Wi-Fi PHY Frames: From 802.11b to Wi-Fi 7
Every Wi-Fi transmission starts with a preamble. Explore each generation's PHY frame field by field, the legacy start they all share, and what an older device can still understand of a newer one.
How to use this tool controls and what to look for
Pick a PHY format and explore its frame field by field, then check what an older device can still understand of it.
Controls to change
- Format: choose 802.11b, 802.11a/g or Wi-Fi 4 to 7, including variants such as HT greenfield or HE multi-user.
- Data (PSDU) size: change how much data follows the preamble.
- View: switch between the Whole frame and a Preamble close-up. Zoom in or out on the time axis.
- Receiver: pick an older device and see which fields it can decode.
What to look for
- Every OFDM format still starts with the same legacy preamble: L-STF, L-LTF and L-SIG.
- Newer generations add their own fields after it (HT-SIG, VHT-SIG, HE-SIG, U-SIG, EHT-SIG), so the preamble grows.
- An older device can't read the data, but it reads L-SIG, works out how long the frame lasts and stays quiet.
- With small data sizes, the preamble can take longer than the data itself.
About this tool
Before any data, every Wi-Fi transmission sends a preamble: fields that let the receiver find the signal, tune in and learn how the data is sent. This tool explores each generation's frame from 802.11b to Wi-Fi 7, shows every preamble side by side on one time axis, and explains what an older device makes of a newer one.
What you'll learn
- What the PLCP preamble and header do in 802.11b
- The legacy preamble (L-STF, L-LTF, L-SIG) that every OFDM format still starts with
- The extra fields added by HT, VHT, HE and EHT
- Why older devices can still defer to newer transmissions
Common questions
Can an 802.11b device read a Wi-Fi 6 preamble?
No. 802.11b uses a different modulation and can't decode OFDM preambles at all. It only defers when it detects enough energy, or when the AP adds protection frames it can understand.
What is the legacy preamble?
L-STF, L-LTF and L-SIG, the first 20 µs of every OFDM Wi-Fi frame since 802.11a. Older OFDM devices read the length from L-SIG and stay quiet for that long.
Why do newer preambles take longer?
Each generation adds training and signal fields for more streams, wider channels and multi-user transmissions, which costs a few extra microseconds per frame.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.