi-Fi 7 (IEEE 802.11be) capability that allows an Access Point to selectively exclude portions of its operating channel affected by interference, while continuing to use the remaining available bandwidth.

In earlier Wi-Fi generations, if a 20 MHz sub-channel within an 80 MHz or 160 MHz channel experienced interference from a neighbouring Wi-Fi device or a non-Wi-Fi transmitter such as radar, the Access Point typically had to change channels or reduce its channel width. Changing channels can disrupt client connectivity, while reducing channel width decreases available capacity.

Preamble puncturing provides another option: puncture or exclude only the affected 20 MHz sub-channel and continue transmitting over the usable portions of the wider channel. 

How Does Preamble Puncturing Work?

Wide Wi-Fi 7 channels are built from multiple contiguous 20 MHz sub-channels for example, an 80 MHz channel is made up of four 20 MHz sub-channels, and a 160 MHz channel is made up of eight. With preamble puncturing, if one of those sub-channels is affected by heavy interference, the Access Point can mark it as punctured in the transmission preamble and use the remaining sub-channels to carry data. A 160 MHz channel with a single punctured 20 MHz sub-channel can still deliver data across the remaining 140 MHz, rather than falling back to an 80 MHz or 40 MHz channel.

What Does Preamble Puncturing Enable?

• Preserves most of the available channel capacity in the presence of narrow-band interference
• Eliminates the need to change channel and/or width, thus avoiding impact on connected clients
• Improves consistency of throughput in offices, campuses, and other high-density deployments where interference is common

Key takeaway: Preamble puncturing keeps Wi-Fi 7 networks react gracefully to narrow-band interference, thus reducing the impact on end-user experience.