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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Gjermunds WiFI Quizzle 1

I made a Kahoot challenge last week. But because of different subscription models only 20 could attend. The winner in that challenge had 8 correct answers out of 10 questions.

I make this blog with the same challenge so everyone who wishes can test themself.

First is the 10 question, each with 4 options.
Then the same 10 questions with the correct answers, and some explanation

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802.11ax Frame Aggregation, a case study

802.11 Frame Aggregation is the technology in WiFi that enables the sender/transmitter to “pack” together several frames and send them in one frame transmission, a TXOP.

I will in this case study drill down in a frame capture and interpret the different parts of an 802.11ax aggregated frame transmission, both a single-user transmission (OFDM) and a multi-user transmission (OFDMA).

The wireless capture I use in this case study contains two-level aggregation, where A-MSDU is sent inside an A-MPDU.
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Data Rata vs Throughput, OFDM vs OFDMA

During Wireless LAN Professional Conference 2019 (WLPC_EU) in Prague, I had a presentation where the WiFi AirTime Calculator was presented. You can read about it and download it from here. And I used the results from the calculator to look at data rate versus throughput in a WiFi network.

This is a theoretical approach and we assume it is no other traffic in the BSS or on the channel. And it is on a 20 MHz channel at the 5 GHz.
A Data field size of 300 bytes is used in this article. I call it the Data field size, other common names are payloads, MPDU, A-MPDU or frame body. The Data field is the correct name according to the standard and it embraces all frame format types.

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Wireless Capturing of UL OFDMA

The process of wireless capturing of 802.11ax OFDMA-frames has evolved. The newest step, for me, is to capture the UL OFDMA frames.

I use the NVIDIA Jetson Nano developer kit with the Intel AX200 NIC for wireless capturing and I have earlier showed how to capture:

  • Single-user 802.11 in this blog
    • But Francois Verges has developed this method, see his blog
  • Multi-user frames during DL OFDMA in this blog
  • UL OFDMA without capturing the data frames in this blog

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