The Importance of Detecting the 802.11 Preamble

I have in my short WiFi life thought when an 802.11 station (WiFi) does carrier detect it would detect all parts of an ongoing frame transmission on the channel and defer its own transmission because of that. But it seems my understanding has been wrong.

The last week’s online discussions has open my eyes to another look at the protocol and the importance of detecting the 802.11 preamble.

In this article I will write about the uniqueness of the 802.11 preamble, how important it is to detect it and how long it travels

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How To Differentiate Between 802.11 PHY Types

Please, set your mind into an 802.11 station and think about what happens during the start of an 802.11 frame reception.
In the preamble there is a field called L-SIGNAL and one of the subfields is called Rate. If the rate indicates 6mbs the rest of the frame could be any of the available PHY types in the 802.11 standards.
In the 5GHz band, it could be either a non-HT, HT, VHT, HE SU, HE MU, MU Trigger-based, or HE ER frame format.
How will you differentiate between those types of frame formats, and receive and process it correctly?

No clue, read this article

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Can 802.11a be more efficient than 802.11ax?

With the introduction of 802.11ax and the newly released frequency band for 802.11 transmission in the 6GHz band (WiFi6E) there have been talks about allowing only 802.11ax frame formats in WiFi6E. A week ago Jim Vajda (@jimvajda) released a blog article on “Whats Different About 802.11ax in 6Ghz“. This article concluded with the use of 802.11a, or non-HT, frame format for some types of control and management frames, and 802.11ax (HE) frame format for the rest.

In this article, I will describe airtime consumption for those two frame formats and show where 802.11a/non-HT frame formats consume less airtime than 802.11ax/HE frame format.

This article is only regarding airtime consumption for single user frame types. Multi-user frame types in 802.11ax/HE solve other issues. 

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