During 802.11ax UL OFDMA magic happens in the RF space. What were RF collisions before is with 802.11ax normal behavior.

I will in this blog briefly explain what happens in the RF space during UL OFDMA.
I recommend reading one of the previous articles where I explain what it looks like in Wireshark.
I will simplify it so it is two clients that will send their data uplink in two different 106-tones RU

A short summary of the UL OFDMA process
– The AP sends a Basic Trigger frame, as a broadcast frame, in the legacy frame format at one of the mandatory rates
– STAs (clients) that are announced in the Basic Trigger frame sends their data uplink to the AP in parallel
— The AP sends a broadcast Multi-STA BlockAck frame to acknowledgment the received data frames

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I am launching the WiFi AirTime Calculator.

WiFi Community, feel free to test it and use it for self-study or during the education of your colleagues, clients or other

You find more information here, in the top menu or in the picture on the right-hand side

During WLPC_EU we had an 802.11ax after-party where we tried to make OFDMA functioning with different vendors AP and we got someone to do OFDMA. But we were kicked out of the meeting room before we got good results.

I have a network at home that does UL ODFMA, but it does not do DL OFDMA.

I have a packet capture of the UL OFDMA transmission and will explain it in this blog.

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My previous article was on how to do wireless capturing on a Jetson Nano, with a big external screen connected to either the HDMI or the Display outputs of the Jetson Nano. And with connected external mouse and keyboard

But what if you want to use favorite packet analyzer on your preferred client where you have all your configured filters, profiles, aliases and so on.

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The NVIDIA Jetson Nano Developer Kit with Intel AX200NGW WiFi6 chips set is one method to make a WIFi6 client. I have some of these.
Earlier today Francois Verges announced at Twitter a method for capturing 802.11ax frames with this kit. And I wasn’t difficult to trigger.

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I have tested the new 802.11ax standard lately and I have suspected that the downlink data frames don’t do Multi User OFDMA (DL OFDMA). I have also sent a question regarding this to some WiFi experts, but no one has answered. So, let us use Wireshark and Sidekick to dive into it.

This test is done with public available devices and software. I have not dived into release notes for each device. This is an article where I use Wireshark and Sidekick to examine how things work.

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This is a blog article on 802.11ax uplink OFDMA (UL OFDMA) and the control frames that are involved.

According to the IEEE802.11ax draft 4 the UL OFDMA process look like this

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The second powerpoint series in my deep dive into the HE/802.11ax protocol is about the Multi User Request to Send (MU-RTS) and Clear to Send (CTS) process.

MU-RTS is one of the new Trigger Frames in the HE process and will be used instead of the legacy RTS.

I’ve have rewritten the slides some times while I have discovered new items during my interpreting of the IEEE802.11ax draft, so the coherence of the slides could have been better.
If I have interpreted it wrong, please tell it to me

My lab is consisting of Cisco equipment and Cisco have not implemented this functionality yet, so nothing is tested in real life.

I hope it useful

 

MU-RTS_CTS_final

 

Last week I got one of my colleagues to install Vmware Workstation and Cisco Catalyst 9800 CL at one of my clients and after 24 hours of configuring and troubleshooting, I finally made it works with APs in FlexConnect mode.

Ciscos documentation on Catalyst 9800 CL and APs in FlexConnect mode is not perfect and I had a lot of challenges during configuration. I have therefore made this recipe for myself and anyone else

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I mentioned in my latest blogarticle that I have read the book “Next Generation Wireless LANs” second edition from Eldad Perahia and Robert Stacy. This is fantastic book that goes way beyonds study material for the CWAP-certification .

To memorize this bit-by-bit stuff I have made myself a ODFM, HT and VHT PHY cheat sheet

Remark: This is a 50% product and in A3 format.

Constructive feedback are welcome

Downloadable file (pdf): OFDM, HT and VHT PHY Reference cheat sheets